Plasmodium knowlesi is a zoonotic malaria parasite that has gained increasing medical interest over the past two decades. This zoonotic parasitic infection is prevalent in Southeast Asia and causes many cases with fulminant pathology. Despite several biogeographical restrictions that limit its distribution, knowlesi malaria cases have been reported in different parts of the world due to travelling and tourism activities. Here, breakthroughs and key information generated from recent (over the past five years, but not limited to) studies conducted on P. knowlesi were reviewed, and the knowledge gap in various research aspects that need to be filled was discussed. Besides, challenges and strategies required to control and eradicate human malaria with this emerging and potentially fatal zoonosis were described.

Five children in Pos Lenjang, Pahang, Malaysia were PCR-positive for vivax malaria and were admitted to the hospital from 5 to 26 July 2019. One of the patients experienced three episodes of recurrence of vivax malaria. Microsatellite analysis showed that reinfection is unlikely. Drug resistance analysis indicated that Riamet (artemether–lumefantrine) is effective. Cytochrome P450 2D6 (CYP2D6) testing showed that this patient has defective CYP2D6 function. Primaquine failure to clear the Plasmodium vivax hypnozoites may be the cause of recurring infections in this patient. This report highlights the need for the development of liver-stage curative antimalarials that do not require metabolism by the CYP2D6 enzyme.

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BackgroundMalaria has been a public health concern for many years. People living in Southeast Asia are now threatened by Plasmodium knowlesi infection which can cause severe complications if not treated immediately. Rapid diagnostic tests (RDTs) targeting at P. knowlesi infection is essential for rapid diagnosis especially in resource limited settings. In this study, circumsporozoite protein (CSP) was assessed using in silico analysis and antibody detection approach to act as a P. knowlesi diagnostic biomarker in RDTs.MethodsAnimal ethics approval was obtained for animal immunization work. Two peptide epitopes specific for P. knowlesi CSP (PkCSP) were identified from amino acid sequence alignment and were used as immunogen to raise antibodies in animal models. The reactivity of the anti-peptide antiserums was evaluated against recombinant PkCSP using Western Blot assays. Results Mouse anti-peptide antiserum generated was able to react with recombinant PkCSP. Western blot assay showed that the mouse anti-peptide antiserum did not probe on any protein in P. knowlesi total protein extract, indicating the absence of PkCSP in the erythrocytic stage. This finding was further confirmed by using anti-recombinant PkCSP antiserum raised in mice models. ConclusionOur study has demonstrated that CSP is not suitable to be used as a diagnostic biomarker for P. knowlesi specific detection. More studies should be done to screen for suitable biomarkers for specific P. knowlesi detection in RDT to allow prompt disease management and epidemiological surveillance.

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