Is There a Risk of Suburban Transmission of Malaria in Selangor, Malaysia?

Abstract

BackgroundThe suburban transmission of malaria in Selangor, Malaysia’s most developed and populous state still remains a concern for public health in this region. Despite much successful control efforts directed at its reduction, sporadic cases, mostly brought in by foreigners have continued to occur. In addition, cases of simian malaria caused by Plasmodium knowlesi, some with fatal outcome have caused grave concern to health workers. The aim of this study was to investigate the possibility of local malaria transmission in suburban regions of Selangor, which are adjacent to secondary rainforests.FindingsA malaria survey spanning 7 years (2006 - 2012) was conducted in Selangor. A total of 1623 laboratory confirmed malaria cases were reported from Selangor’s nine districts. While 72.6% of these cases (1178/1623) were attributed to imported malaria (cases originating from other countries), 25.5% (414/1623) were local cases and 1.9% (31/1623) were considered as relapse and unclassified cases combined. In this study, the most prevalent infection was P. vivax (1239 cases, prevalence 76.3%) followed by P. falciparum (211, 13.0%), P. knowlesi (75, 4.6%), P. malariae (71, 4.4%) and P. ovale (1, 0.06%). Mixed infections comprising of P. vivax and P. falciparum were confirmed (26, 1.6%). Entomological surveys targeting the residences of malaria patients’ showed that the most commonly trapped Anopheles species was An. maculatus. No oocysts or sporozoites were found in the An. maculatus collected. Nevertheless, the possibility of An. maculatus being the malaria vector in the investigated locations was high due to its persistent occurrence in these areas.ConclusionsMalaria cases reported in this study were mostly imported cases. However the co-existence of local cases and potential Plasmodium spp. vectors should be cause for concern. The results of this survey reflect the need of maintaining closely monitored malaria control programs and continuous extensive malaria surveillance in Peninsula Malaysia.

Plasmodium knowlesi malaria an emerging public health problem in Hulu Selangor, Selangor, Malaysia (2009–2013): epidemiologic and entomologic analysis

“…A large number of field workers will have to be distributed throughout the sites in order to select the best sites for the collection of mosquitoes. This is also reflected in an earlier study [ 53 ], where they were not able to incriminate the vector. It is also known that the Asia Pacific Region has the highest number of dominant vector species for human malaria compared to other regions and is important to determine the correct species for control activities to succeed [ 54 ].…”

Prevalence of malaria and its risk factors in Sabah, Malaysia

“…Poor access to education within these regions has inadvertently led to bad sanitation practices and has contributed to the increasing number of malaria infections (Deressa et al, 2008). Braima et al (2013) stated that people who lived by the jungle were at higher risk of contracting malaria, as 35% of malaria cases were recorded within this area (Braima et al, 2013).…”

Simian malaria in wild macaques: first report from Hulu Selangor district, Selangor, Malaysia

“…Most of the cases were contributed by Sabah and Sarawak, while in peninsular Malaysia a high number of P. knowlesi malaria cases were reported from Pahang [ 28 , 29 ]. The most developed state of Malaysia is Selangor which is still vulnerable to malaria [ 30 ]. In the last 5 years, P .…”

“…malariae infection in humans was shown to be highest in Hulu Selangor district, one of the nine districts in Selangor [ 31 ]. This could be due to several factors, such as heightened human infringement into forests, high rate of construction and development, and the presence of secondary rainforests in the locality of urban and suburban residences which offer suitable habitats for mosquitoes and monkeys that can harbour various species of simian malaria parasites [ 30 ].…”