A new way to fight sleeping sickness

We are all now well aware of the effect that diseases caused by microorganisms can have on humans but it’s not just viruses that can cause disease, parasites are big business too. And in particular African sleeping sickness, also called trypanosomiasis, which is spread by tsetse flies, kills thousands. But this week, in work published in PLOS Biology, scientists have shown how a drug called nitisinone, which is already used in humans to treat a genetic disease, turns out to be “kryptonite” for a tsetse fly, and other blood-sucking insects too.  Martin Khechara heard how, from the Liverpool School of Tropical Medicine’s Álvaro Acosta-Serrano...

Álvaro - Tsetse flies, who are responsible for transmitting a deadly disease in Africa, known as African trypanosomiasis, need to digest blood quickly, coming from the blood meal that they take from humans or animals, and they need to metabolise quickly, some of these blood components. One of those is known as tyrosine. Tyrosine is an amino acid. We knew that when we blocked that, the flies died. So by using a specific drug nitisinone, which is the drug that is currently used to treat a rare human disease. And when Tsetse flies are exposed to that drug, they quickly die.

Martin - How did you find out the drugs that you've used in your study actually kills the Tsetse flies?

Álvaro - My collaborator in this work, Dr. Marcos Sterkel, discovered that degradation of tyrosine for other blood feeding insects is also lethal, is fatal for the insects if we block it. So he proposed to study this in Tsetse because Tsetse has a very fast rate of blood digestion, and the faster it is, the more likely it is this drug will act better. And in fact, within a few hours that the flies are exposed, in the presence of blood, for example, definitely they get killed by the action of this drug

Martin - Does killing these flies actually stop people getting the disease?

Álvaro - Absolutely, the best we can do is to reduce the populations of flies that would be close to some urban and more rural areas. So in terms of controlling the diseases, in this case, Tsetse fly transmit. This kind of strategy that we are suggesting would be one way to control transmission, in parallel with a continued supply of drug treatments and using other ways to control Tsetse fly population.

Martin - So could this drug work in other blood sucking things?

Álvaro - This drug works, literally, for any blood feeder insects, that transmit disease in wild places. One of those diseases that we are actually working on is on mosquitoes, and mosquitoes that transmit malaria in Africa. And we got very exciting, preliminary data suggesting that we could potentially use this drug in different ways to control mosquito populations.

Martin - So how would you see this drug working actually in the real world?

Álvaro -Well, there's a long way to go now, and we need to really do the field test. Depending how we use these for animals, or for humans perhaps in outbreak situations, we can say this could help in partnership with other strategies to control what is called vector-borne diseases.

Martin - Is the drug expensive. If it's going to be used in countries where money could be tight?

Álvaro - The drug is a little bit pricey at the moment, because it's only useful to treat these rare genetic diseases, but also there are thousands of compounds working in a similar way. So the idea is to screen for novel compounds, that would be cheaper. So I think there is great potential to exploit these compounds depending on the biology, and depending on the kind of insect that we try to control.