Anopheles Stephensi can transmit multiple parasites, shows high resistance to local insecticides
Gains made against malaria in Kenya and the East African region are under threat following the rapid spread of a new deadly mosquito species, according to scientists. The species was recently detected in parts of northern Kenya, raising alarms about its spread and risk of the vector-borne disease.
Unlike traditional malaria-causing vectors, the new mosquito species transmit two malaria parasites that pose a greater risk of severe illness and even death, said researchers from the Kenya Medical Research Institute (Kemri) and the Ministry of Health’s Division of National Malaria Programme (DNMP). The new transmitter has shown resistance to local insecticides as well.
In Kenya, vector Anopheles Stephensi, originally from Asia, was first detected in Marsabit County, with experts linking the spread to climate change, especially the rising temperatures. But the latest discovery of its rapid spread in Mandera County and other drylands in northern Kenya has further raised alarm.
The deadly species can transmit multiple parasites, posing a significant risk of severe illnesses such as dengue (break-bone fever), yellow fever and chikungunya, said Michael Opiyo, a senior lab technologist at Kemri.
“Anopheles Stephensi behavior differs from mosquitoes usually found here. Apart from transmitting Plasmodium falciparum, it can also transmit Plasmodium vivax, which is uncommon in this region,” said Opiyo.
With the spread of the new species, malaria transmission is likely to continue all year round rather than seasonal as has been the case, considering the mosquito doesn’t follow the standard rainfall patterns, he added.
“Besides being able to survive virtually everywhere, the species has shown very high resistance to any form of control measures, including insecticides available in the region,” said Opiyo.
There are fears that the lethal mosquito could be spreading deeper into the country and down to southern parts of Africa after it was first detected in the countries in the Horn of Africa.
“The vector originated from South and West Asia before finding its way to Africa, spreading to countries in the Horn of Africa like Djibouti (2012), Ethiopia and Sudan (2016), Somali (2019) and now Kenya. Some cases were also reported in Nigeria in 2020,” said Opiyo.
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The detection of the vector poses a significant public health threat to Kenya, which is among 12 countries in Africa that received 18 million doses of the first-ever malaria vaccine in May and other countries where malaria is not a threat currently.
If immediate interventions are not rolled out, the situation could be worse, Opiyo warned. He cited the Djibouti case of 2019 as an example, where a resurgence of malaria prevalence and morbidity saw the World Health Organization (WHO) declare a public health emergency in the country.
Malaria kills an estimated 10,000 people in Kenya each year. Africa shoulders an estimated 95 per cent of malaria infections worldwide, with the disease killing more than 600,000 people annually across the continent. The majority of them are children.
The Deputy Regional Director of the United Nations Environment Programme Africa Office, Richard Munang, warned that more cases of malaria infections are expected across the continent as temperatures rise.
“What is happening in Africa will gradually be experienced elsewhere because of the warming climate. With the changing temperatures, malaria mosquitoes are migrating to other areas conducive for them,” Munag told the press in response to news of the further spread of Anopheles Stephensi in Kenya.
The Principal Research Scientist at Kemri, Damaris Matoke-Muhia told journalists that the latest discovery regarding the rapid spread of the new deadly vector across northern Kenya is a major setback to the great milestones the country has achieved in its intensified war against malaria.
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“We were on the verge of bringing malaria cases to a minimum and non-detectable level,” said Matoke-Muhia, adding that, unfortunately, the number of mosquitoes keeps surging due to climate change. “If the global temperatures continue to rise, it’s likely going to change our story about malaria.”
There is scanty information regarding how the vector expanded its geographic range from Asia to East Africa. But scientists are calling for expanded investigations, especially in countries serviced by the Indian Ocean trade routes, to establish the full extent and future trajectories of the problem.
The species is reported to spread faster in different climatic conditions, especially in countries experiencing rapid urban development like Kenya, with spiralling population growth rates in towns and a high concentration of malaria control programmes in rural areas.
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Unlike traditional malaria-causing vectors, the new mosquito species transmit two malaria parasites. Photo for representation: iStock.png)
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