Types of vector-borne diseases. Classification of natural foci

Faculty: Pharmaceutical.

Department: Biology.

SCIENTIFIC WORK

Performer: Mamedova Jamilya Subkhanovna.

Scientific supervisor: Sobenina Galina Grigorievna.

Chelyabinsk

4. Infectious diseases

Bibliography

1. Vector-borne diseases

Vector-borne animal diseases are characterized by enzootic nature (confined to a specific area, climatic-geographical zone) and seasonality of manifestation. In cases where pathogens are transmitted by flying insects, vector-borne animal diseases usually spread more widely than when the pathogen is transmitted by ticks. Obligate vector-borne diseases of animals include: infectious bluetongue of sheep, hydropericarditis, infectious encephalomyelitis and infectious anemia of horses, African horse sickness, Rift Valley fever, Nairobi disease, Scottish sheep encephalomyelitis, viral nodular dermatitis; optional - anthrax, African swine fever, tularemia and other septic infections. Prevention measures include protecting humans and animals from attacks by blood-sucking arthropods (change of grazing, transfer to stall housing, use of repellents), destruction of vectors and rodents, reclamation measures in breeding areas of vectors, immunization of humans and animals (if developed).

2. Natural focal diseases

Natural focal diseases are an infectious disease, the causative agent of which constantly circulates among certain species of wild animals (birds and mammals are of greatest importance for humans and domestic animals), spreading by arthropod carriers (vector-borne diseases) or through direct contact, bites, etc. Natural focal diseases are transmitted to people and domestic animals by the same carriers, but sometimes through water and food. Naturally focal human diseases include plague, tularemia, tick-borne and mosquito-borne (Japanese) encephalitis, rabies, leptospirosis, hemorrhagic fevers, cutaneous leishmaniasis, tick-borne typhus, some types of helminthiasis (diphyllobothriasis, alveococcosis, echinococcosis, etc.). Some of these diseases are characteristic of domestic animals (rabies, leptospirosis, glanders, foot and mouth disease). For the first time, the idea of ​​natural foci of animal and human diseases was introduced by D.N. Zabolotny in 1899. The connection between these foci and landscapes was formulated by N.A. Gaisky in 1931. Subsequently, the doctrine of natural focality was developed by E.N. Pavlovsky and his school using the example of various diseases (plague - V.V. Kucheruk, tularemia - N.G. Olsufiev, tick-borne encephalitis - N.B. Birulei, etc.). The size of the outbreak depends on the type of pathogen, the natural environment and the social and living conditions of the population. In typhus, dysentery, and scarlet fever, the source of infection is the patient’s apartment or home. In malaria, the outbreak covers an area within which the disease can be transmitted by mosquitoes that become infected on a given patient. As for the relationship between the territory of the outbreak and natural-territorial complexes of various ranks, the smallest territorial unit with which the outbreak of the disease can be associated is the landscape, which represents a genetically isolated part of the landscape envelope. Smaller in size and simpler in structure morphological parts of the landscape (tracts, facies), apparently, do not possess all the qualities necessary for the long-term existence of the pathogen population. However, a complete analogy cannot be drawn between the division of the biosphere into natural-territorial complexes and the identification of disease foci. The landscape area is limited to the foci of many diseases (cutaneous leishmaniasis, tick-borne spirochetosis). The outbreaks of others (plague, etc.) cover an entire landscape area. The foci of diseases have a certain structure.

There are three types of morphological parts or elements of the focus: areas of relatively persistent infection (nucleus of the focus); areas of infection; areas that are constantly free from infectious agents. Depending on how pronounced the differences are between the morphological parts of the lesion, three types of its structure are distinguished: homogeneous (diffuse, homogeneous), heterogeneous (heterogeneous) and sharply heterogeneous (sharply heterogeneous). In diffuse outbreaks, the pathogen is scattered throughout the entire territory of the outbreak, and the danger of infection threatens a person when he is located at almost any point of the outbreak. In heterogeneous foci, the maximum risk of infection is associated with staying in areas of relatively persistent infection. The geographical features of the distribution of outbreaks are determined by their location in the landscapes of different zones. Zonal natural foci (associated with the upland conditions of a particular zone) have tick-borne encephalitis (southern part of the forest zone), plague (arid zones - steppe, desert, as well as corresponding arid mountain belts), tick-borne spirochetosis (desert zone), southern leishmaniasis (desert zone), yellow fever (equatorial and tropical rain forest zone), etc. Intrazonal foci that do not occupy placors in any zone, occurring in several zones, are characteristic of tularemia, mosquito encephalitis and other diseases. Outside of “their” zone, many diseases that have zonal foci transform into extrazonal conditions. Thus, the limestone outcrops of the river valleys of Southern Ukraine are characterized by foci of tick-borne spirochetosis, the birch forests of the Kustanai region - foci of tick-borne encephalitis, etc. Human impact contributes to the expansion of the territory of the outbreaks and their removal beyond the limits of their natural conditions. Thus, Q fever, whose natural foci are associated with arid zones, can affect domestic animals far beyond their borders, for example, in a forest zone; plague carried by rats has in past centuries affected cities located in a wide variety of environmental conditions, etc. A.G. Voronov (1981) proposes to introduce three categories of outbreaks according to the degree of change in natural conditions by humans:

Foci of man-made natural-territorial and natural-technogenic-territorial complexes: a) settlements and buildings; b) “industrial” landscapes (dumps, waste heaps; c) fields and vegetable gardens; d) plantations, gardens and parks; e) sown meadows, forest plantings, canals, reservoirs, reclaimed lands, which have analogues among indigenous communities.

Foci of natural-territorial complexes transformed by man; f) rapidly recovering communities of clearings, fallows, etc. g) long-term continental meadows, small-leaved forests, secondary savannas.

Foci of indigenous natural-territorial complexes, not changed or slightly changed by human activity. Prevention of natural focal diseases consists of immunizing people and domestic animals, repelling and destroying vectors and natural carriers of diseases, using protective equipment and other measures.

Helminths cause helminthiases, of which the most common are ascariasis, hookworm disease, hymenolepiasis, diphyllobothriasis, taeniasis, trichinosis, trichocephalosis, enterobiasis, echinococcosis, etc.

Prevention

On the scale of a specific person:

improving the health of young women and men before marriage can save them from much suffering due to the birth of sick children;

Don't be ignorant about personal health issues.

4. Infectious diseases

Infectious diseases are a group of diseases that are caused by specific pathogens and are characterized by contagiousness, a cyclical course and the formation of post-infectious immunity. The term "infectious diseases" was introduced by Gufeland and gained international currency. It is also used to designate the field of clinical medicine, which studies the pathogenesis, clinical picture of infectious diseases and develops methods for their diagnosis and treatment.

Classification.

Due to the diversity of biological properties of infectious agents, mechanisms of their transmission, pathogenetic features and clinical manifestations of infectious diseases, classifying the latter according to a single criterion is very difficult. The most widespread classification was theoretically substantiated by L.V. Gromashevsky, which is based on the mechanism of transmission of the infectious agent and its localization in the body. Under natural conditions, there are four types of transmission mechanisms: fecal-oral (for intestinal infections), aspiration (for respiratory tract infections), transmissible (for blood infections) and contact (for infections of the external integument). The transmission mechanism in most cases determines the preferential localization of the pathogen in the body. In intestinal infections, the pathogen is mainly localized in the intestine throughout the entire illness or during certain periods; for respiratory tract infections - in the mucous membranes of the pharynx, trachea, bronchi and alveoli, where the inflammatory process develops; for blood infections - circulates in the blood and lymphatic system; In case of infections of the external integument (this also includes wound infections), the skin and mucous membranes are primarily affected. Depending on the main source of the causative agent, infectious diseases are divided into anthroponoses (the source of pathogens is humans) and zoonoses (the source of pathogens is animals).

Some infectious diseases, in addition to the main transmission mechanism that determines their group affiliation, also have another mechanism of pathogen transmission. This leads to the fact that the disease can manifest itself in different clinical forms, corresponding to the mechanism of transmission. Thus, tularemia in humans most often occurs in the bubonic form, but when the pathogen is transmitted through airborne dust, a pulmonary form of the disease develops.

Not all infectious diseases can be classified with sufficient confidence into one group or another (for example, polio, leprosy, tularemia). However, the value of the classification of L.V. Gromashevsky is that as knowledge about the nature of insufficiently studied diseases deepens, they find an appropriate place in it.

) intestinal infections;

) tuberculosis;

) bacterial zoonoses;

) other bacterial diseases;

) polio and other viral diseases c. n. pp., not transmitted by arthropods;

) viral diseases accompanied by rashes;

) viral diseases transmitted by arthropods;

) other diseases caused by viruses and chlamydia;

) rickettsioses and other diseases transmitted by arthropods;

) syphilis and other sexually transmitted diseases;

) other diseases caused by spirochetes;

However, some deviations from the International Classification of Diseases are allowed. Thus, influenza and other acute respiratory viral infections are classified as infectious diseases (first class group), and in the International Classification of Diseases they are included among respiratory diseases.

Etiology and pathogenesis.

The direct cause of infectious diseases is the introduction of pathogenic agents into the human body (sometimes the ingestion of their toxins, mainly with food), with the cells and tissues of which they interact.

The pathogenesis of infectious diseases reflects the main stages of development of the infectious process: introduction and adaptation of the pathogen, its reproduction, breakthrough of protective barriers and generalization of infection, damage to organs and tissues, disruption of their function, the appearance of nonspecific protective reactions (Fever), inflammation (Inflammation), sensitization of the body by components microbial cell, the formation of specific Immunity, cleansing the body of the pathogen, reparation of damaged organs and tissues and restoration of their function. However, not all infectious diseases reveal all stages and links of pathogenesis; their significance in the pathogenesis of one or another nosological form is also different. For example, with tetanus and botulism, the pathogen does not penetrate local protective barriers, and the clinical manifestations of the disease are caused by the action of absorbed toxins. The role of the allergic component is also different. In erysipelas, scarlet fever, brucellosis, and typhoid fever, it plays an important role in the pathogenesis and clinical manifestations of the disease; in dysentery and cholera its role is not significant. The emerging immunity can be long-term and durable (for example, with typhoid fever, viral hepatitis A, smallpox, measles) or short-term (for example, with influenza, dysentery). In some cases, immunity is defective, which can manifest itself in relapses, protracted and chronic course of the infectious process. Finally, with some diseases (for example, erysipelas), immunity is not formed. In a number of infectious diseases, immunopathology develops, leading to a chronic course of the process (viral hepatitis B, slow infections of the nervous system). In the development of the chronic course of the disease, an important role is played by changes in the properties of the pathogen in the process of infectious diseases, in particular its L-transformation.

Circulation of the pathogen and its toxins, disruption of the functional state of organs. tissue damage, accumulation of metabolic products, cellular and tissue decay lead to the development of the most important clinical manifestation of infectious diseases - intoxication (Intoxication).

Restorative and reparative processes after an infectious disease are not always sufficiently complete, therefore post-infectious chronic diseases and pathological conditions often develop, for example, chronic colitis after dysentery, chronic nonspecific lung diseases after repeated acute respiratory viral infections, myocardiosclerosis after infectious myocarditis, joint contractures after brucellosis, intracranial hypertension after bacterial or viral meningitis.

Pathological anatomy.

Basic information about pathological anatomy was obtained on the basis of autopsy data, study of biopsy material and the results of endoscopic studies. These data indicate a wide range of morphological changes in tissues and organs. Some of them are nonspecific, others are specific both in the nature of changes in tissues and organs and in the localization of the pathological process.

For example, dysentery is characterized by damage to the rest of the large intestine, typhoid fever - the distal part of the small intestine, infectious mononucleosis - damage to the lymphoid apparatus, and meningitis - inflammatory damage to the meninges. A number of infectious diseases are characterized by the presence of specific inflammatory granulomas (epidemic typhus, tuberculosis). Many morphological changes are caused by the addition of complications (for example, pneumonia with influenza).

Clinical picture.

Most infectious diseases are characterized by cyclical development, i.e. a certain sequence of appearance, increase and disappearance of symptoms. for example, the appearance of jaundice in viral hepatitis is preceded by a pre-icteric (prodromal) period, a rash in epidemic typhus appears on the 4-6th day of illness, in typhoid fever - on the 8-10th day of illness. With food poisoning, vomiting appears first, then diarrhea; with cholera, it’s the opposite.

The following periods of disease development are distinguished: incubation (latent), prodromal (initial), main manifestations of the disease, extinction of disease symptoms (early period of convalescence), recovery (convalescence).

Incubation period is the period of time from the moment of infection until the appearance of the first wedges. symptoms of the disease.

The prodromal, or initial, period is accompanied by general manifestations of infectious diseases: malaise, often chills, fever, headache, sometimes nausea, minor muscle and joint pain, i.e. signs of a disease that do not have any clear specific manifestations. The prodromal period is not observed in all infectious diseases; it usually lasts 1-2 days.

The period of the main manifestations of the disease is characterized by the occurrence of the most significant and specific symptoms of the disease, morphological and biochemical changes. During the period of the main manifestations of the disease, the patient’s death may occur, or the disease may progress to the next period.

The period of extinction of the disease is characterized by the gradual disappearance of the main symptoms. Normalization of temperature can occur gradually (lysis) or very quickly, within several hours (crisis). The crisis, often observed in patients with typhus, epidemic and relapsing fever, is often accompanied by significant dysfunction of the cardiovascular system and profuse sweating.

The period of convalescence begins with the extinction of clinical symptoms. Its duration varies widely even for the same disease and depends on the form of the disease, severity, immunological characteristics of the body, and the effectiveness of treatment. Clinical recovery almost never coincides with complete morphological restoration of damage, which often lasts for a longer time.

Recovery can be complete when all impaired functions are restored, or incomplete if residual effects persist.

In addition to exacerbations and relapses, complications can develop during any period of infectious diseases, which can be divided into specific and nonspecific. Specific complications arise as a result of the action of the causative agent of this infectious disease and are a consequence of either the unusual severity of typical clinical and morphological manifestations of the disease (perforation of intestinal ulcers in typhoid fever, hepatic coma in viral hepatitis), or atypical localization of tissue damage (for example, Salmonella endocarditis, otitis media in typhoid fever). Complications caused by microorganisms of another type are usually called secondary infections, viral or bacterial superinfections. Reinfections, which are repeated diseases that occur after repeated infection with the same pathogen, should be distinguished from the latter.

There are also early and late complications. Early ones develop during the period of the height of the disease, late ones - during the period of extinction of its symptoms.

Depending on the characteristics, various clinical forms of infectious diseases are distinguished. According to the duration, acute, protracted, subacute and chronic course of the disease is distinguished, and in the latter case it can be continuous and recurrent. According to the severity of the course, mild, moderate, severe and very severe forms of the disease are possible, and the degree of severity is determined both by the severity of specific symptoms and by intoxication, damage to vital organs and the presence of complications. With some I. b. There are also hypertoxic, fulminant (fulminant) forms of the disease, reflecting the extremely rapid development of the pathological process and its severe course. Depending on the presence and severity of characteristic symptoms, it is customary to distinguish between typical and atypical course of the disease. With an atypical course of an infectious disease, the clinical picture is dominated by symptoms that are not characteristic of this disease, for example, with typhoid fever, the symptoms of pneumonia (“pneumotyphoid”) predominate, or the most important symptoms are absent, for example, with meningitis - meningeal syndrome. Atypical forms of infectious diseases also include the abortive course of the disease (the disease ends before the appearance of typical symptoms, for example, typhoid fever in vaccinated people) and the erased course of the disease (the general clinical manifestations of the disease are mild and short-lived, and there are no characteristic symptoms), for example, with the erased course of polio There is only a slight fever and mild catarrhal symptoms, and there are no signs of damage to the nervous system.

The most characteristic manifestations of infectious diseases are fever and intoxication. The presence of fever is typical for the vast majority of infectious diseases, with the exception of cholera, botulism and some others. Fever may be absent with a mild and abortive course of the disease. Many infectious diseases are characterized by certain types of febrile reactions; brucellosis - remitting, many spirochetosis - relapsing type, etc. Intoxication is manifested by weakness, decreased performance, anorexia, sleep disturbances, headache, vomiting, delirium, disturbances of consciousness, meningeal syndrome, pain in muscles, joints, tachycardia, arterial hypotension.

A large group of infectious diseases is characterized by the presence of a rash (exanthema), and the timing of its appearance, localization, morphology, and metamorphosis are typical for the corresponding infectious disease. Less common are rashes on the mucous membranes (enanthema) of the eyes, pharynx, pharynx, and genitals. In a number of vector-borne infectious diseases, inflammatory changes are observed at the site of penetration of the pathogen into the skin - a primary affect that may precede other clinical symptoms of the disease. Symptoms observed in a number of infectious diseases include damage to the lymphatic system in the form of an enlargement of individual groups of lymph nodes (lymphadenitis) or a generalized enlargement of three or more groups of lymph nodes (polyadenitis). Joint damage in the form of mono-, poly- and periarthritis is characteristic of relatively few infectious diseases - brucellosis, pseudotuberculosis, meningococcal infection and some others. The main clinical manifestation of acute respiratory viral infections is catarrhal respiratory syndrome, which is characterized by coughing, sneezing, runny nose, pain and sore throat. Specific pneumonias are observed less frequently (for example, with psittacosis, legionellosis, Q fever, mycoplasmosis). Changes in the cardiovascular system mainly reflect the severity of intoxication and the severity of the disease, however, in some infectious diseases, damage to the heart (for example, diphtheria) or blood vessels (with hemorrhagic fevers, epidemic typhus, meningococcal infection) are characteristic manifestations of the disease. Dyspeptic disorders (abdominal pain, diarrhea, vomiting, loss of appetite) are the most typical symptom of acute intestinal infections; Moreover, for different intestinal infections, their manifestations differ significantly. Thus, the gastrointestinal form of salmonellosis is characterized by epigastric pain and frequent vomiting; with dysentery, pain is localized in the left iliac region, and scanty mucous-bloody stool is characteristic. One of the important manifestations of many infectious diseases in which circulation of the pathogen in the blood is observed is hepatolienal syndrome - a combined enlargement of the liver and spleen (typhoid fever, epidemic typhus, viral hepatitis, infectious mononucleosis, brucellosis, tularemia, leptospirosis, etc.). Specific kidney damage is observed in leptospirosis, hemorrhagic fever with renal syndrome; genital organs - with brucellosis, mumps, and other infectious diseases it is rare.

An important place in the clinic of infectious diseases is occupied by c. n. With. nonspecific (intoxication), specific (toxic, for example, with tetanus, botulism) and inflammatory (for example, with meningitis, meningoencephalitis, encephalitis) nature. In this case, disturbances of consciousness, convulsive and meningeal syndrome, and focal symptoms of damage to the nervous system are observed. Specific lesions of the peripheral nervous system (neuritis, radiculitis, polyneuritis, polyradiculoneuritis) are usually observed during viral infections, but can also have a toxic origin (for example, diphtheria).

When examining infectious patients, significant changes are revealed in the blood picture, indicators of metabolic processes, protein, lipid, carbohydrate composition of plasma, metabolism of biologically active substances, which reflect various aspects of the pathogenesis of infectious diseases and their clinical manifestations.

The diagnosis is based on the patient's complaints, medical history, epidemiological history, results of examination of the patient, data from laboratory and instrumental studies. During the initial examination, a preliminary diagnosis is made, which determines further tactics of examination and implementation of anti-epidemic measures (isolation of the patient, identification of people with whom the patient communicated, possible sources of the infectious agent and the mechanism of transmission of infection). After receiving the results of the examination of the patient and taking into account epidemiological data, a final diagnosis is established. The diagnosis indicates the nosological form, the method of confirming the diagnosis, the severity and characteristics of the course of the disease, its period, the presence of complications and concomitant diseases. For example: "Typhoid fever (blood culture), severe course of the disease, peak period; complication - intestinal bleeding; concomitant disease - diabetes mellitus." The most accurately formulated and detailed diagnosis determines the therapeutic tactics.

In some cases, when clinical data is insufficient and laboratory tests do not allow establishing the etiology of the disease, a syndromic diagnosis is allowed (for example, foodborne illness, acute respiratory viral infection).

Treatment of patients with infectious diseases must be comprehensive and determined by diagnosis, i.e. based on the etiology, severity and other features of the course of the disease, the presence of complications and concomitant diseases, age and immunological characteristics of the patient’s body. At the same time, the scope of treatment measures, in order to avoid the simultaneous (often unjustified) prescription of multiple medications and treatment procedures and unpredictable side effects, should be limited to the minimum necessary in a particular case.

The basis of treatment is etiotropic therapy: the use of antibiotics and chemotherapy drugs, to therapeutic concentrations of which the causative agents of the corresponding infectious diseases are sensitive. The sensitivity of a pathogen to a particular drug is a species property, so drugs are used based on the type of pathogen. Thus, for typhoid fever, chloramphenicol is prescribed, for meningococcal infection - benzyl penicillin, for rickettsiosis - tetracycline drugs, etc. However, due to the frequent drug resistance of a number of pathogens, for example staphylococcus, it is necessary to strive to isolate a culture of the pathogen, determine its antibiogram and, in the absence of a clinical effect from the therapy, carry out its correction. Etiotropic therapy should be started as early as possible and carried out taking into account the localization of the pathogen in the patient’s body, the characteristics of the pathogenesis of the disease, the patient’s age, the mechanism of action and pharmacokinetics of the drug. Based on these parameters, the daily dose, intervals between single doses, route of administration and duration of treatment are determined. Due to the fact that antibiotics and chemotherapy drugs have a number of side effects (toxicity, inhibition of immunogenesis, reparative processes, sensitizing effects, development of dysbacteriosis), they must be used strictly according to indications. Thus, treatment should not be started before a diagnosis is made or before material is taken for bacteriological examination, in case of uncomplicated course of viral infectious diseases (influenza, acute respiratory viral infection, viral meningitis, etc.), in case of mild course of some bacterial infections (for example, dysentery), in the presence of individual intolerance. Only in some cases of severe infectious diseases in a hospital setting is it advisable to use etiotropic drugs until the diagnosis is clarified.

The second important area of ​​treatment of infectious diseases is immunotherapy, which is divided into specific and nonspecific. Antitoxic serums (antitetanus, antibotulinum, antidiphtheria, etc.) and γ- globulins, as well as antimicrobial serums and γ- globulins (anti-influenza, anti-measles, anti-staphylococcal, etc.). Plasma from immunized donors (antistaphylococcal, antipseudomonas, etc.) is also used. These drugs contain ready-made antibodies against toxins and the pathogen itself, i.e. create passive immunity. Vaccine preparations (toxoids, corpuscular killed vaccines) are also used for therapeutic purposes. As a specific treatment method, attempts were made to phage therapy, which turned out to be effective only in a number of cases of staphylococcal infection.

Nonspecific immunotherapy includes the use of nonspecific immunoglobulin preparations (normal human immunoglobulin, polyoglobulin), as well as drugs that affect the body's immune system (immunostimulants, immunomodulators, immunosuppressors), for example T - and B-activin, levamisole, sodium nucleinate, pentoxyl, methyluracil, corticosteroids, etc.

In the treatment of severe forms of infectious diseases, pathogenetic syndromic therapy occupies an important place, including the use of intensive care and resuscitation methods. Detoxification is of great importance, which is carried out by administering colloidal and crystalloid solutions while simultaneously forcing diuresis with saluretics. In severe cases, extracorporeal detoxification methods are used - plasmapheresis, hemosorption, hemodialysis. In the presence of dehydration syndrome, rehydration therapy is carried out. Complex pathogenetic therapy is indicated for the development of infectious-toxic shock, thrombohemorrhagic syndrome, cerebral edema, convulsive syndrome, acute respiratory failure, cardiovascular failure, and severe organ failure. In these cases, methods such as artificial ventilation, Hyperbaric oxygenation, etc. are used.

Drugs are used that affect individual pathogenetic mechanisms of infectious diseases, for example, for hyperthermia - antipyretics, for diarrhea - prostaglandin synthesis inhibitors, for allergies - antihistamines, etc. A rational, nutritious diet enriched with vitamins is of great importance. When prescribing a diet, the pathogenesis of the disease is taken into account. So, for dysentery - a colitis diet, for viral hepatitis - a hepatic diet. In severe cases, when patients cannot eat food on their own (coma, paresis of the swallowing muscles, profound disorders of absorption and digestion of food), tube feeding with special mixtures (enpits), parenteral nutrition and mixed enteral-parenteral nutrition are used.

Compliance with the necessary regime, care of the skin and mucous membranes, control of physiological functions are also important for the outcome of the disease. Physiotherapy and balneotherapy methods are used according to individual indications, and sanatorium-resort treatment is used to treat residual effects. After a number of infectious diseases (for example, neuroinfections, viral hepatitis, brucellosis), patients are monitored at the dispensary until complete recovery and labor rehabilitation. In some cases, a disability group is established as a temporary measure; in rare cases, permanent disability is observed.

The prognosis for the vast majority of infectious diseases is favorable. However, with untimely diagnosis and incorrect therapeutic tactics, an unfavorable outcome, recovery with residual effects and adverse long-term consequences are possible. In some cases, an unfavorable outcome in infectious diseases may be due to the fulminant course of the disease (for example, meningococcal infection), as well as the lack of effective treatment methods (for example, for HIV infection, hemorrhagic fevers and some other viral diseases).

Prevention. Measures to combat infectious diseases are divided into sanitary and preventive measures, carried out regardless of the presence of infectious diseases, and anti-epidemic measures, which are carried out when infectious diseases occur. Both groups of measures are carried out in three directions: neutralization, elimination (isolation) of the source of the infectious agent, and in case of zoonoses, also neutralization of the source of the infectious agent or reduction in numbers or destruction, for example, of rodents; suppression of the mechanism of transmission of the infectious agent, impact on the paths and factors of transmission of pathogens; creating immunity of the population to this infectious disease.

The structure of a natural hearth.

The main components of the outbreak are:

) pathogen

) animal reservoirs

) carrier

) "receptacle of the hearth" in spatial terms

) the presence of environmental factors favorable to the existence of biotic elements of the focus and circulation of the pathogen of the corresponding zoonosis.

In the presence of all these components, a zoonotic autochthonous outbreak, potentially dangerous to humans, flourishes in nature. Its epidemiological significance manifests itself when a person susceptible to the corresponding disease appears in its zone of influence (“anthropurgic factor”). This category of natural foci includes: tick-borne encephalitis, many tick-borne typhus fevers, tularemia, plague, Pendinsky ulcer of the semi-desert zone (marine form), yellow jungle fever, probably Japanese encephalitis in natural conditions, etc.

Their antipode is physioanthropic foci, characterized by the fact that the causative agent of the disease nesting in them is characteristic exclusively of humans and specific carriers; Consequently, animal reservoirs are completely excluded from the number of “constituents” of the focus. An example is malaria, maybe papatachi fever (if the assumption of its natural focality is not justified). Physioanthropic foci arise either on a natural basis or in the immediate environment of a person (up to intra-household infection).

In the first case, specific carriers (anopheles mosquitoes) nest in nature, but with regard to the malaria pathogen they are sterile, because there is no source of its production in nature. “The hearth receptacle” is diffuse; this is the zone used by winged anopheles (reservoirs where they hatch). When gamete carriers penetrate such a zone, they carry the malaria pathogen and attract malaria mosquitoes as a new source of blood feeding. In the process of blood-sucking, mosquitoes acquire malarial plasmodia and, in the presence of favorable environmental factors (mainly temperature), reach an invasive state in which they can transmit malaria to people. In the case considered, anthropurgic factors come down to the appearance of gamete carriers and people susceptible to infection in a natural area inhabited by malaria mosquitoes, and to the failure to take measures to combat and prevent malaria.

However, physioanthropic foci of malaria can be created predominantly on an anthropurgic basis; An excellent example is given by the picture of the movement of malaria into the Karakum Desert during the flooding of the Kolifa Uzboy; humans created new sources of reproduction of Anopheles mosquitoes. moving deeper and deeper into the desert (creation - “container of the hearth”) due to the passive introduction of mosquito larvae among fragments of plants with incoming water; mosquitoes appeared already in the first year of flooding, when water flowed along Uzboy for only 50 km.

Malaria also began to affect workers. Anopheles fed on the blood of not only people, but also wild animals (goitered gazelles, rodents, etc.) and found shelter from the heat of the day in rodent burrows, human habitation and reed thickets (Petrishcheva, 1936).

An example of physianthropic foci that exist on an anthropurgic basis is papatachi fever in cities and villages.

Zoonotic foci, in turn, can be modified by human activity. The causative agent of the disease can enter a newly formed focus in the body of an arriving person or animal reservoir of the virus. These animals, as well as their carriers, can move from life in nature to living in human habitation and services; in the presence of a favorable macro- and microclimate of the biotopes inhabited by carriers, and when there are people susceptible to infection there, the latter become ill at home with a disease that has its roots in natural foci (tick-borne relapsing fever, yellow fever, pendinka in cities).

Nobel Prize winner scientist Zhores Alferov said in one of his television interviews: “The future of all science lies in quantum physics.” The synthesis of her achievements and ancient Eastern acupuncture gave the world an ingenious diagnostic method, which has not yet been properly appreciated by society, and even more so has not yet been properly implemented in practical healthcare.

According to the theory of Chinese acupuncture, all internal organs of the human body are energetically projected onto certain points on the hands and feet. The German doctor R. Voll invented a device with an arrow on which it is possible to measure electrical conductivity at these points - according to the indication of the arrow of the device, one can judge the state of the organ for which the point under study is responsible (acute inflammation, normal, chronic process, etc.)

Particular attention should be paid to the issue of coincidence, or rather, discrepancy, between the results of the examination based on the Voll method and generally accepted laboratory tests.

The lack of information in laboratory stool tests for helminth and protozoan eggs is known to everyone; it is almost always written that they were not detected, whereas there are clear signs of their presence. As for more complex tests - immunological methods for studying blood, there is nothing comforting here either. At the latest scientific and practical symposium “Gene diagnostic technologies in practical healthcare”, which you can believe or not believe; this is an already existing reality in medicine - this parallel science has its own discoveries, scientific journals, scientific congresses and conferences are regularly convened, dissertations are defended.

There is also a special Government Decree No. 211 of June 6, 1989, which gives the right to introduce the Voll method, one of the methods of energy-information diagnostics and therapy, into clinical practice.

In the middle of the 12th century, Redi experimentally proved for the first time that flies and gadflies develop from eggs, which dealt a blow to the theory of spontaneous generation of organisms. The invention of the microscope by the Dutch researcher Leeuwenhoek in the 17th century. ushered in a new era in the history of biology.

Academician K.I. Scriabin created a helminthological school, uniting veterinary, medical, biological and agronomic specialists. This school successfully studies helminths and the diseases they cause - helminthiasis, develops and implements measures to combat them, up to devastation (complete destruction). By specialty K.I. Scriabin is a veterinarian. For his great services in the development of helminthology, he was awarded the title of Hero of Socialist Labor, laureate of the Lenin and two State Prizes, awarded 11 orders, and was elected to actual captivity.

Academy of Sciences of the USSR, Academy of Medical Sciences and All-Union Academy of Agricultural Sciences named after V.I. Lenin (VASKHNIL).K.I. Scriabin wrote over 700 scientific works, including many monographs and several textbooks.

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.Biology. Edited by Academician of the Russian Academy of Medical Sciences Professor V.N. Yarygina. In two volumes. Book 2. Moscow "Higher School" 2000

.Medical genetics. Under the reaction of N.P. Bochkova. Moscow. ACADEMA. 2003

Most diseases do not appear just like that, but are transmitted from the source to a healthy person. We invite you to familiarize yourself with the types of transmission of infections, as well as understand in more detail vector-borne diseases. This is especially true in the warm season.

Types of transmission of infections

The infection can be transmitted to humans in the following ways:

1. Nutritional. The route of transmission is the digestive system. The infection enters the body with food and water containing pathogens (for example, intestinal infections, dysentery, salmonellosis, cholera).
2. Airborne. The route of transmission is inhaled air or dust containing the pathogen.
3. Contact. The route of transmission is the source of infection or disease (for example, a sick person). You can become infected through direct contact, sexual contact, and also through household contact, that is, through the use of common household items with an infected person (for example, a towel or dishes).
4. Blood:

• vertical, during which the mother’s disease passes through the placenta to the child;
• transmissible route of transmission of the disease - infection through the blood with the help of live carriers (insects);
• blood transfusion, when infection occurs through insufficiently processed instruments in the dental office, various medical institutions (hospitals, laboratories, etc.), beauty salons and hairdressers.

Transmission method of transmission

The transmissible route of transmission of infection is the entry of infected blood containing infectious agents into the blood of a healthy person. It is carried out by living carriers. The transmissible route involves the transmission of pathogens through:

• directly from an insect bite;
• after rubbing a killed insect vector over damaged skin (for example, scratches).

Without proper treatment, vector-borne diseases can be fatal.

Methods of transmission and classification of vector-borne diseases

Transmissible transmission of the disease occurs in the following ways:

1. Inoculation - a healthy person becomes infected during an insect bite through its mouthparts. Such transmission will occur several times unless the carrier dies (for example, this is how malaria spreads).
2. Contamination - a person becomes infected by rubbing insect feces into the bitten area. Infection can also be repeated many times, until the death of the carrier (an example of a disease is typhus).
3. Specific contamination - infection of a healthy person occurs when an insect is rubbed into damaged skin (for example, when there are scratches or wounds on it). Transmission occurs once, as the carrier dies (an example of a disease is relapsing fever).

Carriers, in turn, are divided into the following types:

• Specific, in the body of which pathogens undergo development and have several stages of life.
• Mechanical ones, in whose body they do not develop, but only accumulate over time.

Types of diseases that are transmitted vector-borne

Possible infections and diseases transmitted by insects:

• relapsing fever;
• anthrax;
• tularemia;
• plague;
• encephalitis;
• AIDS virus;
• or American trypanosomiasis;
• yellow fever (tropical viral disease);
• various types of fevers;
• Congo-Crimean (high percentage of deaths - from ten to forty percent);
• dengue fever (characteristic of the tropics);
• lymphatic filariasis (characteristic of the tropics);
• river blindness, or onchocerciasis, and many other diseases.

In total, there are about two hundred types of diseases that are transmitted by vectors.

Specific vectors of vector-borne diseases

We wrote above that there are two types of carriers. Let's consider those in whose bodies pathogens multiply or go through a development cycle.

Blood-sucking insect	Disease
Female anopheles mosquitoes	Malaria, wuchereriosis, brugiosis
Biting mosquitoes (Aedes)	Yellow fever and dengue, lymphocytic chorionic meningitis, wuchereriosis, brugiosis
Culex mosquitoes	Brugiosis, wuchereriosis, Japanese encephalitis
	Leishmaniasis: visceral. Pappataci fever
Head, pubic)	Typhus and relapsing fever, Volyn fever, American trypanosomiasis
human fleas	Plague, tularemia
	American trypanosomiasis
	Filariotoses
	Onchocerciasis
Tsetse fly	African trypanosomiasis
Ixodid ticks	Fever: Omsk, Crimean, Marseille, Q fever. Encephalitis: tick-borne, taiga, Scottish. Tularemia
Argasid mites	Q fever, relapsing tick fever, tularemia
Gamasid mites	Rat typhus, encephalitis, tularemia, Q fever
Red mites	Tsutsugamushi

Mechanical vectors of vector-borne infections

These insects transmit the pathogen in the form in which they received it.

Insect	Disease
Cockroaches, house flies	Helminth eggs, protozoan cysts, various viruses and bacteria (for example, pathogens of typhoid fever, dysentery, tuberculosis, and so on)
Autumn zhigalka	Tularemia, anthrax
	Tularemia
	Tularemia, anthrax, polio
Aedes mosquitoes	Tularemia
	Tularemia, anthrax, leprosy

Transmission of human immunodeficiency virus

The number of infectious units in one milliliter of blood of an HIV-infected person is up to three thousand. This is three hundred times more than in seminal fluid. The human immunodeficiency virus is spread in the following ways:

• sexually;
• from a pregnant or nursing mother to a child;
• through blood (injecting drugs; during transfusion of contaminated blood or transplantation of tissues and organs from an HIV-infected person);

Transmissible transmission of HIV infection is practically impossible.

Prevention of vector-borne infections

Preventive measures to prevent the transmission of vector-borne infections:

• deratization, that is, rodent control;
• disinsection, that is, a set of measures to destroy vectors;
• a set of procedures for improving the area (for example, land reclamation);
• the use of individual or collective methods of protection against blood-sucking insects (for example, special bracelets soaked in aromatic oils, repellents, sprays, mosquito nets);
• immunization activities;
• placing the sick and infected in a quarantine zone.

The main goal of preventive measures is to reduce the number of possible vectors. Only this can reduce the likelihood of infection with diseases such as relapsing louse typhus, transmissible anthroponoses, phlebotomy fever and urban cutaneous leishmaniasis.

The scale of preventive work depends on the number of infected people and the characteristics of the infections. Thus, they can be carried out within:

• streets;
• district;
• cities;
• areas and the like.

The success of preventive measures depends on the thoroughness of the work and the level of examination of the source of infection. We wish you good health!

Vector-borne diseases (lat. transmissio - transfer to others) are infectious human diseases, the pathogens of which are transmitted by blood-sucking arthropods (insects and ticks).

For the most part, these are natural focal infections - infections common in areas limited by the habitat of vectors (blood-sucking insects). The causative agents of vector-borne infections can be a variety of microbes that pass from sick animals or people into the body of the carrier, and from them to healthy animals or people.

The transfer of a pathogen can be specific, if the pathogen multiplies and (or) goes through a development cycle in the carrier’s body, or mechanical. Transmission of the pathogen occurs when bitten by mosquitoes, fleas, mosquitoes, ticks, etc., when infected secretions of the carrier come into contact with the skin and mucous membranes.

Along with well-known vector-borne infections such as typhus, malaria, Lyme disease, tick-borne encephalitis, there are little-known infectious diseases that can also be transmitted through the bites of blood-sucking insects.

This: Plague- an acute, especially dangerous zoonotic transmissible infection with severe intoxication and serous-hemorrhagic inflammation in the lymph nodes, lungs and other organs, as well as the possible development of sepsis.

The transmission mechanism is varied, most often transmission, but airborne droplets are also possible. The carriers of the pathogen are fleas (about 100 species) and some types of ticks, which support the epizootic process in nature and transmit the pathogen to synanthropic rodents, camels, cats and dogs, which can carry infected fleas to human habitation. A person becomes infected not so much through a flea bite as after rubbing its feces or masses regurgitated during feeding into the skin.

The natural susceptibility of people is very high, absolute in all age groups and through any route of infection. After an illness, relative immunity develops, which does not protect against re-infection. Repeated cases of the disease are not uncommon and are no less severe than the primary ones.

Hemorrhagic fevers: Yellow fever, Crimean hemorrhagic fever, West Nile fever, Dengue fever, Rift Valley fever.

Yellow fever– This disease is more common in South America, Western, Central and Eastern Africa. Transmitted to humans by mosquitoes. The susceptibility of the disease is universal. The incubation period is 6 days.

Yellow fever is a natural focal disease that has 2 epidemiological types: jungle (natural, zoonotic, primary) and urban (anthroponotic, secondary). The source of infection in natural foci are animals - opossums, marsupials, hedgehogs, most often monkeys, in which the disease occurs in a latent form.

In the urban (anthroponotic) type of the disease, the reservoir and source of infection is a sick person, who becomes dangerous during the last days of the incubation period and the first days of the disease, the carrier of the pathogen is the mosquito Aedes aegypti.

In unvaccinated people, the disease is acute and severe with fever, vomiting, jaundice and intestinal bleeding. The patient complains of headaches, pain in the back muscles and limbs. His face is purple with a bluish tint, the sclera of his eyes are red. Watery eyes and photophobia are also noted.

Complications are possible - pneumonia, mumps, kidney abscesses. Particularly severe complications are myocarditis and encephalitis.

The disease lasts 10–15 days and can lead to death.

Crimean hemorrhagic fever- zoonotic natural focal arboviral infectious disease with intoxication and hemorrhagic syndrome and high mortality.

The natural reservoir of the pathogen is rodents, large and small livestock, birds, wild species of mammals, as well as ticks themselves, which are capable of transmitting the virus to offspring through eggs and are virus carriers for life.

The source of the pathogen is a sick person or an infected animal. The virus is transmitted through a tick bite or through medical procedures involving injections or blood sampling. The main carriers are ticks Hyalomma marginatus, Dermacentor marginatus, Ixodes ricinus.

Outbreaks of the disease in Russia occur annually in the Krasnodar and Stavropol territories, Astrakhan, Volgograd and Rostov regions, in the republics of Dagestan, Kalmykia and Karachay-Cherkessia. The disease also occurs in southern Ukraine and Crimea, Central Asia, China, Bulgaria, Yugoslavia, Pakistan, Central, Eastern and Southern Africa (Congo, Kenya, Uganda, Nigeria, etc.).

West Nile fever– an infection transmitted to humans by a mosquito bite. The causative agent of the infection is West Nile virus. When infected with this virus, the patient may experience nonspecific symptoms, such as fever and headaches, which occur, for example, with respiratory viral infections. However, the danger of this disease is that in a certain proportion of patients, after infection, the disease takes a severe course with the development of inflammation of the brain or encephalitis, the course of which can be accompanied by adverse consequences and death.

The carriers of the virus are mosquitoes, ixodid and argasid ticks, and the reservoir of infection is birds and rodents. The transmission mechanism is transmissible; the disease is transmitted by mosquitoes of the genus Culex, as well as argasid and ixodid ticks.

West Nile fever has a distinct seasonality - late summer and autumn. Young people get sick more often.

Most often, outbreaks of West Nile fever occur in endemic areas during the hot period of summer (usually August and early September), when the mosquito population becomes especially active. The incubation period - the period between the mosquito bite and the appearance of the first symptoms - ranges from 3 to 14 days.

Conditions for infection: staying in an area endemic for West Nile fever (the disease is most common in Mediterranean countries, especially Israel and Egypt; Romania, USA, Canada; cases of the disease have been described in France - on the Mediterranean coast and Corsica, as well as in India and Indonesia; there are natural foci of the disease in Armenia, Turkmenistan, Tajikistan, Azerbaijan, Kazakhstan, Moldova, Russia (in the Astrakhan, Volgograd, Rostov regions)).

Dengue fever- an acute viral disease that occurs with fever, intoxication, muscle pain, joint pain, and rash. Some variants of dengue occur with hemorrhagic syndrome. Refers to vector-borne zoonoses.

The source of infection is a sick person and monkeys, in which the infection can be asymptomatic. The patient is contagious during the period of viremia. The pathogen is transmitted by Aedes aegypti mosquitoes, which become infectious after 8-14 days and remain infectious for life. The virus develops in the body of a mosquito at an air temperature of at least 22 °C. This causes the disease to spread in hot countries between 42° north and 40° south latitude.

The disease is endemic in many countries in Asia, Europe, and Africa. Hundreds of cases of fever have been described in Israel and South Africa. Other outbreaks were observed in Algeria, Azerbaijan, Central African Republic, Zaire, Egypt, Ethiopia, India, Nigeria, Pakistan, Senegal, Sudan, Romania, Czech Republic, Russia.

The risk area for West Nile fever is the Mediterranean basin, where birds fly from Africa. The disease has a distinct seasonality - late summer and autumn. Mostly rural residents are affected, although in France, where the disease is known as “duck fever,” urban residents who come to hunt in the Rhone Valley get sick. Young people are more likely to get sick.

Rift Valley Fever (Rift Valley)- an acute viral transmissible disease characterized by fever, general intoxication, damage to the central nervous system, the organ of vision, hemorrhagic manifestations and jaundice.

First described in humans during an epidemic in the Rift Valley of Kenya (South Africa) in 1950–1951.

The virus was found in mosquitoes Culex pipiens, Eretmapodites chrysogaster, Aedes cabbalus, Aedes circurnluteolus, Culex theiler L.

Infection of humans occurs in various ways and also as a result of the bites of infected mosquitoes, most often Aedes mosquitoes. Transmission of the Rift Valley fever virus by hematophagous flies (blood-eating flies) is also possible.

Tularemia- an acute infectious disease, characterized by a variety of clinical manifestations, transmitted to humans from rodents (water rat, muskrat, hare, gopher, marmot, rat, mouse), less often from other animals - sheep.

This disease is characterized by a variety of transmission routes; in addition, transmission of the pathogen is possible through transmission, i.e. with bites of blood-sucking arthropods - ticks, lice, fleas, as well as other blood-sucking insects - horseflies, mosquitoes, burner flies.

The incubation period, i.e. the period of time from the moment of infection to the appearance of the first clinical symptoms of tularemia ranges from 3 to 7 days (rarely - 2 weeks). The disease begins acutely, after chills, body temperature can rise to 40°C. Patients complain of headaches, pain in the muscles of the lower extremities, lower back, profuse sweating at night. The duration of the disease varies - from 2 weeks to several months.

The form of the disease depends on the route of penetration of the microbe. So, if infection occurs through the skin, then redness appears at the site of penetration of the microbe, then a carbuncle and subsequently an ulcer. The skin on the affected area turns red and swells. The nearby lymph nodes enlarge, become painful on palpation, and may suppurate and ulcerate. When the pathogen gets on the mucous membrane of the eyes, redness and swelling of the eyelids and discharge of pus are noted. When infected through the mouth, damage to the tonsils is observed - redness, swelling, and a grayish coating forms; salivary glands are affected. The disease can occur in intestinal and pulmonary forms.

To avoid infection with vector-borne diseases, you need to know:

Do not create conditions for mosquitoes to breed. Cover containers with water. Remove any open containers that may accumulate moisture. Mosquitoes can breed in any puddle that persists for more than four days.

Try not to appear in those places and at the time that they usually choose for their “meal”. In the tropics, the sun sets early, and therefore people have to do many things in the dark, when insects are especially active. If you sit or sleep outside during the period when insect infections most often occur, your risk of getting sick will increase.

Soap is inexpensive, so wash your clothes and wash your hands frequently, especially after handling people or animals. Do not touch dead animals. Do not touch your mouth, nose, or eyes with your hands. Clothes should be washed regularly, even if they still look clean. Some odors attract insects, so it's best to avoid scented cleaning and personal care products.

While sleeping, it is necessary to use mosquito nets, preferably with insecticidal impregnation. All windows and doors in the room should be covered with screens to protect against insects.

When traveling to the countries of the South American and African continents, where mandatory preventive vaccinations are required, which are the only measure to prevent this dangerous disease, you must receive a single vaccination, which is carried out no later than 10 days before departure, immunity lasts for 10 years, after which re-vaccination is carried out. Without an international certificate of vaccination against yellow fever, travel to disadvantaged countries is prohibited.

You can get a preventive vaccination in the Republic of Belarus and receive an international certificate of vaccination against yellow fever at the 19th Central Clinic of the Pervomaisky District of Minsk (Minsk, Nezavisimosti Ave., 119).

Department of especially dangerous infections

• Vector-borne diseases, which account for more than 17% of all infectious diseases, kill more than 700,000 people every year.
• More than 3.9 billion people in more than 128 countries are at risk of contracting dengue fever alone, with an estimated annual incidence of 96 million cases per year.
• Malaria kills more than 400,000 people worldwide each year, most of them children under 5 years of age.
• Other diseases such as Chagas disease, leishmaniasis and schistosomiasis affect millions of people around the world.
• Many of these diseases can be prevented with proper protective measures.

Main vectors and diseases they transmit

Vectors are living organisms that can transmit infectious diseases between people or from animals to people. Many of these vectors are blood-sucking insects that ingest pathogens through the ingested blood of an infected host (human or animal) and then inject them into the new host during subsequent ingestion.

The most well-known vectors of disease are mosquitoes. They also include ticks, flies, mosquitoes, fleas, triatomine bugs and some freshwater gastropods.

Mosquitoes

• Aedes

• Lymphatic filariasis
• Dengue fever
• Rift Valley Fever
• Yellow fever
• Chikungunya

• Anopheles

• Malaria
• Lymphatic filariasis

• Culex

• Japanese encephalitis
• Lymphatic filariasis
• West Nile fever

Mosquitoes

• Leishmaniasis
• Mosquito fever (phlebotomy fever)

Ticks

• Crimean-Congo hemorrhagic fever
• Lyme disease
• Relapsing fever (borreliosis)
• Rickettsial diseases (typhoid fever and Queensland fever)
• Tick-borne encephalitis
• Tularemia

Triatomine bugs

• Chagas disease (American trypanosomiasis)

Tsetse flies

• Sleeping sickness (African trypanosomiasis)

Fleas

• Plague (transmitted from rats to humans via fleas)
• Rickettsial disease

Midges

• Onchocerciasis (river blindness)

Aquatic gastropods

• Schistosomiasis (bilharzia)

Lice

• Schistosomiasis (bilharzia)
• Typhoid and epidemic relapsing fever

Vector-borne diseases

The major vector-borne diseases collectively account for about 17% of all infectious diseases. The burden of these diseases is highest in tropical and subtropical areas, and the poorest people are disproportionately affected. Since 2014, major outbreaks of dengue, malaria, chikungunya, yellow fever and Zika virus have caused great suffering, claimed many lives and placed enormous pressure on health systems in many countries.

The distribution of vector-borne diseases is determined by a complex of demographic, environmental and social factors. Globalization of trade, increased international travel, uncontrolled urbanization and environmental issues such as climate change can all influence the transmission of pathogens. As a result, the transmission season for a disease may become longer, seasonal disease transmission may become more intense, and some diseases may appear in countries where they have never previously been detected.

Transmission of vector-borne diseases may be affected by changes in agricultural practices due to fluctuations in temperature and precipitation. The proliferation of urban slums, without reliable water supplies or proper waste disposal systems, exposes very large numbers of residents of towns and cities to the risk of contracting mosquito-borne viral diseases. Collectively, such factors influence vector population sizes and pathogen transmission patterns.

WHO activities

Document Global Vector Control Action (GVCA) 2017-2030., endorsed by the World Health Assembly (2017), provides strategic guidance for countries and development partners to rapidly scale up vector control as a fundamental strategy for disease prevention and outbreak response. Achieving this goal requires increased coherence of vector control programs, increased technical capacity, improved infrastructure, strengthened monitoring and surveillance systems, and greater community participation. Ultimately, this will support an integrated approach to vector control that will enable the achievement of national and global disease-specific targets and contribute to achieving the Sustainable Development Goals and universal health coverage.

The WHO Secretariat provides policy, regulatory and technical advice to countries and development partners on strengthening vector control as a fundamental GMPI-based strategy for disease prevention and outbreak response. More specifically, WHO is taking the following actions in response to the problem of vector-borne diseases:

• providing evidence-based recommendations for vector control and protecting people from infection;
• providing technical support to countries to enable them to effectively manage disease cases and respond to outbreaks;
• supporting countries to improve case reporting and disease burden calculations;
• assistance in providing training (capacity building) on ​​clinical management, diagnosis and vector control with selected collaborating centers around the world;
• supporting the development and evaluation of new methods, technologies and approaches to vector-borne diseases, including technologies and tools for vector control and management of vector-borne diseases.

Behavioral changes are important in relation to vector-borne diseases. WHO works with partner organizations to provide education and awareness-raising so that people know how to protect themselves and their communities from mosquitoes, ticks, bedbugs, flies and other vectors.

WHO has initiated programs to control many diseases, such as Chagas disease, malaria, schistosomiasis and leishmaniasis, using donated and subsidized drugs.

A critical factor in disease control and eradication is access to water and sanitation. WHO works with many different government sectors to combat these diseases.

Vector-borne diseases are infectious diseases transmitted by blood-sucking insects and arthropods. Infection occurs when a person or animal is bitten by an infected insect or tick.

These diseases are mainly found in tropical and subtropical areas where access to safe drinking water and sanitation systems is a problem.

Vector-borne diseases are estimated to account for 17% of the global burden of all infectious diseases. Malaria, the deadliest vector-borne disease, was estimated to cause 660,000 deaths in 2010.

However, the incidence of dengue is growing at the fastest rate - over the past 50 years, the incidence of this disease has increased 30 times.

About two hundred official diseases are known that have a vector-borne transmission route. They can be caused by various infectious agents: bacteria and viruses, protozoa and rickettsia, and even helminths. Some of them are transmitted through the bite of blood-sucking arthropods (malaria, typhus, yellow fever), some of them are transmitted indirectly, when cutting the carcass of an infected animal, in turn, bitten by an insect carrier (plague, tularemia, anthrax).

Major vector-borne diseases

Chagas disease

Yellow fever

Yellow fever is a viral disease found in tropical areas of Africa and the Americas. It mainly affects humans and monkeys and is transmitted through the bite of the Aedes mosquito.

Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever is a widespread disease caused by a tick-borne virus (Nairovirus) of the Bunyaviridae family. CCHF virus causes outbreaks of severe viral hemorrhagic fever with a case fatality rate of 10-40%.

Dengue fever

Dengue is spread by the bite of Aedes mosquitoes infected with any one of the four dengue viruses. This disease is common in tropical and subtropical areas of the world.

Lymphatic filariasis

Human African trypanosomiasis (sleeping sickness)

Chikungunya

It is a viral disease spread by mosquitoes. It causes fever and severe joint pain. Other symptoms include muscle pain, headache, nausea, fatigue and rash.

Schistosomiasis

Vectors

There are mechanical and specific carriers.

The pathogen passes through a mechanical carrier in transit (without development or reproduction). It can persist for some time on the proboscis, body surface or in the digestive tract of the arthropod. If at this time a bite occurs or contact with the wound surface occurs, the person will become infected. A typical representative of a mechanical vector is the fly of the family. Muscidae. This insect carries a wide variety of pathogens: bacteria, viruses, protozoa.

Mechanism of transmission of infection

Some insects, such as mosquitoes, suck blood directly from a capillary damaged by the proboscis. Ticks and Tsetse flies with their cutting trunks break the capillaries and suck the blood that has already spilled into the tissue.

The salivary fluid of ticks contains an anesthetic component, which makes the penetration of the tick into the skin and the process of sucking blood completely invisible.

On the contrary, the saliva of horseflies and gadflies, some species of midges and mosquitoes can cause a severe allergic reaction, which is manifested by instant pain, rapid swelling and severe itching.

Epidemiology

Most often, the range of carriers of vector-borne diseases is much wider than the source of these diseases. This is due to higher requirements for the life activity of the pathogen than for the carrier itself. For example, mosquitoes of the genus Anopheles can be found in the most extreme points of the northern hemisphere. However, malaria outbreaks do not occur beyond 64 degrees north latitude.

Individual foci of vector-borne diseases outside the borders of the carriers’ habitats arise due to accidental imports from outside. As a rule, they are quickly extinguished and do not pose an epidemic danger. An exception may be the plague.

Vector-borne diseases have a pronounced seasonality, which is determined by favorable conditions for the existence of the vector, a significant number of them and increased activity in the warm season. Frequent contacts of the population with vectors during berry and mushroom trips, hunting trips, and logging work contribute to seasonality.

Prevention

The main importance is the use of repellents and compliance with the rules of behavior outside the city and in forests. Specific vaccination is effective for the prevention of yellow fever and tularemia.

Prevention of most vector-borne diseases is carried out on a regional scale byreducing the number of vectors . Through this event inUSSRmanaged to eliminate such transmissible anthroponoses as louse-borne relapsing fever, mosquito fever, urbancutaneous leishmaniasis . At natural focal vector-borne diseases, measures to reduce numbers are often more effectivereservoir- wild animals - sources of pathogens (for example, rodents for plague and desert cutaneous leishmaniasis; the use of protective clothing and repellents, in some cases - vaccination (for example, for tularemia, yellow fever); and chemoprophylaxis (for example, for sleeping sickness). Of great importance are carrying out reclamation work, creating zones around populated areas free from wild rodents and carriers of vector-borne diseases.