Anopheles dirus co-infection with human and monkey malaria parasites in Vietnam.

The feasibility of identifying parasite DNA and specific mRNAs from wild-caught Anopheles dirus mosquitoes was assessed using dried mosquito salivary glands preserved on filter paper. We were able to detect Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium knowlesi DNA by conventional PCR and, furthermore, detected P. falciparum gametocyte-specific genes, pfg377 and pfs16 mRNA, P. knowlesi circumsporozoite protein (CSP) and sporozoite surface protein 2 (SSP2) mRNA by reverse transcription-PCR. Using this technique, we were able to confirm the presence of P. vivax, P. falciparum and P. knowlesi in one particular wild-caught mosquito. These results indicate that P. knowlesi may be transmitted by the primary human malaria vector in forested areas in Vietnam. This study also shows that the preservation of mosquito salivary glands on filter paper, and the down-stream extraction of parasite DNA and RNA from those, offers a powerful resource for molecular epidemiological studies on malaria.