“The results of our study are extremely important because they provide a better understanding of the life history traits and ecology of the vector, Aedes aegypti, said second lead author Veronica Armijos, a Ph.D student with CVEC who studies with major professor William Reisen and works part-time in the Scott lab. “Information like this can be used to help improve current vector control and surveillance strategies."

Research team member Christopher Barker, an assistant adjunct professor with CVEC, part of the UC Davis School of Veterinary Medicine’s Department of Pathology, Microbiology, and Immunology, generated “a stage-structured population dynamic model using our empirical data,” Carrington said. “The model predicted that growth rates could be over- or under-estimated relative to constant temperatures, dependent upon the mean and magnitude of the fluctuations.”

“This is an important addition to a growing body of evidence showing that average temperatures are inadequate to explain variation in mosquito development and reproduction in natural systems,” Barker said. “This study demonstrated additional effects of an often-ignored second dimension-- daily cycling between nighttime lows and daytime highs--particularly when average temperatures were near the limits for mosquito survival.”

“These findings are important in the context of climate change because globally, nights have warmed faster than days, and the changes have been quite pronounced in the ‘urban heat islands’ preferred by Aedes aegypti,” Barker said. “As a result, overall warming trends have been accompanied by reduced daily temperature ranges, and understanding the roles of both will be important for predicting future impacts on mosquito populations.”

Said Carrington: “Our results have epidemiological significance for dengue transmission dynamics, and more generally, highlight that it is not always appropriate to extrapolate the results from laboratory-based experiments directly into the field. Sometimes, allowing for the environmental variation that we as scientists usually try to minimize, is actually important for understanding the ecology of a species in the wild.”

Carrington, Armijos, Barker and Thomas Scott,  professor of entomology and director of the Mosquito Research Laboratory, co-authored the paper with Louis Lambrechts, a former Scott lab postdoctoral associate who is now with Insects and Infectious Diseases, Institut Pasteur, France.

Dengue is spread by an infected female Aedes aegypti mosquito, a day-biting, limited flight-range mosquito that prefers human blood to develop its eggs. Dengue is caused by four distinct, but closely related, viruses and the most severe form of disease is life-threatening dengue hemorrhagic fever or DHF.

Some 500,000 people with severe dengue are hospitalized each year, according to the World Health Organization (WHO), and about 2.5 percent of those affected die.

“Dengue takes an enormous toll on human health worldwide, with as many as 4 billion people at risk—half of the world’s population--and 400 million new infections each year,” Scott said.

The National Science Foundation’s Ecology of Infectious Diseases Program funded the project.

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