Get ready to explore one of Africa’s most notorious insects: the tsetse fly. These tiny flies may not look like much, but they play a major role in spreading sleeping sickness, aka human African trypanosomiasis (HAT).
That’s right, these little pests aren’t just a nuisance; they’re responsible for transmitting a parasitic disease that can cause serious health problems in both humans and animals.
But don’t be too quick to blame all tsetse flies for this. There are many different tsetse species, and while some spread this dangerous parasite, others lead relatively low-key lives.
Physical Characteristics
Tsetse flies are about the size of a common housefly, typically measuring between 0.25 to 0.5 inches (6 to 14 mm) in length.
One of the easiest ways to recognize a tsetse fly is by how they fold their wings: When at rest, their wings overlap completely, creating a neat “scissor-like” look. They also have a long, needlelike mouthpart called a proboscis, which they use to pierce the skin of their prey and feed on blood.
The insects belong to the genus Glossina, with the tsetse fly Glossina morsitans species among the most well-known. They have large, prominent eyes that help them zero in on their next victim, whether it’s a human or a wild or domestic animal.
These insects are also strong fliers that can cover long distances in search of a blood meal.
3 Tsetse Fly Species
There are over 30 recognized species of tsetse flies, found primarily throughout Sub-Saharan Africa. They are divided into three main groups based on their habitats: savanna (morsitan), riverine (palpalis) and forest (fusca).
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Glossina morsitans is a savanna species that thrives in the drier regions of eastern and southern Africa. It is primarily associated with transmitting trypanosomiasis in animals (nagana), though it can occasionally affect humans.
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In contrast, riverine species like Glossina palpalis are more commonly found near rivers and lakes in the humid environments of western and central Africa. This species is more responsible for the transmission of human African trypanosomiasis (sleeping sickness).
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Forest species, such as Glossina fuscipes, inhabit the denser, more wooded areas of central and eastern Africa. They can also contribute to the transmission of both human and animal trypanosomiasis.
But remember, not all tsetse fly species transmit diseases; some are just out there minding their own business and living that bug life.
Social Habits
Unlike some insects that live in colonies or work together in groups, tsetse flies are solitary creatures. Adult flies spend their lives mostly alone, focusing on two things: finding a host and reproducing.
When it comes to feeding, tsetse flies are both aggressive and persistent. A tsetse bite can happen quickly and without much warning, and the fly injects saliva containing anticoagulants to prevent blood from clotting while it feeds.
Tsetse flies can feed on both wild and domestic animals, but some species prefer humans as their primary host. These flies are also notorious for being tough to swat away. Once they’ve locked onto a target, they will continue their pursuit until they get their meal.
And speaking of meals, the tsetse fly’s diet has a lot in common with that of vampires.
Diet
Like bedbugs and fleas, tsetse flies are hematophagous, which is a fancy way of saying they feed on blood. Whether from a human, a cow or a wild animal, these flies need blood to survive and reproduce.
Both male and female tsetse flies require blood meals, which is unusual compared to many other blood-feeding species, where typically only the females need blood to reproduce.
A Dangerous Bite
The real danger of the tsetse fly’s feeding habits comes from its ability to transmit the parasite that causes African sleeping sickness. During a tsetse bite, the fly can pass Trypanosoma cruzi parasites into the bloodstream of its host, potentially leading to the development of human African trypanosomiasis.
In the early stages, the disease may cause fever, headaches and fatigue. If left untreated, it can progress to more severe neurological symptoms like confusion and sleep disturbances — hence the name “sleeping sickness.”
Environment
Tsetse flies thrive in many different environments across central Africa, ranging from dry savannas to dense rainforests. Their distribution is largely influenced by the presence of suitable tsetse host animals, including large mammals like cattle, antelope and humans.
In more tropical areas, where humidity is high and vegetation is dense, tsetse flies find ideal breeding grounds.
Western and central Africa are hot spots for tsetse populations, especially in rural areas where people live near livestock. Because tsetse flies are attracted to large mammals, farmers and herders often find themselves and their animals targeted by these pesky insects.
Life Cycle
The life cycle of the tsetse fly is pretty unique compared to other insects.
Female tsetse flies give birth to live larvae rather than laying eggs, which is unusual for insects. The female carries a fertilized egg inside her body, and as the embryo grows, it feeds on secretions from specialized glands.
After about nine days, the female fly deposits a fully developed larva into the soil, where it burrows down and pupates — a process where the larva forms a protective casing, or pupa, and undergoes metamorphosis before emerging as an adult fly.
The pupa stage lasts several weeks, after which a new adult fly emerges, ready to find its first blood meal. Adult tsetse flies can live for several months, feeding and reproducing throughout their lifespan.
Fly Population Control
While tsetse flies are considered pests because of their role in spreading sleeping sickness, they also play an important role in their ecosystems. As parasites and blood feeders, they are part of the natural predator-prey relationships that exist in natural populations of animals in central Africa.
However, because of the severe health risks associated with African trypanosomiasis, many efforts have been made to reduce tsetse populations in areas heavily affected by the disease. Control methods include trapping and insecticide spraying, as well as introducing sterile males into the environment to reduce reproduction rates.
These efforts have been somewhat successful in reducing the spread of human African trypanosomiasis, but the fight against sleeping sickness continues as tsetse flies remain an ongoing threat to human and animal health in many parts of Africa.
We created this article in conjunction with AI technology, then made sure it was edited and fact-checked by a HowStuffWorks editor.
Original article: The Tsetse Fly, Blood Meals and African Sleeping Sickness
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