The tsetse fly has the glory of an extremely dangerous insect. It can cause a disease in humans and animals called trypanosomiasis. There are two forms of this infection: Rhodesian trypanosomiasis, sometimes called East African, and Gambian, or West African. Rhodesian is transmitted from animal to animal and mainly affects cattle, horses, wild ungulates. The Gambian form is common among people, it is usually called sleeping sickness. The tsetse fly lives only in Africa. There are 22 known species of this insect. It is active throughout the day and feeds exclusively on blood.
Most insects are usually negligent parents. The female lays eggs and flies away, leaving the young to survive on their own. The tsetse fly differs from other insects in that it is very careful about its offspring. The female lays one egg, but she keeps it in the safest place - in her uterus. The egg turns into a larva, which grows, eating a fluid rich in fats, called by scientists "intrauterine milk." When the larva completely fills the mother’s uterus, it releases it into moist soil. The larva hides and pupates immediately.
Studies have shown that "milk" contains the enzyme sphingomyelinase, which is activated in an acidic environment in the digestive tract of the larva. Sphingomyelinase is involved in the metabolism of fats and the formation of cell membranes. This enzyme has similar functions in mammals and tsetse flies during lactation, despite the enormous evolutionary distance between these classes. In addition to the parasitic organism, trypanosomes, there is another bacterium that lives in its digestive tract, and has simultaneously evolved with its host over millions of years - the endosymbiotic bacterium Wigglesworthia glossinidia. It provides the insect with nutrients, the ability of the fly to reproduce depends on it. Perhaps this knowledge will someday be used by scientists to prevent the spread of the disease. When bacteria are removed from an insect, scientists can reduce its birth rate and, accordingly, the transmission of the disease.
The tsetse fly bite is very dangerous. It is a carrier of tiny unicellular trypanosome organisms, approximately equal in size to red blood cells. There are several types of parasites, divided into categories according to their effect on vertebrates. Some species do not cause any health problems, while other strains are extremely dangerous. An insect in the process of feeding them from infected vertebrates and then passes it to uninfected animals through saliva.
Trypanosome lives in the digestive tract of the insect for several days, after which it moves to the salivary glands. The tsetse fly most likely does not respond to these parasites, but it is possible that they increase the chance of the survival of the insect. The fact is that trypanosomes have significantly evolved and formed their own life cycle, which requires a certain time, depending on the owners.
Morphologically, the insect exists in two forms: a larva of the third age stage (when it is separated from the mother) and an adult.
The adult tsetse fly is a relatively large insect, with a length of 0.5 to 1.5 centimeters, with clearly defined characters. She has a large head with a characteristic proboscis, large eyes and unusual antennas with awns with hairs branched at the ends. The chest is quite large, the abdomen is wide, but not elongated, it is shorter than the wings, which have a specific sign visible in the front: a segment resembling an ax.