transmissible diseases. Their focality. measures to combat them. Infection vectors Specific and non-specific disease vectors
domestic and wild animals. Occurs when a person develops the territory of the software. This character can acquire foci Japanese encephalitis, cutaneous leishmaniasis, tick-borne relapsing fever, etc.
synanthropic foci. The circulation of pathogens is associated only with domestic animals. Foci of toxoplasmosis, trichinosis.
2. By the number of hosts
Polygostal. Several species of animals serve as a reservoir (ground squirrels, marmots, tarbagans, gerbils in the natural focus of the plague).
3. By the number of carriers
Monovector. Pathogens are transmitted by only one type of carrier. It is determined by the species composition of carriers in a particular biocenosis (only one species of ixodid ticks lives in a certain focus of taiga encephalitis).
Polyvector. The pathogens are transmitted by various types of vectors. (PO tularemia - carriers: various types of mosquitoes, horseflies, ixodid ticks).
Epidemics
Manifestations of the epidemiological process by territory
It should be noted that POs are predominantly characteristic of wild animals, but urbanization creates conditions for the spread of pathogens of these diseases among synanthropic animals and humans. This is how anthropurgic, and then synanthropic foci of diseases arise, which can pose a significant epidemiological danger.
The term pandemic is used to describe an unusually intense epidemic affecting a number of countries.
Vector-borne diseases are infectious diseases transmitted by blood-sucking insects and representatives of the arthropod type. Infection occurs when a person or animal is bitten by an infected insect or tick.
There are about two hundred official diseases that have a transmissible 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 indirectly, when cutting the carcass of an infected animal, in turn, bitten by a vector insect (plague, tularemia, anthrax). Such diseases are divided into two groups:
Obligately vector-borne diseases are those vector-borne diseases that are transmitted only with the participation of the carrier.
Japanese encephalitis;
Loose (lousy and tick-borne) typhus;
Relapsing (lousy and tick-borne) typhus;
Lyme disease, etc.
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Facultatively vector-borne diseases are vector-borne diseases that are spread different ways, including those involving carriers.
Brucellosis;
Tick-borne encephalitis;
Anthrax;
Tularemia, etc.
Carrier classification:
Specific carriers ensure the transfer of the pathogen from the blood
sick animals or humans into the blood of healthy ones. In organism
specific carriers, the pathogen multiplies or accumulates. In this way, fleas transmit plague, lice transmit typhus, mosquitoes transmit Papatachi fever. In the body of some carriers, the pathogen goes through a certain development cycle. So, in the body of a mosquito of the genus Anopheles, the malaria plasmodium performs a sexual development cycle. Along with this, in the body of ticks, the causative agents of tick-borne encephalitis and some rickettsiosis not only multiply and accumulate, but are also transmitted to a new generation through the egg (transovarially). Therefore, the pathogen in the body of a specific carrier can persist (with some exceptions) throughout the life of the carrier;
Nonspecific (mechanical) carriers that perform
mechanical transfer of the causative agent of the disease without its development and reproduction (gadflies, autumn zhigalki and ixodid ticks for causative agents of tularemia, brucellosis, anthrax).
And also vector-borne diseases are divided into two groups depending on pathogens:
Invasions (pathogens - such animals);
Infections (causative agents - viruses, rickettsia and bacteria).
Vector-borne diseases are infectious diseases transmitted by blood-sucking insects and representatives of the arthropod type. Infection occurs when a person or animal is bitten by an infected insect or tick.
There are about two hundred official diseases that have a transmissible 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 indirectly, when cutting the carcass of an infected animal, in turn, bitten by a vector insect (plague, tularemia, anthrax).
carriers
The pathogen passes through a mechanical carrier in transit (without development and reproduction). It can persist for some time on the proboscis, the surface of the body, or in the digestive tract of an arthropod. If at this time a bite occurs or contact with the wound surface occurs, then human infection will occur. A typical representative of a mechanical carrier is a fly of the fam. Muscidae. This insect carries a variety of pathogens: bacteria, viruses, protozoa.
As already mentioned, according to the method of transmission of the pathogen by an arthropod vector from an infected vertebrate donor to a vertebrate recipient, natural focal diseases are divided into 2 types:
obligate-transmissible, in which the transmission of the pathogen from the vertebrate donor to the recipient vertebrate is carried out only through a blood-sucking arthropod during blood-sucking;
facultative-transmissible natural focal diseases in which the participation of a blood-sucking arthropod (carrier) in the transmission of the pathogen is possible, but not necessary. In other words, along with the transmissible (through a bloodsucker), there are other ways of transmitting the pathogen from a vertebrate donor to a recipient vertebrate and a person (for example, oral, alimentary, contact, etc.).
According to E. N. Pavlovsky (Fig. 1.1), the phenomenon natural foci vector-borne diseases is that, regardless of the person in the territory of certain geographical landscapes, there may be foci diseases to which a person is susceptible.
Such foci were formed in the course of a long evolution of biocenoses with the inclusion of three main links in their composition:
Populations pathogens illness;
Populations of wild animals - natural reservoir hosts(donors and recipients);
Populations of blood-sucking arthropods - carriers of pathogens illness.
It should be borne in mind that each population of both natural reservoirs (wild animals) and vectors (arthropods) occupies a certain territory with a specific geographical landscape, which is why each focus of infection (invasion) occupies a certain territory.
In this regard, for the existence of a natural focus of the disease, along with the three links mentioned above (causative agent, natural reservoir and carrier), the fourth link is also of paramount importance:
natural landscape(taiga, mixed forests, steppes, semi-deserts, deserts, various water bodies, etc.).
Within the same geographical landscape, there may be natural foci of several diseases, which are called conjugated. This is important to know when vaccinating.
Under favorable environmental conditions, the circulation of pathogens between carriers and animals - natural reservoirs can occur indefinitely. for a long time. In some cases, infection of animals leads to their disease, in others, asymptomatic carriage is noted.
By origin natural focal diseases are typical zoonoses, i.e., the circulation of the pathogen occurs only between wild vertebrates, but the existence of foci is also possible for anthropozoonotic infections.
According to E. N. Pavlovsky, natural foci of vector-borne diseases are monovector, if in
the transmission of the pathogen involves one type of carrier (lice relapsing and typhus), and polyvector, if the transmission of the same type of pathogen occurs through carriers of two, three or more species of arthropods. The foci of such diseases are the majority (encephalitis - taiga, or early spring, and Japanese, or summer-autumn; spirochetosis - tick-borne relapsing fever; rickettsiosis - tick-borne typhus North Asian, etc.).
The doctrine of natural foci indicates the unequal epidemiological significance of the entire territory of the natural focus of the disease due to the concentration of infected vectors only in certain microstations. Such a focus becomes diffuse.
In connection with general economic or purposeful human activity and the expansion of urbanized territories, mankind has created conditions for the mass distribution of so-called synanthropic animals (cockroaches, bedbugs, rats, house mice, some ticks and other arthropods). As a result, humanity is faced with an unprecedented phenomenon of the formation anthropogenic foci of disease, which can sometimes become even more dangerous than natural foci.
Due to human economic activity, irradiation (spread) of the old focus of the disease to new places is possible if they have favorable conditions for the habitat of carriers and animals - donors of the pathogen (construction of reservoirs, rice fields, etc.).
Meanwhile, it is not excluded destruction(destruction) of natural foci during the loss of its members from the composition of the biocenosis, which take part in the circulation of the pathogen (during the drainage of swamps and lakes, deforestation).
In some natural foci, ecological succession(replacement of some biocenoses by others) when new components of the biocenosis appear in them, capable of being included in the circulation chain of the pathogen. For example, the acclimatization of the muskrat in natural foci of tularemia led to the inclusion of this animal in the circulation chain of the causative agent of the disease.
E. N. Pavlovsky (1946) identifies a special group of foci - anthropourgical foci, the emergence and existence of which is associated with any type of human activity and also with the ability of many species of arthropods - inoculators (bloodsucking mosquitoes, ticks, mosquitoes that carry viruses, rickettsia, spirochetes and other pathogens) to move to synanthropic lifestyle. Such arthropod vectors live and breed in settlements of both rural and urban types. Anthropourgical foci arose secondarily; In addition to wild animals, domestic animals, including birds, and humans are included in the circulation of the pathogen, so such foci often become very tense. Thus, large outbreaks of Japanese encephalitis have been noted in Tokyo, Seoul, Singapore and other large settlements in Southeast Asia.
Anthropourgical character can also acquire foci of tick-borne relapsing fever, cutaneous leishmaniasis, trypanosomiasis, etc.
The stability of natural foci of some diseases is primarily due to the continuous exchange of pathogens between carriers and animals - natural reservoirs (donors and recipients), but the circulation of pathogens (viruses, rickettsia, spirochetes, protozoa) in the peripheral blood of warm-blooded animals - natural reservoirs is most often limited in time and lasts for several days.
Meanwhile, the causative agents of diseases such as tick-borne encephalitis, tick-borne relapsing fever, etc., multiply intensively in the intestines of tick-carriers, perform transcoelomic migration and are introduced with hemolymph into various organs, including the ovaries and salivary glands. As a result, an infected female lays infected eggs, i.e., transovarial transmission pathogen to the offspring of the carrier, while the pathogens in the course of further metamorphosis of the tick from the larva to the nymph and further to the adult are not lost, i.e. transphase transmission pathogen.
In addition, ticks retain pathogens in their body for a long time. EN Pavlovsky (1951) traced the duration of spirochaetonity in ornithodorin ticks to 14 years or more.
Thus, in natural foci, ticks serve as the main link in the epidemic chain, being not only carriers, but also persistent natural keepers (reservoirs) of pathogens.
The doctrine of natural foci considers in detail the methods of transmission of pathogens by carriers, which is important for understanding the possible ways of infecting a person with a particular disease and for its prevention.
Immunoprophylactic methods include immunization of the population. These methods are widely used for the prevention infectious diseases. The development of immunoprophylaxis of invasions has a number of significant difficulties and is currently at the development stage. Measures for the prevention of natural focal diseases include measures to control the number of disease carriers (reservoir hosts) and arthropod vectors by influencing their habitat conditions and their reproduction rates in order to interrupt the circulation of the pathogen within the natural focus.
62. general characteristics protozoa (Protozoa) Overview of the structure of protozoa
This type is represented by unicellular organisms, the body of which consists of the cytoplasm and one or more nuclei. The cell of the simplest is an independent individual, showing all the basic properties of living matter. It performs the functions of the whole organism, while the cells of multicellular organisms are only part of the organism, each cell depends on many others.
It is generally accepted that unicellular beings are more primitive than multicellular ones. However, since the entire body of unicellular organisms, by definition, consists of one cell, this cell must be able to do everything: eat, and move, and attack, and escape from enemies, and survive adverse environmental conditions, and multiply, and get rid of metabolic products, and to be protected from drying out and from excessive penetration of water into the cell.
A multicellular organism can also do all this, but each of its cells, taken separately, is good at doing only one thing. In this sense, a cell of the simplest is by no means more primitive than a cell of a multicellular organism. Most representatives of the class have microscopic dimensions - 3-150 microns. Only the largest representatives of the species (shell rhizomes) reach 2-3 cm in diameter.
Digestive organelles - digestive vacuoles with digestive enzymes (similar in origin to lysosomes). Nutrition occurs by pino- or phagocytosis. Undigested residues are thrown out. Some protozoa have chloroplasts and feed on photosynthesis.
Freshwater protozoa have osmoregulatory organs - contractile vacuoles, which periodically release excess fluid and dissimilation products into the external environment.
Most protozoa have one nucleus, but there are representatives with several nuclei. The nuclei of some protozoa are characterized by polyploidy.
The cytoplasm is heterogeneous. It is subdivided into a lighter and more homogeneous outer layer, or ectoplasm, and a granular inner layer, or endoplasm. The outer integument is represented by either a cytoplasmic membrane (in amoeba) or a pellicle (in euglena). Foraminifera and sunflowers, inhabitants of the sea, have a mineral, or organic, shell.
Irritability is represented by taxis (motor reactions). There are phototaxis, chemotaxis, etc.
Reproduction of protozoa Asexual - by mitosis of the nucleus and cell division in two (in amoeba, euglena, ciliates), as well as by schizogony - multiple division (in sporozoans).
Sexual - copulation. The cell of the protozoan becomes a functional gamete; As a result of the fusion of gametes, a zygote is formed.
Ciliates are characterized by a sexual process - conjugation. It lies in the fact that cells exchange genetic information, but there is no increase in the number of individuals. Many protozoa are able to exist in two forms - a trophozoite (a vegetative form capable of active nutrition and movement) and a cyst, which is formed under adverse conditions. The cell is immobilized, dehydrated, covered with a dense membrane, the metabolism slows down sharply. In this form, the protozoa are easily carried over long distances by animals, by the wind, and are dispersed. When exposed to favorable living conditions, excystation occurs, the cell begins to function in a trophozoite state. Thus, encystation is not a method of reproduction, but helps the cell to survive adverse environmental conditions.
Many representatives of the Protozoa phylum are characterized by the presence of a life cycle consisting in a regular alternation of life forms. As a rule, there is a change of generations with asexual and sexual reproduction. Cyst formation is not part of a regular life cycle.
The generation time for protozoa is 6-24 hours. This means that, once in the host organism, the cells begin to multiply exponentially and theoretically can lead to its death. However, this does not happen, since the protective mechanisms of the host organism come into force.
Of medical importance are representatives of the protozoa, belonging to the classes of sarcodes, flagellates, ciliates and sporozoans.
Diseases that are transmitted only from animals to animals are called zoonoses (plague chickens and pigs).
Diseases whose pathogens are transmitted only from person to person are called anthroponoses.(measles, diphtheria).
Diseases whose pathogens are transmitted from one organism to another by means of blood-sucking carriers (insects, ticks) are called transmissible (malaria, taiga encephalitis).
They are divided into:
1) obligate-transmissible, the pathogens of which are transmitted through specific carriers (malaria - by mosquitoes of the genus Anopheles, taiga encephalitis - by taiga ticks);
2) facultative-transmissible, the pathogens of which can be transmitted both through carriers and
and in other ways (infection with tularemia and anthrax is possible through numerous vectors and when cutting the carcasses of sick animals).
Vectors of vector-borne diseases can be specific and mechanical. In the body of a specific carrier, the pathogen goes through part of the life cycle (the plague bacillus multiplies in the digestive tract of the flea; malarial plasmodia go through the sexual development cycle in mosquitoes of the genus Anopheles).
The causative agents of diseases in mechanical carriers (flies, cockroaches) are on the integument of the body, on the limbs and parts of the oral apparatus.
The entrance gate of the pathogen is always the oral apparatus of a specific carrier. The exit of the pathogen from the carrier can occur through the anus or through the oral apparatus.
In the first case, the pathogen transits through the intestines (rickettsia of lousy typhus). Infection of the host occurs when the excrement of the carrier is rubbed into the skin during scratching of the bite site. This method of infection is called contamination.
If the pathogen passes through the body cavity of the carrier and accumulates in the salivary glands (malarial plasmodia sporozoites), then the infection of the host occurs through the oral apparatus during bloodsucking. The mode of infection is called inoculation.
The exciter exit gate may be missing. In this case, the pathogen accumulates in the body cavity of the carrier. Infection of the host occurs when the carrier is crushed and the hemolymph with the pathogen is rubbed into the skin during scratching - a variety contamination(transmission of relapsing fever spirochetes by lice).
In the first and second cases, the carrier can transmit pathogens many times, in the third - only once, since the transmission of the pathogen is associated with the death of the carrier.
Many vectors are characterized by transovarial (through eggs) transmission of vector-borne disease pathogens. If the female taiga tick contains the encephalitis virus, then during sexual reproduction she will pass it on to subsequent generations.
Natural focal diseases are called diseases associated with a complex of natural conditions. They exist in certain biogeocenoses independently of a person, and trophic links are important for their maintenance. E. N. Pavlovsky gave the following definition of natural focal diseases: “ Natural foci of vector-borne diseases- this is a phenomenon when the pathogen, its specific carrier and animal reservoirs of the pathogen during the change of their generations exist indefinitely for a long time natural conditions regardless of man, both in the course of his already past evolution, and in its present period.
natural hearth- this is the smallest territory of one or several landscapes where circulation is carried out without its introduction from the outside for an indefinitely long period.
Components of the natural focus of the disease:
1) the causative agent of the disease;
2) organisms susceptible to this pathogen;
3) carriers of the pathogen;
4) certain environmental conditions (biotope)
For example: diagram of a natural focus of plague
specific carrier
rodents man
In the focus, the pathogen circulates from sick animals (pathogen donors) through the carrier to healthy (recipients), which later become pathogen donors. Carriers are blood-sucking arthropods, while rodents and birds can be donors and recipients. If a person enters the natural focus of the disease, then he becomes first a recipient, and then a donor of the pathogen. Natural hotspots exist long time, but they acquire epidemiological significance when a person gets into them and becomes infected
Carriers (blood-sucking arthropods)
Donors Recipients
(wild animals, (wild animals)
mostly rodents)
Classification of natural foci:
Origin allocate foci:
1) natural (tick-borne encephalitis);
2) synanthropic - exist in the settlement, where the circulation of the pathogen is carried out at the expense of synanthropic animals (scabies);
3) anthropurgic - arise as a result of transformation natural environment man (opisthorchiasis in places of artificially created reservoirs);
4) mixed (trichinosis).
The range of natural foci is determined by the range of natural hosts of the pathogen and the range of the carrier.
Length (area) foci can be:
1) narrowly limited (rodent burrow, bird's nest - a focus of tick-borne relapsing fever);
2) diffuse (taiga - focus of taiga encephalitis);
3) conjugated, if pathogens of several transmissible diseases (tularemia and plague) circulate in the outbreak.
The result of infection of the recipient in a natural focus may be his death (in the case of high virulence of the pathogen), illness with subsequent recovery, or vaccination (the formation of immune protective bodies without pronounced clinical signs of the disease - with a weak virulence of the pathogen).
The outcome of infection of the recipient in the focus is also affected by the following factors:
1) pathogenicity of the pathogen for this recipient;
2) "aggressiveness" of the carrier (frequency of bloodsucking);
3) the dose of the pathogen introduced into the body of the recipient;
4) the degree of severity of nonspecific and specific immune reactions of the recipient.
Some natural focal diseases are characterized by endemism, i.e. occurrence in strictly limited areas. This is due to the fact that the causative agents of the corresponding diseases, their intermediate hosts, animal reservoirs or carriers are found only in certain biogeocenoses. So, only in some areas of Japan, four species of lung flukes from p. Paragonimus. Their dispersal is hindered by a narrow specificity in relation to intermediate hosts, which live only in some water bodies of Japan, and endemic animal species such as the Japanese prairie mouse or Japanese marten are a natural reservoir.
Viruses of some forms of hemorrhagic fever are found only in certain areas East Africa, because here is the range of their specific carriers - ticks from the river. Ambliomma.
A small number of natural focal diseases are found almost everywhere. These are diseases, the causative agents of which, as a rule, are not associated in the cycle of their development with external environment and strike a wide variety of hosts. Such diseases include, for example, toxoplasmosis and trichinosis. A person can become infected with these natural-focal diseases in any natural-climatic zone and in any ecological system.
The vast majority of natural focal diseases affect a person only if he gets into the appropriate focus (hunting, fishing, hiking, geological parties, etc.) under conditions of his susceptibility to them. So, a person becomes infected with taiga encephalitis when bitten by an infected tick, and with opisthorchiasis - by eating insufficiently thermally processed fish with cat fluke larvae.
Prevention of natural focal diseases presents particular difficulties. Due to the fact that a large number of hosts, and often carriers, are included in the circulation of the pathogen, the destruction of entire biogeocenotic complexes that have arisen as a result of the evolutionary process is ecologically unreasonable, harmful, and even technically impossible. Only in cases where the foci are small and well studied, is it possible to complexly transform such biogeocenoses in a direction that excludes the circulation of the pathogen. Thus, the reclamation of desert landscapes with the creation of irrigated horticultural farms in their place, carried out against the background of the fight against desert rodents and mosquitoes, can dramatically reduce the incidence of leishmaniasis in the population. In most cases of natural focal diseases, their prevention should be aimed primarily at personal protection(prevention of bites by blood-sucking arthropods, heat treatment food products etc.) in accordance with the pathways of circulation in nature of specific pathogens.
Medical Protistology
1. Morphophysiological characteristics of the subkingdom Protozoa
2. Subtype Sarcode
3. Subtype Flagellates
4. Type of Infusoria
5. Class Sporovidae
Specific - in their body, the pathogen goes through certain stages of its development (the female mosquito of the genus Anopheles for malarial plasmodia);
Mechanical - in their body, the pathogen does not go through its development, but only accumulates and moves with the help of a carrier in space (cockroaches).
Specific carriers have pathogen entry and exit gates:
- 1. Entrance gate - the mouth apparatus of the carrier, through which the causative agent of the disease enters the body of a blood-sucking arthropod from the body of a sick host.
- 2. Exit gate - either the oral apparatus or the anus of the carrier, through which the pathogen enters the body of a healthy host and infects it.
Specific carriers
1. Ticks of the genus Ixodes.
The length of the pliers is 1-10 mm. About 1000 species of ixodid ticks have been described. Fertility - up to 10,000, in some species - up to 30,000 eggs.
The body of the mite is oval, covered with an elastic cuticle.
Males reach a length of 2.5 mm, their color is brown. The hungry female also has a brown body. As it becomes saturated with blood, the color changes from yellow to reddish. The length of a hungry female is 4 mm, well-fed - up to 11 mm in length. On the dorsal side there is a shield, which in males covers the entire dorsal side. In females, larvae and nymphs, the chitinous shield is small and covers only a portion of the anterior part of the back. On the rest of the body, the covers are soft, which makes it possible to significantly increase the volume of the body when absorbing blood. The development cycle is long - up to 7 years. transmissible insect inoculation contamination
Ixodinae are unable to form a cemented proboscis sheath. Feeding is accompanied by the injection of saliva into the body of the host. The saliva of ixodid ticks has osmoregulatory and immunosuppressive properties. Ixodinae ingest partially hemolyzed blood.
Nutrition is accompanied by a significant increase in body size by the type of neosomia (accumulation of food products in the midgut for 5-6, 9-10 days). Individuals that have completed cavitary digestion enter diapause. In unfertilized females, bloodsucking does not end, complete saturation does not occur. Ixodid ticks are vectors and reservoirs of pathogens of infectious diseases.
entrance gate- oral apparatus
Method of infection Inoculation
tularemia, taiga encephalitis, Scottish encephalitis.
2. Ticks of the genus Dermacentor
To characteristic morphological features The genus Dermacentor includes the presence of light enamel pigments in the form of spots of various shapes and sizes, best expressed on the dorsal shield, and to a lesser extent on the legs and proboscis. The shape of enamel spots and their number vary considerably within one species and even one population.
entrance gate- oral apparatus
Method of infection Inoculation
What pathogens does it carry? Tularemia, Taiga encephalitis, Tick-borne encephalitis Sypnoitif, Brucellosis.
3. Ticks of the genus Hyalomma
Most species are found in steppe-desert and desert landscapes. Some species inhabit enclosed spaces: cattle yards, barns, stalls. H. marginatum Koch- large pincers. Development occurs according to a two-host cycle (the development of a larva into a nymph and a nymph into an adult tick occurs on the same host. The adult tick is looking for a new victim.). Imago feeds on large domestic animals during the entire warm period, larvae and nymphs on birds and small mammals. The development cycle lasts 1 year. From eggs laid by females, after 1.5-2 months. larvae hatch. Larvae and nymphs feed on rodents, hedgehogs, ground-feeding birds. Well-fed nymphs molt to adults in the same season. Hungry adults hibernate. Ticks of the genus Hyalomma- actively attacking bloodsuckers. From a distance of several meters, they pursue animals (humans), guided by their sense of smell and vision. After leaving the host, well-fed females crawl into shelters before the onset of heat, leaving a characteristic mark on the sand. The virus is transmitted to ticks by the bite of an infected domestic or wild animal. Babesiosis is also transmitted. Ticks of the genus Hyalomma are distinguished by increased resistance to acaricides.
Bites from Hyalomma mites cause the surrounding tissue to die and become necrotic. Dead tissue will peel off the body after a few days. The wounds look very serious, but usually heal without any intervention and generally do not become infected further.
entrance gate- oral apparatus
Method of infection Inoculation
What pathogens does it carry? Tularemia, Crimean hemorrhagic fever.
4. Ticks of the family Argasidae
The body has a length of 3 to 30 mm, flattened, oval. The integument is leathery, the color of ticks drunk with blood is lilac, in hungry ticks it is grayish, yellow-borax. The mouth apparatus of argas ticks is located on the ventral side of the body and does not protrude forward. There is no chitinous shield on the dorsal side. Instead, there are numerous chitinous tubercles and outgrowths, so the outer integument of the body is highly extensible. A wide welt runs along the edge of the body. The length of hungry ticks is 2-13 mm.
entrance gate- oral apparatus
Method of infection Inoculation
What pathogens does it carry? Tularemia, tick-borne, relapsing fever.
5. Ticks of the family Gamasoidea
The body is oval or oblong (0.3--4 mm), covered with scutes (solid or double dorsal and several ventral); body with numerous setae, constant in number and position. The legs are six-segmented, with claws and a sucker. Mouthparts gnawing-sucking or piercing-sucking.
Infection occurs through contact with infected birds and rodents. The disease manifests itself in the form of dermatitis, accompanied by itching. Mouse mites and rat mites also attack humans. As a rule, the main bite zones are those places where the clothes fit more tightly to the skin: zones of cuffs, elastic bands, belts. At first, a person feels a slight tingling, then a burning sensation and itching. Itchy rashes go on the skin, an inflammatory process begins, which spreads.
entrance gate- oral apparatus
Method of infection Inoculation
What pathogens does it carry? Tularemia, Rat, typhus, Q fever, encephalitis.
6. Human flea (Pulexirritans)
The body color is brown (from light brown to black brown). Life expectancy - up to 513 days.
Her body is ovoid; head rounded, without spines on lower margin. The first thoracic ring is very narrow, with an entire margin and also without spines. The hind legs are very strongly developed. The eyes are large and rounded. Length approximately 2.2 mm (male) or 3-4 mm (female).
Found everywhere. With a length of 1.6--3.2 mm, they can jump up to 30 cm in height and up to 50 cm in length.
Pulexirritans lives on humans, but can spread to domestic cats and dogs. It feeds on the blood of humans or animals on which it lives. It can make very large jumps, up to 1 meter in height.
The mouthparts of fleas are adapted for piercing the skin and sucking out blood; the puncture of the skin is carried out by jagged mandibles. Feeding, fleas fill the stomach with blood, which can greatly swell. Male fleas are smaller than females. Fertilized females forcefully eject eggs, usually in batches of several pieces so that the eggs do not remain on the animal's fur, but fall to the ground, usually in the hole of the host animal or in other places it constantly visits. A legless, but very mobile, worm-like larva with a well-developed head emerges from the egg. A human flea lays 7-8 eggs at a time (over 500 eggs in a lifetime) in floor crevices, rags, rat nests, dog kennels, bird nests, soil, plant waste.
entrance gate- Proboscis, anus.
Method of infection Inoculation, contamination
What pathogens does it carry? Tularemia, Plague.
7. Lice Pediculus humanus (human louse)
The body is oval or oblong, flattened in the dorsal-abdominal direction, 0.5-6.5 mm long, 0.2-2.5 mm wide, the color is grayish-brown, in individuals fed with fresh blood, it varies from reddish to black in depending on the degree of digestion.
Their body consists of three sections: the head, chest and abdomen. The head is small, tapering anteriorly, has five-membered antennae (antennae), behind them are simple eyes with a transparent cornea, under which accumulations of pigment are visible. The front edge of the head is correctly rounded, with a small mouth opening, the oral apparatus is of a piercing-sucking type, consists of three stylets: the lower one, the top of which is notched, serves to pierce the skin, blood is pumped along the upper zholobovatoy, saliva enters the wound through the tubular middle stylet. salivary gland ducts. At rest, all stylets are hidden inside the head and are not visible from the outside at all. Males are usually smaller than females. Lice are oviparous. Eggs (nits) are oblong-oval in shape (1.0-1.5 mm in length), covered with a flat lid on top. Nits are yellowish-white in color, glued with the lower end to the hair or villi of the fabric with a secret secreted by the female during laying. Metamorphosis is incomplete, accompanied by three molts. All three larvae (or nymphs) differ from adults in the absence of external genitalia, size, and slightly different body proportions. Nymphs usually have a relatively large head and thorax and a vaguely delimited short abdomen that enlarges after each successive molt. After the 3rd molt, the nymph turns into a male or female, by this time the genitals are formed and the lice are able to copulate. Lice are kept on the hairline near the skin, body lice - mainly on clothes. Infection of people with lice occurs through contact with lice-covered persons, for example, through contact of children in groups (kindergartens, boarding schools, camps, etc.), in crowded transport, when sharing clothes, bedding, bedding, combs, brushes, etc. .d. Infection of adults with pubic lice occurs through intimate contact, and in children - from adults caring for them, as well as through underwear.
entrance gate- anus
Method of infection Inoculation
What pathogens does it carry? typhus, relapsing fever.
8. Kissing bug (Triatominae Jeannel)
It has a strongly flattened body with a length of 3 to 8.4 mm, depending on blood saturation. Males are on average smaller than females. Coloration from dirty yellow to dark Brown. A proboscis extends from the front edge of the head, adapted for puncturing tissues and sucking blood. The upper and lower jaws look like piercing undivided bristles and form two channels: a wide one for receiving blood and a narrow one for secreting saliva at the injection site.
Due to the geometry and flexibility of the segmented body, the hungry bug is weakly vulnerable to mechanical methods of dealing with it. A well-fed bug becomes less mobile, its body acquires a more rounded shape and a color corresponding to blood (by the color of which - from scarlet to black - you can roughly determine when this individual last ate). The average lifespan of bed bugs is one year. Bedbugs can fall into a state similar to suspended animation, in the absence of food or when low temperatures. In adverse conditions, they are able to migrate between rooms along ventilation ducts, summer on the outer walls of houses. An adult bug crawls 1.25 m in one minute, a larva - up to 25 cm. The bugs have a well-developed sense of smell, they drink blood in all phases of development, for one bloodsucking of 10-15 minutes, the bug drinks 7 μl of blood, which is equal to its double weight . It usually feeds regularly every 5-10 days, mostly on human blood, but can also attack domestic animals, birds, rats and mice. In rural areas, they often crawl from infected poultry houses to houses.
Bedbugs are able to survive in a limited temperature range. At a temperature of 50? With bugs and their eggs perish instantly.
Bed bugs mate by traumatic insemination. The male pierces the female's abdomen with his sexual organ and injects sperm into the resulting hole. In all types of bed bugs, except Primicimex cavernis, sperm enters one of the compartments of the Berlese organ. There, gametes can stay for a long time, then they penetrate the hemolymph into the ovarioles to the formed eggs. This method of reproduction increases the chances of survival in case of prolonged starvation, since stored gametes can be phagocytosed. Insect with incomplete metamorphosis. Females lay up to 5 eggs per day. In total, during the life of 250 to 500 eggs. The full development cycle from egg to adult is 30-40 days. Under adverse conditions -- 80--100 days.
entrance gate- Anus.
Method of infection Contamination
What pathogens does it carry? American trypanosomiasis.
9. Mosquitoes (Phlebotominae).
Size - 1.5-2 mm, rarely exceeds 3 mm, color varies from almost white to almost black. The legs and proboscis are quite long. Mosquitoes have three distinctive characteristics: at rest, the wings are raised at an angle over the abdomen, the body is covered with hairs, before biting, the female usually makes several jumps on the host before digging into him. They usually move in short jumps, fly poorly, the flight speed usually does not exceed 1 m / s.
Subfamily of long-whiskered dipterous insects of the gnat complex. They are distributed mainly in the tropics and subtropics. Includes several genera, notably Phlebotomus and Sergentomyia in the Old World and Lutzomyia in the New World, which include a total of over 700 species. Representatives of these genera are important as carriers of human and animal diseases.
Mosquitoes live mainly in warm regions, but the northern limit of their range is just north of 50 ° north latitude in Canada and a little south of the fiftieth parallel in northern France and Mongolia.
Like all other dipterous insects, mosquitoes have 4 phases of development: egg, larva, pupa, adult. Mosquitoes usually feed on natural sugars - plant sap, aphid honeydew, but for the maturation of eggs, females require blood. The number of blood draws may vary depending on the species. Egg maturation time depends on species, blood digestion rate and temperature environment; in laboratory conditions - usually 4--8 days. Eggs are laid in places favorable for the development of preimaginal stages. The preimaginal stages include an egg, three (or four) larval stages, and a pupa. Mosquito breeding sites have not been studied enough, but it is known that their larvae, unlike most butterflies, are not aquatic, and from observations of laboratory colonies it can be concluded that the main requirements for a breeding site are humidity, coolness and the presence of organic matter. Most mosquitoes are active at dusk and at night. Unlike mosquitoes, they fly silently. Italian name mosquito, which gave the name to the type species - "pappa tachi" - means "bites silently"
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? Cutaneous, mucocutaneous and visceral leishmaniasis, Pappatachi fever.
10. Biting midges (Ceratopogonidae).
Small insects 1 - 2.5 mm long. They are the smallest of the blood-sucking Diptera. They differ from midges in a more slender body and more long legs; antennae consist of 13 or 14 segments, and palps - of 5 segments; on the third, thickened, are the sense organs. The mouth apparatus is of a piercing-sucking type, the length of the proboscis is almost equal to the length of the head. The wings are usually spotted.
A family of very small (the largest species in the world do not exceed 4 mm, the vast majority are less than 1 mm) dipterous insects of the long-nosed suborder, the adult females of which in most cases are a component of the midges complex.
Like all other dipterous insects, midges have 4 developmental phases: egg, larva, pupa, imago. At the same time, all phases, except adults, live in water bodies or are semi-aquatic-semi-soil inhabitants. Biting larvae are saprophages or predators that feed on aquatic and soil organisms or their remains. The diet of adults is varied. Representatives of different genera of the family can be saprophages, phytophages, predators, and their diet can be dual: biting biting females drink the blood of mammals, birds or reptiles; at the same time, both males and females feed on the nectar of flowering plants.
The larvae of biting midges are worm-like, with a well-defined sclerotized head capsule and a body consisting of 3 thoracic and 9 abdominal segments, outwardly little different from each other, and in varying degrees pronounced cervical segment - the neck, the body is devoid of appendages. Some species lay up to 20,000 eggs. The larvae of some species of biting midges live in water, others - in wet places on land, in the forest floor, hollows, under bark and even in garbage. Their breeding grounds are very diverse. These are reservoirs, floodplains of lakes, channels, temporary streams, puddles in water meadows, small rivers with a slow flow of water, backwaters, swamps without hummocks with a clay bottom, temporary reservoirs near taiga villages, puddles near wells, on livestock farms. Some species live in the brackish water of salt lakes, in the bays of the Aral Sea, etc. The maximum activity occurs in the early morning and evening. Active season in middle lane Russia lasts from May to September, in the south - from April to October - November. Optimum activity is observed at a temperature of 13 - 23°C.
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? Onchocerciasis, eastern equine encephalomyelitis, disease blue tongue sheep, livestock and human filariasis, their bites can cause an allergic reaction.
12. MukhaTse-Tse (Glossinapalpalis)
The body length is 9-14 mm, there is an expressive proboscis, an oblong shape attached to the bottom of the head and directed forward. At rest tsetse adds up wings completely, superimposing one wing on top of the other, in the middle part of the wing a characteristic segment in the form of an ax is clearly visible. The antennae of the tsetse fly have awns with hairs that branch out at the ends.
Type genus of insects from the family of flies Glossinidae live in tropical and subtropical Africa.
The tsetse fly can be distinguished from the house flies common in Europe by the nature of the folding of the wings (their ends lie flat on each other) and by the strong, piercing proboscis protruding from the front of the head. The chest of the fly is reddish-gray with four dark brown longitudinal stripes, and the abdomen is yellow above and gray below.
The usual food source for tsetse flies is the blood of large wild mammals.
All tsetse species are viviparous, the larvae are born ready to pupate. The female bears the larvae for a week or two, at one time she lays a fully developed larva on the ground, which burrows and immediately pupates. By this time, the fly is hiding in a shady place. During its life, a fly gives birth to larvae 8-10 times.
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? African trypanosomiasis (sleeping sickness).
13. Horseflies (Tabanidae).
Large flies (body length 6--30 mm ) , with a fleshy proboscis, inside which are enclosed hard and sharp piercing and cutting stylets; palps clear, with swollen end segment hanging in front of proboscis; antennae 4-segmented, projecting forward; wing scales well developed in front of halteres; the eyes are huge, with stripes and spots of iridescent colors; mouth parts consist of mandibles, jaws, upper lip and subglottis; lower lip with wide lobes. In horseflies, sexual dimorphism is observed - according to appearance males can be distinguished from females. In females, the eyes are separated by a frontal strip, in males, the distance between the eyes is almost imperceptible, and the abdomen is pointed at the end.
Horseflies inhabit all continents except Antarctica. In addition, they are absent from Iceland, Greenland and some oceanic islands. The largest number of horseflies, both in terms of numbers and number of species (up to 20 in each locality), is found in wetlands, on the borders of different ecotopes, in grazing areas. From the neighborhood of a person, their number only increases.
Like all other dipterous insects, horseflies have 4 phases of development: egg, larva, pupa, imago. Horsefly larvae - predators or saprophages - feed on aquatic and soil invertebrates. The nutrition of adults is dual: females of most species of horseflies drink the blood of warm-blooded animals: mammals and birds; at the same time, males, of all horsefly species without exception, feed on the nectar of flowering plants. Imagoes fly, spending most of their time in the air, orienting themselves mainly with the help of vision. Active during the day in warm, sunny weather. Horsefly females lay eggs in large groups of 500-1000 pieces. Horsefly eggs are elongated, gray, brown or black. The larvae are most often light fusiform, devoid of limbs. The pupae slightly resemble a butterfly chrysalis.
Horsefly eggs are attached to plants near water and above water. Egg laying with a dense, shiny shell. The hatched larvae immediately fall into the water and live at the bottom in the silt. The larvae are white, their body is covered with motor tubercles, the head is very small. They develop in or near water, in damp soil, under stones. They feed on organic remains, plant roots, some species attack insect larvae, crustaceans, earthworms.
On hot days, herds of animals are attacked by tens of thousands of horseflies. They are especially abundant in places with ponds and thickets of plants.
Only female adult horseflies bite cattle and drink blood, each of which can suck up to 20 mg of blood at a time. Only after that she is able to lay eggs. Horseflies from time to time fly to the reservoir and capture a drop of water from the surface. Males feed on the nectar of flowers. With their bites, horseflies exhaust animals, reducing their productivity, and greatly annoy people.
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? Loiasis, anthrax, tularemia, trypanosomiasis, filariasis.
14. Mosquitoes of the genus Aedes.
The length is from 2 to 10 mm and has a black and white color in the form of stripes and spots.
The male is 20% smaller than the female, but their morphology is similar. However, like all blood-sucking mosquitoes, the antennae of males, unlike females, are elongated and thick. The antennae also serve as an auditory receptor, with which he can hear the squeak of the female.
An adult develops from an egg within 6-8 weeks. In its development, the biter goes through all stages of development: egg - larva - pupa - adult insect. Eggs are white or yellowish during laying, but quickly turn brown. Females either lay them one at a time or stick them together in "rafts" that include from 25 to several hundred eggs. The larvae live in the water and feed on dead plant tissue, algae and microorganisms, although predators are also known to attack the larvae of other mosquito species. The pupae are similar to tadpoles and swim due to the bending of the abdomen. In the end, the pupa floats to the surface, the dorsal integument of its chest bursts, and an adult mosquito emerges from under them. For some time, until the wings are straightened, he sits on the shell of the pupa, and then flies away to the shelter, which he finds not far from the breeding site, where the final hardening of his covers takes place.
The mosquito bites most actively at dusk and dawn, but also at daytime indoors or in cloudy weather. In clear sunny weather, they hide in the shade.
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? dengue fever, chikungunya, yellow fever, wuhereriosis, brugiasis.
15. Mosquitoes of the genus Anopheles.
Slender Diptera with an elongated body, small head, long thin proboscis, mostly with long legs. The wings, covered with scales along the veins, at rest fold horizontally over the abdomen, leaning one on top of the other. The body is fragile, mechanical strength does not differ.
Widely distributed on all continents except Antarctica]. Absent in desert areas and on far north(the extreme northern point of the range is the south of Karelia). There are about 430 species in the world fauna, in Russia and neighboring countries-- 10 kinds. In Russia, they live in the European part and Siberia.
Mosquito larvae have a well-developed head with oral brushes used for feeding, a large chest and a segmented abdomen. Legs are missing. Compared to other mosquitoes, malarial mosquito larvae lack a respiratory siphon and therefore the larvae keep themselves in the water parallel to the water surface. They breathe with the help of spiracles located on the eighth abdominal segment and therefore must periodically return to the surface of the water to inhale air.
Pupae in the form of a comma, when viewed from the side. The head and thorax are fused into the cephalothorax. Like larvae, pupae must periodically rise to the surface of the water to inhale, but inhalation is done using breathing tubes on the cephalothorax.
Like other mosquitoes, malaria go through all the same stages of development: egg, larva, pupa and adult. In the first three stages, they develop in the water of various reservoirs and last a total of 5-14 days, depending on the type and ambient temperature. The lifespan of adults is up to a month in natural environment, in captivity even more, but in nature often does not exceed one to two weeks. females different types lay 50-200 eggs. Eggs are placed one at a time on the surface of the water. They tend to float upward on either side. Not drought tolerant. The larvae appear within two to three days, but hatching may be delayed up to two to three weeks in colder areas. The development of larvae consists of four stages, or instars, at the end of which they turn into pupae. At the end of each stage, the larva molts in order to increase in size. At the end of development in the pupal stage, the cephalothorax cracks and separates and an adult mosquito emerges from it.
A mosquito becomes infected with malarial plasmodium from a person - a patient or a carrier. The malarial Plasmodium goes through a cycle of sexual reproduction in the body of the mosquito. An infected mosquito becomes a source of infection for humans 4-10 days after infection and remains so for 16-45 days. Mosquitoes serve as carriers of other types of Plasmodium that cause malaria in animals.
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? Malaria.
16. Mosquitoes of the genus Culex.
An adult mosquito reaches 4-10 mm in length. It has a body structure common for insects: a head, chest and abdomen, having a proboscis with dark bristly and dark short palps. Wings 3.5-4 mm long with narrow black brushes. The male, unlike the female, has a fluffy antennae.
Females feed on plant sap (to maintain life) and blood (to develop eggs), mainly from humans, while the male feeds exclusively on plant sap.
From the eggs laid by the female common mosquito, larvae develop, which, after four stages of metamorphosis, separated by three molts, molt for the fourth time, turning into pupae, and from them, in turn, mature mosquitoes (imagoes) emerge.
The larva is characterized by a relatively short siphon bearing a comb of 12-15 teeth. The siphon does not expand at the end, its length is not more than six times the width at the base. There are four pairs of siphon bundles, the length of which slightly exceeds or does not exceed the diameter of the siphon at the point of their attachment. The pair closest to the base of the siphon lies at an appreciable distance closer to the apex from the most distal tooth of the ridge. The lateral hair on the last segment is usually simple.
The siphon is located on the eighth segment of the abdomen and serves to breathe air. At the end of the siphon there are valves that close when the larva is immersed deep in the water. The larva moves thanks to the caudal fin on the last, ninth segment of the abdomen, consisting of bristles.
The pupa of the common mosquito looks very different from the larva. She has a large transparent cephalothorax, through which the body of the future mature mosquito can be seen. It differs from the pupae of the malarial mosquito in that the two respiratory tubes extending from the cephalothorax, with which the pupa is attached to the surface of the water and breathes air, have the same cross section throughout; in addition, it has no spines on the abdominal segments. The abdomen consists of nine segments, the eighth of which has a caudal fin in the form of two plates. Moves due to the movements of the abdomen. The duration of the stage is a couple of days.
The female lays her eggs in warm stagnant water with organic materials or aquatic vegetation. Eggs are laid in the form of rafts that float freely in the pond. In one raft there may be 20 to 30 eggs stuck together. The duration of development is from 40 hours to 8 days, it depends on the temperature of the water in which development occurs.
Deep terrain or waves are detrimental to mosquito larvae.
Often the habitat of the common mosquito is an urban area. With the onset of cold weather, mosquitoes often fly into the basements of residential buildings, where, at room temperature and the presence of stagnant water, favorable conditions are created for their reproduction and the subsequent development of larvae and pupae. Mature mosquitoes from basements enter the apartments of residential buildings, this can often happen in winter.
entrance gate- Proboscis.
Method of infection Inoculation.
What pathogens does it carry? Wuchereriosis, brugiasis, Japanese encephalitis.
Mechanical carriers
1. Cockroaches (Blattoptera, or Blattodea).
The body is flattened, oblong-oval in shape, in a red cockroach up to 13 mm long, in a black one up to 30 mm. Mouth apparatus gnawing type. Antennae long, consisting of 75-90 segments. There is a pair of compound eyes and a pair of simple eyes. The legs are running, ending in two claws and suckers between them. The wings are delicate, transparent, at rest hidden under the elytra. The abdomen is flat, consisting of 8-10 tergites and 7-9 sternites. Leads a predominantly nocturnal lifestyle.
It is characterized by an incomplete development cycle. Adults reach a length of 10-16 mm and are colored in various shades brown with two dark stripes on the dorsal side of the prothorax. It has developed wings and is capable of short flight (planning). Male individuals have a narrower body, the edge of the abdomen is wedge-shaped, its last segments are not covered by wings. In females, the body is wide, the edge of the abdomen is rounded and covered from above by wings. Females lay 30-40 eggs in an ootheca, a brown capsule up to 8x3x2 mm in size. Cockroaches often carry ootheca on themselves until, after 14-35 days, nymphs hatch from eggs, which differ from adults only in the absence of wings and, usually, in a darker color. The number of links through which the nymph turns into an adult varies, however, usually equals six. The time it takes for this to happen is about 60 days.
The life span of adults is 20-30 weeks. One female can produce from four to nine ootheca in her life.
Cockroaches, having contact both with garbage, dirt accumulated in the cracks, garbage, and with fresh human food, can cause the spread of various diseases.
What pathogens does it carry? Protozoan cysts, helminth eggs; viruses, bacteria (causative agents of dysentery, typhoid, paratyphoid, tuberculosis, etc.
2. house flies(Muscadomestica).
The body is dark, sometimes yellow, also sometimes with a metallic sheen (blue or green), body length 7-9 mm. From above, the body is covered with hairs and setae, from 2 to 20 mm long. Members of the family have a single pair of membranous wings and a pair of halteres transformed from the hindwings. The head is quite large, mobile, while the mouth apparatus in the form of a proboscis is adapted for sucking or licking liquid food.
A family of short-whiskered dipterous insects, which includes about five thousand species, divided into more than a hundred genera.
The larvae are white, worm-like, legless, do not have a separate head and are dressed in a thin transparent shell. At the end of their development, the larvae pupate, for which they crawl to drier and cooler places. The pupa is in an oval-cylindrical brown cocoon. The duration of development depends on temperature and averages 10-15 days. A fly emerging from a chrysalis cannot fly for the first two hours of its life. She crawls until her wings dry and harden. Adult flies feed on a wide variety of solid and liquid substances of plant and animal origin.
What pathogens does it carry? Protozoan cysts, helminth eggs; viruses, bacteria (causative agents of dysentery, typhoid, paratyphoid, tuberculosis, etc.)
3. Autumn Stinger (Stomoxys calcitrans).
Length 5.5--7 mm. It has a gray color with dark stripes on the chest and spots on the abdomen. The proboscis is strongly elongated and carries plates with chitinous “teeth” at the end.
By rubbing the proboscis against the skin, the fly scrapes off the epidermis and, feeding on blood, simultaneously lets in poisonous saliva, causing severe irritation. Females and males feed on blood, attacking mainly animals, but sometimes humans. Fertility is 300-400 eggs, laid in groups of 20-25 in manure, less often on rotting plant residues, sometimes in wounds of animals and humans, where the larvae develop .. Eggs and larvae develop at a temperature not higher than 30-35? The larvae pupate in a dry substrate. The larvae and adults in the state of diapause overwinter in cold stables.
What pathogens does it carry? Anthrax, tularemia, trypanosomiasis.
4. Midges (Simuliidae).
Adult midges range in size from 1.5 to 6 mm.
Females lay their eggs in streams and rivers with fast-flowing water, gluing them to stones and leaves submerged in water. The development cycle of insects is from 10 to 40 days, and in the case of wintering - up to 10 months. They attack during daylight hours, in the northern latitudes during the polar day - around the clock (sometimes up to several thousand individuals per person at the same time). Insect saliva contains a strong hemolytic poison.
Like all other dipteran insects, midges have 4 phases of development: egg, larva, pupa, imago. At the same time, all phases, except adults, live in water bodies, mostly flowing (streams and rivers with fast-flowing fresh water).
Midge eggs are laid on constantly wetted stones, leaves and other objects. Females of some species, when laying eggs, descend along the substrate under water, while others drop eggs into the water in flight, which immediately sink. The eggs of midges are round-triangular in shape. Freshly laid eggs are white, but as the embryo matures, they darken to brown or black. Midges are characterized by the desire of females of one species to lay eggs one near the other. During joint oviposition, tens, and sometimes millions of individuals accumulate in one place, and the eggs laid cover tens of square meters of the substrate surface. When eggs dry or freeze in ice, the embryos die. The development of eggs lasts 4 - 15 days, depending on the temperature of the environment. In the case of wintering, their development and hatching of larvae can be delayed by 8 - 10 months.
When attacked, the midge bites the flesh, while mosquitoes pierce the skin with thin stylet-like mouthparts.
What pathogens does it carry? Tularemia, anthrax, leprosy, bird leukocytosis, onchocerciasis of cattle and humans, allergic reactions.
5. Biting midges (Ceratopogonidae).
Small insects 1 - 2.5 mm long. They differ from midges in a more slender body and longer legs; antennae consist of 13 or 14 segments, and palps - of 5 segments; on the third, thickened, are the sense organs. The mouth apparatus is of a piercing-sucking type, the length of the proboscis is almost equal to the length of the head. The wings are usually spotted.
Some species lay up to 20,000 eggs. The larvae of some species of biting midges live in water, while others live in wet places on land, in forest litter, hollows, under bark, and even in garbage. Their breeding grounds are very diverse.
Biting midges have 4 phases of development: egg, larva, pupa, adult. At the same time, all phases, except adults, live in water bodies or are semi-aquatic-semi-soil inhabitants. Biting larvae are saprophages or predators that feed on aquatic and soil organisms or their remains. The diet of adults is varied. Representatives of different genera of the family can be saprophages, phytophages, predators, and their diet can be dual: biting biting females drink the blood of mammals, birds or reptiles; at the same time, both males and females feed on the nectar of flowering plants.
Larvae (up to 15 mm) swim serpentine in water. The entire development cycle of biting midges (at a temperature of 24 - 26 ° C) lasts an average of 30 - 60 days. During the life of the female can do several cycles. Biting females attack animals and people, usually in open areas, occasionally in enclosed spaces. The maximum activity occurs in the early morning and evening. Optimum activity is observed at a temperature of 13 - 23°C.
What pathogens does it carry? eastern equine encephalomyelitis, bluetongue disease in sheep, filariasis in cattle and humans, tularemia.
