The term “tootsie fly” is a common misnomer for the tsetse fly, an insect found across tropical Africa. These flies transmit diseases to humans and animals. Their presence has historically influenced settlement patterns and agricultural development in large parts of sub-Saharan Africa. The primary concern is their ability to spread African trypanosomiasis, commonly known as sleeping sickness.
Identifying the Tsetse Fly
Tsetse flies are brownish insects, 6 to 16 millimeters long, similar to a housefly. They possess a forward-projecting proboscis used for blood feeding. Their wing venation includes a hatchet-shaped cell.
These flies inhabit diverse environments across sub-Saharan Africa, including riverine areas, woodlands, and savannas. Unlike many insects that lay eggs, female tsetse flies give birth to live larvae, usually one at a time, which then burrow into the soil to pupate before metamorphosing into an adult fly. This reproductive strategy, combined with their physical traits, distinguishes them from other biting flies in their habitat.
The Link to Sleeping Sickness
The tsetse fly acts as a biological vector for the parasite Trypanosoma brucei, which causes African trypanosomiasis (sleeping sickness). When an infected tsetse fly takes a blood meal from a human or animal, the parasites are transferred into the host’s bloodstream through the fly’s saliva. Inside the fly, parasites develop before becoming infectious.
There are two forms of human African trypanosomiasis, each caused by a specific parasite subspecies and linked to different tsetse fly species and geographical areas. Trypanosoma brucei gambiense causes the chronic Gambian form, prevalent in western and central Africa, often transmitted by riverine tsetse species like Glossina palpalis. The more acute Rhodesian form, caused by Trypanosoma brucei rhodesiense, is found in eastern and southern Africa and is primarily transmitted by savanna tsetse species such as Glossina morsitans.
Understanding Sleeping Sickness
African trypanosomiasis progresses through two stages if left untreated. The initial hemolymphatic stage begins with symptoms appearing days to weeks after a bite. These include intermittent fevers, headaches, joint pain, and swollen lymph nodes, often called Winterbottom’s sign, particularly in the neck. During this phase, the parasites circulate in the blood and lymphatic system, and symptoms can be easily mistaken for other illnesses.
As the disease advances, after months to years for the Gambian form or weeks to months for the Rhodesian form, it enters the neurological stage. Parasites cross the blood-brain barrier, affecting the central nervous system. Symptoms become more severe, including sleep disturbances, behavioral changes, confusion, and motor coordination problems such as tremors or slurred speech. Without treatment, the neurological damage becomes irreversible, leading to coma and death.
Preventing Bites and Disease
Protecting oneself from tsetse fly bites prevents African trypanosomiasis. Individuals in affected regions should wear neutral-colored clothing that covers arms and legs, as tsetse flies are attracted to bright and dark colors. Using insect repellents containing DEET on exposed skin offers protection. Avoid dense bush areas, especially during peak biting times, as these are preferred habitats for tsetse flies.
Beyond individual actions, broader control efforts reduce tsetse fly populations. These include insecticide-treated traps and screens that attract and kill flies. In some areas, targeted application of insecticides or even the sterile insect technique, which involves releasing sterilized male flies to reduce reproduction, are employed. These strategies lessen the risk of disease transmission in affected communities.