Abstract
BackgroundPlasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malaysian Borneo. However, little is known about the incidence and distribution of this parasite in the Sandakan division, Malaysian Borneo. Therefore, the aim of the present epidemiological study was to investigate the incidence and distribution of P. knowlesi as well as other Plasmodium species in this division based on a most recent developed hexaplex PCR system (PlasmoNex™).MethodsA total of 189 whole blood samples were collected from Telupid Health Clinic, Sabah, Malaysia, from 2008 to 2011. All patients who participated in the study were microscopically malaria positive before recruitment. Complete demographic details and haematological profiles were obtained from 85 patients (13 females and 72 males). Identification of Plasmodium species was conducted using PlasmoNex™ targeting the 18S ssu rRNA gene.ResultsA total of 178 samples were positive for Plasmodium species by using PlasmoNex™. Plasmodium falciparum was identified in 68 samples (38.2%) followed by 64 cases (36.0%) of Plasmodium vivax, 42 (23.6%) cases of P. knowlesi, two (1.1%) cases of Plasmodium malariae and two (1.1%) mixed-species infections (i e, P. vivax/P. falciparum). Thirty-five PlasmoNex™ positive P. knowlesi samples were misdiagnosed as P. malariae by microscopy. Plasmodium knowlesi was detected in all four districts of Sandakan division with the highest incidence in the Kinabatangan district. Thrombocytopaenia and anaemia showed to be the most frequent malaria-associated haematological complications in this study.ConclusionsThe discovery of P. knowlesi in Sandakan division showed that prospective studies on the epidemiological risk factors and transmission dynamics of P. knowlesi in these areas are crucial in order to develop strategies for effective malaria control. The availability of advanced diagnostic tool PlasmoNex™ enhanced the accuracy and accelerated the speed in the diagnosis of malaria.
Highlights
Plasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malaysian Borneo
There was no P. knowlesi and P. ovale malaria infection reported from the microscopic examination
According to the haematological profiles, the present study showed that the overall median concentration of haemoglobin level (Hb), platelet count and total white blood cell counts (TWBC) for the patients was 128.0 g/l (IQR = 109.0-140.0), 91,000 cells/cmm (IQR = 61,500-132,500) and TWBC was 6.6 × 109 cells/L (IQR = 5.1-8.8), respectively (Table 3)
Summary
Plasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malaysian Borneo. According to the World Malaria Report 2011, an estimated 3.3 billion people were at risk of malaria in 2010. Malaria is the most common vector-borne parasitic disease in Malaysia, responsible for 20–40 deaths per year over the last decade, and it is estimated that 3% of total Malaysian population live in malaria risk areas. Human malaria can be caused by four Plasmodium species, which include Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale. Infection caused by P. falciparum is severe and may be fatal in the absence of prompt recognition of the disease and its complications, while the disease caused by P. vivax, P. ovale and P. malariae is usually milder and rarely fatal
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