Investigations on the occurrence of Plasmodium knowlesi in travellers returning from the endemic areas of simian malaria.

Malaria remains an important public health issue all over the world. Among 5 Plasmodium species invasive to humans, Plasmodium knowlesi has been identified most recently. It is sometimes difficult to differentiate this species from P. malariae with the use of microscopic examination. However, P. knowlesi infection may be associated with rapidly increasing parasitaemia and severe clinical course with the risk of death. Samples from Polish travellers returning from areas where simian malaria is endemic were examined with the use of polymerase chain reaction (PCR). The small subunit of ribosomal RNA (SSU rRNA) genes was subjected to analysis using nested PCR reaction. No positive results of P. knowlesi were obtained. Due to morphological similarities to P. malariae, potentially severe clinical course of infection and P. knowlesi endemic regions being a common tourist destination, diagnostic and clinical vigilance is necessary, including molecular methods use for precise parasite identification.