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Tsetse Fly's Weakness May Be Its Symbiotic Bacteria

  • Ben Thompson

FILE - Dead tsetse flies are seen in a laboratory in Ghibe Valley, southwest of Addis Ababa, Ethiopia, June 1, 2002.

The fly that carries African sleeping sickness may carry the seeds of its own destruction, according to new research.

Scientists have detailed the unique relationship between the tsetse fly and bacteria in its gut the fly can't live without.

The tsetse fly spreads African sleeping sickness to humans from wild animals and has caused several major epidemics in the past.

The parasite responsible for sleeping sickness is one of the few pathogens able to pass from the blood into the brain. It disrupts the sleep cycle and leads to mood changes, confusion, tremors and ultimately organ failure.

Researchers have long hoped to take advantage of a number of the fly's unusual properties. Like mammals, the tsetse fly lactates and gives birth to live young.

The tsetse milk contains bacteria called Wigglesworthia that the mother passes on to its young. Despite having one of the smallest known genomes, Wigglesworthia is a big deal for the tsetse fly. Without it, the fly becomes infertile.

In the report published Wednesday in the Proceedings of the Royal Society, researchers from Yale University in New Haven, Connecticut, and the University of Pavia in Italy described a number of ways that the tsetse fly depends on Wigglesworthia. The bacteria supply B vitamins that the fly can't produce on its own and doesn't get from blood, its only food source. Without B vitamins, the fly can't properly nourish its young, and they starve.

Proteins' roles

The scientists also examined the tissue that houses the bacteria. The fly produces a special protein that guides the bacteria where they are needed. Another protein hides the bacteria from the fly's immune system.

This leaves the researchers with several attack strategies as they move forward. They could try to produce drugs that target Wigglesworthia directly, or unleash the flies' immune system on the bacteria, or block one of the several pathways that the bacteria use to support the fly.

"There's a lot of potential places you could throw a wrench into the works," study co-author and entomologist Geoffrey Attardo told VOA. "It's just finding a place that's optimal."

Recent efforts to stem the spread of sleeping sickness have been largely successful. According to the World Health Organization, the number of reported cases fell from almost 40,000 in 1998 to just 2,804 in 2015.

But researchers say it is still important to develop new control methods that are cheaper, easier to deploy and more effective.

"During epidemics, the political will to address this is there, but then when the disease goes away, the control efforts stop," said Attardo. "Then flies come back in from wild areas, and the cycle starts again. And 20 or 30 years later, you have another epidemic."

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