Why the tsetse fly bite is greatly feared?


A vector picture of a tsetse fly.


It Feeds on Blood


There are 22 different species of tsetse flies.

All, both males and females, gorge themselves on vertebrate blood, sucking up as much as three times their weight in blood with a single bite.

They feast on a wide range of grazing animals—both those native to Africa and those that are not.

They bite people too.

The bite is a deep, bloodsucking stab, sharp and painful. It itches and hurts at the same time. It raises a welt.

Tsetse flies are skillful at their work.

They do not waste time buzzing around your head.

They can fly at someone like a bullet and somehow put on the brakes and land on the face so gently that they are not felt.

They can be like thieves; you sometimes do not know they have stolen some blood until after they are gone—when all that remains for you to do is assess the damage.

Usually they go for exposed flesh. (They seem to like the back of my neck!)

Sometimes, however, they decide to crawl up a trouser leg or shirtsleeve before tapping a blood vessel.

Or if they choose, they can bite through clothing—that’s not a problem for an insect that can pierce even the tough hide of a rhinoceros.

People accuse the tsetse fly of being not only smart but also cunning.

So the first charge against the tsetse fly is that it is a bloodsucker with a painful bite.


It Kills Animals



Some varieties of tsetse flies transmit a disease caused by tiny parasites called trypanosomes.

When the tsetse fly sucks the blood of an animal that has the disease, it swallows blood containing the parasites.

These develop and multiply inside the fly. When the fly bites another animal, parasites pass from the fly into the bloodstream of the animal.

The disease is trypanosomiasis.

The form that occurs in animals is called nagana.

Nagana parasites thrive in the bloodstream of many animals native to Africa, especially antelope, buffalo, bushpigs, duikers, reedbuck, and warthogs.

The parasites do not kill these animals.

But the parasites devastate livestock not native to Africa—camels, dogs, donkeys, goats, horses, mules, oxen, pigs, and sheep.

According to National Geographic magazine, nagana kills three million cattle each year.

Cattle herders, such as the Masai of East Africa, have learned how to avoid the areas where tsetse flies are most plentiful, but drought and lack of pasture sometimes make this impossible.

During a recent drought, four families who kept their 600 cattle together were losing an animal each day to the fly.

 Lesalon, a family elder says:

“We Masai are courageous people. We spear the lion and face the charging buffalo. We club the black mamba and confront the angry elephant. But with orkimbai [tsetse fly]? Helpless we are.”

Drugs exist to cure nagana, but some governments permit their use only under a veterinarian’s supervision.

There is good reason for that, since partial dosages not only doom the animal but generate parasites that are resistant to drugs.

It may be difficult for the cattle herder in the bush to find a vet in time to treat his dying animals.

The first two charges against the tsetse fly have been proved beyond dispute—it feeds on blood and spreads a disease that kills animals.

But there is more.


Tsetse fly sleeping sickness



Humans are not afflicted with nagana trypanosome.

But the tsetse fly delivers another type of trypanosome from human to human.

This form of trypanosomiasis is called sleeping sickness.

Do not think that a person with sleeping sickness merely sleeps a lot.

The disease is not a blissful sleep.

It begins with malaise, fatigue, and a low fever.

After that come prolonged drowsiness, high fever, joint pains, swollen tissues, and enlarged liver and spleen.

In the final stages, as the parasites penetrate the central nervous system, the patient suffers mental deterioration, seizures, coma, and death.

Although sleeping sickness is fatal if untreated, drugs exist to treat it.


In defense of tsetse fly



What then of the tsetse fly?

Is there something to be said in defense of this apparent villain?

Perhaps the strongest defense so far is that its role in the destruction of cattle has worked to protect native African wildlife reserves.

Vast areas of Africa are similar to the grasslands of the western United States—the land itself is capable of supporting domestic livestock.

But thanks to the tsetse fly, domestic animals are killed by trypanosomes that do not kill native grazing animals.

Many believe that if it were not for the tsetse fly, the great wildlife reserves of Africa would have long ago been replaced by herds of cattle.

 Willie van Niekerk, a guide in a Botswana wildlife reserve says:

 “I promote tsetse, eliminate the tsetse and cattle will invade, and cattle are the despoilers of Africa, bulldozing the continent into one big wasteland.” 

He added:

“The fly must stay.”

Not everyone agrees with that, of course.

The argument does little to convince the man who watches his children or cattle suffer from trypanosomiasis.

Neither does it convince those who argue that Africa needs cattle to feed itself.

Nevertheless, there is undoubtedly still much to learn about the role the tsetse fly plays in nature.