What discovery of 'new' mosquito means and what you should do now

Robai, who is employed as a nanny lives with her employers (a family) in Kitengela - the township South-East of Nairobi.

"When we went down to her room, she was on the floor, rolling and writhing in pain. She had a fever and was sweating heavily," says Lilian Makena, Robai's boss.

"She was vomiting too. We found her in a state not many would be comfortable being found in. We could also tell that she was very sick," Makena says.

"She was not coordinating well mentally: her manner of talking and the stuff she was saying were not 100 per cent coherent," she adds.

Makena's husband, a medical doctor, prescribed some emergency quick-action painkillers. "The painkillers did not work," Makena says.

The couple rushed Robai to a hospital nearby. Upon noting the patient's vital signs and taking her travel history, Robai's doctor recommended a malaria test.

The previous week, on January 27, Robai had travelled to the village in Kitale to visit her children.

"I travelled back on February 4. All was well until the night of February 6 when I started feeling sickly," she says.

Robai says she did not sleep under a mosquito net during her visit to the village.

The test came back positive for malaria, Makena says, "the doctor actually told us that the level of infection was so high, it was approaching the levels of cerebral malaria."

Dr Jesse Gitaka is a medical doctor and a senior malaria researcher in Kenya. He is also a lecturer at Mt Kenya University School of Medicine.

He says: "Malaria is caused by a parasite known as plasmodium. In the body, the parasite enters the red blood cells (RBC) and starts eating them up.

"RBCs then change from the normal doughnut shape - which is the best shape for oxygen uptake and transportation - to some weird shapes.

The new mosquito originally habits South-East Asia, the Middle East, and Arabian Peninsula. [iStockphoto]

"Those who travel to western Kenya might get infected and travel back with the parasite already in their bloodstream," says Dr Gitaka. This, he believes, explains cases like Robai's.

However, as of the third week of February 2023, a new (to Kenya) malaria-transmitting mosquito that survives in urban areas better had been found to be present in the country.

Known as Anopheles stephensi (A. stephensi), the mosquito transmits Plasmodium vivax - one of five plasmodium parasites that cause malaria.

The new mosquito originally habits South-East Asia, the Middle East, and Arabian Peninsula. But in the last decade, it has been detected in West and East Africa.

Samples collected by KEMRI entomologists, together with colleagues from the Division of National Malaria Programme, have pointed to the presence of A. Stephensi in Laisamis and Saku sub-counties of Marsabit County.

Until then, Anopheles mosquitoes in Kenya were Anopheles gambiae and Anopheles funfests: the ones that prefer fresh, clean and free-flowing water.

The entry of A. stephensi may be a game changer in the fight against malaria, says Dr. Matoke.

"The new mosquito survives better in urban and peri-urban areas. It is also very adaptable to new climatic conditions.

"A. Stephensi behaves like culex: they can breed in stagnant and dirty water that has pooled in containers and so on," she says.

According to Matoke, there is a chance that the new mosquito is already in other areas apart from Marsabit.

"We definitely need to step up surveillance. Remember vectors such as mosquitoes travel far and wide. So, there is a likelihood that it will move to other parts of Kenya."

If A. stephensi will (if it hasn't already) establish in Nairobi, the city's residents will no longer be able to say, "Nairobi mosquitoes don't spread malaria."

In such an event, symptoms such as Robai's may become commonplace for city dwellers who may have felt relatively safe from malaria.