Tsetse fly which is known scientifically as Glossina, is an obliged parasite that feeds on mammals to survive.
Extensive analysis and studies have been carried out on tsetse due to the part they play in transmitting diseases.
They also have a special economic effect in sub-Saharan Africa as the biological transmitters of trypanosomes which is responsible for sleeping sickness in humans and animals.
Tsetse fly can be differentiated from other bigger flies by two simple observed characteristics; first, by the way they fold their wings totally while resting such that one wing rests directly on the other wing over their thorax, secondly through their long proboscis which pushes forward and is joined by a well-defined bulb to the bottom of their heads.
Scientific Classification
- Scientific Name: Glossina
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Diptera
- Section: Schizophora
- Subsection: Calyptratae
- Superfamily: Hippoboscoidea
- Family: Glossinidae Theobald, 1903
- Genus: Glossina Wiedemann, 1830
Morphology
Tsetse flies can be seen in two separate forms as independent individuals: first as adults, and secondly as third-instar larvae.
During the third larvae instar, the progeny first separates from their mothers, at that time they have the appearance of maggots.
It is almost impossible to observe the Tsetse fly at this stage outside the laboratory, as the life stage is very short, lasting only for few hours.
Next, the Tsetse fly develops a hard external case, the puparium, and becomes pupae – small, hard-shelled, elongated ones with two prominent, small, dark lobes at the end of the tail (end of the breathing).
Tsetse pupae are less than 1 inch (O. 5). as, Within the pupal shell, the tsetse fly completes the last two larval stages and the pupal stage.
At the end of the pupal stage, tsetse fly appears as adult flies. The adults are 0.5 to 1.5 centimeters in length, making them relatively large and have a recognizable shape or blueprint that makes them easy to differentiate from other flies.
Tsetse flies have large heads, clearly separated eyes, and unusual antennae. The abdomen is quite large while the belly is broad rather than elongated and shorter than the wings.
Anatomy
Tsetse flies have an adult body consisting of three separate conspicuous parts namely: the head, thorax and the abdomen.
The tsetse flies’ eyes are large in size, clearly separated on each side, and a pronounced, forward-pointing trunk, which is attached below by a large bulb.
The thorax is large and consists of three fused segments. Three pairs of legs are attached to the chest, as well as two wings and two halters.
The belly is short but wide and changes in volume dramatically during feeding.
The internal body structure of the tsetse fly is moderately typical of insects.
The crop is big enough to accommodate a huge increase in size during the blood meal, as tsetse fly can accommodate a blood meal of equal weight for itself.
The reproductive tract of a female adult includes a uterus that can grow large enough to accommodate the third instar larva at the end of each pregnancy.
The article Parasitic Flies from Pets provides a diagram of the body structure of dipteran flies.
Life cycle
Tsetse flies have an unusual life cycle, possibly due to the wealth of their food source.
A female tsetse fly fertilizes just one egg at a time and keeps each egg in her uterus so that the offspring can develop internally in the first three larval stages.
This method is called adenotrophic viviparity. During this time, the developing offspring is fed with a milky substance secreted by a modified gland in the uterus of the female tsetse fly.
The tsetse fly larva leaves the uterus in the third larval stage and commences its independent life.
The newly independent tsetse fly larva creeps into the ground and develops a puparial fall (hard outer shell) in which its morphological transformation into an adult fly is completed.
Trypanosomiasis
Trypanosomes which belong to the species Trypanosoma brucei are parasites that are responsible for human trypanosomiasis also known as sleeping sickness.
If left untreated, the disease can be very fatal, but it can almost always be cured with topical medication if diagnosed early enough.
Trypanosomiasis starts with a bite from tsetse fly which results in inoculation in the subcutaneous tissue.
This infection goes to the lymphatic system, thereby causing the lymph glands to swell and this phenomenon is called Winterbottom’s sign.
This infection advances into the bloodstream and finally moves over to the central nervous system and attacks the brain resulting in severe lethargy and possible death.
Control
Different measures can be put in place to control the spread of this fatal disease transmitted by the tsetse fly; this control techniques are listed below;
Use of Pesticides
The use of pesticides is effective in controlling the spreading the transmission of trypanosomiasis by tsetse flies.
Organic pesticides can be sprayed on the back of cattle to kill these tsetse flies.
Clearing of Lands
Keeping of lands and bushes low prevents these flies from settling there, this method is very important especially in areas where there are large population of humans.
Use of Traps
Tsetse fly Traps like electric bulb cloth are very effective as these flies are usually attracted to color.
Hides of buffaloes and cows also attract tsetse flies as the colors of these animals are largely dark, which can be used to trap these flies.
Chemicals can also be used to draw tsetse flies to their Traps.
The Resistance of Tsetse Flies to Trypanosome Infection
Tsetse flies have an arsenal of immune defense mechanisms to withstand every stage of the trypanosome infection cycle and are, therefore, relatively resistant to trypanosome infections.
One of the defense mechanisms of the host flies is the production of hydrogen peroxide, a reactive oxygen species that damage DNA.
