Anopheles mosquito pupa. Mosquitoes of the genera Culex and Anopheles and their role in the spread of malaria. The structure and medical significance of mosquitoes
Order Diptera (Diptera)
Diptera are a detachment of insects with complete metamorphosis. A distinctive feature of the detachment, which well delimits it from other groups of insects, is the presence of only one front pair of wings. The posterior pair of them is transformed into club-shaped organs of balance - halteres - and does not carry a locomotor function. The science of dipterous insects is dipterology.
About 120,000 species of Diptera have been described. The most characteristic representatives of Diptera are mosquitoes, midges, horseflies, real flies.
Many blood-sucking Diptera are carriers of infectious diseases (malaria, yellow fever, etc.). However, at the same time, they are of great importance for Agriculture, because they are pollinators of various plants, including cultivated ones. The body shape of adult dipterans is very diverse. Everyone knows slender long-legged mosquitoes and stocky short-bodied flies, but only experts will attribute to this order a microscopic wingless "bee louse" or a female of one of the humpback species found in anthills, which looks more like a very small cockroach.
Morphology of the imaginal stages of malarial and nonmalarial mosquitoes.
Slim elongated body. On the head are large compound eyes, long antennae. Females have piercing-sucking mouthparts, males sucking, piercing parts are reduced (feed on nectar). On the sides of the mouthparts are segmented antennae. A pair of transparent wings are attached to the mesothorax. Abdomen - 10 segments, the last 2 are modified into genital appendages. At the end of the abdomen, the female has genital appendages in the form of a pair of protrusions; the male has a complex pincer-shaped copulatory organ. The shape of the genitals is the most reliable way to determine the sex and type of mosquito. The ties are thin, long. The body of mosquitoes is covered with scales or hairs (the shape and location are different).
Imagoes differ in landing, wing pattern and structure of head appendages.
In Culex and Aedes, the abdomen is parallel to the surface on which they sit; in Anopheles, the posterior end is raised.
Some species of malarial mosquitoes have dark spots on their wings, non-malarial mosquitoes do not.
The heads of males of all mosquitoes have strongly lowered mandibular antennae, in females they are slightly lowered. In females, Anopheles are equal in length to the proboscis, Culex and Aedes are a third or a quarter of the proboscis. In males of Anopheles, the proboscis is equal and there are club-shaped thickenings at the end, in non-malarial ones the proboscis is longer and there are no thickenings.
The shield of the mesothorax in malaria is rounded (entirely marginal), in non-malaria along the posterior edge it is three-lobed
The legs of malaria are longer.
development cycle of mosquitoes.
A new generation of mosquitoes hatched from pupae goes through a maturation period (about 4 days). At this time, they live near water bodies, feed on nectar. Then, at dusk, the males form a swarm, the females fly into it, mate, after the females must definitely drink blood for the development of eggs. They actively search for prey at a distance of up to 3 km from the reservoir, flying into the premises. After drinking blood, the females hide for several days in a darkened room or thicket. During the digestion of blood, the maturation of eggs (gonotorphic cycle). Monocyclic (1 cycle per summer) or polycyclic (2-7). Females live approx 1 month, males 10-15 days. After maturation of eggs, the female flies to the reservoir, lays 350-450 eggs. Larvae emerge from the eggs, the duration of development depends on t water (15 days at 25 "C), not less than 10. The larvae feed on bacteria and grow on the remains, molt several times and turn into pupae, adults emerge from the cat.
In Anophelis and Culex, the females hibernate, while Aedes have eggs. With the onset of cold weather, males fertilize females and die. Females feed on blood to form a fat body, at the expense of the cat hibernate. Egg development is retarded. In spring they feed again and lay eggs.
Differences between eggs, larvae, pupae of malarial and non-malarial mosquitoes.
Anopheles - in standing or low-flowing unshaded water bodies with clean water. The eggs have a belt with air chambers and swim one at a time.
Aedes - lay eggs one at a time in temporary reservoirs (puddles, cans, hollows). Elongated oval without air chambers
Culex - wedge-shaped without air chambers, deposited on the surface of the water glued in the form of a boat
Culex and Aedes - on the penultimate segment of the abdomen, a respiratory siphon in the form of a narrow tube, at the end of the cat there are stigmas (tracheal openings). Are located at an angle to the surface of the water, breathe atmospheric air
Aedes - non-simultaneous hatching of larvae from eggs of the same clutch, stretches for weeks and months (adaptation to drying up reservoirs)
Anopheles - do not have a siphon, located parallel to the surface of the water. A pair of stigmas, through which they breathe atmospheric air, are located on the penultimate segment of the abdomen
Comma form. On the dorsal side of the cephalothorax, a pair of breathing siphons. With their help, the pupae are "suspended" to the surface of the water. Culex and Aedes have cylindrical siphons, while Anopheles have conical siphons.
Medical significance of mosquitoes.
mosquitoesAnopheles are specific vectors and definitive hosts of malaria pathogens, specific vectors and intermediate hosts vuhererii and brugii.
mosquitoesAedes- specific carriers of pathogens of Japanese encephalitis, yellow fever, Dengue fever, lymphocytic choriomeningitis, anthrax, wuchereriosis, brugiosis, tularemia.
mosquitoesCule xspecific carriers of pathogens of Japanese encephalitis, tularemia and wuhereriosis.
Structure and medical significance mosquitoes.
Mosquitoes (subfamilyPhlebotomidae) live in countries with a warm and hot climate, kept mainly in human housing. In addition, they live in caves, in rodent burrows, etc. Size 1.5-3.5 mm, color brown-gray or light yellow. The head is small. The oral apparatus is piercing-sucking. The legs are long and thin. The body and wings are strongly lowered. The eggs are laid in places protected from the sun: rodent burrows, caves, hollows of trees, in bird nests, in garbage. Males feed on plant juices, females - on blood (at dusk and at night). The bites are painful, blisters and itching appear at the site of the bites.
Mosquitoes are specific carriers of leishmaniasis and pappataci fever. They are characterized by transovarial transmission of pathogens.
Morphology and life cycle of the housefly.
house fly (muscle domestica) widespread everywhere.
Morphological features: sizes of females up to 7.5 mm. The body and legs are dark in color, covered with hairs. The paws have claws and sticky pads that allow the flies to move on any surface. The oral apparatus is licking-sucking. The lower lip is turned into a proboscis, at its end there are two sucking lobules, between which the oral opening is located.
Saliva contains enzymes that liquefy solid organic matter which she then licks off. Flies feed on food and various decaying organic residues.
Life cycle: 4-8 days after mating at a temperature of 17-18 C, the female lays up to 150 eggs in rotting organic residues, kitchen waste, manure, human feces, etc. at the optimum temperature (35-45C) in a day, larvae emerge from the eggs, which pupate in 1-2 weeks.
Pupation occurs in the soil at a lower temperature (not higher than 25C). A new generation of flies appears in about a month. Their life span is about one month.
Epidemiological significance of the housefly.
Flies are mechanical carriers of pathogens intestinal infections(cholera, paratyphoid, dysentery, typhoid fever), tuberculosis, diphtheria, helminth eggs and protist cysts. On the body of a fly there are up to 6 million bacteria, and in the intestine - up to 28 million.
Fly fighting lead at different stages of their life cycle. To combat winged flies, insecticides, stickies, baits with poisons are used, and mechanically destroyed. To combat the preimaginal stages, the improvement of populated areas is of great importance: the presence of sewers, closed garbage bins, manure storages, toilets, timely removal of waste, and the use of insecticides.
Structure, life cycle, Medical Significance Of The Wolffart Fly.
Wolfart fly (wohlfahrtia magnifica) widespread in countries with a temperate and hot climate.
Morphological features: the body is light gray color, length 9-13 mm, three dark longitudinal stripes on the chest
Children are especially affected by myiasis. With intensive infection, complete destruction of the soft tissues of the eye socket and head is possible; sometimes the disease ends in death. Occasional intestinal myiasis can be caused by housefly and blowfly larvae.
Preventive measures are aimed at protecting people from the attack of flies.
Tse-tse flies: morphology and medical significance.
Tse-tse fly (glossinapalpalis) is distributed only in the western regions of the African continent. It lives near human dwellings along the banks of rivers and lakes with high soil moisture, overgrown with shrubs and trees.
The sizes are large (up to 13 mm), the proboscis is strongly chitinized, protrudes forward. The coloration is dark brown. Females are viviparous, laying only one larva on the soil surface. The larva penetrates the soil, pupates, and after 3-4 weeks the imaginal form emerges. For the whole life (3-6 months) females lay 6-12 larvae.
It feeds on the blood of animals and humans and is the main reservoir and specific carrier of African trypanosomiasis pathogens.
Control measures: cutting down shrubs and trees along the banks of rivers and lakes near settlements and along roads. Insecticides are used to control adult flies.
Morphology, development cycles, medical significance of cockroaches.
Squad of cockroaches (Blattoidea)
Morphological features: large insects, body length reaches 3 cm.
The body is flattened in the dorso-ventral direction. They have 2 pairs of wings: the upper ones are leathery, the lower ones are membranous. In females, the wings are reduced. Mouth apparatus gnawing type. Cockroaches have special skin odorous glands, the secretion of which attracts other individuals, so they exist in large groups.
Life cycle: development with incomplete transformation lasts several months. Females lay their eggs in cocoons, which they carry with them for 14-15 days. Nocturnal activity is characteristic, during the day they hide in crevices. They are found in human dwellings, at food industry and public catering enterprises, etc. The obligatory conditions for their existence in a person’s dwelling are: the presence of moisture, a certain temperature, and a sufficient amount of food. They feed on food, human excretions and various garbage.
Representatives: black cockroach or kitchen cockroach (blattaorientalis), red cockroach or Prussian cockroach (blattellagermanica) and American cockroach (periplanetaamericana).
Medical Significance: mechanical carriers of pathogens of infectious and invasive diseases (typhoid, paratyphoid, dysentery, diphtheria, tuberculosis, helminth eggs, protist cysts, etc.). cockroaches can attack sleeping babies, gnaw the epidermis in the nasolabial triangle and infect.
Measures to combat mosquitoes, mosquitoes, flies, cockroaches.
Measures to combat mosquitoes are reduced to the following areas:
Immediate protection against mosquito attack (wearing closed clothing, use of repellents, notching the windows of residential premises, zooprophylaxis - the creation of biological barriers ( livestock farms) between mosquito breeding sites and residential buildings, etc.).
Fight against winged mosquitoes - spraying insecticides in places of wintering and overnight stays of mosquitoes (basements, attics, barnyards).
Fight against larvae:
A) drainage of small, not having economic importance, reservoirs;
B) the use of pesticides;
C) shading of reservoirs with trees;
D) land reclamation work on draining swamps, deepening reservoirs, straightening river beds;
E) splashing on the surface of reservoirs of mineral oils that clog stigmas;
E) breeding gambusia fish (biological control method)
Mosquito control measures: treatment of residential premises with insecticides, screening windows, the use of repellents.
To fight cockroaches insecticides (dichlorvos, karbofos), borax baits are used, ecological methods are used (flowers must not be watered at night, food leftovers, leftovers left on the tables, it is necessary to regularly clean the room, seal cracks in the floors, etc.)
Mosquitoes of this genus are found everywhere except Antarctica. However, only in endemic areas is mosquito transmission possible. different types.The persistent mosquito population and the continued possibility of mosquito infection with Plasmodium malaria poses a risk of repeated outbreaks of malaria in humans.
Mosquito development.
Evolution occurs in four stages: egg, larva, pupa, and adult. The first three stages take place in water and the adult insect lives for 5-14 days, depending on the species and ambient temperature.
Adult females lay 50-200 eggs. Eggs are laid in water, are not resistant to desiccation and open within 2-3 days, when adverse conditions may exist until the next stage up to 2-3 weeks.
Larvae of mosquitoes of the genus Anopheles are not adapted to breathing in water and therefore are located near the surface, breathe through spiracles located in the 8th segment of the abdomen.
The larvae feed on algae, bacteria and other microorganisms and swim in jerky movements. Larvae also develop in 4 stages, the change of stages is accompanied by a change in the outer chitinous shell - molting. For the development of the mosquito, it is necessary to have reservoirs with fresh, clean water - swamps, mangrove swamps, rice fields, grassy ditches, banks of streams and rivers, temporary rainwater reservoirs, possibly in pools and even in leaf axils filled with water.
The mosquito pupa is shaped like a comma, and is also located near the surface of the water for breathing. The duration of evolution from an egg to an adult mosquito depends on the species and habitat conditions, averaging 10-14 days in tropical conditions.
adult mosquitoes
Like all mosquitoes, adult anophelines have a head, thorax, and belly. On the head are eyes, sensory antennae, a proboscis for food. On the chest are 3 pairs of legs and a pair of wings. The stomach contains the digestive and reproductive organs. The abdomen can increase significantly in size as it fills with blood and the eggs mature. Blood is digested over time. Mosquitoes of the genus Anopheles can be distinguished by the palps located next to the proboscis, by the presence of a distinct pattern on the wings, as well as by their typical position before the bite. After transformation from a pupa, adults are not very active for several days, males gather in flocks to attract females for mating. Males live for about a week, feeding on plant nectar. Female individuals can also feed on nectar, but for the normal development of offspring they need to receive blood. After the bite, the females rest for several days, during which time the blood is digested and the eggs mature. The duration depends on external conditions usually takes 2-3 days in tropical conditions. As soon as the eggs are fully mature, the female lays them in a pond, and again looks for an opportunity to feed on blood until she dies. The life span of the female reaches 1 month.
Factors associated with malaria transmission and malaria control
For the transmission and development of plasmodia in the body of a mosquito, a certain life span of the intermediate mosquito host is necessary. On average, it takes 10 to 21 days for Plasmodium to develop into a form that is infectious to humans. Therefore, reducing the life of a mosquito will lead to a decrease in human morbidity. This is facilitated by the use of insecticides.
Feeding factor of mosquitoes in the twilight (active at dusk or dawn), or nocturnal (active at night) period, the place of feeding and rest after feeding is outdoors (exophilic and exophagic) or indoors (endophilic and endophagic). Limiting the ability of the mosquito to bite at its convenient time and place through the use of mosquito nets and the construction of facilities with limited access will also lead to limiting the transmission of malaria from the mosquito to humans.
The factor in reducing the number of places for the development of the aquatic phase of the mosquito is the drainage of swamps, the distance from dwellings.
insecticide resistance
Resistance to chemicals can occur fairly quickly due to birth a large number generations during the year. There are over 125 mosquito species with resistance to one or more insecticides.
Modern developments.
Some species of Anopheles are able to independently eliminate plasmodia that have entered the body. These species are being carefully studied with the goal of introducing a similar mechanism to the entire mosquito population.
malarial mosquito is a carrier of malaria, the most common disease in the globe, Japanese encephalitis and brungiosis. Malaria is prevalent in more than 100 African countries, South America and Asia. Malaria affects millions of people every year. So in 2014, 214 million cases of the disease were registered. 480 thousand patients died of malaria.
The maximum number of cases and deaths (up to 90%) occurs in countries African continent located south of the Sahara, where the most severe form of the disease, tropical malaria, is recorded. Cases of malaria have been reported in India, Sri Lanka, Vietnam, Brazil, the Solomon Islands and Colombia. About 1 million children die from malaria every year. In a number of countries where malaria is not common, more than 30 thousand cases of “imported” malaria are registered, 30% of which are fatal.
Rice. 1. Prevalence of malaria.
Family Culicidae(mosquitoes) belong to the suborder Nematocera(long-haired). The most common mosquitoes of the genus Culex, Anopheles(subfamily Anophelinae), Aedes, Culiceta, Mansonia(subfamily Culicinae). Plasmodium malaria is transmitted by female Anopheles mosquitoes. Of the 400 species of Anopheles mosquitoes, only 30 are carriers of this infection.
Malarial mosquitoes transmit 4 types of malarial Plasmodium to humans:
- Plasmodium vivax is the causative agent of three-day malaria.
- Plasmodium malariae is the causative agent of four-day malaria.
- Plasmodium falciparum is the causative agent of tropical malaria.
- Plasmodium ovale - causative agents of malaria, similar to three-day.
Rice. 2. The bite of a malarial mosquito (photo on the left) and a non-malarial mosquito (photo on the right).
Rice. 3. At the time of the bite, the back of the abdomen of the malarial mosquito rises and is at an angle to the skin.
Rice. 4. Anopheles mosquito bite. In a calm state, the wings of females fold along the abdomen in a horizontal state.
What does a malarial mosquito look like: the structure of an insect
The mosquito's eyes are scalloped and consist of many ommatidia.
Rice. 5. The mosquito's eyes are scalloped and consist of many ommatidia.
oral apparatus
oral apparatus mosquito is a piercing and cutting tool, represented by a proboscis, which consists of the upper and lower lips, the hypopharynx (subpharynx) and two pairs of upper (mandibles) and lower (maxillas) jaws.
The lower lip is a tube. It serves as a support for piercing stilettos. Blood passes through it during absorption. Blood is consumed only by females, for whom it serves as a nutrient for the maturation of eggs. Males feed only on plant juices, so the piercing parts of their mouth apparatus are atrophied.
The organs of touch and taste in mosquitoes are 5-segmented palps extending from the base of the lower jaws. Their length and shape are distinguishing features of malarial and non-malarial mosquitoes: in malarial mosquitoes, the palps and the length of the proboscis are equal in length and have club-shaped thickenings at the ends, in non-malarial mosquitoes, the palps are longer than the proboscis and do not have club-shaped thickenings at the ends.
Rice. 6. The structure of malarial mosquitoes.
Antennas
Antennae or antennae, located on the front surface of the head, perform the function of recognizing smells and touch. In males, the antennae are covered with thick and fluffy hairs, in females - short and sparse.
Legs, wings and halteres
The malarial mosquito has a pair of wings, three pairs of thin legs and halteres that are attached to the mosquito's chest.
mosquito wings
The wings of malarial mosquitoes are elongated-oval with large quantity transverse and longitudinal veins, covered with microtrichia (small hairs). Different types of mosquitoes have their own pattern. In malarial mosquitoes, 4 brown spots can be seen on the wings. Nonmalarial mosquitoes have alternating dark and light spots. At the mosquito at rest, the wings fold along the abdomen in a horizontal state.
Abdomen
The abdomen of mosquitoes consists of ten segments, the ninth and tenth of which are part of the external genital apparatus. The body of mosquitoes is elongated, the head is small, the legs are long. When landing in mosquitoes of the genus the back of the abdomen is raised; in non-malarial mosquitoes, the abdomen is parallel to the skin.
Rice. 7. Bite of female malarial (left photo) and non-malarial (right photo) mosquitoes.
Rice. Fig. 8. The structure of a mosquito of the genus Culex (left figure) and Anopheles (right photo).
Biological features of mosquitoes
The life of a female consists of repeating cycles: searching for a host (prey), bloodsucking, developing sexual forms, flying to a reservoir, and laying eggs. Such cycles are repeated 8 to 10 times. In this case, up to 20% of females die.
Places of breeding
Before the maturation of eggs, female malarial mosquitoes hide in well-lit and heated, vegetation-rich reservoirs. female mosquitoes of the genus Culex hiding near housing - in pits, ditches, barrels, sheds, attics, burrows, artificial reservoirs.
Locations of the attack
To mature eggs, female mosquitoes need human or animal blood. females Anopheles maculipennis more often attacks in houses, Anopheleshyrcamus- in the open air, females of the genus Cules- near dwellings, in houses, near settlements.
seasonality
The period of activity of female malaria mosquitoes from spring to autumn. The maximum of those bitten is recorded in July and August. Female nonmalarial mosquitoes are more likely to bite humans in August and September. In the tropics, the period of activity of mosquitoes reaches 8 - 10 months, in the equatorial countries of Africa - all year round.
egg laying
Females of malarial and non-malarial mosquitoes lay their eggs one by one on the water, non-malarial mosquitoes also lay their eggs near the water - at the bottom of a dried-up reservoir or its shore.
Rice. 9. Pictured is a Culex mosquito bite.
Mosquito development cycle
In mosquitoes of the genus Culex the eggs are glued to each other and form a "boat" floating freely in the water. They have an elongated shape and an extended front part with a saucer-shaped rim, which allows them to float on the surface of the water. A characteristic concavity is formed on the surface of the "boat".
Eggs of a female mosquito located one by one, bordered by a concave belt, have 2 air chambers-floats that allow them to stay on the surface of the water.
eggs of the female genus Aedes lays on the bottom of drying reservoirs, are located one by one, oval in shape, micropyle (small entrance) is located at one of the ends. After 2-14 days, larvae emerge from the eggs.
Rice. 10. Mosquito eggs.
Rice. 11. Eggs and larvae of mosquitoes of the genus Culex.
Larvae
The larvae feed intensively and grow. Until the moment of pupation, they increase by more than 500 times in volume and more than 8 times in length.
- In mosquito larvae Culex and Aedes there is a special respiratory tube-siphon, which departs from the penultimate (ninth) segment of the abdomen. With the help of a siphon tube, the larvae are held at the surface of the water, located perpendicular to the surface of the reservoir. Air enters the siphon through spiracles. This design helps mosquitoes survive in heavily polluted water bodies, ditches, puddles, water vessels and tree hollows.
- In mosquito larvae no siphon tube. A pair of stigmas extending from the penultimate segment of the abdomen help them to stay parallel to the water surface. The larvae survive only in clean water bodies.
The nutrition of the larvae occurs through the flow of liquid with microscopic nutrients, which is created by the fans located at the head end. The particle size is limited, which is taken into account when using dust-like pesticides.
Larvae in their development go through 4 stages, separated by molts. After the last molt, the larvae turn into pupae.
Rice. 12. Anopheles mosquito larva (left photo) and Culex (right photo).
Rice. 13. Anopheles mosquito larva at the surface of a reservoir (top picture) and Culex (bottom picture).
Rice. 14. In the photo, the larvae of the Anopheles mosquito.
pupae
In the pupal stage, the insect develops eyes, wings, proboscis and legs. Mosquito pupae are mobile.
pupae Culex and Aedes have a cylindrical breathing siphon. pupae have a respiratory siphon in the form of a "mail horn". This stage ends with the exit from the chitinous shell of a winged mosquito - an imago. The phase of development in water before the release of the winged form lasts 14-30 days. The warmer the water, the faster the release of winged forms of insects.
Rice. 15. Anopheles pupa (left photo) and Culex pupa (right photo).
Rice. 16. Anopheles pupa (left picture) and Culex pupa (right picture).
Winged forms
- Malarial mosquitoes live near human dwellings - in non-residential buildings, near water bodies (places of breeding). During the day, females and males hide in dark corners. At dusk, they fly out in search of food, which they find by smell. Insects feed on vegetable juices, milk, use a solution of sugar and liquid from cesspools.
- After mating, the female must suck on blood, without which the eggs do not develop, for which they attack humans, domestic and wild animals. Females feel accumulations of animals at a distance of up to 3 km.
- Females suck blood from 0.5 to 2 minutes and suck out blood more than their body weight - up to 3 mg. If this happens in spring and summer, then eggs are formed in the female. If in the fall, a fatty body is formed from the pumped blood, and the eggs do not develop.
- After that, they hide in dark places, most often in human dwellings and premises where livestock is kept. After 2-14 days, larvae emerge from the eggs.
- Insects hibernate in basements, cellars, pantries, rooms for animals - wherever there are no drafts and light. In winter, mosquitoes are in a state of stupor. The ability to lay eggs in the female appears already in the middle of winter, but only after sucking blood. Mosquitoes leave their shelters en masse only in warm time year, bite at dawn and dusk.
- AT warm days females migrate to the reservoir, where they lay their eggs. The first laying of eggs is carried out by overwintered females.
- After laying their eggs, the females fly away in search of food. One female may repeat the egg-laying cycle several times.
Plasmodium malarial vectors are mosquitoes of the genus Anopheles. During wintering, the sporozoites in the body of the female die. For its infection, a new infection from a sick person is required.
Rice. 17. Winged form of mosquitoes (adults) Anopheles (picture above) and Culex (picture below).
Ecology of adult mosquitoes
There are a number of features in mosquitoes of the genus , the knowledge of which makes it possible to assess their role in the transmission of infection:
- Female malarial mosquitoes feed not only on plant nectar, but also suck the blood of mammals, which allows them to survive for a long time in winter period and ripen eggs.
- female mosquitoes of the genus and other types of mosquitoes dual nature food are carriers of a number of diseases. The malarial mosquito carries 4 species of malarial plasmodia, the causative agent of Japanese encephalitis and one species of Brugia. Mosquitoes of the genus Culex are carriers of Japanese encephalitis and 2 types of Japanese encephalitis filariae.
- In female mosquitoes of the genus Culex and Aedes the presence of desosomes in the cells of the intestinal epithelium ensures their adhesion. In female mosquitoes of the genus intestinal epithelial cells are poor in desosomes.
- Proboscis cutting apparatus has teeth along the edge. Other types of mosquitoes do not have them. The hypopharynx, which serves to pour out saliva, has finger-like outgrowths at the ends, which increases the number of sporozoites that have entered the blood of a person or animal. This is also facilitated by the presence of a gap in the salivary canal. Dissected salivary canals allow the female mosquito to drink blood 2 to 3 times longer than normal mosquitoes.
- Mosquitoes of the genus pierce the skin at an angle. The narrow mouthparts and the curvature of the stabbing parts help to suck blood from the most superficial capillaries, where the maximum number of young sporozoites accumulate in a malaria patient.
Rice. 18. Schematic representation of the moment of bloodsucking by the female Anopheles.
Mosquitoes, or real mosquitoes, or blood-sucking mosquitoes (lat. Culicidae) are a family of two-winged insects belonging to the group of long-whiskers (Nematocera). There are more than 3,000 species of mosquitoes in the world, belonging to 38 genera. Representatives of 100 species belonging to the genera of true mosquitoes (Culex), biters (Aedes), Culiseta, malarial mosquitoes (Anopheles), Toxorhinchites, Uranotaenia, Orthopodomyia, Coquillettidia live in Russia.
Mosquitoes are insects thin body(length 4-14 mm), long legs and narrow transparent wings. The body color is yellow, brown or gray. The abdomen is elongated, consisting of 10 segments. The chest is wider than the abdomen. The legs end in a pair of claws. The wings are covered with scales, clusters of which sometimes form spots. Antennae long, composed of 15 segments. The oral apparatus is of a piercing-sucking type. In females, the proboscis is long and consists of piercing bristles, in males - without them.
Mosquito insects have 4 phases of development: egg, larva, pupa, adult. At the same time, all phases, except adults, live in water bodies. Mosquito larvae and pupae living in water breathe atmospheric air through respiratory tubes, exposing them to the surface. Mosquito larvae - filter feeders or scrapers - feed on aquatic microorganisms. The nutrition of adults is often dual: females of most mosquito species drink the blood of vertebrates: mammals, birds, reptiles and amphibians; at the same time, males of all mosquito species without exception feed on the nectar of flowering plants.
BREEDING. Female mosquitoes during the mating season attract the attention of males with a characteristic thin sound, reminiscent of a squeak, which is created with the help of wings. Mosquitoes pick up sound vibrations with their sensitive antennae. Females squeak a little thinner than males, young ones - not like old ones. And male mosquitoes hear this and make a choice in favor of adult females. Mosquitoes form a swarm, where males and females mate. The female mosquito lays 30-150, and even 280 eggs (for malarial mosquitoes) every 2-3 days. The egg develops into an adult mosquito within a week. To reproduce eggs, mosquitoes require blood, so the egg-laying cycle is directly dependent on blood consumption. Eggs are laid in stagnant or low-flowing bodies of water on the surface of the water ( genera Anopheles and Culex), on moist soil at the edge of water bodies that dry up in summer and are flooded in spring, or stick to objects floating and washed by water (Aedes).
MEDICAL SIGNIFICANCE. Mosquitoes are an integral component natural communities. The number of groups of animals for which they are food is in the tens. In addition, mosquitoes, like other insects, whose larvae actively feed in aquatic environment, are one of the main reasons for the inexhaustibility of soils
Mosquitoes are carriers of dangerous diseases: malaria, yellow fever, dengue and some encephalitis. Of these diseases, malaria alone causes about two million deaths each year. In addition, their bites can cause itching and allergic reaction.
| Phylum: Arthropoda P/type: Tracheata Class: Insecta Order: Diptera Family: Culicidae Genus: Culex | Phylum: Arthropoda P/phylum: Tracheata Class: Insecta Order: Diptera Family: Culicidae Genus: Anopheles |
| Imago. Female: mandibular palpi several times shorter than proboscis. Male: mandibular palps longer than proboscis, without club-shaped thickenings at the ends. When landing, the body is bent, the abdomen is inclined to the substrate or parallel to it. | Female: mandibular palps equal in length to proboscis. Male: mandibular palps are equal in length to the proboscis, with club-shaped thickenings at the ends. When landing, the body is kept elevated and at an angle to the surface. |
| Eggs. They do not have a belt and cameras. They are deposited on the surface of the water in groups in the form of boats. | Lay scattered on the surface of the water. Each is bordered by a concave belt and equipped with swimming chambers. |
| Larvae. They have a respiratory siphon on the penultimate segment. In water, they are located at an angle, attaching by a siphon to the surface of the water. | The respiratory siphon is absent. They have only one pair of respiratory openings on the penultimate segment and therefore are located horizontally in the water. |
| Pupae. The chrysalis is shaped like a comma. The breathing tube has a cylindrical shape. | The chrysalis is shaped like a comma. It differs in the structure of the respiratory tube, it has a conical shape. |
They are widely distributed on all continents except Antarctica. Absent in desert areas and on far north(the extreme northern point of the range is the south of Karelia). There are about 430 species in the world fauna, in Russia and neighboring countries- 10 types. In Russia, they live in the European part and Western Siberia. They do not live in Eastern Siberia, where winters are too harsh for them. A mosquito becomes infected with malarial plasmodium from a person - a patient or a carrier. The malarial Plasmodium goes through a cycle of sexual reproduction in the body of the mosquito. An infected mosquito becomes a source of infection for humans 4-10 days after infection and remains so for 16-45 days. Mosquitoes serve as carriers of other types of Plasmodium that cause malaria in animals.
Malaria: pathogenic significance, diagnosis, prevention.
In malaria caused by P. malariae, the intervals between attacks are 72 hours. Asymptomatic carriage is common.
In tropical malaria, at the onset of the disease, the intervals between attacks may be different, but then they are repeated every 24 hours. With this type of malaria, the danger is great lethal outcome due to complications from the central nervous system or kidneys. Tropical malaria is especially dangerous for Caucasians.
A person can become infected with malaria not only through the bite of an infected mosquito. Infection is also possible through hemotransfusion (transfusion) of infected donor blood. Most often, this method of infection occurs with four-day malaria, since there are few schizonts in erythrocytes, they may not be detected when examining the blood of donors.
Diagnostics
It is possible only during the period of erythrocyte schizogony, when the pathogen can be detected in the blood. Plasmodium, recently penetrated into the erythrocyte, has the form of a ring. The cytoplasm in it in the form of a rim surrounds a large vacuole. The nucleus is displaced to the edge.
It occupies almost the entire erythrocyte. Further, fragmentation of the schizont occurs: a deformed erythrocyte contains many merozoites, each of which contains a nucleus. In addition to asexual forms, gametocytes can also be found in erythrocytes. They are larger, do not have pseudopods and vacuoles.
Prevention
Identification and treatment of all patients with malaria (elimination of the source of mosquito invasion) and the destruction of mosquitoes (elimination of vectors) with the help of special insecticides and reclamation works (draining swamps).
When traveling to areas unfavorable for malaria, you should take prophylactic antimalarial drugs, protect yourself from mosquito bites (use mosquito nets, apply repellents to the skin).
Mosquitoes. Their body is divided into head, chest, abdomen. On the head are large compound eyes, antennae (antennae), palps and proboscis. Males differ from females in strongly pubescent antennae. The proboscis, with which the mosquito pierces the skin of humans and animals, consists of the upper and lower lips, a pair of upper and lower jaws, and the hypopharynx (the proboscis itself). All elements of the proboscis are involved in piercing the skin, except for the lower lip, which bends at the time of the bite and is a case in which all the piercing parts are embedded. In males, parts of the oral apparatus are underdeveloped; they feed on plant sap.
Eggs are oblong, 1 mm long. The body of the larva is divided into head, thorax and abdomen. The larva goes through 4 stages and turns into a comma-shaped pupa.
Biology and ecology of malarial mosquitoes
In spring, at a temperature of 5-7 0 C, overwintered females fly out, attack animals or humans, and suck blood. After saturation with blood, the females hide in secluded places: they digest the blood and ripen the eggs.
The period of time from the moment of bloodsucking to the laying of eggs is called the gonotrophic cycle. During her life, the female has time
P
Rice. 6. Heads of mosquitoes: A - culex, B - anopheles: a - females, b - males, 1 - eyes, 2 - antennae, 3 - labial tentacles, 4 - proboscis.
Biology and ecology of nonmalarial mosquitoes
These include representatives of the genera Aedes and Culex.
Nonmalarial mosquitoes of the genus Aedes overwinter in the egg stage. Females lay their eggs in depressions in the soil, which are filled with melt water in the spring of the following year, where the larvae develop. During the summer
Rice. 7. Main features malarial and non-malarial mosquitoes.
1 - Anopheles egg floats; 2 - spiracles of larvae; 3 - respiratory tubes of pupae;
4 - antennae (antennas); 5 - lower jaw palps; 6 - proboscis; 7 - eyes; 8 - thoracic; 9 - the abdomen of an adult mosquito.
usually one generation is bred. The maximum number of mosquitoes is observed at the beginning of summer (June). Mosquitoes of the genus Culex are thermophilic, and in the forest belt their maximum number is observed at the end of summer. Breeding sites are permanent and artificial reservoirs.
The larvae live in water and feed on microscopic particles that are on the surface of the water. The pupae do not feed.
The maximum number of mosquitoes is observed at the beginning of summer (June). Mosquitoes of the genus Culex are thermophilic, and in the forest belt their maximum number is observed at the end of summer. Breeding places are permanent and artificial reservoirs: pits, ditches, barrels with rainwater. Females hibernate in cellars and burrows.
Epidemiological significance of mosquitoes.
Among malarial mosquitoes, the main vector of malaria is the Anopheles maculipennis mosquito, represented by five subspecies. The species A.hyrcanus is widespread in the Far East.
Mosquitoes, along with an unpleasant injection, are dangerous because they carry pathogens of various diseases. The most dangerous tropical species of mosquitoes, which, when bitten by a person, infect malaria and yellow fever.
MALARIA - an infectious disease caused by malarial plasmodia, characterized by periodic bouts of fever, enlargement of the liver and spleen, anemia, recurrent course.
The life cycle of the malaria pathogen includes two hosts: humans and mosquitoes. In the body of a mosquito-carrier, plasmodia undergo sexual development (sexual process and sporogony), in the human body - asexual development (schizogony).
All clinical manifestations of malaria are due to erythrocyte schizogony. Its consequence is a malarial attack that occurs in response to the release of merozoites into the plasma during the destruction of erythrocytes.
The possibility of spreading malaria in any area is determined by a combination of a number of conditions. It is necessary that there are those species of malarial mosquitoes that are susceptible to infection by malaria pathogens. The number of mosquitoes should be high enough, and the life expectancy should exceed the period of development of the pathogen in mosquitoes. The summer generations of mosquitoes (June) have the greatest epidemiological significance in the transmission of malaria. In the southern regions, 5-6 generations of mosquitoes may have epidemiological significance. Mosquitoes of the last generation of plasmodia do not transmit, since in the fall, leaving for the winter, they feed on plant juices, and in the spring they die before they have time to complete sporogony.
Mosquitoes of the genera Aedes and Culex are specific carriers of many arbovirus infections: Japanese encephalitis, yellow fever, dengue fever, etc.
JAPANESE ENCEPHALITIS - syn. mosquito encephalitis, autumn encephalitis - a viral transmissible zoonosis with natural foci. In 1933-1936. Japanese researchers discovered the virus that causes the disease and proved its transmission through blood-sucking mosquitoes.
The reservoir of the virus in nature are wild mammals and birds. Nonmalarial mosquitoes serve as carriers of the virus to humans and animals.
Seasonality is one of the main features of Japanese encephalitis.
The virus accumulates and multiplies in nervous tissue. There is swelling of the membranes of the brain, small hemorrhages in the soft membranes and substance of the brain.
Point hemorrhages occur on serous and mucous membranes, parenchymal degeneration of the heart muscle, kidneys, liver is observed, pneumonic foci appear in the lungs.
The incubation period lasts from 5 to 14 days. The onset of the disease is acute, a sharp rise in body temperature. Chills, headache, especially in the forehead, pain in the lower back, abdomen, limbs, nausea, vomiting are the first symptoms of the disease.
When the virus enters the brain parenchyma, brain tissue edema develops. From 3-4 days of illness, symptoms of a focal lesion of the nervous system appear, depression of consciousness increases up to coma. Sometimes there is delusions, hallucinations.
Lethal outcomes are 25-80%. Death occurs in the first 7 days with a coma, convulsive seizures. Of the residual manifestations, the most common are mental disorders in the form of a decrease in intelligence, psychosis.
Diagnosis based on clinical, epidemiological and laboratory data. Of decisive importance in the diagnosis is the isolation of the virus from the cerebrospinal fluid and blood of patients. The brain of the deceased is examined for the presence of the virus.
Prevention. To fight mosquitoes, to create active immunity in the population and domestic animals in endemic foci, an inactivated vaccine is used, obtained from an emulsion of the brain of infected mice and neutralized with formalin.
YELLOW FEVER - a transmissible natural focal disease.
The causative agent is a virus . The vector of the infection is a mosquito of the genusAnopheles.
The incubation period lasts from 3 to 6 days. Clinically, two periods of the disease are distinguished. The first period, the so-called stage of hyperemia, is characterized by an acute onset with fever, chills, headache, and severe back pain. On examination, attention is drawn to a sharp hyperemia and puffiness of the face, a pronounced injection of the vessels of the sclera (the eyes are "bloodshot"), swelling of the lips, and a bright red color of the tongue. Against the background of a high febrile reaction, tachycardia and an increase in blood pressure are observed. These phenomena persist for 3-4 days, then there is a temporary improvement.
With moderate and severe course of the disease, after remission, the second phase occurs, which is accompanied by swelling and redness of the skin, the latter are replaced by pallor, the body temperature rises again to 39-40 0 .
In the future, the manifestations of the hemorrhagic syndrome increase - vomiting of the color of coffee grounds appears. The skin and sclera may become icteric. The liver and spleen are enlarged, painful on palpation. The prognosis is currently relatively favorable.
DENGUE FEVER, joint fever, seven-day fever is an acute viral zoonosis with natural focality, occurring in tropical and subtropical countries.
The causative agent is the dengue virus (dandy) enters the blood of humans and animals when bitten by non-malarial mosquitoes of the genusAedes. With blood it spreads to various organs (kidneys, liver, heart, brain), causing degenerative changes in them.
The virus that entered the human body with mosquito saliva multiplies in epithelial cells for 5-16 days, after which it spreads to the kidneys, liver, muscles, brain and other organs.
In the classic form of fever, the disease begins acutely with an increase in temperature to 39-40 0 , the appearance of chills, severe weakness. From the first day there is a severe headache, myalgia, mainly in the muscles of the back, pain in the sacrum, spine, joints (especially in the knees). The movements in the joints are limited and the patient's gait becomes slow and tense (like a dandy). There are pains during the movement of the eyeballs, there may be violations of cardiac activity. On the 3-5th day of illness, a rash appears on the trunk, which spreads to the face and limbs, merging and forming a peculiar pattern. In severe and moderate forms of the disease, lymphadenopathy, anorexia, perversion of taste sensations, and constipation are noted. The liver is slightly enlarged.
The first phase of the disease lasts up to 5 days, then the patient's condition improves. The repeated rise in temperature is usually easier and lasts 2-3 days. The total duration of illness is on average 10 days.
The prognosis is usually favorable, mortality does not exceed 0.1-0.5%.
Diagnosis is based on epidemiological prerequisites and the results of clinical and laboratory examination of patients. Serological tests are also used.
Prevention . Carrying out a set of measures to combat mosquitoes, protecting people from mosquito attacks with the help of repellents and protective nets. A vaccine has been created.
VUCHERERIOZ - transmissible anthroponosis, characterized by a chronic course and a predominant lesion of the lymphatic system.
Pathogen – Wuchereria bancrofti . The female is 80 mm long, the male is about 40 cm long. The females are viviparous, the larvae are microfilariae.
Intermediate hosts of the helminth are various species of mosquitoes of the genusAnopheles, Culex, Aedes, Mansony. Microfilariae, once in the body of a mosquito, develop to the invasive stage.
Wuchereriosis is the most common human filariasis. It is found in many regions with tropical and subtropical climates.
The development of wuhereria in the human body is very slow and they reach sexual maturity only 3-18 months after the introduction of the infective larva into the tissue.
There are three stages pathological changes in the lymphatic system: acute, subacute and chronic.
Clinical symptoms of the disease appear between 5-18 months after possible infection. The most characteristic manifestation late stages disease is elephantiasis (elephantiasis) of the lower extremities, scrotum, less often the upper extremities, mammary glands, eyelids. The legs can reach colossal sizes, taking the form of shapeless blocks covered with thick transverse folds. Papillomatous and warty growths, eczema, trophic ulcers appear on the skin of the extremities, muscles atrophy.
Diagnosis. The presence of lymphangitis in a patient, accompanied by a general febrile reaction, enlarged lymph nodes, blood eosinophilia, and often the development of elephantiasis, makes one think of wuchereriosis. Microfilariae are found in the blood. Immunological methods are also used to diagnose wuchereriosis.
Prevention . Identification and treatment of patients, the fight against vectors, protection from their attacks.
Mosquitoes of the subfamily Culicinae are mechanical carriers of some viruses and bacteria, in particular tularemia (see fleas).
Mosquitoes subspecies Culex pipiens molestus breed all year round in puddles of water in basements, underground galleries of heating plants, subways, swimming pools, etc. Through the ventilation systems of buildings, female mosquitoes can enter living quarters and attack residents even on the upper floors of buildings. The bites of these mosquitoes are painful.
3.2.2. Midges. Morphology, biology, epidemiological significance of midges.
M Rice. 8. Midge(simulidae)
The general body color of midges is black or dark brown. The proboscis is short, thick, much shorter than the head.
The larvae are worm-like. So-called fans are visible on their heads - bundles of thick bristles that serve to filter water and trap food. The chest bears an unpaired protrusion - a “leg”, seated at the end with tiny hooks. Similar but more numerous hooks are located at the posterior end of the body. These organs serve as attachment devices, with the help of which (as well as with the help of a web thread secreted by special glands) the larva resists the flow of water and is held on underwater objects.
The pupae of midges are immobile. They are inside cocoons tightly attached to the substrate. The walls of the cocoons are fibrous, branched respiratory filaments of pupae stick out. Larvae and pupae breathe oxygen dissolved in water.
The development of midges occurs in streams and rivers. Fertilized females lay eggs in water, sticking them to the leaves and stems of plants, stones and other objects submerged in water.
Unlike biting midges, midges are capable of long-distance migrations and can be found at a distance of 5-10 km from the breeding site. Only females drink blood. Midges attack only in the open air and during daylight hours.
Midges are common in all landscape zones of Russia, including the tundra. AT most they are found in the forest zone, especially in areas along the rivers of Siberia and the Far East.
Midges primarily cause harm as bloodsuckers. Without the use of protective equipment, a long stay in the open air in places where there are a lot of midges is impossible.
The importance of midges as carriers of pathogens is still poorly understood. In the tropical zone of Africa, South and Central America, midges are intermediate hosts of the filaria Onchocerca volvulus, which causes onchocerciasis person.
Midges can be mechanical carriers of pathogens tularemia(see above).
Prevention: a) public - the destruction of midges in places of permanent residence of people; b) personal - protection against midge bites (use of repellents and protective nets).
ONCHOCERCOSIS - transmissible anthroponosis.
Both adult worms and their larvae have a pathogenic effect on the human body. In the presence of mature individuals in the subcutaneous tissue, a connective tissue capsule usually forms around them. The presence of microfilariae in the lymphatic vessels leads to infiltration of the vascular wall and adjacent tissues, as well as to the development of lymphostasis. The penetration of microfilariae into the organ of vision causes the development of inflammatory reactions, the formation of small nodules in the conjunctiva, and hemorrhages.
Onchocerciasis can occur in the form of erased, subclinical forms and severe cases, accompanied by blindness, elephantiasis, and a violation of the protective function of the skin.
The first manifestations of the disease usually appear 2 months after infection. Patients develop a rash on their body and usually have a fever. When microfilariae appear in the thickness of the skin (after 6-8 months from the moment of infection) on the skin of the back, buttocks, upper limbs, an abundant papulopapular rash is found, accompanied by severe itching, malaise, fever, headaches. In the future, ulcers remain in place of the papules, healing with the formation of scars.
In the late phases of the disease, patchy depigmentation of the skin occurs, mainly on the back and neck, the so-called leopard skin or crocodile skin. In the final stages, the skin loses its elasticity so much that it takes on the appearance of crumpled parchment paper.
Onchocerciasis is accompanied by severe lesions of the organs of vision: in the anterior chamber - the conjunctiva, cornea, iris, and in the posterior chamber - the choroid, retina and optic nerve. In severe cases, blindness occurs.
Diagnosis is based on the detection of microfilariae in skin sections, in the eye - using an ophthalmoscope.