Failure to detect a Plasmodium vivax-like malaria parasite in globally collected blood samples.

Two variants of the circumsporozoite (CS) protein of Plasmodium vivax (VK210 and VK247) have been identified. Recently, a putative third CS variant of P. vivax, referred to as causing P. vivax-like malaria, has been reported from Papua New Guinea. The objective of this study was to confirm and extend findings on the global distribution of the P. vivax-like parasite. Blood samples were obtained from 126 untreated patients with P. vivax infection acquired in Central America, South America, Africa, Southeast Asia, and the Indian subcontinent. The P. vivax CS gene was amplified by polymerase chain reaction and hybridized with probes specific for the VK210, VK247, and P. vivax-like CS variants. All samples were positive for VK210, VK247, or both. No sample was positive for P. vivax-like DNA. Therefore, the existence of a third variant of P. vivax cannot be confirmed in the geographic areas studied.