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Fulltext Plasmodium knowlesi: reservoir hosts and tracking the emergence in humans and macaques

Lee KS, Divis PC, Zakaria SK, Matusop A, Julin RA, Conway DJ, et al.

PLoS Pathog, 2011 Apr;7(4):e1002015.
PMID: 21490952 DOI: 10.1371/journal.ppat.1002015

Plasmodium knowlesi, a malaria parasite originally thought to be restricted to macaques in Southeast Asia, has recently been recognized as a significant cause of human malaria. Unlike the benign and morphologically similar P. malariae, these parasites can lead to fatal infections. Malaria parasites, including P. knowlesi, have not yet been detected in macaques of the Kapit Division of Malaysian Borneo, where the majority of human knowlesi malaria cases have been reported. In order to extend our understanding of the epidemiology and evolutionary history of P. knowlesi, we examined 108 wild macaques for malaria parasites and sequenced the circumsporozoite protein (csp) gene and mitochondrial (mt) DNA of P. knowlesi isolates derived from macaques and humans. We detected five species of Plasmodium (P. knowlesi, P. inui, P. cynomolgi, P. fieldi and P. coatneyi) in the long-tailed and pig-tailed macaques, and an extremely high prevalence of P. inui and P. knowlesi. Macaques had a higher number of P. knowlesi genotypes per infection than humans, and some diverse alleles of the P. knowlesi csp gene and certain mtDNA haplotypes were shared between both hosts. Analyses of DNA sequence data indicate that there are no mtDNA lineages associated exclusively with either host. Furthermore, our analyses of the mtDNA data reveal that P. knowlesi is derived from an ancestral parasite population that existed prior to human settlement in Southeast Asia, and underwent significant population expansion approximately 30,000-40,000 years ago. Our results indicate that human infections with P. knowlesi are not newly emergent in Southeast Asia and that knowlesi malaria is primarily a zoonosis with wild macaques as the reservoir hosts. However, ongoing ecological changes resulting from deforestation, with an associated increase in the human population, could enable this pathogenic species of Plasmodium to switch to humans as the preferred host.

Matched MeSH terms: DNA, Protozoan/genetics
Fulltext Acute respiratory distress syndrome and acute renal failure from Plasmodium ovale infection with fatal outcome

Lau YL, Lee WC, Tan LH, Kamarulzaman A, Syed Omar SF, Fong MY, et al.

Malar J, 2013 Nov 04;12:389.
PMID: 24180319 DOI: 10.1186/1475-2875-12-389

BACKGROUND: Plasmodium ovale is one of the causative agents of human malaria. Plasmodium ovale infection has long been thought to be non-fatal. Due to its lower morbidity, P. ovale receives little attention in malaria research.
METHODS: Two Malaysians went to Nigeria for two weeks. After returning to Malaysia, they fell sick and were admitted to different hospitals. Plasmodium ovale parasites were identified from blood smears of these patients. The species identification was further confirmed with nested PCR. One of them was successfully treated with no incident of relapse within 12-month medical follow-up. The other patient came down with malaria-induced respiratory complication during the course of treatment. Although parasites were cleared off the circulation, the patient's condition worsened. He succumbed to multiple complications including acute respiratory distress syndrome and acute renal failure.
RESULTS: Sequencing of the malaria parasite DNA from both cases, followed by multiple sequence alignment and phylogenetic tree construction suggested that the causative agent for both malaria cases was P. ovale curtisi.
DISCUSSION: In this report, the differences between both cases were discussed, and the potential capability of P. ovale in causing severe complications and death as seen in this case report was highlighted.
CONCLUSION: Plasmodium ovale is potentially capable of causing severe complications, if not death. Complete travel and clinical history of malaria patient are vital for successful diagnoses and treatment. Monitoring of respiratory and renal function of malaria patients, regardless of the species of malaria parasites involved is crucial during the course of hospital admission.

Matched MeSH terms: DNA, Protozoan/genetics
Fulltext Light microscopy and molecular identification of Sarcocystis spp. in meat producing animals in Selangor, Malaysia

Latif B, Kannan Kutty M, Muslim A, Hussaini J, Omar E, Heo CC, et al.

Trop Biomed, 2015 Sep;32(3):444-52.
PMID: 26695204 MyJurnal

One thousand and forty-five tissue samples of skeletal muscles, tongue, heart, diaphragm and esophagus were collected from 209 animals (43 sheep, 89 goats and 77 cattle) from an abattoir in Selangor between February and October, 2013. Each sample was divided into three pieces with each piece measuring 2-3 mm3. Each piece was then squeezed between two glass slides and examined microscopically at x 10 magnification for the presence of sarcocystosis. Three positive samples from each animal species were then fixed in 10% formalin for histological processing. Seven positive samples collected from each animal species were preserved at -80°C or 90% ethanol for gene expression studies. Microsarcocysts were detected in 114 (54.5%) animals by light microscopy (LM). The infection rates in sheep, goat and cattle were 86, 61.8 and 28.6% respectively. The highest rate of infection was in the skeletal muscles of sheep (64.9%) and goats (63.6%) and in the heart of cattle (63.6%). The cysts were spindle to oval in shape and two stages were recognized, the peripheral metrocytes and centrally located banana-shaped bradyzoites. 18S rRNA gene expression studies confirmed the isolates from the sheep as S. ovicanis, goats as S. capracanis and cattle as S. bovicanis. This, to the best of our knowledge, is the first molecular identification of an isolate of S. ovicanis and S. capracanis in Malaysia. Further studies with electron microscopy (EM) are required in the future to compare the features of different types of Sarcocysts spp.

Matched MeSH terms: DNA, Protozoan/genetics

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