Malaria in Kikuyu: Kemri uncovers hidden threat in a supposedly safe zone

Ondiri in Kikuyu. Research indicates that rising temperatures have expanded mosquito habitats.

For a long time, the Kenyan Central Highlands have been considered a malaria-free zone. But new research suggests this is no longer be the case.

A recent study conducted in Kikuyu, Kiambu County, found evidence of malaria transmission, challenging the assumption that high-altitude areas in Kenya are safe from the disease.

The study, published in the Malaria Journal on January 13, examined malaria prevalence, transmission potential, and the effectiveness of artemisinin-based combination therapy (ACT) in Kikuyu. Kikuyu is a high-altitude area next to the tea-growing Limuru.

The area is generally cold and wet with the temperatures ranging from 10.9 to 24.6 degrees. Researchers from the Kenya Medical Research Institute (Kemri) recruited 838 people with suspected malaria from local hospitals.

They report that 5.6 per cent of the 838 people tested microscopically had malaria, an alarming discovery in a region previously thought to be malaria-free.

“This finding indicates that, contrary to the general assumption, the study area is not a malaria-free zone,” the researchers stated in their report, titled “Malaria prevalence, transmission potential and efficacy of artemisinin-based combination therapy in the Kenyan Central highlands: a zone previously characterized as malaria-free”.

The big question is whether these malaria cases were brought in by travelers or if they were acquired locally. Half of the people who tested positive had recently traveled to malaria-endemic areas like western Kenya or the coast.

However, the remaining half had no recent travel history, raising concerns that malaria transmission could be happening within Kikuyu itself. The researchers also collected mosquitoes from the Karai Rurii and Ondiri Swamps, and from nearby homes.

Adult mosquitoes sampled were tested individually for the presence of Plasmodium falciparum, the deadliest parasite that causes malaria.

“The presence of highly competent malaria mosquito vectors, coupled with climate change and shifting weather patterns, suggests that there is a real chance of sustained malaria transmission in this region,” the study notes.

However, few adult mosquitoes were found inside homes, which could mean that malaria transmission is still at an early stage or occurring outdoors. Malaria is spread when an infected mosquito bites a person, transmitting the Plasmodium parasite.

The study suggests that if these mosquitoes continue to breed and bite humans, the risk of malaria transmission in Kikuyu will increase. Malaria transmission in high-altitude regions is not unique to Kikuyu.

Studies have shown that malaria-carrying mosquitoes have been steadily moving into the Kenyan highlands over the past few decades due to climate change. Research published in the Lancet Planetary Health found that rising temperatures have expanded mosquito habitats, allowing them to survive and breed at higher elevations.

A past study by the Kenya Medical Research Institute (KEMRI) also reported malaria outbreaks in areas like Kericho and Nandi, which were once considered malaria-free. This shift is largely attributed to global warming, which is increasing temperatures in highland areas.

Warmer conditions allow malaria parasites to develop more quickly within mosquitoes, increasing the likelihood of transmission. Scientists warn that if these trends continue, malaria could become a serious health threat in previously unaffected regions.

Kikuyu, which lies at an altitude of over 1,500 metres, was previously too cold for malaria-carrying mosquitoes to thrive. However, rising temperatures may be making it easier for mosquitoes to survive and transmit the disease.

“Global weather patterns are changing, and we must adapt our malaria control strategies to address new risks in areas previously considered malaria-free,” the researchers warn.

But there is some good news. The researchers tested the effectiveness of ACT, the main treatment for malaria in Kenya, and found that the drugs are still highly effective. All patients in Kikuyu were treated with ACT recovered fully, and there was no sign of drug resistance.

This is an important finding because malaria parasites in some parts of Africa and Asia have started developing resistance to ACT, making treatment more difficult. The researchers recommend further studies to determine whether malaria is truly being transmitted locally or if the cases are mostly imported.

They also suggest increased mosquito surveillance, better malaria diagnosis in health facilities, and possible reclassification of Kikuyu from a malaria-free zone to a low-risk zone. “This presents a likely changing malaria transmission scenario in this part of the country, requiring further investigations, possible re-classification, and immediate interventions,” the study concludes.