Plasmodium knowlesi: an update

Abstract

There were only four species of Plasmodium that were thought to cause malaria in humans until a large number of human infections by Plasmodium knowlesi, a malaria parasite typically found in long-tailed and pig-tailed macaques, were reported in 2004 in Malaysian Borneo. Since then, cases of knowlesi malaria have been reported throughout South-east Asia and also in travellers returning from the region. This article describes the molecular, entomological and epidemiological data which indicate that P. knowlesi is an ancient parasite that is primarily zoonotic, and there are three highly divergent sub-populations. It also describes the detection methods for P. knowlesi, which is morphologicaly similar to P. malariae, and the clinical features and treatment of this malaria parasite that is potentially fatal. Malaria parasites and discovery of large focus of human knowlesi malaria casesMalaria is caused by parasites that belong to the genus Plasmodium and there are more than 150 species of Plasmodium that infect reptiles, birds and mammals 1 . These parasites, in general, tend to be host-specific. Long-tailed and pig-tailed macaques (Macaca fascicularis and M. nemestrina respectively) are hosts to five species (P. knowlesi, P. inui, P. cynomolgi, P. fieldi and P. coatneyi). Only four species of Plasmodium, namely P. falciparum, P. vivax, P. malariae and P. ovale, were thought to cause malaria in humans until a large number of human cases due to P. knowlesi were reported in Sarawak, Malaysian Borneo over 11 years ago 2 . The study in Kapit was prompted by observations that cases diagnosed by microscopy as P. malariae had high parasitaemias, required hospitalization and that 95% of patients were adults. This was in contrast to P. malariae infections which typically are asymptomatic with low parasitaemia and occur in all age groups. When blood samples from 208 malaria patients at Kapit Hospital were analysed by PCR assays, none were identified as P. malariae, although 141had been diagnosed as P. malariae by microscopy. Fifty-eight percent (120) were either single P. knowlesi infections or mixed infections of P. knowlesi with P. falciparum and P. vivax. Misdiagnosis had occurred because the blood stages of P. knowlesi and P. malariae are morphologically indistinguishable

Infeksi Malaria Plasmodium knowlesi pada Manusia

“…Habitat nyamuk ini umumnya di dalam hutan belantara, namun kadang ada juga di area terbuka di pinggir hutan. 6,8,12,13 Intensitas gigitan nyamuk grup Leucosphyrus berbeda tergantung lokasi habitatnya yaitu tinggi di tepi hutan (6,74%), sedang di dalam hutan (1,85%) dan rendah di dalam rumah adat Malaysia (0,28%). 2 5,15 Diperkirakan sekitar 500 juta penduduk berisiko untuk terinfeksi.…”

“…14 Infeksi P. knowlesi berbeda dengan infeksi P. malariae, dimana malaria malariae biasanya asimptomatik, dapat menyerang semua umur dan kadar parasitemia yang rendah. 13 Selama kurun waktu 2005-2012 telah dilaporkan 15 kasus impor malaria knowlesi pada wisatawan yang berkunjung di wilayah Asia Tenggara dengan faktor risiko jenis kelamin laki-laki dan riwayat bepergian ke hutan atau kontak dengan kera. 15,18 Peningkatan kasus malaria P. knowlesi di Asia tenggara mungkin disebabkan karena semakin dekatnya hunian penduduk dengan hutan dan meningkatnya eksploitasi hutan baik untuk industri maupun pariwisata.…”

Recombinase Polymerase Amplification Combined with a Lateral Flow Strip for the Detection of Plasmodium knowlesi

“…Plasmodium knowlesi is the main cause of malaria in Malaysia, and cases have been reported throughout Southeast Asia, including cases in Thailand, Indonesia, Singapore, Philippines, Vietnam, Cambodia, Indonesia, and Myanmar. 3 The World Health Organization (WHO) Malaria Policy Advisory Committee recognized the importance of this parasite and constituted an Evidence Review Group on P. knowlesi to discuss strategy control, mitigation, and appropriate preventive methods. 1 Humans are a good reservoir for P. knowlesi; however, it has been proved that it remains a zoonosis that naturally infects long-tailed and pig-tailed macaques.…”

“…1 Humans are a good reservoir for P. knowlesi; however, it has been proved that it remains a zoonosis that naturally infects long-tailed and pig-tailed macaques. 3 A wide variety of reservoirs threaten the effort of eliminating malaria infection. In addition, the lack of adequate diagnostic approaches contributes to this factor too.…”

“…The primer sequence for PK R was labelled with biotin-tag (B) at 5' end. The PK LF probe and Plas genus probe used in this study were particularly created with an insertion of an abasic nucleotide analogue (a tetrahydrofuran residue, H) flanked by a dT-FAM (F) at 5' end and carbon blocker (C3 spacer, [3]) at 3'end. Plas genus R primer was labelled with digoxigenintag (D) at 5'end.…”