Pioneering to Combat Monkey Malaria

August 20 is World Mosquito Day, a commemoration of the 1897 discovery by British doctor Ronald Ross that female anopheles mosquitoes transmit malarial parasites to humans. 121 years on, despite significant scientific progress in treating and preventing malaria, mosquitoes remain the world’s deadliest animal. These tiny insects cause more than half a million deaths annually, not just from malaria, but also a range of other diseases such as yellow fever, dengue and chikungunya.

In most cases of human malaria, one of four species of Plasmodium parasite is transmitted directly between mosquitoes and people, but in some parts of rural south east Asia, another species, known as ‘Monkey Malaria’ is on the rise. In this rarer form of the disease, a fifth species of the parasite can be transmitted by mosquitoes between monkeys and people. In Malaysia, Bayer is partnering with the Ministry of Health on new research to help protect local populations from this little-known disease.

Dr. Rohani Ahmad is currently the Head of Medical Entomology Unit at the Institute for Medical Research (IMR), the research arm of the Ministry of Health of Malaysia. Since 2015, she has been studying the effectiveness of residual spraying of insecticide to prevent Monkey Malaria in six rural villages on the island of Borneo in eastern Malaysia. One of the first of its kind, her study is funded principally by the MOH of Malaysia and are supported by Bayer’s Asia Pacific Vector Control team, led by the ES team in Malaysia and Say Piau Lim, Vector Control Market Segment Manager APAC.

Say Piau Lim

“Cases of human malaria have dropped rapidly in Malaysia since 2000 and the Ministry of Health aims to eradicate the disease by 2020. But cases of monkey malaria in humans have been on the rise since the country’s first reported cases in 2008. Indeed incidence has increased by over 170% to 3614 cases between 2016 and 2017.

In 2014, our Vector Control team began testing outdoor residual spraying of K-Othrine PolyZone®, a new formulation of deltamethrin, for dengue prevention in Malaysia. This involves the targetted application of this polymer-enhanced formulation to surfaces immediately adjacent to domestic dwellings (eg. outdoor walls or under verandahs). Dr. Rohani noted the effectiveness of the product and saw an opportunity to carry out a similar experiment in areas where monkey malaria is transmitted in rural Sabah, the Malaysian portion of Borneo, where it is now the most common form of the disease. Bayer has a successful long-term partnership with the Ministry of Health and has signed a Memorandum of Understanding with IMR to strengthen research and development of vector control in public health. Our support of the trial is fully in line with our commitment to protecting rural populations in Asia.”

Dr. Rohani Ahmad
Dr. Rohani Ahmad
Dr. Rohani Ahmad, Head of Medical Entomology Unit at the Institute for Medical Research (IMR), Malaysia

Say Piau Lim, Vector Control Market Segment Manager APAC
Say Piau Lim, Vector Control Market Segment Manager APAC
Say Piau Lim, Vector Control Market Segment Manager APAC

Dr. Rohani Ahmad

“This form of malaria is endemic to monkeys living in the rain forests of Borneo and is caused by Plasmodium knowlesi. The parasite proliferates in Anopheles balabacensis mosquitoes that commonly bite infected monkeys. The mosquitoes then transmit it to humans, causing symptoms that are similar to human malaria, but with a shorter incubation period of under one week. Monkey malaria can be cured if treated rapidly, but there have been fatalities reported when treatment was delayed.

Recent changes in land development and deforestation have led to a shift in monkey populations towards rural villages and this in turn has led to the sharp rise in the number of cases in humans. Initial results of our study show that outdoor residual spraying could play an important role in preventing the disease.”

Dr. Rohani and her team are focusing on six villages deep in the rural areas around the town of Tenom in the eastern Malaysian state of Sabah. The project began in late 2015 with colonies of Anopheles balabacensis mosquitoes collected and studied in the laboratory before being returned and monitored in the field. As the mosquitoes mainly remain and bite outside dwellings, exterior walls were sprayed, with K-Othrine Polyzone, first in April 2016 and again in November/December 2016.

Dr. Rohani Ahmad

“The first results are very positive, especially in what we call outdoor covered areas, such as roofed terraces where local populations meet to eat or sit. After monitoring the number of mosquitoes that died following exposure to walls in these areas, we estimate that the product retains 90-100% efficacy after six months. The number of cases of monkey malaria reported also dropped dramatically in the six villages, compared to other local villages where monkey malaria is still increasing.

We are already working on the second phase of the study and the next spraying campaign will begin in December in line with the promising initial findings.”

Say Piau Lim

“Education of the local population is another important part of the project. Dr. Rohani and her team have involved the heads of all of the six villages, who help them to organize meetings to explain how the disease is transmitted, how the spraying is being organized and how it can help.

Her study is the first of its kind in Asia and is generating a lot of interest. At Bayer, we are proud to be supporting this kind of new research that, if its early promise is confirmed by further studies, could play a part in combating an emerging disease and offering a better life to rural populations in the region.”

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