Abstract
Plasmodium knowlesi is the main cause of malaria in Sarawak, where studies on vectors of P. knowlesi have been conducted in only two districts. Anopheles balabacensis and An. donaldi were incriminated as vectors in Lawas and An. latens in Kapit. We studied a third location in Sarawak, Betong, where of 2169 mosquitoes collected over 36 days using human-landing catches, 169 (7.8%) were Anopheles spp. PCR and phylogenetic analyses identified P. knowlesi and/or P. cynomolgi, P. fieldi, P. inui, P. coatneyi and possibly novel Plasmodium spp. in salivary glands of An. latens and An. introlatus from the Leucosphyrus Group and in An. collessi and An. roperi from the Umbrosus Group. Phylogenetic analyses of cytochrome oxidase subunit I sequences indicated three P. knowlesi-positive An. introlatus had been misidentified morphologically as An. latens, while An. collessi and An. roperi could not be delineated using the region sequenced. Almost all vectors from the Leucosphyrus Group were biting after 1800 h but those belonging to the Umbrosus Group were also biting between 0700 and 1100 h. Our study incriminated new vectors of knowlesi malaria in Sarawak and underscores the importance of including entomological studies during the daytime to obtain a comprehensive understanding of the transmission dynamics of malaria.
Highlights
Plasmodium knowlesi is the main cause of malaria in Sarawak, where studies on vectors of P. knowlesi have been conducted in only two districts
From 2017 to 2019, a total of 10,968 knowlesi malaria cases were reported in Malaysia, with 87% occurring in the Malaysian Borneo states of Sabah and Sarawak[3]
Long-tailed and pig-tailed macaques were identified as the reservoir hosts for P. knowlesi and other simian malaria parasites (P. coatneyi, P. cynomolgi, P. fieldi, and P. inui) in Sarawak[4]
Summary
Plasmodium knowlesi is the main cause of malaria in Sarawak, where studies on vectors of P. knowlesi have been conducted in only two districts. PCR and phylogenetic analyses identified P. knowlesi and/or P. cynomolgi, P. fieldi, P. inui, P. coatneyi and possibly novel Plasmodium spp. in salivary glands of An. latens and An. introlatus from the Leucosphyrus Group and in An. collessi and An. roperi from the Umbrosus Group. An effective vector control strategy is key to successful malaria prevention and control, but it will have to be devised based on accurate understanding of the identity and bionomics of the vectors at the location of transmission This was previously demonstrated in Vietnam where a non-vector (An. varuna) was misidentified as the vector An. minimus and subsequently wrongly targeted for vector control[19], causing the ineffective use of valuable and limited resources. The mosquitoes were morphologically identified, in certain studies they were dissected, and DNA that was extracted was analysed by PCR assays These assays were designed to only detect the five simian malaria parasites initially described in m acaques[4]. The aims of the current study were to identify vector(s) and the species of Plasmodium they transmit in the Betong District of Sarawak and to determine whether there are any vectors that feed earlier in the day
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