Tsetse fly: lifestyle and harmfulness of an African insect

Without exaggeration, the tsetse fly can be considered an enemy of humanity. Because of insect bites, about 50 thousand people die annually in African countries. Carriers of sleeping sickness do not allow the local population to develop the best agricultural sites located near water bodies. Obligatory parasites have a long life span. Tsetse fly captured about 10 million square meters. km of the African continent, people and animals living next to it are at daily risk of contracting a deadly disease.

Insect classification

Tsetse (Glossina) - a genus that unites 23 species of flies of the family Glossinidae. Most representatives of this genus are carriers of sleeping sickness of humans and Nagans - animals. All species are divided into three groups by habitat:

• G. palpalis - live on the banks of rivers and other bodies of water;
• G. fusca - settle in tropical forests;
• G. morsitans - found in dry savannahs.

Appearance Features

As in all representatives of the diptera squad, tsetse flies have 3 main parts of the body: head, chest, and abdomen. The size of the insect is 9-14 mm. Large facet eyes of a dark brown color stand out on the head. The organs of vision are clearly divided among themselves.
You can distinguish a dangerous insect from an ordinary housefly by four characteristic signs:

• Short antennae have hairs bifurcated at the ends.
• A solid proboscis, capable of piercing the skin of a buffalo and antelope, is directed forward.
• Folding the wings on the back of one another at rest.
• On transparent wings, a vein pattern in the form of an ax.

The chest consists of three segments fused together. Its color is reddish-gray, with four brown longitudinal stripes on the back side. Three pairs of legs and wings are attached to the chest. The abdomen is short and wide. In the process of feeding, it increases in size. The insect is able to drink an amount of blood equal to its own weight. In females, the reproductive organ, the uterus, is located in the abdomen. It is large enough to accommodate a third-instar larva.

Information. Why is the tsetse fly so called? The name "tsetse" or tsetse (tse-tse) in the language of the African tribe Bantu means - "fly." This word is translated into other local languages.

The oral apparatus is suited for sucking blood. It consists of a solid lower lip, in which a sharp tongue is hidden, and an elongated upper lip covering it. After skin damage, saliva is introduced, which does not allow blood to clot.

Area of ​​resettlement

The tsetse fly is found in Africa. Its habitat extends south of the Sahara, between 14 and 20 parallel to the south. w. It is noted in the equatorial and subequatorial zones. Gabon, Cameroon, Nigeria, Uganda, Kenya - all in the list of 37 countries. In the territory where the tsetse fly lives, 32 of the world's poorest states. Territory with fertile lands cannot be used due to the presence of the parasite. Scientists are in search of means to destroy Glossina, colossal funds are being spent on research.

African capture story

The beginning of the mass distribution of a dangerous insect is considered to be 1887. It was then that the plague virus was introduced from Europe, causing a massive death of wild animals and livestock. Many local residents who did not have immunity to the disease died out. A few years later, the pastures were overgrown with shrubs, which became a refuge for the tsetse fly. The reduction in the number of people has led to an increase in the number of wild animals. Several factors have developed in such a way that pests have settled in many parts of Africa where they have not previously been encountered. The spread of Glossina was accompanied by human infection with trypanosomes. Millions of people died from sleeping sickness.

Sites occupied by tsetse flies are free from human activities. Most areas have national wildlife parks.

Lifestyle

The choice of habitats and food objects depends on belonging to one of three groups.

• Palpalis - prefer forest thickets and shrubs growing near the water. Reptiles bite, attack a person.
• Fusca - the species hides in the depths of the rainforest, selects areas with high humidity and moderate temperature. In humans, it does not eat.
• Morsitans - live in savannahs in southern Africa, feed on wild ungulates and livestock. Danger to humans.

Unlike many insects, tsetse spends most of its life cycle in an adult state. Adults live 6-7 months. In the dry season, they gather at the remains of ponds, hide under the leaves, look for places where there is damp. At such a time, they almost do not fly. This is not necessary, because the food itself comes to a watering place. Females and males drink blood, eat often. What is the danger of a tsetse fly bite for an animal? It is a carrier of a type of trypanosome that causes Nagan disease. Infected animals weaken and die. The disease affects predators, artiodactyls, horses. Among the many species, zebras were safe. They are saved by a black and white color that tsetse does not perceive.

Interesting fact. Tsetse is attracted by heat and dark color. Dark-skinned animals and black people are at greater risk. They avoid white and moving objects. There are cases when two-winged bloodsuckers attacked a hot car engine.

Propagation Features

Insects mate only once. After fertilization, the females do not lay eggs, but carry them in a special bag. The larvae develop one at a time. Being in the body of a fly, they feed on the secretions of a special gland. The development of offspring takes 1-2 weeks, then it is born. The larva spends very little time outside the mother's body. She is born already in the third last age.

After a few hours, the larva burrows 2-3 cm into the soil and turns into a pupa. The solid body of the pupa is dark brown or black. In length reaches 10 mm. This phase lasts 3-4 weeks. A young fly emerges from it.

Due to the nutritional value of blood, the larva and pupa do not require additional feed resources. They exist and develop due to stocks made by adults. During its life, a viviparous female brings 8-10 larvae.

Information. Glossina fly quickly and silently, they are very persistent and tenacious. Killing a fly is not easy, even after hitting and damaging the wings, it again attacks the victim.

Harmful insects

The tsetse fly is a carrier of deadly protozoan parasites - trypanosomes. The most dangerous species is Palpalis, it spreads sleeping sickness more often than others. The protozoa, which are the causative agents of the disease, enter the body of the fly while feeding on a sick animal. In her stomach, parasites multiply and enter the salivary glands of the proboscis. It takes about 18 days to develop the parasite. The exact period depends on the air temperature. When bitten, along with the saliva, trypanosomes enter the blood of a new host. The causative agent Nagana (Nagana) goes through the same cycle in the tsetse body.

Symptoms of sleeping sickness

The causative agent of a dangerous illness is trypanosome, the simplest unicellular organism. It parasitizes in various hosts. The only way to get infected is through an insect bite. The tsetse fly spreads sleeping sickness and Chagas disease among people. As a result of infection, the nervous and immune systems suffer.

Attention. Trypanosome is a tortuous, oblong organism of 20-30 microns in size. A flagellum is located on one edge of the body. Propagated by division.

Doctors distinguish African and Latin American trypanosomiasis. African, in turn, is divided into two types:

1. West African or Gambian sleeping sickness - features a long course of the process. It is divided into two periods. The first lasts from 1 year to 5 years. He is accompanied by fever, headaches, an increase in the occipital lymph nodes, erythematous rashes. Latent course of the disease, the absence of acute symptoms leads to neglected forms. The second period is acute, drowsiness, trembling of the extremities appear, paralysis is possible. The destroyed nervous system signals noticeable mental disorders. The period in terms does not exceed 7-8 months.
2. Eastern or Rhodesian form - is distinguished by clear signs and rapid course. The brain and heart of a person is affected, death occurs after 6 months.

The Gambian form of the disease is transferred by G. papalis, and the Rhodesian - G. morsitans. When infected, a dense tumor appears at the site of the bite, painful when pressed. Its diameter is 10-20 mm.

The main symptoms of sleeping sickness that occur after a bite of a tsetse fly include:

• fever and fever;
• joint pain;
• confusion of consciousness;
• numbness of the limbs;
• sleep disturbance;
• impaired coordination.

The appearance on the arms or legs of a person of chancres resembling boils is one of the main symptoms of trypanosomiasis. After two weeks, they heal, leaving only a scar. Then begins a fever, headache. If untreated, trypanosomes affect the brain.

Treatment of human sleeping sickness

Diagnose the disease by analyzing blood and fluid from the lymph node. If the disease is detected in the first period of development and has not affected the nervous system, then the treatment is quick and effective. Special drugs pentamidine and suramin have been developed to get rid of parasites in the blood. When sleeping sickness goes into the second stage, it is more difficult to cope with it. The drugs used for treatment have serious side effects - nausea, increased pressure. The choice of means and methods of combating the disease is complicated by the constant mutation of protozoan parasites. In the second stage of the disease, the introduction of melarsoprol helps.

In Africa, 70 million people live daily at risk of contracting sleeping sickness. The risk group includes tourists visiting the tropical regions of the continent. If you suspect a tsetse fly bite, doctors advise you to immediately contact an infectious disease specialist. Timely detection of protozoan parasites gives a high chance of cure without complications. Patient treatment is selected individually, the doctor takes into account the form and stage of the disease. Tourists are advised to get a pentamidine vaccine before the trip.

The consequences of a tsetse bite on animals

Infection of livestock with trypanosomes provokes the development of Nagan disease. She has several negative manifestations:

• Decrease in working capacity of draft cattle.
• The decline in meat and milk production.
• An increase in the number of spontaneous abortions.
• The annual deaths are up to three million heads.

Animals need preventive vaccination against trypanosomiasis, but not all nomads containing thousands of cattle find the opportunity to be vaccinated. At risk are cattle, horses, and pigs.

Tsetse control methods

60 million people living in rural areas are under constant threat of sleeping sickness in Africa. At the same time, danger hung over 50 million animals.In the XX century. used various tactics of insect control:

1. Scorched earth - to reduce or completely destroy Glossina, they killed all the animals on which it fed. Having lost their food source, the flies died. The method is doubtful, gives a short-term result. One misconception was the assumption that tsetse feeds only on large mammals. Without pity they killed, antelopes, lions, elephants. It turned out that the blood-sucking parasite feeds on reptiles and rodents.
2. Deforestation is a practice similar to the previous tactic, only trees were destroyed. This deprived the adult tsetse of habitual living conditions. It turned out that deforestation does more harm than good.
3. Pesticides - pest control products were sprayed from aircraft and applied to animals. The method was ineffective.
4. Traps - one of the simplest and most primitive methods gives good results. To attract insects, an artificially created odor is used, similar to the respiration of animals or cattle urine. The trap itself is a dark cloth or buffalo skin soaked with insecticides.
5. Sterile males are one of the most successful solutions to reducing the harmful parasite population. Tsetse males are irradiated with radiation and released to insect habitats. After mating, the females cannot produce offspring; their eggs remain unfertilized. This method gave a good result in Zanzibar. The only negative is the lack of a water barrier with neighboring countries, from where healthy males can be received.

Tip. Tourists traveling to the African continent should take care of personal safety equipment. These include repellents, white protective clothing and a mesh on the face.

There is a diametrically opposite view of the significance of the tsetse fly in the development of Africa. One of the defenders of the wild, Bernard Grzimek, believes that its existence protects the country's ecosystem from the invasion of Western civilization. The territories where the insect lives, remain free from humans, they completely belong to the local inhabitants.