Mosquito genetics may explain why Zika virus outbreaks are rare in Africa: climate change could shift the balance

Africa’s low incidence of the Zika virus may be due to a surprising factor: the genetic makeup of local mosquito populations, a study has found.

Research by scientists at Princeton University’s High Meadows Environmental Institute (HMEI), the Pasteur Institute, and the University of California, San Diego, reveals the causes of birth defects and devastating epidemics across the Americas in 2015 and 2016. The study revealed why Zika remains relatively rare. In Africa, the first continent discovered. The study was published Dec. 11 in The Lancet Planetary Health.

A team of researchers led by HMEI Associate Researcher Dr. Jamie Caldwell has discovered that African native mosquito populations may hold the answer.

“There are two forms of the mosquito species that spread Zika, each with different feeding preferences and abilities to transmit the disease,” Caldwell explains. “This genetic difference may explain why Africa has been largely spared from Zika, despite the continent’s large mosquito populations and favorable climatic conditions for mosquito activity. ”

The two mosquito forms differ in their feeding habits and ability to infect. The human specialist form is well known for its preference for biting humans and its tendency to live in densely populated urban areas. In contrast, the African ancestral type that predominates in Africa is a “generalist” that eats both humans and animals.

Infectious mosquitoes are less likely to bite a person when mixed feed is consumed. Furthermore, the African ancestry type is less effective at transmitting and transmitting Zika compared to human experts, creating a natural barrier to limit the spread of Zika virus in Africa.

Both types live in Africa, but researchers suspect that the amount of variation within mosquito populations may be responsible for the variation in Zika in Africa. Alternatively, the lower disease burden may be due to temperature. Many areas of sub-Saharan Africa have ideal climates for Zika virus transmission, but the spread of Zika virus may be limited in areas where temperatures are too hot or too cold for the virus.

Climate is thought to be one of the main factors in the spread of other diseases spread by the same mosquito species, such as dengue and yellow fever. This is because climate influences many factors important for transmission, such as how often mosquitoes bite and how quickly they develop into humans. -Bites adults.

The researchers developed a model that takes into account genetic influences on mosquito bite preference and the ability of the virus to transmit, as well as the role of temperature in influencing mosquito development, survival and ability to transmit.

They found that mosquito population genetics more strongly influenced Zika transmission in Africa than climate, and thus the proportion of human specialist mosquitoes in different populations across Africa They found that the burden is very similar to that of viral infections.

However, climate change and rapid urbanization may make African cities more vulnerable to Zika virus outbreaks in the future. Caldwell’s team estimated that 23 of Africa’s 59 cities with populations of more than 1 million people, or 39%, meet conditions suitable for a Zika outbreak.

If current climate and population growth projections and predicted mosquito impacts prove accurate, an additional 22 cities will become suitable for Zika outbreaks, bringing the total to Africa’s most populous city. This will reach 76% of the cities with the highest number of people.

“Our study highlights the urgent need for mosquito surveillance, especially in cities with rapidly growing populations,” said the study’s co-authors, originally from Princeton University. said Dr. Noah Rose, who contributed to this research as a postdoctoral researcher and is now an assistant professor. at the University of California, San Diego.

The findings highlight the importance of proactive public health measures to monitor and control mosquito populations in Africa’s growing urban centres. This study changes the narrative about the Zika pandemic and highlights how climate change could alter disease dynamics in unexpected ways.