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Deforestation linked to emergence of zoonotic malaria
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Researchers reported that deforestation and other environmental changes led to a greater incidence of the zoonotic malaria species Plasmodium knowlesi in Malaysian Borneo.
“Deforestation and related forest activities have been associated with changes in malaria vector populations and related disease incidence globally,” Kimberly M. Fornace, MSc, a research fellow at the London School of Hygiene & Tropical Medicine, and colleagues wrote. “In Malaysia, studies have implicated the primarily exophagic Anopheles leucosphyrus group of mosquitoes as the main vector of P. knowlesi and have found relatively high biting rates in farm edges bordering forests and forest areas. … The effects of these changes at forest edges have been described for malaria and other vector-borne zoonotic diseases but not for P. knowlesi.”
Kimberly M. Fornace
To that end, Fornace and colleagues analyzed village-level incidence data for P. knowlesi in the areas of Kudat and Kota Marudu in northwestern Sabah, Malaysia, on the island of Borneo, during 2008 to 2012.
According to the researchers, 2,006 malaria patients were reported across 405 villages in Kudat and Kota Marudu. Of those, 739 (95% CI, 664-794) were estimated to have P. knowlesi infection. In addition, the researchers observed that 39% of villages lost more than 10% of forest cover within a 1-km radius during the 5-year period, 44% lost more than 10% within a 2-km radius, and 51% lost more than 10% of forest cover within a 5-km radius.
Further analysis suggested lower elevations and higher historical forest loss were associated with greater incidence of P. knowlesi infections.
According to Fornace and colleagues, the association between deforestation and greater P. knowlesi incidence could result from changes in macaque or mosquito habitats and increased human activity, among other causes.
“Although clearing of forests may initially deplete vector populations and thereby reduce malaria transmission, this reduction may be followed by colonization of cleared areas by more efficient vector species and subsequent increases in transmission,” they wrote. – by Jason Laday
Disclosure: The researchers report no relevant financial disclosures.
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