Plasmodium knowlesi Malaria in Sabah, Malaysia, 2015–2017: Ongoing Increase in Incidence Despite Near-elimination of the Human-only Plasmodium Species

Abstract

Background Malaysia aims to eliminate malaria by 2020. However, while cases of Plasmodium falciparum and Plasmodium vivax have decreased substantially, the incidence of zoonotic malaria from Plasmodium knowlesi continues to increase, presenting a major challenge to regional malaria control efforts. Here we report incidence of all Plasmodium species in Sabah, including zoonotic P. knowlesi, during 2015–2017. Methods Microscopy-based malaria notification data and polymerase chain reaction (PCR) results were obtained from the Sabah Department of Health and State Public Health Laboratory, respectively, from January 2015 to December 2017. From January 2016 this was complemented by a statewide prospective hospital surveillance study. Databases were matched, and species was determined by PCR, or microscopy if PCR was not available. Results A total of 3867 malaria cases were recorded between 2015 and 2017, with PCR performed in 93%. Using PCR results, and microscopy if PCR was unavailable, P. knowlesi accounted for 817 (80%), 677 (88%), and 2030 (98%) malaria cases in 2015, 2016, and 2017, respectively. P. falciparum accounted for 110 (11%), 45 (6%), and 23 (1%) cases and P. vivax accounted for 61 (6%), 17 (2%), and 8 (0.4%) cases, respectively. Of those with P. knowlesi, the median age was 35 (interquartile range: 24–47) years, and 85% were male. Conclusions Malaysia is approaching elimination of the human-only Plasmodium species. However, the ongoing increase in P. knowlesi incidence presents a major challenge to malaria control and warrants increased focus on knowlesi-specific prevention activities. Wider molecular surveillance in surrounding countries is required.

Seroprevalence and parasite rates ofPlasmodium malariaein a high malaria transmission setting of southern Nigeria

“…As a result, the burden and population at risk in most endemic areas remain largely unknown. A recent study reported persistent detection of P. malariae over a 22-year period in an area of declining P. falciparum infections in Tanzania (9), suggesting that decline of P. falciparum could provide a favorable ecological niche for other malaria parasite species as also recently reported with the zoonotic malaria parasite species P. knowlesi in Malaysia (10).…”

Spatial and epidemiologic features of dengue in Sabah, Malaysia

“…The island possesses rapidly developing urban areas in close proximity to disturbed forest environments, with potential risk of spill-over of sylvatic pathogens to human populations (15). Sabah state, positioned on the northern tip of Borneo, reports the highest incidence of the sylvatic malaria parasite Plasmodium knowlesi , with transmission risk linked to deforestation (16, 17). The emergence of other zoonotic pathogens has also been documented in Sabah (18, 19), including Zika virus in 2015 (20).…”

Spatial-temporal Distribution and Demography of Knowlesi Malaria in Peninsular Malaysia, 2011 to 2018

“…These measures include distribution of ITNs, larvaciding, residual spraying, and repellents to the high-risk groups in order to reduce malaria vector population and human-mosquito contacts. Otherwise, the El Nino phenomenon which led to anomalous rainfall pattern and strong drought in Southeast Asia in 2015, accompanied with severe haze episodes could have contributed to changes in vector density and reduced malaria transmission [12,36,37].…”

“…Besides, cluster detection can aid in more emphasized epidemiological surveillance of reservoir hosts and research on bionomics of vectors. Recently, research based on spatial-temporal analysis has been conducted extensively to study malaria distribution in Sabah, Malaysian Borneo [12,13,14]. However, similar study to investigate transmission patterns in the Peninsular Malaysia is lacking.…”