The threat of increased transmission of non-knowlesi zoonotic malaria in humans: a systematic review.

Of the 5 human malarial parasites, Plasmodium falciparum and Plasmodium vivax are the most prevalent species globally, while Plasmodium malariae, Plasmodium ovale curtisi and Plasmodium ovale wallikeri are less prevalent and typically occur as mixed-infections. Plasmodium knowlesi, previously considered a non-human primate (NHP) infecting species, is now a cause of human malaria in Malaysia. The other NHP Plasmodium species, Plasmodium cynomolgi, Plasmodium brasilianum, Plasmodium inui, Plasmodium simium, Plasmodium coatneyi and Plasmodium fieldi cause malaria in primates, which are mainly reported in southeast Asia and South America. The non-knowlesi NHP Plasmodium species also emerged and were found to cross-transmit from their natural hosts (NHP) ­ to human hosts in natural settings. Here we have reviewed and collated data from the literature on the NHPs-to-human-transmitting non-knowlesi Plasmodium species. It was observed that the natural transmission of these NHP parasites to humans had been reported from 2010 onwards. This study shows that: (1) the majority of the non-knowlesi NHP Plasmodium mixed species infecting human cases were from Yala province of Thailand; (2) mono/mixed P. cynomolgi infections with other human-infecting Plasmodium species were prevalent in Malaysia and Thailand and (3) P. brasilianum and P. simium were found in Central and South America.

Role of Human Twin Studies to Identify Genetic Linkage of Malaria Pathogenesis and Outcomes.

Malaria remains a major public health challenge that needs attention, especially when the world is aiming at malaria elimination in the near future. It is crucial to understand the underlying genetic factors and epigenetics involved in malaria susceptibility and the dynamics of host immune responses that affect disease outcomes and relapses in Plasmodium vivax and Plasmodium ovale. Studies in newborn and adult twins can help in understanding the comparative roles of environmental and genetic factors on disease pathogenesis and outcome. These studies can help in providing insights into the factors responsible for malaria susceptibility, clinical presentation, responsiveness toward existing as well as candidate antimalarials, and even identification of novel therapeutic targets. The results and outcomes from twin studies can be further applied to the entire population. In the present manuscript, we analyze the available literature on malaria and human twins and discuss the significance and benefits of twin studies to help in better understanding malaria.