Methods: Blood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong
province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays.
Positive samples were also investigated by PCR for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae
and Plasmodium ovale, and were confirmed by sequencing the gene encoding the circumsporozoite protein (csp).