<i>Plasmodium knowlesi</i>Infection in Humans, Cambodia, 2007–2010

Khim, Nimol; Sovannaroth, Siv; Kim, Saorin; Mueller, Tara; Fleischmann, Erna; Singh, Balbir; Divis, Paul Cliff Simon; Steenkeste, Nicolas; Duval, Linda; Bouchier, Christiane; Socheat, Duong; Ariey, Frédéric; Ménard, Didier

doi:10.3201/eid1710.110355

Cited by 92 publications

(82 citation statements)

References 8 publications

(11 reference statements)

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“…At this point, the majority of the studies and elimination programmes have focused in first instance on P. falciparum [13, 27, 38, 45, 46, 52, 56], which is easier to eliminate than P. vivax due to possible relapses in the latter one [57]. However, in contrast to other studies the current study was carried out in Southeast Asia (Cambodia) where all human malaria parasites are co-occurring [26, 58] and in which occupational and behavioural factors define the risk for malaria exposure [59–61]. As such, adolescents and mainly adults performing plantation work and forest activities are the main risk groups for malaria infection [59–62].…”

Section: Discussionmentioning

confidence: 99%

Serological markers to measure recent changes in malaria at population level in Cambodia

Kerkhof

Sluydts

Willen

et al. 2016

Malar J

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BackgroundSerological markers for exposure to different Plasmodium species have recently been used in multiplex immunoassays based on the Luminex technology. However, interpretation of the assay results requires consideration of the half-life of specific antibodies against these markers. Therefore, the aim of the present study was to document the half-life of malaria specific serological makers, as well as assessing the sensitivity of these markers to pick up recent changes in malaria exposure.MethodsA recently developed multiplex immunoassay was used to measure the intensity of antibody (Ab) responses against 19 different Plasmodium specific antigens, covering different human malaria parasites and two vector saliva antigens. Therefore, 8439 blood samples from five cross-sectional surveys in Ratanakiri, Cambodia, were analysed. These involve a random selection from two selected surveys, and an additional set of blood samples of individuals that were randomly re-sampled three, four or five times. A generalized estimating equation model and linear regression models were fitted on log transformed antibody intensity data.ResultsResults showed that most (17/21) Ab-responses are higher in PCR positive than PCR negative individuals. Furthermore, these antibody-responses follow the same upward trend within each age group. Estimation of the half-lives showed differences between serological markers that reflect short- (seasonal) and long-term (year round) transmission trends. Ab levels declined significantly together with a decrease of PCR prevalence in a group of malaria endemic villages.ConclusionFor Plasmodium falciparum, antibodies against LSA3.RE, GLURP and Pf.GLURP.R2 are most likely to be a reflexion of recent (range from 6 to 8 months) exposure in the Mekong Subregion. PvEBP is the only Plasmodium vivax Ag responding reasonably well, in spite of an estimated Ab half-life of more than 1 year. The use of Ab intensity data rather dichotomizing the continuous Ab-titre data (positive vs negative) will lead to an improved approach for serological surveillance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1576-z) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Serological markers to measure recent changes in malaria at population level in Cambodia

Kerkhof

Sluydts

Willen

et al. 2016

Malar J

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“…Due to its zoonotic nature, infection prevalence of Plasmodium knowlesi in humans in South East Asia is very low with an estimated annual incidence of 1% (95% CI: 0.4–1.7%) in southern Vietnam [25], 0.3% in Cambodia [26], and 0.65% in Thailand. In contrast, macaque P. knowlesi infection prevalence in the wild is extremely high at over 90%.…”

Section: Methodsmentioning

confidence: 99%

Transmission and Control of Plasmodium knowlesi: A Mathematical Modelling Study

et al. 2014

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Introduction Plasmodium knowlesi is now recognised as a leading cause of malaria in Malaysia. As humans come into increasing contact with the reservoir host (long-tailed macaques) as a consequence of deforestation, assessing the potential for a shift from zoonotic to sustained P. knowlesi transmission between humans is critical.MethodsA multi-host, multi-site transmission model was developed, taking into account the three areas (forest, farm, and village) where transmission is thought to occur. Latin hypercube sampling of model parameters was used to identify parameter sets consistent with possible prevalence in macaques and humans inferred from observed data. We then explore the consequences of increasing human-macaque contact in the farm, the likely impact of rapid treatment, and the use of long-lasting insecticide-treated nets (LLINs) in preventing wider spread of this emerging infection.ResultsIdentified model parameters were consistent with transmission being sustained by the macaques with spill over infections into the human population and with high overall basic reproduction numbers (up to 2267). The extent to which macaques forage in the farms had a non-linear relationship with human infection prevalence, the highest prevalence occurring when macaques forage in the farms but return frequently to the forest where they experience higher contact with vectors and hence sustain transmission. Only one of 1,046 parameter sets was consistent with sustained human-to-human transmission in the absence of macaques, although with a low human reproduction number (R0H = 1.04). Simulations showed LLINs and rapid treatment provide personal protection to humans with maximal estimated reductions in human prevalence of 42% and 95%, respectively.ConclusionThis model simulates conditions where P. knowlesi transmission may occur and the potential impact of control measures. Predictions suggest that conventional control measures are sufficient at reducing the risk of infection in humans, but they must be actively implemented if P. knowlesi is to be controlled.

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“…The primate malaria Plasmodium knowlesi has recently been documented as causing human infections in multiple countries in Southeast Asia [5–11], and is a serious public health problem within Malaysia [12–19]. In the Malaysian state of Sabah, this parasite is now responsible for the greatest number of malaria cases with 815 and 996 cases reported respectively in 2012 and 2013 [20].…”

Section: Introductionmentioning

confidence: 99%

Seasonal and Spatial Dynamics of the Primary Vector of Plasmodium knowlesi within a Major Transmission Focus in Sabah, Malaysia

et al. 2015

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BackgroundThe simian malaria parasite Plasmodium knowlesi is emerging as a public health problem in Southeast Asia, particularly in Malaysian Borneo where it now accounts for the greatest burden of malaria cases and deaths. Control is hindered by limited understanding of the ecology of potential vector species.Methodology/Principal FindingsWe conducted a one year longitudinal study of P. knowlesi vectors in three sites within an endemic area of Sabah, Malaysia. All mosquitoes were captured using human landing catch. Anopheles mosquitoes were dissected to determine, oocyst, sporozoites and parous rate. Anopheles balabacensis is confirmed as the primary vector of. P. knowlesi (using nested PCR) in Sabah for the first time. Vector densities were significantly higher and more seasonally variable in the village than forest or small scale farming site. However An. balabacensis survival and P. knowlesi infection rates were highest in forest and small scale farm sites. Anopheles balabacensis mostly bites humans outdoors in the early evening between 1800 to 2000hrs.Conclusions/SignificanceThis study indicates transmission is unlikely to be prevented by bednets. This combined with its high vectorial capacity poses a threat to malaria elimination programmes within the region.

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Plasmodium knowlesiInfection in Humans, Cambodia, 2007–2010

Cited by 92 publications

References 8 publications

Serological markers to measure recent changes in malaria at population level in Cambodia

Serological markers to measure recent changes in malaria at population level in Cambodia

Transmission and Control of Plasmodium knowlesi: A Mathematical Modelling Study

Seasonal and Spatial Dynamics of the Primary Vector of Plasmodium knowlesi within a Major Transmission Focus in Sabah, Malaysia

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