The Role of Monkeys as a Reservoir for the Lymphatic Filarial Parasite Brugia malayi on Belitung Island, Indonesia

In May 2023 Irina Diekmann, a veterinarian and postdoc at Washington University, traveled to Belitung Island, Indonesia to assist Professor Taniawati Supali and her team at the Universitas Indonesia, trap crab-eating macaques for blood collection to determine if they are a potential animal reservoir of B. malayi. B. malayi, a filarial nematode and one of the leading causes of lymphatic filariasis, can occur in animals but there is little knowledge if genes flow between parasite populations in humans and animals.

The Belitung region was assumed to be free of lymphatic filariasis in humans in 2017 following five rounds of mass drug administration (MDA) and several WHO-recommended surveys. Yet, further surveillance two years later showed that human infections still occur. In response, the Indonesia Ministry of Health requested assistance to determine why these infections reoccurred. One explanation could be a spill-over from an animal reservoir into the human population if both are bitten by the same vectors mosquitos. With funding from the Bill & Melinda Gates Foundation, the Indonesia team collected blood samples from cats and dogs in 2022, which are currently being analyzed at Washington University and are now looking at monkeys.

During her fieldwork, Irina learned how to set up different types of traps, including determining the right location and best types of bait to lure monkeys into cages. As it turns out, a mixture of jackfruit, cassava, palm oil fruits and bananas work the best. Once the macaques were safely trapped, she helped the team take blood samples from the sedated animals. These samples will be examined by microscopy and by DNA studies for B. malayi and other filarial species. Ultimately, this work will elucidate whether areas with lymphatic filariasis caused by zoonotic B. malayi need special attention as part of the Global Program to Eliminate Lymphatic Filariasis.

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