Abstract
BackgroundThe vectors for Plasmodium knowlesi, a significant cause of human malaria in Southeast Asia, identified previously in nature all belong to the Anopheles Leucosphyrus Group. Only one study has been previously undertaken in Sarawak, Malaysian Borneo, to identify vectors of P. knowlesi, where Anopheles latens was incriminated as the vector in Kapit, central Sarawak. A study was therefore undertaken to identify malaria vectors in a different location in Sarawak. MethodsMosquitoes found landing on humans and resting on leaves over a 5-day period at two sites in the Lawas District of northern Sarawak were collected and identified. DNA samples extracted from salivary glands of anophelines were subjected to nested PCR malaria-detection assays. The small sub-unit ribosomal RNA (SSUrRNA) genes of Plasmodium, and the internal transcribed spacer 2 (ITS2) and mitochondrial cytochrome c oxidase subunit 1 (CO1) sequences of the mosquitoes were derived from the Plasmodium-positive samples for phylogenetic analyses. ResultsA total of 65 anophelines and 127 culicines were collected. By PCR, six An. balabacensis and five An. barbirostris were found to have single P. knowlesi infecions while three other An. balabacensis had either single, double or triple infections with P. inui, P. fieldi, P. cynomolgi and P. knowlesi. Phylogenetic analyses of the Plasmodium SSUrRNA genes confirmed 3 An. barbirostris and 3 An. balabacensis with single P. knowlesi infections, while 3 other An. balabacensis had two or more Plasmodium species of P. inui, P. knowlesi, P. cynomolgi and possibly novel species of Plasmodium. Phylogenies inferred from the ITS2 and CO1 sequences of An. balabacensis and An. barbirostris indicate that the former is genetically indistinguishable from An. balabacensis in Borneo while the latter is a novel sibling species belonging to the Anopheles Barbirostris Subgroup. ConclusionsNew vectors for P. knowlesi in Sarawak were identified, including An. barbirostris, which is a species that does not belong to the Anopheles Leucosphyrus Group.
Bionomics of Anopheles latens in Kapit, Sarawak, Malaysian Borneo in relation to the transmission of zoonotic simian malaria parasite Plasmodium knowlesi