Malaria is a disease caused by parasites which are transmitted from person to person by mosquitoes that bite malaria-infected patients. Consequently, the mosquitoes themselves get infected and transmit the parasites to healthy persons during the next blood meal. On 17 May 2017, Ms Annette Busula from Kenya will defend her thesis at Wageningen University & Research on the interaction between malaria parasites, mosquitoes with the ability to transmit malaria (malaria mosquitoes) and skin bacteria of infected patients (that affect body odour). Busula has shown that people infected with malaria parasites exude a stronger body odour when the parasite enters into its transmittable stage. This scent is very attractive to malaria mosquitoes. Therefore, these patients are likely to be bitten more frequently, and the malaria parasites are able to infect more people.
As part of her research project, Busula conducted an experiment in which Kenyan school children aged 5 to 12 years were screened for malaria and divided into four groups based on the screening results. One group was malaria-free, whereas the other three groups were infected with different life cycle stages of the malaria parasite (i.e. asexual, submicroscopic gametocyte and microscopic gametocyte stages). In the microscopic gametocyte stage, the parasite can be transmitted to the next host. During the experiment, the mosquitoes were exposed to the different body odours of the groups. The mosquitoes were prevented from approaching the children directly by flying into a tube which the children’s body odour passed through. The children’s body odour was shown to be more attractive to mosquitoes than a control odour (a standardised synthetic human body odour). The children who were infected with malaria parasites in a transmittable stage (i.e. the microscopic gametocyte stage) were shown to attract twice as many mosquitoes as parasite-free children or children with very low malaria parasite levels in their blood.
World Malaria Day
Today, on World Malaria Day, the World Health Organisation (WHO) is calling for closing the gap in malaria prevention. According to estimates from the WHO, 429,000 people died from malaria in 2015, nearly 70% of whom were African children aged under 5 years. In Africa, malaria causes 20% of all child deaths. Annette Busula’s study increases knowledge of the way malaria is being spread. If infected children are bitten by mosquitoes more frequently, the disease will spread more easily. The study results can be used when drawing up malaria control programmes. This finding can also help prevent malaria. By imitating the scent of a malaria-infected child, mosquitoes can be intercepted by odour-baited traps in a very effective way. As a result, the population of mosquitoes able to transmit malaria is being reduced, allowing fewer people to contract the disease.