Order Fleas, morphology, development, medical significance. Fleas are specific carriers of the plague pathogen, its circulation routes and nature. Control measures, prevention. Class Insects. Squad Lice. Flea Squad. Morphology, development cycles, medical significance

1. Characteristic features of the organization and medical significance of representatives of the class Insects.

Phylum Arthropods ( Arthropoda).

Subtype Tracheal-breathing ( Tracheata).

Class Insects ( Insecta).

Morphophysiological characteristics.

The body is clearly divided into three sections: head, chest, abdomen. Three pairs of legs are located in pairs on three segments of the chest, hence another name for the class - six-legged, or Hexapoda.

Digestive system represented by the foregut, starting from the oral cavity and dividing into the pharynx and esophagus, the posterior section of which expands, forming a goiter (not in everyone). Available salivary glands(up to three pairs), the secretion of which digests food. In blood-sucking insects, saliva contains a substance that prevents blood clotting. The midgut of insects is devoid of digestive glands, the hindgut ends with the anus.

The excretory organs are represented by Malpighian vessels (from 2 to 200) and the fat body, which performs the function of “storage buds”.

Respiratory organs - trachea. Stigmas are located segment by segment (up to 10 pairs). Large main trunks (tracheas) begin from the stigmas, which branch into smaller tubes. They even penetrate inside individual cells. Thus, the tracheal system replaces the functions of the circulatory system in supplying tissues with oxygen.

The circulatory system, in accordance with the characteristics of the respiratory organs, is relatively poorly developed. The heart is tube-shaped and consists of many chambers.

The nervous system reaches exclusively high level development. Consists of the brain and ventral nerve cord. The brain consists of three sections - anterior, middle, posterior and has a very complex structure. In the anterior part of the brain, mushroom bodies are highly developed, thanks to which insects are capable of forming complex conditioned reflexes. The behavior of insects, which is based on instincts, can be very complex (especially among social ones).

The sense organs (touch, smell, vision, taste, hearing) reach an exceptionally high level of development. The organs of vision play a leading role in orientation in external environment along with the olfactory organs. Insects have simple and complex ( faceted) eyes. Compound eyes consist of a huge number of individual prisms; this eye structure gives “mosaic” vision. Higher insects (bees, butterflies, ants) have color vision.

Insects are dioecious organisms; they have well-defined sexual dimorphism.

Life cycle.

In the Insect class there are Various types postembryonic development: direct and indirect (with complete metamorphosis). Complete metamorphosis includes the stages of egg, larva, pupa and adult. The larva differs sharply in structure and habitat from the adult forms. Thus, mosquito larvae live in water, and adults live in air environment. The pupae do not feed; at this stage, the larval organs are replaced by the organs of adult insects.

2. Lice (head, body, pubic)

Phylum Arthropods ( Arthropoda).

Subtype Tracheal-breathing ( Tracheata).

Class Insects ( Insecta).

Troop Lice ( Anoplura).

small sizes

limbs are equipped with a fixation device to the skin, hair and clothing

piercing-sucking type mouthparts

the development cycle is simplified (development with incomplete metamorphosis),

all stages of the life cycle live and feed on one host.

Head louse (Pediculus humanus capitis

Localized on the scalp. Dimensions 2-3 mm. The body is flattened, the head is small, well demarcated from the chest. On the head there is a pair of antennae, a pair of simple eyes (sometimes absent), and a piercing-sucking mouthparts. At rest, the oral apparatus is retracted inside the head and is not visible from the outside. The thoracic segments are fused, and the chest bears three pairs of legs. The last segment of the tarsus has a highly developed claw, which, together with the growth of the penultimate segment, forms a slamming device, like a claw. With this device, the louse is firmly held on the hair. There are no wings.

The abdomen is somewhat wider than the thoracic region and consists of 10 segments. In males, the copulatory apparatus is visible at the end of the abdomen. Stigmas are located on the lateral sides of the thoracic and abdominal segments.

Development with incomplete metamorphosis. The laid eggs (nits) are glued to the hair by the secretion of the adhesive glands. All development takes place on the human body. A larva emerges from the egg, similar in basic characteristics to the adult. After molting, she turns into an imago. They feed on blood. Maximum lifespan is 38 days.

Medical significance.

Prevention and control measures.

Cootie (Pediculus humanus humanus) causes the disease pediculosis.

Lives on underwear and clothing, and when sucking blood it spreads to the body. By appearance and development is very similar to a head louse.

Features:

has larger dimensions (up to 4.7mm),

less deep notches along the edge of the abdomen,

less pronounced pigmentation of the lateral parts of the abdominal segments.

Lays eggs on hairs of clothing.

The entire development cycle occurs in humans. Life expectancy is up to 48 days. Mobile, at a temperature of 27°C crawls 35 cm per minute.

Medical significance.

Only humans serve as the reservoir for both diseases. When sucking the blood of a sick person, pathogens enter the intestines of the louse, where they undergo a complex development cycle. Pathogens of typhus Rickettsia Provacek develop in the cells of the intestinal wall of lice, together with dead cells they enter the intestinal cavity and are carried out with feces. A lice bite is not dangerous, since there are no pathogens in the saliva. Infection occurs when insect feces are rubbed into a bite wound or into scratches and abrasions on the body.

Causative agents of relapsing fever Obermeyer's spirochetes From the intestine, lice pass into the hemolymph of the insect. Infection occurs when a louse is crushed and hemolymph enters the bite wound or scratches.

Prevention and control measures. Same as for head lice.

Pubic louse (Phthirus pubis). The disease is phthiriasis.

Dimensions 1–1.5 mm. The body is shortened, wide, narrowed posteriorly. The border between the chest and abdomen, unlike head and body lice, is not pronounced. Life expectancy is up to 26 days.

Distributed everywhere. It lives on the pubis, armpits, and sometimes on the eyebrows and eyelashes. At the same time, it penetrates almost completely under the skin, exposing the tip of the abdomen, where the stigmas are located, to the surface. The female lays up to 50 eggs throughout her life.

Prevention and control measures.

First of all, it is necessary to maintain sexual hygiene. Otherwise, the same measures as for other lice.

3. Fleas.

Flea Squad ( Aphaniptera).

A typical representative is human flea (Pulex irritans). The flea's body is flattened laterally, there are no wings, the body length is from 1 to 5 mm. The head bears short antennae, a pair of simple eyes, and a piercing-sucking mouthparts. The limbs are highly developed, especially the last pair, which is much longer and is used for moving by jumping. The abdomen consists of ten segments; in males, the end of the abdomen is curved upward.

Development with complete transformation. Eggs are laid indoors in crevices, floor cracks, behind baseboards and wallpaper, and in dry garbage. IN natural conditions- in rodent burrows. A legless, white, worm-like larva emerges from the egg. It feeds on decaying organic matter, including the feces of adult fleas. After 3-4 weeks, the larva forms a cocoon and then turns into a pupa. Mature insects emerge from the pupa. Adult insects feed on blood.

Each type of flea lives on a host of a certain species: the rat flea lives on rats, the dog flea lives on dogs, and the gopher flea lives on gophers. Some species can switch to animals of another species. This determines the importance of fleas as carriers of human diseases.

Medical significance.

Plague pathogens actively multiply in the flea's stomach, forming a plug that closes its lumen, or a “plague block.” When a flea tries to drink blood, the block interferes with the passage of blood, the flea regurgitates it into the wound and, thanks to this, introduces a huge amount of bacteria into the host’s body. Currently, it is believed that infection through a bite is possible only when a block is formed. Infection is also possible through flea feces, which contain plague pathogens when they get into wounds when scratched.

The most dangerous carriers of plague are the rat flea and the marmot flea. The human flea can also transmit plague.

A person can become infected with plague not only through carriers, but also through contact with animals (for example, when skinning) or with a sick person. The pneumonic form of plague is especially easily transmitted. In addition to plague, fleas can transmit tularemia.

Prevention and control measures.

Prevention measures include ordinary sanitary and hygienic measures: maintaining cleanliness in the premises, wet cleaning, eliminating flea breeding sites such as crevices, cracks in the floor, etc. Insecticides are used to kill fleas indoors or on clothing.

IN field conditions destroy rodents in burrows using appropriate pesticides and thereby eliminate fleas.

Give effect and measures personal protection, such as repellents used on clothing and bedding.

4. House fly, house fly, Wohlfarth fly.

Order Diptera ( Diptera).

The order includes the largest number of species of medical importance. Representatives of the order have one (front) pair of transparent membranous or colored wings. The posterior pair has turned into small appendages (haleteres) that perform the function of balance organs. The head is connected to the chest by a thin soft stalk, which provides greater mobility.

Housefly (Musca domestica).

Distributed throughout the globe. Quite a large insect of a dark color. Body dimensions 6-8 mm, color gray-brown. On the sides of the head there are large compound eyes. Four dark longitudinal stripes stand out on the chest. The legs have claws and adhesive blades that allow the fly to move along any plane.

Oral apparatus – licking-sucking. The saliva of flies contains enzymes that dissolve solids. After the food is liquefied, the fly licks it off. The fly feeds on human food and various organic substances.

Flies lay eggs (100-150 pieces) in rotting substances of plant or animal origin. In urban settlements, these are accumulations of food waste in garbage dumps, garbage receptacles, landfills, waste Food Industry. IN rural areas breeding sites include accumulations of domestic animal manure, human feces, and human feces on the soil. After 5-10 days, a segmented white worm-like larva emerges from the egg. It feeds on liquid food, mainly decaying organic matter. Optimal conditions for the development of larvae (temperature - 35-45°C, humidity - 46-84%) are created in manure heaps. After 4-7 days the larva will pupate.

The pupa is motionless, covered on the outside with a thick cuticle Brown. The fly coming out of it passes through quite thick layer soil. Flies become sexually mature on days 5-6. Life expectancy is about 1 month. During this time, the female lays eggs 5-6 times (about 600).

Medical significance.

The housefly is a mechanical carrier of pathogens of intestinal infections - cholera, dysentery, typhoid fever etc. The spread of this particular group of diseases is determined by the fact that flies feed on contaminated feces and swallow pathogens of intestinal infections or contaminate the surface of the body with them, after which they transfer them to human food. With food, pathogens enter the human intestine, where they find favorable conditions. In fly excrement, bacteria remain alive for a day or more. In addition to intestinal diseases, houseflies can carry pathogens and other diseases, for example, diphtheria, tuberculosis, etc., as well as helminth eggs and protozoan cysts.

House fly (Muscina stabulans).

Distributed everywhere. Body colored brown, legs and palps yellow color. It feeds on feces as well as human food. The main breeding sites are human feces in unsewered latrines and on the soil. In addition, it can develop in the feces of domestic animals and food waste. Adult flies live in yard latrines.

Medical significance: mechanical carrier of pathogens of intestinal diseases.

Fighting flies.

timely collection and disposal of waste, at least once every three days,

garbage dumps and latrines must be hermetically sealed and easy to clean,

prevent soil contamination with human feces,

Insecticides and larvocides are used in fly breeding areas.

Distributed in the Caucasus and Central Asia, but can also be found in more northern regions.

A large fly, light gray in color, with black round spots on its abdomen. Viviparous. Attracted by the smell of decomposing tissues (wounds, purulent discharge), the fly incurs larvae into the tissues of an animal or a person, which immediately penetrate into the soft tissues and feed on them there. Before pupation, the larvae leave the host and go into the soil. During one clutch, the fly hatches up to 120 larvae. Adult forms feed on flower nectar.

Medical significance. Children are especially affected by myiasis. In severe cases, complete destruction of the soft tissues of the orbit, soft tissues of the head, etc. is possible. There are known cases of myiasis with a fatal outcome.

Mosquitoes.

Order Diptera ( Diptera). Family Mosquitoes ( Culicidae).

Blood-sucking insects. Distributed from the tundra zone to desert oases. On the territory of Russia, three genera are most often found: Anopheles, Culex, Aedes.

Small insects with a narrow and elongated body. The head bears large compound eyes. The mouthparts are piercing-sucking, but only females are bloodsuckers, and males feed on nectar and have sucking mouthparts.

Development with complete transformation. Eggs are laid in water or wet soil. The larva that emerges actively feeds and molts several times. The body of the larva is clearly divided into head, thorax and abdomen. The head is round in shape, bears antennae, eyes and fan-shaped fans. As they move, the fans force water and the particles it contains into the larvae’s mouth. The larva swallows any particles of a certain size, regardless of whether they are food or not. This is the basis for the use of pesticides sprayed into water bodies.

The respiratory organs are the trachea.

The pupa has a comma shape due to its massive cephalothorax and narrow abdomen; it does not feed and moves with the help of rapid movements of the abdomen.

Hatched females and males live near bodies of water, feeding on nectar. After fertilization, females need to drink blood to develop eggs, so they actively search for a host and are able to detect it at a distance of up to 3 km using smell and then vision. Females suck the blood of animals or humans. During the digestion of blood, the eggs mature (gonotrophic cycle), which lasts 2-3 days. Some mosquito species have only one gonotrophic cycle per summer, while others may have several cycles.

Mosquitoes are most active in the evening and early morning hours. During the daytime hours high temperature and low air humidity, mosquitoes are in shelters and do not feed.

Life expectancy of a female warm time years up to 3 months, and males - 10-15 days. In the fall, the males die, and the females go into suspended animation and overwinter.

Each type of mosquito has its own ecological characteristics, so organizing control measures requires precise definition genus present in a given area. To do this, it is necessary to dwell on the signs that are important for the differential diagnosis of various genera of mosquitoes. Differences exist at all stages of the cycle, as reflected in the table:

Prevention and control measures.

Personal: protection against mosquito bites.

Public prevention: destruction of mosquito larvae and breeding sites. The pupae cannot be destroyed because they do not feed and are protected by thick chitin.

The fight against larvae consists of a number of measures:

destruction of all small abandoned water tanks;

spraying pesticides into reservoirs serving as breeding sites;

oil production small bodies of water, preventing the flow of oxygen;

drainage of the area, reclamation work;

biological control measures: breeding mosquito fish that feed on mosquito larvae;

Fighting imago:

zooprevention - livestock farms are located between mosquito breeding sites and residential buildings, since mosquitoes readily feed on the blood of animals;

spraying insecticides in areas where mosquitoes hibernate: basements, attics, barnyards.

6. Mosquitoes

Order Diptera ( Diptera).

Family Mosquitoes ( Phlebotomidae).

Only mosquitoes of the genus are of medical importance Phlebotomus.

Small insects - body length 1.5-3.5 mm. The color is brown-gray or light yellow. The head is small, bears a short piercing-sucking apparatus, antennae and compound eyes. The widest part of the body is the chest, the abdomen consists of ten segments, of which the last two are modified and represent the external parts of the genital apparatus. The legs are long and thin. The body and wings are heavily covered with hairs.

Mosquitoes are found in tropical and subtropical zones on all continents.

Development with complete metamorphosis. The eggs are brown, elongated oval in shape. The larva is legless with a head covered with hairs and lives in the soil. Feeds on organic matter. The pupa is club-shaped and does not feed.

Males feed on plant sap; Only females drink blood. Just like female mosquitoes, female mosquitoes have a gonotrophic cycle. However, many species of mosquitoes suck blood repeatedly during egg maturation. Capable of transovarial transmission of pathogens.

Mosquitoes are crepuscular and nocturnal insects. They attack prey before sunset and in the first hours after sunset. outdoors and indoors. They can live in the wild and in populated areas. Habitats in populated areas include burrows of house rodents, the space under the floors of residential buildings, at the base of adobe buildings, under heaps of construction waste, etc.

In the wild, breeding sites include rodent burrows (gerbils, gophers, etc.), bird nests, jackal and fox dens, caves, cracks, and tree hollows. From their holes, mosquitoes fly to villages, covering a distance of up to 1.5 km.

Medical significance.

Prevention and control measures.

In villages, residential premises are treated with insecticides; in natural conditions, rodents in burrows and mosquito breeding sites are destroyed. Personal protection against bites is also effective.

To combat fleas in residential premises, especially where a dog or cat is kept, sanitary and hygienic measures are of primary importance: wet cleaning of the premises, regular washing of floors with salt water, soapy water or creolin solution, sealing (puttying) cracks in the floor, etc. In case of mass appearance of fleas, DDT, dieldrin, lindane in the form or dusts are used (see Disinfectants); linen and clothing are dusted with 10% DDT dust. Personal protection in conditions where a mass appearance of infected fleas is possible consists of wearing special protective suits and using (kyuzol, benzimine, diethyltoluamide, etc.). Dogs affected by fleas are bathed using creolin emulsin, DDT soap, or sprinkled with 10% DDT dust (to prevent the animal from licking the drug!). To destroy fleas in burrows, especially in areas affected by the plague, 10% DDT dust is used, introducing it into the burrows with special devices, as well as chloropicrin or methyl bromide, strictly observing all the rules for personal safety (see, Deratization). See also .

Fleas go through a complete metamorphosis cycle. The body of the flea is solid, laterally flattened, covered with hard chitin. On the convex-rounded head there is a pair of simple eyes. Some types of fleas are blind. Stinging-sucking mouthparts hang from the lower anterior edge of the head; behind them there is a ridge of flat teeth (ctenidia). Three pairs of legs are attached to the chest below; The last pair, the longest, is the jumping pair. On the back of the ninth segment of the abdomen lies the ethmoid sensory organ - the pygidium. The color of the flea ranges from pale yellow to dark brown. Fleas move well in the thick fur of their host, and jump along the ground. Flea eggs are not sticky and easily fall out of the fur onto the bedding of the owner's bed. The flea larva is worm-shaped. The head bears mouthparts that scrape off dried blood stains and organic debris. The flea pupa is motionless and does not feed. The length of the life cycle varies among different flea species; she is influenced outside temperature and power frequency. Flea saliva is irritating.

A plug of plague bacteria (indicated in black) in the stomach of a flea.

The fight against fleas consists of hygienic maintenance of living quarters, dusting rodent burrows with DDT and hexachlorane dusts. A simultaneous fight against their rodent hosts is necessary. See also Vectors, Natural focality.

Order Lice (Anopiura)

The head louse (Pediculus humanus capitis) lives on the scalp. The body length of the male is 2-3 mm, of the female - 3-4 mm. The rear end of the male's body is rounded, while that of the female is forked. The mouthparts are piercing-sucking type. It feeds only on human blood 2-3 times a day and can fast for several days. Eggs (nits) stick to the hair with a sticky secretion. A larva emerges from the egg and looks like an adult. After a few days, she turns into an adult. During her life (up to 38 days), the female lays about 300 eggs. The duration of the life cycle is 2-3 weeks.

The body louse (Pediculus humanus humanus) lives on underwear and bedding and feeds on humans. It is larger in size than the head one (up to 4.7 mm), has shallower notches along the edge of the abdomen and has weak pigmentation. Nits stick to the fibers of clothing. Life expectancy is up to 48 days, life cycle is at least 16 days.

Most Important epidemiological significance have lice like specific carriers causative agents of relapsing and typhus. The causative agents of relapsing fever - Obermeyer's spirochetes - enter the louse's stomach with the patient's blood and from there into the body cavity (hemolymph). There is no exit gate from the carrier's body, so lice bites do not infect healthy person. The pathogen is transmitted only when the louse is crushed and its hemolymph is rubbed into the skin by scratching (specific contamination).

Order Fleas (Aphaniptera)

The flea's body has a dense chitinous cover, flattened on the sides. There are no wings. There are numerous hairs, bristles, and denticles on the surface of the body. The head bears short antennae and a pair of simple eyes. The last pair of legs is longer than the others and is used for jumping. The mouthparts are piercing-sucking type.

Fleas lay eggs in crevices and cracks in the floor, in dry garbage. Development comes with complete metamorphosis. The larvae are worm-shaped and have no limbs. After some time, the larva pupates. The minimum development period for a flea is 19 days.

Each type of flea has a specific host: rat fleas - rats, dog fleas - dogs, gopher fleas - gophers. But many types of fleas can feed on animals of different species. Fleas feed only on warm blood. They leave the dead owner and look for a living provider. This feature is important in the rapid spread of the plague.

The secretion of the salivary glands of fleas when bitten causes itching and dermatitis in humans: when scratching the itchy areas, a secondary infection occurs. However, the main epidemiological significance of fleas is the transmission of pathogens of vector-borne diseases - plague and tularemia. The natural reservoir of plague is various rodents - rats, gophers, tarbagans, marmots, etc. Plague pathogens actively multiply in the flea's stomach and close its lumen, forming a so-called "plague block". When sucking blood, the blood does not pass into the stomach and is regurgitated, carrying it into the wound a large number of plague bacteria. Infection of a person with plague is also possible through flea feces when they come into contact with the plague bacillus on skin damaged by scratching. A person can become infected with the plague through contact with sick animals (skinning) or with a sick person. Human susceptibility to plague is absolute.

Insecticides are used to control fleas. Prevention measures include: maintaining cleanliness in the premises, wet cleaning, eliminating cracks and crevices in the floor and walls, rodent control (deratization). In tropical countries it is not recommended to walk on the ground without shoes.

Class Insects. Order Diptera. Systematics, morphology, medical significance. Prevention of diseases they carry.

Order Diptera (Diptera)

The order includes a large number of species of medical importance. Representatives of the order have one (front) pair of membranous transparent wings. The posterior pair has turned into small haltere appendages that serve as an organ of balance. The large head is connected to the thoracic region by a thin soft stalk, which ensures its mobility. There are large compound eyes on the head. The mouthparts are licking, sucking or piercing-sucking.

Family Flies (Muscidae)

Of medical interest are flies - mechanical carriers of pathogens (house flies, meat flies, cheese flies, zhigalka, etc.) and specific carriers (tsetse fly). The larvae of some flies (Wohlfarth flies, gadflies) can be causative agents of diseases in humans and animals, which are called myiases.

The housefly (Musca domestical) is distributed throughout the globe. Females measure up to 7.5 mm. The body and legs are dark in color and covered with hairs. The legs have claws and sticky pads that allow flies to move on any plane.

The oral apparatus is licking and sucking. The lower lip is transformed into a proboscis; at its end there are two sucking lobules, between which the oral opening is located. The fly's saliva contains enzymes that liquefy solid organic matter, which it then licks off. Flies feed on human food and various decaying organic debris.

4-8 days after mating at a temperature environment At temperatures not lower than 17-18°C, the female fly lays up to 150 eggs at a time. Common places for egg laying are rotting organic matter, kitchen waste, manure, human excrement, etc. At optimal temperature(35-45°C) after a day, larvae emerge from the eggs, which pupate after 1-2 weeks. Pupation usually occurs in the soil at a lower temperature (not higher than 25°C). A new generation of flies appears in about a month. Their lifespan is about one month.

On the integument of the body, on the legs, on parts of the oral apparatus, flies mechanically transmit pathogens of intestinal infections (cholera, dysentery, typhoid fever), as well as tuberculosis, diphtheria, paratyphoid fever, anthrax, helminth eggs and protozoan cysts. There are up to 6 million bacteria on the body of a fly, and up to 28 million in the intestine.

Flies are controlled at different stages of their life cycle. To combat winged flies, insecticides, Velcro, baits with poisons are used, and they are destroyed mechanically. To combat preimaginal stages great importance has the improvement of populated areas: the presence of sewerage, closed garbage containers, manure storage facilities, toilets, timely removal of waste, the use of insecticides.

The autumn firefly (Stomoxys caicitrans) is ubiquitous. In morphology and biology, the firefly is similar to a housefly, but differs in its long, thin proboscis. It has a brown body color with dark stripes on the chest and spots on the abdomen. At the end of the proboscis there are plates with chitinous teeth. By rubbing the proboscis against the skin, the fly scrapes off the epidermis and feeds on blood; saliva contains it toxic substances, causing severe irritation. Its bites are painful. The population of flies reaches its greatest numbers in August-September.

The autumn fly is a mechanical carrier of anthrax and sepsis pathogens.

The tsetse fly (Gtossina palpalis) is distributed only in the western regions of the African continent. It lives near human habitation along the banks of rivers and lakes with high soil moisture, overgrown with shrubs and trees.

The fly is large in size (up to 13 mm), has a highly chitinized proboscis protruding forward and dark spots on the dorsal side of the abdomen. The body color is dark brown. Females are viviparous and lay only one larva on the soil surface. The larva penetrates the soil, pupates, and after 3-4 weeks the imaginal form emerges. Over the course of their entire life (3-6 months), females lay 6-12 larvae.

The tsetse fly feeds on the blood of animals and humans and is the main reservoir and specific carrier of the pathogens of African trypanosomiasis.

Measures to combat the fly consist of cutting down bushes and trees along the banks of rivers and lakes near settlements and along roads. Insecticides are used to control adult flies.

The Wohlfart fly (Wohlfahrtia magnifiea) is common in temperate and hot climates.

The body of the fly is light gray in color and has a length of 9-13 mm. There are dark longitudinal stripes on the chest.

The disease caused by the larvae of the Wohlfarth fly is called myiasis. Children are especially affected by myiasis. With intense infection, complete destruction of the soft tissues of the orbit and head is possible; sometimes the disease ends in death.

Occasional intestinal myiases can be caused by housefly and blowfly larvae.

The best known are the human flea Pulex imtans and the rat flea Xenopsylla cheopis (Fig. 21.11, A, B). Both species prefer to feed on the blood of humans and rats, respectively, but also easily switch to other types of animals. The rat flea lives in rat burrows, and the human flea lives in floor cracks, behind baseboards and wallpaper. Here, females lay eggs, from which worm-like larvae develop, feeding on decaying organic matter, including the feces of adult fleas. After 3-4 weeks they pupate and turn into mature insects.

Fleas visit humans at night. Their bites are painful and cause severe itching. But the main significance of fleas is that they are carriers of bacteria that cause plague. Plague bacteria, once in the flea's stomach, multiply there so intensively that they completely close its lumen. If a flea begins to feed on a healthy animal or person, after piercing the skin, it first burps a bacterial lump into the wound, due to which a huge number of pathogens immediately enter the bloodstream.

The natural reservoir of plague is rodents - rats, gophers, marmots, etc. These animals suffer from a number of other infectious diseases: tularemia, rat typhus, etc. Therefore, fleas are known as carriers of pathogens and these natural focal diseases. It is interesting that in addition to the transmissible method of infection with these diseases, there are other ways: through contact with infected animals, by drinking water from open reservoirs, etc., but with a flea bite, infection is the most likely, and the clinical picture is the most severe.

Flea control - maintenance of residential premises and outbuildings clean, use of insecticides and various means rodent control. Personal protective measures, such as repellents that are applied to clothing and bedding, also have an effect.

50. Class Insects, order Diptera: mosquitoes. Life cycle, representatives and their medical significance.

Diptera are united by the common concept of gnus.

Mosquitoes of the genera Anopheles, Culex, and Aedes are of medical importance.

Their bites are painful, as their saliva contains substances that cause allergic reactions. They are specific carriers of pathogens: malaria (p. Anopheles), filariasis and infectious diseases: tularemia, Japanese encephalitis, anthrax, etc.

51. Class Insects, order Diptera: mosquitoes. Life cycle, representatives and their medical significance.

Representatives of this order have a pair of wings, their mouthparts have the shape

proboscis designed for sucking liquid food from plants or animals

tissues or for licking it from the surface. Development with complete metamorphosis.

Representatives of this order are of greatest importance as temporary bloodsuckers.

of this order, breeding in the summer in the tundra and taiga in a huge

quantity, make human life almost unbearable. Different types bloodsucking

Diptera are united by the common concept of gnus

Mosquitoes of the genus Phlebotomus are of medical importance. The bites are painful. An inflammatory reaction and itching develop at the site of the bite. Secondary infection of wounds due to scratching is possible. Multiple bites can cause a general reaction in the body: poor sleep, fever. Specific carriers of pathogens of a number of diseases: visceral and feline leishmaniasis, pappataci fever.

52. Class Insects, order Diptera: flies, horseflies, gadflies. Life cycle, representatives and their medical significance.

Many types of flies are mechanical carriers of pathogens of intestinal infections (cholera, typhoid fever, dysentery).

The saliva of blood-sucking species is toxic, especially for children, and causes pronounced allergic reactions.

Larvae of some species feeding soft tissues, pluck out intestinal and tissue myiases (botfly, tungsten fly = Wohlfahrtia magnifica)

Damage to organs and tissues of humans and animals by dipteran larvae is called myiasis. They belong to entomoses.

Flies and botflies can lay eggs and larvae on the human body. Female flies lay eggs in the eyes, ears, nose, wounds of people or inject them subcutaneously; visceral damage is less commonly observed due to accidental ingestion of larvae. Larvae can penetrate a person from the ground, mosquitoes, laundry, etc.

Swallowed fly eggs, if they do not die, are absorbed into the blood and spread throughout the body, penetrating the brain, heart, etc. (in very rare cases) or (more often) causing intestinal myiasis.

54. Insects are specific carriers of transmissible protozoa.

Sandflies of the genus Phlebotomus, when bitten, transmit the disease visceral leishmaniasis and cutaneous leishmaniasis. The leptomonas form of Leishmania dovani develops in the mosquito's body.

African trypanosomiasis is transmitted by the bite of a specific vector, the tsetse fly of the genus Glossina. The trypanosomal form develops in the body of the fly.

American trypanosomiasis is transmitted by the bite of a vector flying bug of the genus Triatoma or Rhodnins)

Anopheles mosquito is a specific carrier of malarial plasmodium.

55. Insects are mechanical carriers of infectious and invasive diseases.

Ixodes persulcatus, ricinus, Dermacentor pictus are natural reservoir and carriers of pathogens of a number of infectious diseases: spring-summer viral tick-borne encephalitis, tularemia, tick-borne typhus, Lyme disease.

Pulex irritans is a specific carrier of the plague pathogen.

Pediculus humanis capitis: is a specific carrier of the causative agent of relapsing fever and typhus.

Blood-sucking flies are specific carriers of pathogens of infective and infectious diseases: tsetse fly (p. Glossina), sleeping sickness, flies (p. Stomoxys) - tularemia, anthrax, plague, midges (p. Similium) - onchocerciasis, horseflies ( p. Chrysops)-loalase.

56. Insects are pathogens.

Some insects, especially blood-sucking ones, are carriers of pathogens that cause dangerous diseases in humans, farm animals, and game animals. These include, for example, the housefly, the autumn fly and other flies, and malaria mosquitoes.

The housefly and autumn fly carry pathogens of typhoid fever, dysentery, cholera and other dangerous diseases. Flies carry bacteria that cause certain diseases and ascaris eggs on their legs from sewage to accessible food products. The reproduction of flies is associated with sewage, various rotting organic residues, and manure: here they lay eggs, from which legless and headless worm-like larvae develop. After completion of development, the larvae pupate in the soil, and soon adult insects emerge from the pupae.

House flies live in human housing, in garbage dumps, and on farms with domestic animals. The autumn zhigalka appears in residential areas from the end of summer and is familiar to many because of its painful bites.

Malaria mosquitoes are carriers of malaria pathogens. The malaria mosquito can be distinguished from the common mosquito by its position: the common mosquito holds its body parallel to the surface on which it sits, while the malaria mosquito holds its body at an angle. Their larvae also differ. Some of them, having risen to the surface, hold their body parallel to the surface film of water (malarial mosquito larvae), others - at an angle to it (common mosquito larvae). There are other differences as well. Malarial and common mosquitoes are bloodsuckers, and their larvae, developing in water, feed on microorganisms and suspended organic debris. The larvae breathe atmospheric air using a breathing tube. Mosquito pupae are mobile and comma-shaped. Adult mosquitoes overwinter in cellars, basements, barnyards, and tree hollows. To reduce the number malaria mosquitoes They drain swamps and breed fish that eat mosquito larvae and pupae. Their natural enemies - insectivorous birds (swallows, swifts) and dragonflies - play a major role in reducing the number of mosquitoes.

B l o h i

Females and males prefer to feed on the blood of warm-blooded animals, but can also attack people. In their development, fleas go through stages from egg, larva, pupa, and adult.

Females lay eggs in waste and dust that accumulates in the burrows and nests of animals and birds, sometimes lightly gluing them to the host’s fur. Fleas living in human homes lay eggs in floor cracks, behind baseboards, and in animal bedding. During her life, 1 female can lay up to 500 eggs. The duration of the entire development cycle of a flea in optimal conditions takes 16-49 days, the lifespan of imago fleas ranges from 3 months to 1.5 years. The adults emerging from the cocoons can immediately begin to suck blood, but they are capable of starving for a long time - up to 1.5 years. Blood sucking lasts from 1 minute to several hours.

Epidemiological significance. Massive flea bites greatly annoy people; scratching can cause skin irritation and suppuration. But greatest harm fleas are carriers of pathogens of some dangerous diseases and, first of all, the plague. A flea becomes infected with plague bacteria when it sucks blood on a sick animal shortly before its death. The plague microbe multiplies in the flea's digestive canal and forms a block. If blood sucks again, the blood cannot pass into the block and returns back to the wound, saturated with plague bacteria from the block. In the body of a flea, plague microbes remain viable for more than a year.

In addition, fleas infected with tularemia microbes, tick-borne encephalitis viruses, and HFRS have been found in nature. Fleas of cats and dogs serve as intermediate hosts of helminths: cestodes of dogs and rats

Methods of struggle and protection. In order to prevent the proliferation of fleas in residential premises, it is necessary to seal cracks in the floor, clean the premises with a vacuum cleaner, remove dust from cracks, crevices, regular cleaning bedding for domestic animals, cows, etc. It is necessary to systematically wash the floors, adding soap or washing powder. Pets should be washed periodically with pet shampoo or soap containing an insecticide. When rodents appear in the premises, it is necessary to carry out deratization, after which disinsection is mandatory, preventing the transfer of fleas from dead animals to humans.

To prevent the proliferation of fleas in basements, it is necessary to destroy rodents, seal up their burrows, remove stray dogs and cats, seal cracks in floors and walls, cement earthen floors, remove sand and debris, and seal ventilation holes in the foundation. Attics must be inaccessible to animals and birds and free from debris and dust.

Rat flea

The rat flea also has a worldwide distribution. As an active carrier of plague pathogens, as well as a carrier of rat typhus pathogens, it has important epidemiological significance.

Biology rat fleas similar to the biology of dog and cat fleas. Distinctive feature is the ability to develop with more low temperatures, which is an adaptation to life in basements.

Dog and cat fleas

Dog and cat fleas are found throughout the world. The biology of these fleas is similar because they live in the same conditions, and are also similar in both morphology and size. After digestion of blood and development of eggs, female dog fleas lay eggs on the fur of the owner or in the bedding of their owners, and female cat fleas lay eggs under baseboards, in cracks or crevices of the floor filled with dust, various food crumbs and dirt, and in basements- in various garbage.

Depending on the amount of blood they drink, females lay from 10 to 20 eggs daily, and over a lifetime they can lay up to 400 eggs.

The optimal conditions for the development of eggs and the life of larvae are temperatures of 20-250 C and relative humidity 60-70%. The entire development of fleas from egg to adult lasts from 16 to 50 days, but under unfavorable conditions it can be very prolonged (up to two years). The dog flea strictly feeds on the blood of dogs and does not take on other hosts. Occasionally it can “accidentally” bite a person in the absence of a dog, but quickly retreats. The cat flea readily attacks humans, and usually bites the legs up to the knees. Back in the 50s of the last century, cat fleas became quite numerous in the basements of buildings in large cities, and since the late 90s there has been a sharp increase in the number and prevalence of this flea in city basements, which is associated with the “mastering” of a new host by the flea, namely the gray rat.

Having switched to feeding on the blood of a gray rat (without leaving its former owner - the cat), the cat flea gradually began to displace its competitor - the rat flea.

Disinsection measures

In residential and office premises fleas live in crevices of parquet and plank floors, cracks in linoleum, laminate, carpeting, and under baseboards, so frequent wet cleaning of indoor floors leads to a decrease in the viability of flea imagoes. If there are animals in the premises, fleas concentrate in places where they lie, and under bedding, sleeping baskets, and upholstered furniture.

For instant destruction of fleas in small spaces, aerosol products designed to combat flightless insects and liquid or dry insecticides can be used. various groups, intended for use in domestic conditions.

Carrying out extermination activities

Conduct general cleaning apartments. To carry out the treatment, the prepared solution is poured into a sprayer and the surface to be treated is irrigated. When killing fleas indoors, insecticides are used to treat the surface of the floor (paying attention to cracks and cracks in them, joints with baseboards), walls to a height of up to 1 m, bedding for animals, which must be washed before use, and furniture items selectively - in areas where fleas live and on the ways of their penetration into the premises.

All flea-infested rooms in one building are treated simultaneously (on the same day) or for 2-4 days in a row. At longer intervals, disinsection is ineffective.

Precautionary measures

Treatment of premises should be carried out in the absence of people, pets, birds and fish, with open windows. Food and utensils should be removed or carefully covered before processing. After treatment, the room should be well ventilated for at least 2 hours.

Persons carrying out disinfestation are required to use by individual means protection (respirator). Do not smoke, eat or drink in the treated area. After finishing work, rinse your mouth, wash your hands and face with soap.

First aid for insecticide damage

In case of violation of safety rules or accidents, it may develop acute poisoning. Signs of poisoning: unpleasant taste in the mouth, salivation, vomiting, headache, nausea (increased by smoking, eating), abdominal pain, constriction of the pupil, irritation of the respiratory system..

In case of poisoning through Airways take the victim out of the room into fresh air, remove contaminated clothing, rinse mouth with water or 2% solution baking soda.

If the product accidentally gets into your eyes, rinse them thoroughly with a stream of water or a 2% solution of baking soda, generously for several minutes. If irritation of the mucous membrane occurs, drop 30% sodium sulfacyl into the eyes, and if painful, 2% novocaine solution.

Contact your doctor immediately.

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