A type of mosquito that transmits malaria has been detected in Ethiopia for the first time, and the discovery has implications for putting more people at risk for malaria in new regions, according to a study led by a Baylor University researcher. The mosquito, Anopheles stephensi, normally is found in the Middle East, Indian Subcontinent and China. Previous research shows that more than 68 percent of Ethiopia's population is at risk for malaria, with an average of 2.5 million cases reported annually, according to the World Malaria Report of 2017.

"From a public health standpoint, or that mosquito populations are increasing where they were once were scarce," said researcher Tamar Carter, Ph.D. "If these mosquitoes carry malaria, we may see an emergence of malaria in new regions," she said.

Anopheles stephensi carries malaria parasites in Ethiopia

"We need to confirm that Anopheles stephensi carries malaria parasites in Ethiopia," Carter said. "We also need to investigate how the Anopheles stephensi got to Ethiopia and other parts of the Horn of Africa. The question I am particularly interested in is if Anopheles stephensi is a relatively recent introduction or something that has been flying under the radar in Ethiopia for a long time.

"Clarifying this will help guide better mosquito control efforts in Ethiopia," she said. "We plan to use genomic techniques to study the history of Anopheles stephensi in Ethiopia. More research is needed on the feeding and breeding behavior of the Ethiopian Anopheles stephensi, and how well it responds to insecticides, to determine best ways to control the mosquito population."

If Anopheles stephensi's propensity for feeding indoors is observed in Ethiopia, different malaria control strategies may need to be implemented, such as insecticide-treated bed nets and indoor residual insecticide spraying. Researchers from Jigjiga University in Ethiopia collected mosquito larvae and pupae from water reservoirs in Kebri Dehar, an eastern Ethiopian city with a population of 1.3 million, in the Ethiopian Somali Regional State.

Highest transmission in the north, west and eastern lowland

These larvae were reared to adulthood. Subsequent review of the morphological data confirmed findings from the genetic analysis. The highest levels of malaria transmission are observed in the north, west and eastern lowland of Ethiopia, according to the research article. Malaria transmission exhibits a seasonal and unstable pattern there, varying with altitude and rainfall.

In the eastern lowlands, such as Afar and the Ethiopian Somali Regional State, malaria is endemic along the rivers, where small-scale irrigation activities are practiced for agricultural purposes.

To date, 44 species and subspecies of anopheline mosquitoes have been documented in Ethiopia, with the predominant malaria type being Anopheles arabiensis. Researchers believe the effort should center on the eastern portion, where they said information on malaria vectors in general is scarce. They said both rural and urban surveys are needed, particularly to investigate the role that livestock presence plays in Anopheles stephensi abundance.