Human Infections and Detection of Plasmodium knowlesi

Abstract

SUMMARY Plasmodium knowlesi is a malaria parasite that is found in nature in long-tailed and pig-tailed macaques. Naturally acquired human infections were thought to be extremely rare until a large focus of human infections was reported in 2004 in Sarawak, Malaysian Borneo. Human infections have since been described throughout Southeast Asia, and P. knowlesi is now recognized as the fifth species of Plasmodium causing malaria in humans. The molecular, entomological, and epidemiological data indicate that human infections with P. knowlesi are not newly emergent and that knowlesi malaria is primarily a zoonosis. Human infections were undiagnosed until molecular detection methods that could distinguish P. knowlesi from the morphologically similar human malaria parasite P. malariae became available. P. knowlesi infections cause a spectrum of disease and are potentially fatal, but if detected early enough, infections in humans are readily treatable. In this review on knowlesi malaria, we describe the early studies on P. knowlesi and focus on the epidemiology, diagnosis, clinical aspects, and treatment of knowlesi malaria. We also discuss the gaps in our knowledge and the challenges that lie ahead in studying the epidemiology and pathogenesis of knowlesi malaria and in the prevention and control of this zoonotic infection.

A Review of Plasmodium knowlesi among Macaques in Malaysia

“…Due to the morphological similarities of some Plasmodium parasites at certain stages of the life cycle in the vertebrate host blood, microscopy may be challenging to differentiate among them. Plasmodium species which show similar morphological features to human Plasmodium species include P. cynomolgi, P. fieldi and P. inuii to that of P. vivax, P. ovale and P. malariae, respectively (Antinori et al, 2013;Singh and Daneshvar, 2013).…”

“…RDTs are user friendly, time saving, economical and do not require any specialized laboratory equipment. There is no specific RDT developed for the detection of P. knowlesi commercially while the existing RDTs used for the identification of P. knowlesi showed incorrect results as tested in blood samples of humans and macaques (Foster et al, 2014;Singh and Daneshvar, 2013).Though the RDT is a rapid tool for the detection of malaria but certain improvements are required for better detection and its accuracy to differentiate between the different Plasmodium species, true results in case of low parasetimia and detection of multiple parasite infections (Moody, 2002;Murray and Bennett, 2009). Due to the above mentioned limitations, other diagnosis techniques are adopted for confirmation and characterization of the infections, and monitoring its treatment regimes.…”

“…Some of the merozoites undergo development of gametocytes producing microgametocytes (male) and macrogametocytes (female). Patients will experience fever patterns as a result of releasing toxins into the body by rupturing of the infected erythrocyte, which is one of the common symptoms of malaria infections (Singh and Daneshvar, 2013).…”

“…The spatial distribution patterns of both mosquito vectors and macaques plays a role in the transmission of the disease (Singh and Daneshvar, 2013).…”

Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission

“…B 370: 20130551 population impacts) are clearly sensitive to temperature (as demonstrated, for instance, with avian malaria in Hawaii [108,109]). In addition, economically driven anthropogenic effects may affect zoonotic VBD dynamics [110], whereas socio-economic factors have also been suggested as driving recent increases in human cases of the monkey malaria Plasmodium knowlesi [111].…”