Human Plasmodium knowlesi infections in young children in central Vietnam

Eede, Peter Van den; Van, Hong Nguyen; Overmeir, Chantal Van; Vythilingam, Indra; Duc, Thang Ngo; Hưng, Lê Xuân; Manh, Hung Nguyen; Anné, Jozef; D’Alessandro, Umberto; Erhart, Annette

doi:10.1186/1475-2875-8-249

Cited by 122 publications

(88 citation statements)

References 22 publications

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“…However, P. knowlesi is now the most common cause of malaria in Sabah, Malaysia and true numbers of human infections may be missed by passive case detection at facilities. Recent studies have shown that all ages and both sexes are susceptible to infection with cases also reported in Malaysian children [29], and Vietnamese children [37], [38]. Additionally, familial clustering of cases has been demonstrated indicating transmission is probably now occurring peri-domestically contrary to previous reports, and that this may be linked to deforestation and/or land-use change in these environments [14].…”

Section: Discussionmentioning

confidence: 95%

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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Section: Discussionmentioning

confidence: 95%

Transmission and Control of Plasmodium knowlesi: A Mathematical Modelling Study

et al. 2014

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“…The sensitivity of this method of detection is between 1 and 6 parasites/l blood, when a DNA template is prepared with a simple boiling procedure with a chelating agent from blood spots collected onto filter paper (112). The initial knowlesispecific primers that were developed in Sarawak, Pmk8 and Pmkr9, were found in certain laboratories to nonspecifically amplify a proportion of P. vivax isolates, resulting in P. vivax infections being identified as mixed P. vivax and P. knowlesi infections (63,65,113). In epidemiological studies undertaken in Sarawak, 512 single P. vivax infections and 28 P. vivax infections mixed with P. knowlesi infections have been detected (3,28,33).…”

Section: Molecular Detection Methodsmentioning

confidence: 99%

“…For example, in Sarawak, Malaysian Borneo, where most cases of knowlesi malaria have been reported, the majority of knowlesi malaria patients are adults who are subsistence farmers, hunters, and logging camp workers (3,5,28). Those acquiring their infections in Vietnam appear to be very similar to those in Sarawak in that they are people in the forest fringe who enter the forests to collect bamboo and rattan and work on their farms on mountain slopes (62), and there have also been cases of children living in forest communities with knowlesi malaria (63). In Singapore, servicemen acquired knowlesi malaria while training in a forested area (61 (66), and Thailand (52).…”

Section: Populations At Riskmentioning

confidence: 99%

“…In some hospitals in Malaysian Borneo, knowlesi malaria accounts for the majority of malaria cases admitted to hospitals (29,38,43). Human cases are not restricted to Malaysia, with reports of infections acquired in Thailand (48)(49)(50)(51)(52)(53), the Philippines (54-56), Myanmar (57,58), Singapore (59-61), Vietnam (62,63), Indonesia (64,65), Brunei (66), and Cambodia (67) (Fig. 1).…”

Section: Epidemiology Distributionmentioning

confidence: 99%

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Human Infections and Detection of Plasmodium knowlesi

2013

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SUMMARY Plasmodium knowlesi is a malaria parasite that is found in nature in long-tailed and pig-tailed macaques. Naturally acquired human infections were thought to be extremely rare until a large focus of human infections was reported in 2004 in Sarawak, Malaysian Borneo. Human infections have since been described throughout Southeast Asia, and P. knowlesi is now recognized as the fifth species of Plasmodium causing malaria in humans. The molecular, entomological, and epidemiological data indicate that human infections with P. knowlesi are not newly emergent and that knowlesi malaria is primarily a zoonosis. Human infections were undiagnosed until molecular detection methods that could distinguish P. knowlesi from the morphologically similar human malaria parasite P. malariae became available. P. knowlesi infections cause a spectrum of disease and are potentially fatal, but if detected early enough, infections in humans are readily treatable. In this review on knowlesi malaria, we describe the early studies on P. knowlesi and focus on the epidemiology, diagnosis, clinical aspects, and treatment of knowlesi malaria. We also discuss the gaps in our knowledge and the challenges that lie ahead in studying the epidemiology and pathogenesis of knowlesi malaria and in the prevention and control of this zoonotic infection.

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“…El primer caso reconocido de infección natural por P. knowlesi en humanos se reportó en 1965 (4) y luego se informó un presunto caso en 1971 (5), pero sólo desde el 2004 (2) se ha venido informando sistemáticamente la presencia de infecciones naturales en humanos en diferentes países del sureste de Asia, como en Tailandia (2004) (6), China (2006) (7), Singapur (2008) (8), Filipinas (2008) (9,10), Vietnam (2009) (11) y Malasia (12,13).…”

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Natural Plasmodium knowlesi malaria infections in humans

2012

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El primer caso informado de transmisión natural de Plasmodium knowlesi en humanos se publicó en 1965. En el sureste de Asia la presentación atípica de casos de malaria, tanto por cambios en la distribución de las especies diagnosticadas de Plasmodium, como por su morfología, motivó diversos estudios que han confirmado la infección en humanos por este plasmodio que infecta naturalmente distintas especies de simios, que son endémicos de las selvas de esta región. Los estudios recientes sugieren que la malaria por P. knowlesi no es una enfermedad emergente en humanos sino que no estaba siendo diagnosticada, debido a la similitud morfológica de este plasmodio con P. malariae y P. falciparum, lo cual dificulta su reconocimiento mediante examen microscópico. Actualmente, se puede confirmar el diagnóstico mediante reacción en cadena de la polimerasa que permite identificar cebadores específicos de P. knowlesi. La malaria por P. knowlesi ha ocasionado desenlaces fatales en humanos, lo que plantea diversos retos como la búsqueda de métodos operativos de diagnóstico para las zonas endémicas, el estudio de los vectores involucrados y la eficacia terapéutica de los medicamentos para su tratamiento. En las regiones selváticas de Suramérica se hace imperativa la vigilancia de parásitos y vectores de la malaria en simios, que potencialmente puedan ocasionar esta zoonosis. Palabras clave: malaria/epidemiología, Plasmodium knowlesi, infección, humanos Natural Plasmodium knowlesi malaria infections in humansThe first reported case of natural transmission of Plasmodium knowlesi to humans was published in 1965. In Southeast Asia, the atypical presentation of malaria cases, the changes in the distribution of the Plasmodium species diagnosed and their atypical morphology prompted several studies that confirmed natural infections in humans by this protozoon which naturally infects different species of apes which are endemic in the forests of this region. Recent studies suggest that P. knowlesi malaria is not an emerging disease in humans but was rather being misdiagnosed due to its morphological similarity with P. malariae and P. falciparum, hampering its correct diagnosis by microscopic examination. Currently, the diagnosis can be confirmed by polymerase chain reaction using P. knowlesi specific primers. Malaria by P. knowlesi has lead to fatal outcomes in humans and poses several challenges such as the development of useful diagnostic tools for endemic areas, the study of the vectors involved and the therapeutic efficacy of the drugs for its treatment. In the jungle regions of South America it is imperative to monitor the parasites of simian malaria and the vectors that have the potential to transmit this zoonosis.

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Human Plasmodium knowlesi infections in young children in central Vietnam

Cited by 122 publications

References 22 publications

Transmission and Control of Plasmodium knowlesi: A Mathematical Modelling Study

Transmission and Control of Plasmodium knowlesi: A Mathematical Modelling Study

Human Infections and Detection of Plasmodium knowlesi

Natural Plasmodium knowlesi malaria infections in humans

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