image by: Steve Torr

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In The Fight Against Tsetse Flies, Blue Is The New Black

Walk along one of the many streams and rivers in the West Nile region of Uganda, and you'll notice something funny. All along the riverbanks, you'll see small pieces of blue cloth, attached to wooden stakes in the ground. There's one every 50 yards or so. No, this isn't some half-baked public art project. These dinky contraptions are actually flytraps, designed to lure and kill tsetse flies, whose bites transmit a parasitic disease called sleeping sickness, which, like rabies, drives victims mad before it kills them.

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 Creepy Crawlies: The Tsetse Fly

So, what are Tsetse flies? They are flies (...) that can be super testy sometimes. HAHAHA, just a bit of entomology humour for you there. Scientifically, they’re called Glossina sp., and they’re the bad dudes who spread Human African Trypanosomiasis (also known as Sleeping Sickness or HAT). They’re large flies relative to other insects, and have a long, straight probocis (remember this for later, when I'll explain the interesting way that they feed). However, the most awesome visible feature of Tsetse flies is the “hatchet cell” on their wings – a pattern which looks like a cleaver or a hatchet. How badass is that?

 Deep Look Inside the Tsetse Fly

The tsetse fly (Genus Glossina) is notable for two things: it carries parasites called trypanosomes, which cause sleeping sickness in humans and nagana in cattle in sub-Saharan Africa; and it gives birth to live young. Attempts to control these devastating diseases have focused on controlling the insect vectors, particularly because they breed slowly raising only one larva at a time.

 The Tsetse Fly

Why Zebras have stripes………… could it be to avoid a Tsetse Fly?

Articles of Interest

Bloodthirsty tsetse flies nurse their young, one live birth at a time – understanding this unusual strategy could help fight the disease they spread

Tsetse flies stand out from their blood-feeding cousins the mosquitoes and ticks because of their unique reproductive biology. They give birth to live young and, even more unusual, the mother lactates and provides milk for her offspring. Here’s how it all works – and why their unusual reproduction strategy might be a key to controlling tsetse flies and the parasite they carry once and for all.

LSTM project Tiny Targets highlighted as a success in an open letter from the CEO of the Bill & Melinda Gates Foundation

Use of these tiny targets has already led to a reduction in cases where they have been used in Guinea, Uganda and Chad and their size makes them much for affordable to produce, distribute and deploy in the field than the traditional larger and more complicated traps. Current research suggests that they work for around six months and could prove to be an effective tool in moving to elimination of the disease where it is currently endemic.

Tsetse Fly—Africa’s Curse?

There are 22 different species of tsetse flies. All live in sub-Saharan Africa. 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.

“I have been bitten by a tsetse fly.” – Sukuma (Tanzania) Proverb

This humorous Sukuma proverb in Tanzania refers to a person who relentlessly pesters another person until he or she pays off a debt. There is a similar Sukuma proverb that says To promise an eye to a blind person meaning that the blind person will pester you until you fulfill your promise. The proverb also refers to a person who, like a tsetse fly, persistently and relentlessly keeps coming after you again and again until he or she gets what the person wants. In Swahili there are three words for a tsetse fly: mbung’o, ndorobo, and chafuo. Usage varies from place to place. The most commonly used word is mbung’o.

A tsetse fly aphrodisiac is identified

Tsetse flies produce a single embryo approximately every 10 days. The embryo develops in utero, where it passes through larval stages, being fed a milky substance produced by a modified gland. It is deposited as a final stage instar, and pupates in the soil. Eliminating a few tsetse flies can cause a rapid decline in the population, making the use of baited traps a successful control measure. Tsetse traps are made of insecticide-impregnated screens of blue and black material that move in the wind. Much attention has been paid to the response by various tsetse species to odorants such as “odor of ox”, that can act as bait in these traps.

Fly and Human Mothers Share a Milk Enzyme

Female tsetse flies produce only one egg at a time. The larva hatches in the mother’s uterus, and she feeds it with a milklike substance that she produces. Now, researchers report that tsetse milk contains an enzyme called sphingomyelinase, or sMase, that is also important in mammalian lactation.

Gut Bacteria Neutralizes Disease-Carrying Tsetse Flies

The Kosakonia bacteria increases the acidity of the fly’s gut to the point of making it less hospitable for the disease-causing trypanosomes. Taken together with the insect sterilization technique, the use of Kosakonia bacteria could greatly enhance the effectiveness of currently employed tsetse control programs, the researchers said.

How Africans developed scientific knowledge of the deadly tsetse fly

Few animals are more problematic than the tiny African insect known to English speakers as the tsetse fly. This is the carrier of “sleeping sickness,” an often deadly neurological illness in humans, as well as a disease that has killed millions of cattle, reshaping the landscape and economy in some parts of the continent.

Pesky Tsetse Flies

The tsetse fly is about the same size as a honeybee, surprisingly quick, and therefore very difficult to swat. Even if you are lucky enough to thwack one with your hand or guide book, they have this strange ability to recover quickly and continue to fly on in their own merrily annoying way. In most cases, the tsetse fly bite is simply an irritant, but they do transmit a parasite that causes African trypanosomiasis (sleeping sickness).

Science: Tsetse Fly

The blackest horror in darkest Africa is sleeping sickness. Very different from encephalitis lethargica, the sleeping sickness found in the U. S., this disease is caused by trypanosomes (parasitic protozoa) carried by the tsetse fly. Its toll is about 100,000 human victims a year and all the domestic animals the tsetse fly can find.

Science: Tsetse War

The tsetse, carrier of dreaded, parasitic African sleeping sickness, which kills men and cattle alike, has for generations been Africa’s great curse. The parasite comes mostly from wild animals. Despite all the South African Government’s efforts, including the slaughter of more than 65,000 jungle animals in the last four years, the tsetse has been gaining.

Scientists crack genetic code of deadly tsetse fly

Experts unlock genome sequence of bloodsucking pest that spreads sleeping sickness in sub-Saharan Africa.

Sequencing Tsetse Fly Genome Reveals Surprises That May Save Lives

The tsetse fly has long been an oddball among disease-transmitting insects. The fly carries the parasite for sleeping sickness,... But these bloodsuckers are also oddly mammalian. Females get pregnant with single young that they nourish with milk inside a womb. The female then gives birth, much like squeezing a slug of toothpaste from a tube, to a single undulating larva nearly her own size

Targeting the Tsetse Fly

Attardo says that these "flies are distinguished from other Diptera by unique adaptations including male specific reproductive adaptations, lactation and the birthing of live young (obligate viviparity), exclusive blood feeding by to the sexes and visually based host seeking. To understand the genetic changes underlying these adaptations, we sequence the genomes of six species of tsetse flies representing three sub-genera. These sub-genera represent different habitats, host preferences and vectorial capacity."

The enemy within

A group of scientists from more than 10 countries, with support from institutions such as the Wellcome Trust and the World Health Organization have just completed mapping the genes that provide the genetic code for the tsetse fly (in our case the species Glossina morsitans morsitans), an insect that spreads the lethal disease trypanosomosis, the feared sleeping sickness, in humans and nagana in livestock. We hope that knowing a little more about the inner workings of the tsetse fly will help us find a way to control it.

Tsetse Flies: Who Knew?

In terms of "fascinating physiological adaptations," Attardo considers the tsetse fly "one of the champions of the insect world!" As he explained to us in a 2017 news story: "In addition to being vectors of a deadly disease, Trypanosomiasis, these flies have undergone amazing alterations to their physiology relative to other insects. Some examples of this are their ability feed exclusively on blood, their obligate relationship with a bacterial symbiont, the fact that they lactate and that they give birth to fully developed larval offspring."

Tsetse fly: can castration end one of Africa’s oldest development problems?

Tsetse fly: can castration end one of Africa’s oldest development problems Radiation castration is helping to eradicate tsetse populations that have been preventing farmers from using animals to work their land.

World NTD Day: How tsetse control programme Tiny Targets helped to eliminate sleeping sickness in Uganda

The targets are deployed along river banks where tsetse concentrate. These riverine areas are also where people visit to collect water, wash, or farm in nearby fields, bringing them into contact with infected tsetse. Remembering the period before Tiny Targets were available, Dr Mugenyi said: "We used to have a range of interventions: ground spraying, traps, large targets which were the size of a blanket. These were unaffordable or not practicable in northern Uganda. People avoided rivers if they could because of the risk of sleeping sickness and the pain of being bitten by tsetse." This changed once Tiny Targets became available.

Resources

Tsetse.org

Scientists from the Liverpool School of Tropical Medicine, working with partners from Africa and Europe, and are developing new methods of controlling tsetse.