Health Ministry: Monkey malaria spike due to better diagnosis, but deforestation raises risk

Ranjit Singh
The ministry said its Malaria Elimination Programme since 2011 has resulted in a reduction in human malaria, and improved awareness among medical practitioners of monkey malaria. — Reuters pic

KUALA LUMPUR, Nov 7 — The Ministry of Health (MoH) has explained today that the spike in monkey malaria reports in the last 10 years was due to improvements in diagnosis that can differentiate between such cases and other variants that affect humans.

In a statement in response to reports by Malay Mail and ScienceNews, it clarified that the number of human malaria cases here has dwindled from 6,071 cases in 2008 to 85 cases in 2017, while the number of monkey malaria cases rose from 376 cases in 2008 to 3,614 cases in 2017.

“It is important to highlight that among the reasons for this increase were due to improvement in diagnosis capacity to differentiate knowlesi malaria from the other human malaria variants,” ministry director-general Datuk Dr Noor Hisham Abdullah said, referring to P. knowlesi, the parasite variant responsible for monkey malaria.

“The MoH Malaysia had introduced molecular-based diagnosis for malaria in 2009, which is more sensitive in diagnosing knowlesi malaria. Since then, more knowlesi malaria was detected instead of it previously being classified as human malaria (which is done through microscopic identification).”

The ministry said its Malaria Elimination Programme since 2011 has resulted in a reduction in human malaria, and improved awareness among medical practitioners of monkey malaria.

Despite that, Dr Noor Hisham said the reduction in malaria cases meant lesser exposure, and subsequently, the loss or lack of immunity among Malaysians in general, including against monkey malaria.

He also acknowledged that the rise in monkey malaria cases was also due to the change in land use, leading to a greater chance of humans getting infected.

The ministry’s surveillance system showed that people involved with forest-related activities have a higher risk of contracting monkey malaria. These include farming, plantation work, logging, forest foraging, hunting and forest-related recreational activities.

According to London School of Hygiene and Tropical Medicine epidemiologist Kimberly Fornace, the rise of malaria here is tied to rapid deforestation, particularly in the Borneo states where large swathes of land are regularly cleared to make way for oil palm plantations.

This brings the human population into close contact with monkeys that are carriers of the disease, needing only mosquitoes to connect the two by blood.

Dr Noor Hisham said the MoH has already taken steps to combat monkey malaria, including increasing surveillance and providing better facilities for diagnosis, and intensifying education programmes.

The Institute of Medical Research is also studying the effectiveness of spraying insecticide outdoors to control it.

“Ministry of Health would like to encourage the involvement of employers from the agricultural and plantation sectors in providing protection to their workers, such as the use of insecticide nets and repellents, as prevention of knowlesi malaria.

“MoH also encourages local researchers to conduct studies on monkey malaria, including its natural host which is the macaque. Interagency involvement in the prevention of knowlesi malaria is important in reducing the burden of this disease,” he said.

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