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Malaria Journal Apr 2019Macaca fascicularis (long-tailed macaque) is the most widespread species of macaque in Southeast Asia and the only species of monkey found naturally in the Philippines....
BACKGROUND
Macaca fascicularis (long-tailed macaque) is the most widespread species of macaque in Southeast Asia and the only species of monkey found naturally in the Philippines. The species is the natural host for the zoonotic malaria species, Plasmodium knowlesi and Plasmodium cynomolgi and for the potentially zoonotic species, Plasmodium inui. Moreover, other Plasmodium species such as Plasmodium coatneyi and Plasmodium fieldi are also natural parasites of M. fascicularis. The aims of this study were to identify and determine the prevalence of Plasmodium species infecting wild and captive long-tailed macaques from the Philippines.
METHODS
A total of 95 blood samples from long-tailed macaques in the Philippines were collected from three locations; 30 were from captive macaques at the National Wildlife Rescue and Rehabilitation Center (NWRRC) in Luzon, 25 were from captive macaques at the Palawan Wildlife Rescue and Conservation Center (PWRCC) in Palawan and 40 were from wild macaques from Puerto Princesa Subterranean River National Park (PPSRNP) in Palawan. The Plasmodium spp. infecting the macaques were identified using nested PCR assays on DNA extracted from these blood samples.
RESULTS
All 40 of the wild macaques from PPSRNP in Palawan and 5 of 25 captive macaques from PWRCC in Palawan were Plasmodium-positive; while none of the 30 captive macaques from the NWRRC in Luzon had any malaria parasites. Overall, P. inui was the most prevalent malaria parasite (44.2%), followed by P. fieldi (41.1%), P. cynomolgi (23.2%), P. coatneyi (21.1%), and P. knowlesi (19%). Mixed species infections were also observed in 39 of the 45 Plasmodium-positive macaques. There was a significant difference in the prevalence of P. knowlesi among the troops of wild macaques from PPSRNP.
CONCLUSION
Wild long-tailed macaques from the island of Palawan, the Philippines are infected with P. knowlesi, P. inui, P. coatneyi, P. fieldi and P. cynomolgi. The prevalence of these Plasmodium spp. varied among the sites of collection and among troops of wild macaques at one site. The presence of these simian Plasmodium parasites, especially P. knowlesi and P. cynomolgi in the long-tailed macaques in Palawan presents risks for zoonotic transmission in the area.
Topics: Animals; Animals, Wild; Islands; Macaca fascicularis; Malaria; Monkey Diseases; Parks, Recreational; Philippines; Plasmodium cynomolgi; Plasmodium knowlesi; Prevalence; Zoonoses
PubMed: 31014342
DOI: 10.1186/s12936-019-2780-4 -
Annual Review of Entomology 2012Plasmodium knowlesi is a malaria parasite of monkeys of Southeast Asia that is transmitted by mosquitoes of the Anopheles leucosphyrus group. Humans are frequently... (Review)
Review
Plasmodium knowlesi is a malaria parasite of monkeys of Southeast Asia that is transmitted by mosquitoes of the Anopheles leucosphyrus group. Humans are frequently infected with this parasite and misdiagnosed as being infected with Plasmodium malariae. The parasite was a major monkey animal model for developing antimalarial vaccines and investigations of the biology of parasite invasion. P. knowlesi is the first monkey malaria parasite genome to be sequenced and annotated.
Topics: Animals; Haplorhini; Host-Parasite Interactions; Humans; Insect Vectors; Malaria; Monkey Diseases; Plasmodium knowlesi
PubMed: 22149265
DOI: 10.1146/annurev-ento-121510-133540 -
Clinical Microbiology Reviews Apr 2013Plasmodium 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... (Review)
Review
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.
Topics: Animals; Antimalarials; Asia, Southeastern; Communicable Disease Control; Disease Reservoirs; Humans; Macaca; Malaria; Plasmodium knowlesi; Zoonoses
PubMed: 23554413
DOI: 10.1128/CMR.00079-12 -
Journal of Physiological Anthropology Apr 2022Plasmodium knowlesi malaria infection in humans has been reported throughout southeast Asia. The communities at risk are those living in areas where Macaque monkeys and... (Review)
Review
Plasmodium knowlesi malaria infection in humans has been reported throughout southeast Asia. The communities at risk are those living in areas where Macaque monkeys and Anopheles mosquito are present. Zoonotic malaria control is challenging due to the presence of the reservoir host and the possibility of human-vector-human transmission. Current control measures, including insecticide-treated nets (ITNs) and indoor residual spraying (IRS), are insufficient to address this threat due to gaps in protection associated with outdoor and early evening vector biting and social and economic activities, such as agricultural and forest work. Understanding the challenges faced by affected communities in preventing mosquito bites is important for reducing disease transmission. This opinion paper discusses opportunities to improve P. knowlesi malaria control through understanding the challenges faced by communities at risk and increasing community engagement and ownership of control measures. The paper highlights this issue by describing how the concept of reimagining malaria can be adapted to zoonotic malaria control measures including identifying current gaps in vector control, understanding interactions between environmental, economic, and human behavioral factors, and increasing community participation in and ownership of control measures.
Topics: Animals; Anopheles; Humans; Insecticides; Malaria; Mosquito Vectors; Plasmodium knowlesi
PubMed: 35413881
DOI: 10.1186/s40101-022-00288-y -
International Journal of Environmental... Mar 2022is a non-human parasite that causes zoonotic disease in humans. This systematic review aims to highlight and summarize studies describing human behaviors and activities... (Review)
Review
OBJECTIVES
is a non-human parasite that causes zoonotic disease in humans. This systematic review aims to highlight and summarize studies describing human behaviors and activities that expose humans to mosquito bites. English entries in PubMed, Web of Science, and Science Direct from 2010 to 2020 were systematically perused, and the results were synthesized. Methodological quality was assessed using the Joanna Briggs Institute quality appraisal checklists.
SETTING
Studies that described malaria preventive measures were included. Laboratory, in vivo, in vitro, and animal studies were excluded.
PRIMARY AND SECONDARY OUTCOME MEASURES
The main outcome of the review was findings from studies describing the behavior that exposed a person or a group to infection.
RESULTS
Twelve eligible studies were of good or medium quality. Attitude, disease misconceptions, perceived threat of disease, lack of motivation, and supernatural or traditional beliefs causing individuals to seek treatment from traditional healers influenced the exposure of individuals or communities to malaria. Other factors were forestry activities (2.48, 1.45-4.23,95% CI, = 0.0010) and sleeping outdoors (3.611, 1.48-8.85, 95% CI, = 0.0049).
CONCLUSIONS
Future studies must consider the importance of human behavior and community perspective on the infection to provide novel information to improve the current zoonotic malaria programs. Policymakers should concentrate on understanding human behavior and activities that expose individuals or communities to mosquito bites, in order to better design socially feasible interventions.
Topics: Animals; Humans; Insect Bites and Stings; Malaria; Motivation; Plasmodium knowlesi; Zoonoses
PubMed: 35329359
DOI: 10.3390/ijerph19063675 -
The Medical Journal of Malaysia Sep 2010Plasmodium knowlesi, a simian malaria parasite, is now recognised as the fifth cause of human malaria and can lead to fatal infections in humans. Knowlesi malaria cases... (Review)
Review
Plasmodium knowlesi, a simian malaria parasite, is now recognised as the fifth cause of human malaria and can lead to fatal infections in humans. Knowlesi malaria cases are widely distributed in East and West Malaysia and account for more than 50% of admissions for malaria in certain hospitals in the state of Sarawak. This paper will begin with a description of the early studies on P. knowlesi, followed by a review of the epidemiology, diagnosis, clinical and laboratory features, and treatment of knowlesi malaria.
Topics: Antimalarials; Humans; Malaria; Malaysia; Plasmodium knowlesi
PubMed: 21939162
DOI: No ID Found -
Journal of the Royal Army Medical Corps Dec 2012Plasmodium knowlesi is a zoonosis and is now recognised as the fifth commonly occurring form of human malaria. It is endemic in South East Asia, including some areas... (Review)
Review
Plasmodium knowlesi is a zoonosis and is now recognised as the fifth commonly occurring form of human malaria. It is endemic in South East Asia, including some areas previously declared malaria free or at low risk for malaria. The epidemiology of the disease is very different to other forms of malaria which are determined by transmission by anthrophilic mosquitoes from human reservoirs. In contrast Plasmodium knowlesi malaria has a monkey reservoir and disease is transmitted to humans by mosquitoes that normally feed on animals. People become accidentally infected when they enter the ranges of the vector mosquitoes and animal hosts. Improved and novel diagnostic methods have indicated that human disease is much more common than previously thought. Although the greatest disease burden falls on local populations living in endemic areas, visitors entering such zones are also at risk. The changing nature of tourism with deep jungle expeditions being more heavily marketed, and short visits to endemic zones now common, mean that new populations are increasingly recognised as being at risk. One such group are military personnel undergoing jungle training or deployed on Operations. The potential for severe disease in areas previously considered at low risk for malaria means that risk assessment needs to be reviewed, coupled with communication strategies to address prevention of a zoonotic form of the disease. The role of chemoprophylaxis in some specific groups may need to be considered.
Topics: Animals; Communicable Disease Control; Humans; Incidence; Malaria; Military Personnel; Plasmodium knowlesi; Risk Assessment; Risk Factors; United Kingdom
PubMed: 23402069
DOI: 10.1136/jramc-158-04-08 -
Malaria Journal Dec 2023Plasmodium knowlesi is an established experimental model for basic and pre-clinical malaria vaccine research. Historically, rhesus macaques have been the most common...
BACKGROUND
Plasmodium knowlesi is an established experimental model for basic and pre-clinical malaria vaccine research. Historically, rhesus macaques have been the most common host for malaria vaccine studies with P. knowlesi parasites. However, rhesus are not natural hosts for P. knowlesi, and there is interest in identifying alternative hosts for vaccine research. The study team previously reported that pig-tailed macaques (PTM), a natural host for P. knowlesi, could be challenged with cryopreserved P. knowlesi sporozoites (PkSPZ), with time to blood stage infection equivalent to in rhesus. Here, additional exploratory studies were performed to evaluate PTM as potential hosts for malaria vaccine studies. The aim was to further characterize the parasitological and veterinary health outcomes after PkSPZ challenge in this macaque species.
METHODS
Malaria-naïve PTM were intravenously challenged with 2.5 × 10 PkSPZ and monitored for blood stage infection by Plasmodium 18S rRNA RT-PCR and thin blood smears. Disease signs were evaluated by daily observations, complete blood counts, serum chemistry tests, and veterinary examinations. After anti-malarial drug treatment, a subset of animals was re-challenged and monitored as above. Whole blood gene expression analysis was performed on selected animals to assess host response to infection.
RESULTS
In naïve animals, the kinetics of P. knowlesi blood stage replication was reproducible, with parasite burden rising linearly during an initial acute phase of infection from 6 to 11 days post-challenge, before plateauing and transitioning into a chronic low-grade infection. After re-challenge, infections were again reproducible, but with lower blood stage parasite densities. Clinical signs of disease were absent or mild and anti-malarial treatment was not needed until the pre-defined study day. Whole blood gene expression analysis identified immunological changes associated with acute and chronic phases of infection, and further differences between initial challenge versus re-challenge.
CONCLUSIONS
The ability to challenge PTM with PkSPZ and achieve reliable blood stage infections indicate this model has significant potential for malaria vaccine studies. Blood stage P. knowlesi infection in PTM is characterized by low parasite burdens and a benign disease course, in contrast with the virulent P. knowlesi disease course commonly reported in rhesus macaques. These findings identify new opportunities for malaria vaccine research using this natural host-parasite combination.
Topics: Animals; Plasmodium knowlesi; Malaria Vaccines; Macaca nemestrina; Macaca mulatta; Antimalarials; Malaria
PubMed: 38093306
DOI: 10.1186/s12936-023-04788-9 -
Journal of Travel Medicine Dec 2023
Topics: Humans; Plasmodium knowlesi; Plasmodium vivax; Coinfection; Malaria; Plasmodium falciparum
PubMed: 37694850
DOI: 10.1093/jtm/taad120 -
Current Opinion in Infectious Diseases Oct 2012The emergence of Plasmodium knowlesi, a parasite of Southeast Asian macaques, into the human population is ongoing and widespread across Southeast Asia. Humans entering... (Review)
Review
PURPOSE OF REVIEW
The emergence of Plasmodium knowlesi, a parasite of Southeast Asian macaques, into the human population is ongoing and widespread across Southeast Asia. Humans entering P. knowlesi transmission areas are at risk. Patients present with uncomplicated, complicated and fatal disease, therefore prompt accurate diagnosis and treatment are essential. This review focuses on recent descriptions of asymptomatic and symptomatic infections in children, pathophysiology in adults, treatment and diagnosis, and highlights the importance of monitoring transmission and host-switch events.
RECENT FINDINGS
New reports on P. knowlesi infections identify regional differences in aetiology and vector species. Parasitaemia is associated with disease severity and specific diagnostic tools are required. Treatment failures have not been reported. The severe form of P. knowlesi malaria can be compared with severe falciparum malaria to inform the pathophysiology of both infections.
SUMMARY
P. knowlesi presents new challenges to malaria-control efforts in Southeast Asia. Sensitive and specific diagnostic tools are required for communities and travellers at risk. Currently P. knowlesi transmission appears to occur away from human settlements. However, ongoing host-switch events from macaques to humans cannot be excluded. Changes in P. knowlesi transmission across the region should be monitored to preempt outbreaks of this virulent pathogen.
Topics: Animals; Antimalarials; Asia; Communicable Diseases, Emerging; Disease Reservoirs; Disease Vectors; Humans; Macaca; Malaria; Parasitemia; Plasmodium knowlesi
PubMed: 22710318
DOI: 10.1097/QCO.0b013e3283558780