Tsetse flies feel the heat in Zimbabwe
Over the last decade, cattle farmers in the Zambezi Valley, in Zimbabwe’s Mashonaland West province, have noticed an odd thing.
Tsetse flies, once a major threat to their animals, have slowly been disappearing, resulting in fewer cattle deaths, they say.
“When I first came to live in this area about 12 years ago, I lost a number of cattle due to diseases caused by tsetse flies,” Chinhanga area farmer Taurai Muindisi said.
“But now, I’m no longer losing my cattle. Tsetse flies are no longer a big problem in our area,” he said.
Researchers now think they know what is going on.
Hotter weather, the result of climate change, is making it much harder for tsetse flies to thrive.
A study published in the journal PLOS Medicine says that as temperatures have risen since the 1990s in the valley, tsetse fly numbers have plunged.
Data collected over 27 years at Mana Pools National Park suggest that hotter conditions are making it harder for tsetse flies to survive.
In 1990, researchers in the park captured more than 50 flies per animal each time they did a collection.
But by 2017, it took 10 catching sessions to find even one fly per animal.
Since 1975, average daily temperatures in the park have risen by about 1°C, with that increase reaching 2°C in the hottest month – November – the study said.
That change suggests disease problems may decline as some long-suffering tsetse fly areas in Africa grow hotter, though they could surge in other ones as the flies move, seeking cooler areas, Jennifer Lord, an author of the study, said.
Lord, of the Liverpool School of Tropical Medicine, carried out the study with colleagues from Stellenbosch University and the Natural Resources Institute at the University of Greenwich.
Tsetse flies carry trypanosomiasis, a parasite that causes a disease called nagana in livestock and sleeping sickness in humans.
The disease, which affects the nervous system, is a longstanding plague in Africa, causing fever, loss of appetite and in some cases death if untreated.
Found in 36 sub-Saharan African countries, it is a particular problem in nations like the Democratic Republic of Congo and the Central African Republic, according to the World Health Organisation. –