Biology and medical significance of the human flea. Medical encyclopedia - fleas

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 and viruses have been found in nature. tick-borne encephalitis, HFRS. 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 is important epidemiological significance.

The biology of rat fleas is 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 if not favorable conditions can take a long time (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 major 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 “development” 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, under baseboards, so frequent wet cleaning floors of premises leads to a decrease in the viability of adult fleas. 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, when 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, drooling, 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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Order "fleas" (aphaniptera)

Fleas are carriers of the plague pathogen. Fleas of marmots, gophers, and rats are of epidemiological importance. Infection with flea plague occurs through blood sucking on sick animals with intense bacteremia. Plague bacteria multiply in the body of fleas and do some life cycle and during reproduction, the fleas clog the forestomach, creating an obstruction in it. During the process of blood sucking, the ingested blood hits the bacterial plug and returns back to the wound, bringing bacteria with it. The causative agents of plague can persist in the body of a flea for more than a year. Plague microbes are also released in the feces of infected fleas and can be rubbed into skin damaged by scratching. Rat fleas are specific carriers of endemic flea typhus. They easily become infected by it when feeding on infected rats, retaining rickettsiae in their bodies for life and excreting them in their feces. A person becomes infected when feces of infected fleas come into contact with the conjunctiva of the eye, in the respiratory tract, or in scratches on the skin.

When a flea bites, saliva enters the wound, causing various allergic reactions. In tropical countries of both hemispheres, humans are attacked by female fleas Tunga penetrans, which almost completely burrow into the skin (usually between the toes) and remain there until the end of their lives; increasing in size to a pea, they cause severe suffering to humans.

Fleas are distributed across all continents of the globe. More than 1000 species and subspecies of fleas are known, of which about 500 species have been registered in Russia, belonging to 5 genera and 5 families.

The body length of the flea is from 0.5 to 5 mm; some species, after sucking blood, become greatly inflated, reaching a length of 16 mm. Color ranges from light yellow to dark brown. The body is laterally compressed, adapted for movement in the hair or feathers.

The head is usually rounded at the front. It contains a piercing-sucking type mouthpart, a pair of simple eyes, and a pair of short three-segmented antennae.

The oral apparatus consists of the following organs: the upper lip in the form of a thin long tube; pairs of skeletal-shaped upper jaws (mandibles), serrated along the outer edge and at the end; hypopharynx, which has an excretory duct salivary glands; pairs of triangular lamellar mandibles (maxill); the lower lip with two segmented lower labial palps, which, when brought closer together, become a case for the piercing parts of the oral apparatus (Fig. 1).

Fig. 1 The structure of the flea's mouthparts

1 – mandibular palps; 2 - lower jaws; 3 - upper lip; 4 - upper jaws; 5 – lower labial palps

There are cuticular formations on the body of fleas: teeth, spines, bristles. The teeth arranged in rows are called ctenidia, they can be in the anterior part of the head, pronotum and metanotum.

Fig.2. Gopher flea - Ceratophyllus tesquorum Wang., female

g - eye; y - antennae; mandibular palp; nch - lower jaw; x - proboscis; pg - prothorax; kt - thoracic ctenidium; sg - mesothorax; zg - metathorax; t - basin; c - trochanter; b-thigh; goal - shin; l - foot; 1-У1П -I - VII1 tergites; 1-8cm - I - VIII sternites; psh - prepygidial setae p - pygidium; c – church; ac - anal segment; sp – seminal receptacle.

Not all types of fleas can attack humans. It was established that fleas that willingly bite humans belong to 36 species, those that bite reluctantly belong to 6 species, and those that do not bite belong to 29 out of 71 species of fleas taken into the experiment.

Mature fleas tolerate relatively long periods of fasting. Thus, some fleas in their nests live for up to 1.5 years without eating, while fleas in wool and human homes live for shorter periods.

In fleas, blood sucking, mating and laying eggs occur multiple times. After mating, a drunk female lays eggs in portions, with the number of eggs ranging from one to several dozen. The total number of eggs that a dog flea lays, for example, reaches 450 pieces. Flea nests lay eggs on the substrate (nests, animal burrows, floors of rooms). Hair fleas lay eggs on their host's fur. The development of fleas occurs with complete transformation. The worm-like larva feeds on the feces of adult fleas, which contain semi-digested blood. If there is a lack of food, the larvae can starve for about a month. However, they do not tolerate too much or too little moisture. The larva molts three times. At the end of the 3rd stage, she dresses herself in a web cocoon and becomes a non-feeding pupa. The formation of an adult flea occurs in the cocoon. The period of development from egg to adult is subject to significant fluctuations, with different types flea growth depends on the quality of food, its quantity, temperature, and humidity of the substrate in which development occurs.

Fleas are very annoying insects. When they bite, they inject saliva into the host's body, under the influence of which spots with an intensely pigmented center appear on the skin. Saliva causes local inflammation of the skin, and some swelling of the tissue is observed. However, fleas are of primary importance as carriers of pathogens of a number of diseases.

Currently, 124 species of fleas have been registered, from which the plague causative agent has been isolated under natural conditions. The list will apparently continue to grow.

Under similar conditions, the circulation of the plague pathogen is influenced by the biology of both the fleas themselves and their hosts - rodents. If rodents are the main carriers of the plague pathogen, then fleas are not only the specific carriers of this pathogen. “Fleas become infected by feeding on the blood of infected rodents and some other animals. With one portion of the blood of infected animals, a flea can absorb up to 100 thousand microbial bodies. The infecting dose must be at least 10,000 microbes.

In the proventriculus and stomach of the flea, intensive proliferation of microbes occurs, which, sticking together into a viscous mass, occupy the lumen of the proventriculus, and then the stomach, forming a block. Intensive reproduction of plague microbes leads to complete or partial blockage of the flea's intestines with the plague block.

In this case, part of the block is brought out along with microbes that enter the wound from a bite or scratch. This is how plague infection occurs. It is also possible to become infected with the plague through a bite when the block has not yet formed.

Fleas of the genus Xenopsylla are distinguished by the highest level of maturity in relation to the plague pathogen. In many ways, they play the main role in the spread of this infection. Fleas of the same species, depending on the fact environment can play different roles. Representatives of the genus Ceratophyllus at elevated temperatures in steppes and deserts have a noticeably reduced infectious potential, while in temperate climates these fleas are the main carriers of plague pathogens.

Fleas are carriers of Rickettsia mooseri, the causative agent of epidemic typhus. They easily become infected with rickettsiae by feeding on infected rats. Rickettsia multiply in the intestines of fleas without penetrating into the body cavity and salivary glands. They persist throughout the life of fleas and are excreted in their feces, as well as in the urine of sick rats. In dry flea feces, rickettsiae remain viable and virulent for up to 4.5 years. It is the dry infected feces of fleas, as well as the urine of sick rats, that are the factor in the dispersion of rickettsia. Human infection occurs through food products contaminated by rodents, when infected flea feces come into contact with mucous membranes or when the skin is scratched. The maximum number of human diseases occurs during the cold season.

Among the diseases spread by fleas is tularemia, the causative agent of which is the flea as an accidental mechanical carrier. The experiment noted the ability of fleas to retain the tuberculosis pathogen within themselves for up to 112 days and to infect healthy animals through a bite. A Salmonella culture was isolated from fleas collected from rodents. The possibility of transmission of the causative agent of glanders by fleas through a bite cannot be ruled out.

The fight against fleas should be reduced to creating conditions that prevent the reproduction of these insects and destroying them on animals and in places where they accumulate. Residential and service premises must be rodent-proof and kept clean. Particular attention should be paid to domestic animals - cats and dogs.

Extermination measures are aimed mainly at the destruction of adult fleas. For this purpose, insecticides are used in the form of powders, suspensions, emulsions, etc. Floors, baseboards, bottom edges walls, bed dress. IN field conditions Preparations that destroy not only fleas, but also their hosts, rodents, are widely used. In this regard, chloropicrin followed by dusting the exit hole of the burrow has become famous. Personal protection measures against fleas should not be ignored. In this regard, repellent preparations that completely or partially impregnate outer clothing or bedding deserve attention.

M.: Medicine, 1984. - 560 p.
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Medical significance. Only an ectoparasite, does not tolerate pathogens.
Prevention and control measures. The same as for other types of lice.
18.3.3. Order Fleas (Aplianiptera)
A typical representative is the human flea (Pulex irritans). The flea's body is flattened laterally and has no wings. The head bears short antennae, a pair of simple eyes, and a piercing-sucking apparatus. The limbs are highly developed; especially the last pair, which is much longer and is used for jumping. The abdomen consists of ten segments; in males, the end of the abdomen is curved upward. Characteristic are various appendages of the cuticle - palps, denticles, setae, which are important for taxonomy.
Development with complete transformation. Eggs are laid indoors in crevices, cracks in the floor, and in dry garbage. IN natural conditions- in rodent burrows. A legless, worm-like larva emerges from the egg. white. It feeds on decaying organic matter. After some time, the larva forms a cocoon and then turns into a 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. As an ectoparasite, the flea causes itching, scratching, secondary infection, suppuration, etc. But the main significance of fleas is determined by the fact that they especially tolerate dangerous disease- plague.
The natural reservoirs of the plague are various rodents - gophers, rats, marmots, marmots, etc. Animals suffer from the plague and die. After the death of the owner, fleas move to other individuals of the same or another species and infect them.
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. In different types of fleas, the frequency of block formation during sucking is not the same. The highest rate is in the rat flea - 63%, while in other species it is much lower - from 43 to 5%.
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 Xenopsylla cheopis (see Fig. 215, e), which parasitizes rats, gerbils and easily spreads to humans, and the marmot flea (Oropsylla silanlievi). 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 the field, rodents in burrows are destroyed using appropriate pesticides (chloronicrin) and thereby eliminate fleas.
18.3.4. Order Diptera (Dip(era)
The order includes the largest number of species with medical significance. Representatives of the order have one (front) pair of membranous transparent or colored wings. The posterior pair has turned into small appendages of the haltere, performing the function of balance organs. The head is spherical or hemispherical, connected to the chest by a thin soft stalk, which provides greater mobility.
Some types of flies are closely related to humans (synanthropic), these include the housefly, housefly, and autumn fly.
House fly (Musca domestiea). Distributed throughout the globe.
Quite a large insect of a dark color. The head is semi-spherical, has large compound eyes on the sides, and an oral cavity in front.
Rice. 216. Housefly.
general form; b eggs; in larva; g-dolls
apparatus. The legs have claws and adhesive blades that allow the fly to move along any plane.
The oral apparatus is licking and sucking. The lower lip is transformed into a proboscis, at the end of which there are two sucking lobules, with an oral opening located between them. The upper jaws and the first pair of lower jaws are atrophied. The upper lip and tongue are located on the front wall of the proboscis. 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. One clutch contains up to 100-150 eggs. The transformation is complete. Under favorable conditions they can reproduce all year round.

Fossil fleas have been found in Baltic amber and Lower Oligocene deposits near Aix (France). To collect and study these animals, they are fixed on glass slides, since they have to be examined under a microscope. The world's best collection of fleas, now kept in the British Museum, was collected in Tring (England) by N. Rothschild and K. Jordan.

In addition to human fleas, dog fleas readily settle on humans. Cat fleas, on the contrary, rarely (unless they are very hungry!) and live on people for a short time. The rat flea is especially dangerous, as well as fleas from the burrows of gophers, marmots, and gerbils, which are carriers of plague, tularemia, and helminthic infestations.

From an epidemiological perspective, the most important are the human flea (Pulex irritans) and rodent fleas, in particular Xenopsilla cheopis and Ceratophillus fasciatus.

Human flea (Pulex irritans)

The flea's body is hard, smooth, flattened laterally, covered with backward-directed setae, and often also with ridges of wide teeth (ctenidia) on the head or chest. The head bears short antennae, a pair of simple eyes, and piercing-sucking mouthparts. There are no wings. The limbs are highly developed, especially the last (third) pair, which is much longer and is used for jumping. Jumping human flea reach up to 32 cm in length and 9 cm in height. The abdomen consists of ten segments; in males, the end of the abdomen is curved upward. Characteristic are various appendages of the cuticle - palps, denticles, setae, which are important for taxonomy.

Fleas reproduce by eggs, which the female “shoots” into external environment. Under favorable circumstances - in garbage or in damp soil - the eggs hatch into worm-like larvae with sparse, long, bristly hairs. Larvae develop in plant debris, are common in basements, under floors, warehouses, and in nature - in mammal burrows, bird nests, etc. The larva feeds on decaying organic matter. After a few weeks, the larva forms a cocoon and then turns into a pupa (pupates). Later, adult fleas (imago) emerge from the pupa and feed only on blood.

A female human flea lays up to 450 eggs. Development comes with complete transformation. The entire development period takes, depending on temperature and other conditions, from 20 days to a year. An adult flea lives 2-5 years.

In the Middle Ages, entire cities died out from the plague, spread by mice and rats and transmitted to humans by fleas that drank the blood of sick rodents. However, even in our time, in areas where numerous colonies of gophers, marmots and other rodents susceptible to plague live - in Central Asia, Kazakhstan, Transbaikalia, Mongolia, China - there remains a danger of infection of domestic animals and humans with this deadly disease.

Plague is a facultative-transmissible disease with natural focality. The causative agent of this particular dangerous infection- plague stick. Natural reservoirs of plague are various rodents - gophers, rats, tarbagans, marmots, etc., in which the plague bacillus is found in significant quantities in the blood. Fleas support the disease among rodents, and during periods of epizootics (mass animal disease) they transfer the pathogen from animals with plague to humans.

A flea becomes infected with plague bacteria when it sucks the blood of a sick rodent shortly before its death, during the period when the blood in the capillary vessels is saturated with microbes. Plague pathogens actively multiply in the flea's stomach, forming a plug that closes its lumen, or a “plague block.” After the death of a sick animal, “plague fleas”, which need warm blood, leave the corpse and look for a new owner. Being not too closely related to the owner of a certain species, they can attack humans.

When an infected flea begins to suck blood on another, healthy animal or on a person, the blood cannot pass through the block and returns back to the wound, washing away the bacteria from the block; sometimes the flea regurgitates them, introducing tens of thousands of microbial cells into the blood of a healthy person. In the body of a flea, viable plague microbes can persist throughout their life, that is, often for more than a year.

Currently, it is believed that infection through a bite is possible only when a block is formed. In different types of fleas, the frequency of block formation during sucking is not the same. The highest rate is in the rat flea - 63%, while in other species it is significantly lower - from 43 to 5%. Infection is also possible through flea feces, which contain plague pathogens when they get into wounds when scratched.

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.

A number of flea species can be infected with tularemia microbes. These include fleas of water rats, mice and other rodents - carriers of this disease. It should be noted that laboratory experiments have shown that transmission of tularemia pathogens through fleas is rare and only when the number of animals is high.

In cities, fleas of synanthropic rodents - rats and house mice - from time to time find bacteria of diseases of these rodents that also infect people: pseudotuberculosis, listeriosis, erysipeloid, as well as typhoid fever and anthrax. Fleas of rats, house mice, cats and dogs play a significant role in the spread of rickettsia, the causative agent of endemic (rat) typhus. Human infection occurs through damaged skin, mucous membranes of the eyes and nose when infected flea feces fall on them. Transmission through a bite is also possible, since rickettsiae penetrate the salivary glands of the flea.

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.

Cootie(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.

Lice are the most important epidemiological significance as specific carriers of pathogens 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, canines - dogs, gophers - 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 has 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. Natural reservoir Plague is caused by 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 widespread throughout to the globe. Females measure up to 7.5 mm. The body and paws are dark in color and covered with hairs. The legs have claws and sticky pads that allow flies to move along any surface.

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 an ambient temperature of at least 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.

The fight against flies is carried out on different stages 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 landscaping populated areas: availability of sewerage, closed garbage containers, manure storage facilities, toilets, timely disposal of waste, 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. Lives near human habitation along the banks of rivers and lakes with high humidity soil 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 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.