LONDON (AP) – Scientists say an invasive mosquito species was likely responsible for a major malaria epidemic in Ethiopia earlier this year, a finding that experts called a worrying sign that progress against the disease are in danger of unraveling.
The mosquito species, known as Anopheles stephensi, has been seen mainly in India and the Persian Gulf. In 2012 it was discovered in Djibouti and has since been found in Sudan, Somalia, Yemen and Nigeria. Mosquitoes are suspected to be behind a recent rise in malaria in Djibouti, prompting the World Health Organization to try to prevent the insects from spreading further to Africa.
On Tuesday, malaria scientist Fitsum Tadesse presented the research at a meeting of the American Society of Tropical Medicine in Seattle, suggesting that invasive mosquitoes were also responsible for an outbreak in Ethiopia.
In January, health officials in Dire Dawa, a major transportation hub, reported a rapid rise in malaria. Tadesse, chief scientist at Addis Ababa’s Armauer Hansen Research Institute, stepped in with his team to investigate. They monitored more than 200 cases of malaria, examined nearby mosquito sites, and tested invasive mosquitoes for the malaria parasite.
They haven’t found many of the mosquitoes that usually spread malaria in Africa. Instead, they found high densities of invasive mosquitoes. Tadesse and colleagues concluded that 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 connected to the research.
He said most of Africa’s widespread malaria has been in rural areas, as native mosquitoes don’t usually like to breed in polluted cities or artificial containers such as buckets. But invasive mosquitoes can thrive in such conditions.
“If these mosquitoes take a hold in Africa, it could be phenomenal,” he said. Major mosquito control measures used in Africa, such as mosquito nets and indoor spraying, are unlikely to work against invasive insects, as they tend to bite people outdoors.
However, Churcher said erratic surveillance means scientists don’t know how common invasive mosquitoes are or how much malaria they are causing.
Ethiopian malaria researcher Aklilu Getnet said officials have seen a sharp rise in the disease this year. He blamed longer rainy seasons and the conflict in northern Ethiopia, which drained resources from malaria.
“We are very concerned,” he said, saying that until recently Ethiopia had seen a sharp decline in malaria. “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 fight mosquitoes, such as introducing fish that eat larvae. or the prohibition of containers with stagnant water.
He said slowing progress against malaria is further complicating efforts to stop the parasitic disease, which is estimated to kill more than 600,000 people each year, mainly in Africa.
“We are waiting to see the impact of new tools like pesticides and vaccines,” he said. “But if this mosquito starts taking off, we may be out of time.”
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.