Methods for Detection and Identification of Plasmodium knowlesi: A Review Article

Background: Plasmodium knowlesi is a simian malaria parasite capable of causing malaria in human. Naturally acquired human infections with P. knowlesi have been detected in many South East Asian countries. As P. knowlesi can cause severe malaria with life threatening complications, early detection is of great importance in management of knowlesi malaria. Objective: To provide insight into the detection methods used for diagnosis of knowlesi malaria. Method: We performed the detailed reviews of the previous studies on knowlesi malaria with the particular emphasis on diagnostic methods, especially polymerase chain reaction-based molecular detection methods. Result: For detection of P. knowlesi, blood film microscopy is not a reliable method due to the morphological similarities between P. knowlesi and other malaria parasites infecting human. Rapid diagnostic methods based on P. knowlesi-specific antibodies have not been available yet. Nested PCR has been used as the standard method for identification of P. knowlesi for half a decade. While requiring sophisticated equipment, real-time PCR provides rapid results and higher specificity and sensitivity, and is thus used in reference laboratories. Loop-mediated isothermal amplification is a promising method for diagnosis of knowlesi malaria in the field. These methods detect small subunit ribosomal RNA as the molecular target. However, recent studies demonstrated the use of multicopy, repetitive sequence as the molecular target in single-step PCR detection of P. knowlesi. Conclusion: P. knowlesi is commonly mistaken for P. malariae by microscopy, which is responsible for some of the fatalities due to P. knowlesi infections because P. knowlesi produces more severe malaria compared to P. malariae. Although molecular diagnostic methods are sensitive and specific for P. knowlesi, these methods are not International Journal of Collaborative Research on Internal Medicine & Public Health Vol. 6 No. 1 (2014) 12 available in the rural areas where knowlesi malaria is endemic. Therefore, in addition to these methods, a high index of suspicion would be helpful in preventing death resulting from knowlesi malaria.