LONDON (AP) — Scientists say an invasive mosquito species was likely responsible for a major malaria outbreak in Ethiopia earlier this year, a finding experts called a troubling sign that advances against the disease are at risk of unraveling.
The mosquito species, known as Anopheles stephensi, is mainly seen in India and the Persian Gulf. It was discovered in Djibouti in 2012, and has since been found in Sudan, Somalia, Yemen and Nigeria. Mosquitoes are suspected to be the cause of a recent rise in malaria in Djibouti, causing the World Health Organisation to try to prevent the insects from spreading further into Africa.
Malaria scientist Fitsum Tadesse presented research on Tuesday at a meeting of the American Society of Tropical Medicine in Seattle, suggesting the invasive mosquitoes were also responsible for an outbreak in Ethiopia.
In January, health officials in Dire Dawa, a major transportation hub, reported a rapid increase in malaria. Tadesse, chief scientist at the Armauer Hansen Research Institute in Addis Ababa, jumped in with his team to investigate. They tracked more than 200 malaria cases, surveyed nearby mosquito sites and tested invasive mosquitoes for the malaria parasite.
They didn’t find many of the mosquitoes that normally spread malaria in Africa. Instead, they found high densities of the invasive mosquitoes. Tadesse and colleagues concluded that the invasive mosquitoes were “strongly linked” to the outbreak.
“This new evidence is terrifying,” said Thomas Churcher, a professor of infectious disease dynamics at Imperial College London, who was not involved in the study.
He said most of the malaria spreading in Africa has occurred in rural areas, as native mosquitoes usually don’t like to breed in polluted cities or artificial containers such as buckets. But the invasive mosquitoes can thrive in such conditions.
“If these mosquitoes get a foothold in Africa, it could be phenomenal,” he said. The main mosquito control measures used in Africa, such as mosquito nets and indoor spraying, are unlikely to work against the invasive insects, as they tend to bite people outdoors.
Still, Churcher said patchy surveillance means scientists don’t know how common the invasive mosquitoes are or how much malaria they cause.
Ethiopian malaria researcher Aklilu Getnet said officials have seen a large increase in the disease this year. He blamed longer rainy seasons and the conflict in northern Ethiopia, which has drained resources from malaria.
“We are very concerned,” he said, saying Ethiopia had seen a major decline in malaria until recently. “What we are seeing now is a significant increase.”
Anne Wilson, an infectious disease expert at the Liverpool School of Tropical Medicine, said African communities could consider adapting measures used in India to control the mosquitoes, such as introducing fish that eat the larvae. or prohibiting containers of standing water.
She said slowing progress against malaria further complicates efforts to stop the parasitic disease, which is estimated to kill more than 600,000 people annually, mainly in Africa.
“We are waiting to see the impact of new tools like pesticides and vaccines,” she said. “But if this mosquito starts taking off, we may run out of time.”
The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.