Rat flea has medical significance. Class Insects. Squad Lice. Flea Squad. Morphology, development cycles, medical significance. Prevention of diseases they carry
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.
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.
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 under unfavorable conditions it can be greatly delayed (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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Prevention and control measures. To combat cockroaches, insecticides are used, various
decoys and other means. Must be made inaccessible to them food products and water, then they themselves will look for another habitat.
Family Cimicidae (bed bugs). Morphology and developmental biology. People are being attacked Cimex lectularius And C. hemipterus.Bed bugs(Fig. 4.25) have a flattened body with lost wings. Oral apparatus piercing-sucking type. The eyes are bulging, but they see bugs
Badly. They have the most developed sense of smell. Bug on the big one
Distinguishes the smell of prey from a distance (up to several meters) and crawls towards it. The legs are running, with three-jointed tarsi.
The size and color of the bug depend on the degree of its saturation: a bug that has sucked blood swells to 0.5-0.8 cm, its color becomes redder. The saliva contains poisonous secretions, so the bites are painful. Representatives of this family are characterized by odorous glands. The eggs have a cap at the upper end.
Female bed bugs lay 1 to 12 eggs daily,
Rice. 4.25. Bed bug Cimex lectu-
laris.
which are glued with a gelatinous secretion to walls, furniture and other places. At room temperature The development of the egg until one larva emerges lasts 6-8 weeks. To transition to subsequent stages of development, the larva must be pumped with blood each time, and the volume of blood consumed increases from 1-3 to 7 mg. Older larvae and mature bedbugs can fast for 18 months. A hungry bug becomes almost transparent, flat and colorless. A bed bug is nocturnal, but a hungry bug’s behavior changes: it crawls out “to hunt” even in bright light. An adult bedbug covers a distance of over 1 m in 1 minute. Other types of bedbugs can also attack humans, the natural hosts of which are pigeons, barn swallows or the bats. In the absence of people, they bite mice, rats, chickens and other animals. Blood sucking lasts about 10-15 minutes in adults and less in nymphs and is repeated every 3 days. During the day, insects hide in dark, dry places in beds, mattresses, wall cracks, floor crevices and furniture. They can also be found behind paintings and wallpaper. They breed in places of shelter. In countries with warm climates, bedbugs are present in abundance in bedrooms. In colder climates, they live in heated bedrooms because they can only thrive at temperatures of at least 13°C. Adults can survive without food for several years. Bed bugs are ubiquitous.
Fleas are secondary wingless insects.
Geographical distribution- ubiquitous.
Morphological characteristics. The body is fused, laterally flattened, 1-5 mm in length, yellowish - Brown. The chitinous cover is smooth, compacted with backward-directed setae and teeth. 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 longer than the others and is used for jumping. The abdomen consists of ten segments. In males, the end of the abdomen is curved upward. Teeth - appendages of the cuticle have diagnostic value.
Life cycle . Development with complete transformation. The fertilized female lays eggs (about 0.5 mm in length) in dry garbage, in floor cracks and crevices in rooms, as well as in rodent burrows. Worm-shaped flea larva. Their body is covered with numerous long hairs and consists of 13 segments. The larvae molt three times and pupate. The pupa is motionless and resembles adult. The development period is 19 days.
Diagnostics. Flea bites can be found on exposed areas of the body that are itchy and inflamed.
Prevention: a) public – sanitary and educational work, sanitary and hygienic measures in public spaces, extermination of rodents; b) personal – maintaining cleanliness in living quarters, wet cleaning, sealing cracks and cracks, using insecticides, periodically washing pets with pet shampoo, etc.
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 point of view, the most important 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. The jumps of a human flea reach 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 into salivary glands fleas.
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. Give effect and measures personal protection, such as repellents used on clothing and bedding.
50. Class Insects, order Diptera: mosquitoes. Life cycle, representatives and their medical significance.
Diptera unite general concept vile.
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.
Highest value representatives of this order have both temporary blood-sucking
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 – specific vectors vector-borne 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 others 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.
Houseflies 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 (larvae malaria mosquito), 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. 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 of malaria mosquitoes, swamps are drained and fish are bred to eat mosquito larvae and pupae. Their natural enemies - insectivorous birds (swallows, swifts) and dragonflies - play a major role in reducing the number of mosquitoes.
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