Mosquito genetics could explain lack of large Zika outbreak in Africa
Aedes aegypti mosquitoes can obtain and transmit Zika virus more easily than a sub-Saharan Africa-dwelling relative, potentially explaining why the Americas suffered a large Zika outbreak and Africa did not, researchers said.
The difference, the researchers explained in Science, is genetics.
“In broad terms, the African mosquito populations are less permissive to the virus than the globally invasive populations outside Africa,” Louis Lambrechts, PhD, research director in the department of virology at the Pasteur Institute in Paris, France, told Healio. “Geographical variation in mosquito susceptibility to arboviruses was previously documented, but this is the first time such variation for Zika virus is unequivocally linked to distinct mosquito subspecies.”
According to Lambrechts and colleagues, A. aegypti is thought to have evolved from ancestors in western Africa, spreading globally as a “domestic” pest living close to humans, which fueled pandemics of dengue and yellow fever. It remains a major global vector of those two diseases and has also become the main vector of Zika, which can cause serious adverse outcomes, including .
One of the mysteries of Zika, a virus discovered in Uganda more than 70 years ago, is why some places — like the Americas — experienced large outbreaks and some — like Africa — did not.
For their study, Lambrechts and colleagues tested 14 mosquito colonies collected in Africa, Asia and the Americas for susceptibility to Zika, individually scoring the infection status of 3,113 female mosquitos.
The researchers found that the African subspecies named A. aegypti formosus was less likely to acquire Zika virus in blood meals. According to Lambrechts and colleagues, the increased Zika susceptibility in non-African A. aegypti may be caused by genetic differences located on the mosquito chromosome 2.
“The most surprising result was the fact that the difference in Zika virus susceptibility between the two mosquito subspecies was observed irrespective of the virus strain,” Lambrechts said. “Future analyses will address the underlying mechanisms that render mosquitoes more or less susceptible to Zika virus infection.”