Sabah health authorities are actively hunting down the Anopheles mosquitoes, as they are known to transmit an emerging disease called Plasmodium knowlesi malaria from monkeys to humans.

Dr Timothy William, president of Infectious Disease Society of Kota Kinabalu, had said that steps are being taken to diminish breeding sites of the mosquitoes apart from spraying insecticides where these insects are prevalent. He also said that authorities were doing whatever it takes to optimise the treatment of Plasmodium knowlesi malaria – more commonly known as monkey malaria – in humans through early detection.

“Those known to be suffering from this disease are given immediate treatment with Artemisinin combination therapy and early referral to tertiary care hospitals for severe cases. There is continuing research on this emerging disease,” said William, co-author of the report.

Case-control study to determine associated factors

The research team found that farmers in this region who work on plantations, clearing vegetation and taking part in forestry work were most at risk of contracting this monkey malaria. Currently, P. knowlesi is the most common form of human malaria in many regions of Malaysia. The Ministry of Health in Malaysia reported 2,584 out of the country's 3,923 malaria cases derived from P. knowlesi, and that number is increasing in trend.

The research team carried out a case control study of over 1,000 individuals in the districts of Kudat and Kota Marudu. They compared people with P. knowlesi to those with other types of human malaria and a control group without malaria. Participants filled out detailed questionnaires to obtain information on their daily activities, residence and the frequency of which they had monkey sightings.

Results showed that men were four times more likely to have P. knowlesi infection than women.

Also, male farmers were more prone to contracting monkey malaria but they were not at an increased risk of contracting other variants of malaria. Indoor work such as shopkeeping, traditional female household duties, as well as studying, were linked to a decreased risk of P. knowlesi malaria in these populations.

Study provides insights into need for social interventions

The prinicipal collaborator on the monkey malaria study and professor at the London School of Hygiene & Tropical Medicine, Chris Drakeley commented on the complexity and potentially life-threatening nature of the P. knowlesi parasite.

“Conventional approaches used to tackle malaria such as drugs or bed nets cannot be used to combat P. knowlesi as monkeys are the host and the risk is associated with outdoor work.”

“Our study offers important insight into where social interventions are likely to have the biggest impact,” he added.

Drakeley continued, “We will continue to work with our colleagues in the Malaysian Health Ministry to improve awareness and education for local residents about areas of risk and how they can prevent mosquito bites.”

Dr Matthew Grigg, Menzies Research fellow and lead author of the study, commented on the factors that influenced the prevalence of this disease. He said, “Malaysia’s national malaria eradication plan is proving extremely effective in reducing case numbers of other types of malaria.”

“However, we found that cases of P. knowlesi are on the rise due to a number of human behavioural factors such as farming, land clearing activities, working on oil palm plantations, and travelling or sleeping outside,” he explained. MIMS

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