December 2, 2021

I, Science

The science magazine of Imperial College

Flatworm infection spike around Lake Malaŵi has been linked to manmade environmental changes ...

Shore_Lake_Malawi (1)

Children play in the water. Their mothers wash clothes, while fishermen cast nets from their boats, but this idyllic scene on the shores of Lake Malaŵi is stained by the presence of a killer looming large. This killer has multiplied ten-fold as a result of manmade environmental changes, including climate change.

Cases of flatworm infections are rocketing. They now cause over 200,000 fatalities each year and contribute to many more. The specific flatworm infection spreading along the shores of Lake Malaŵi is urogenital schistosomiasis. In some lakeside villages 73% of people, and up to 94% of schoolchildren, are carriers of this debilitating disease, but how do victims get infected? Simply by coming into contact with contaminated water.

“Whenever humans get into the water the larvae can penetrate the skin and migrate to the intestines where they develop into adult worms,” said Bert Van Bocxlaer, from The Smithsonian Museum, Washington. “This causes pain in the abdominal region but, as their eggs travel in the blood, they can also become embedded in muscle tissue and so cause lesions. They can even affect the brain region. The disease can be fatal.”

Flatworms have always been a problem for residents on the shore of Lake Malaŵi but Van Bocxlaer has shown how a recent infection spike is the result of manmade environmental change. The problem is a population boom in the snail that carries flatworm eggs. Climate change has increased rainfall during the rainy season, which has led to faster runoff and more sedimentation and so created the ideal conditions for the carrier snails to breed. Also, a tripling in the Malawian population in the last 40 years has led to intensive fishing to feed the extra mouths, and this has diminished the numbers of the snails’ natural predators. The result is a ten-fold increase in snail numbers.

What measures can be taken to help the growing number of infected individuals? The drug praziquantel has been shown to effectively treat the disease and the World Health Organisation (WHO) has recommended mass administration of the drug through schools in endemic areas such as the shoreline of Lake Malaŵi.

“Kids like to play in the water, especially when it’s really hot,” said Van Bocxlaer. “During these moments they can easily get infected.” While environmental change has increased flatworm infections, mass treatment of children around Lake Malaŵi should keep this potentially fatal disease at bay, for now.

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