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Tuesday, February 9, 2016

Zika virus not a major threat to Rhode Island

Mosquito ecology key to controlling disease
An unlikely visitor, but that could change. And the disease could
change, too

KINGSTON, R.I. –The Zika virus is alarming people throughout Latin America and the Pacific and forcing many people to re-think their travel plans, but a University of Rhode Island post-doctoral researcher says Rhode Islanders have little to worry about. 

According Jannelle Couret, the mosquito that transmits the virus, Aedes aegypti, isn’t found within 1,400 miles of the Ocean State, and the virus is not airborne so it is not passed from person to person in the way of colds or flu.

A resident of Narragansett, Couret studies the ecology and development of mosquitoes, how they respond to changing environmental conditions, and how those changing conditions affect disease transmission. And the Ae. aegypti mosquito is central to her research. That’s because the species transmits a wide range of diseases, including dengue, chikungunya, yellow fever and now Zika.

“It’s an important vector for these diseases because it only feeds on humans, it lives around human settlements, it doesn’t fly very far, and it bites during the day,” said Couret, who began work at URI just a month ago. “That’s why it’s such a problem.”

Zika virus was discovered in 1947 in Uganda. It was limited to Africa and parts of Asia until 2007, when it was found on islands in the Pacific. Only recently has it spread to Latin America. Those infected by the virus, which is seldom fatal, exhibit flu-like symptoms, as well as pain in their joints and red eyes. Zika also can cause birth defects in pregnant women who become sick with the virus.

The disease vector, Ae. aegypti, experienced a huge range expansion beginning in the 1950s, pushing its way into parts of the United States before the Asian tiger mosquito, Ae. albopictus, arrived and outcompeted A. aegypti from nearly all of its U.S. range except south Florida and parts of Texas. 

The Asian tiger mosquito, whose range has reached Connecticut and Massachusetts but not Rhode Island, has been shown in laboratory studies to be able to replicate the virus, but whether it can effectively transmit Zika to human populations remains to be seen.

Because vaccines are currently unavailable, Couret said the key to controlling many vector-borne diseases is understanding the ecology of the vector and the effect of environmental change. So she raises mosquitoes in the insect facilities at the Centers for Disease Control and Prevention in Atlanta and manipulates the environment to track how it alters mosquito development, survival and mating success. She is testing whether different ecological conditions can benefit or deter natural mosquito abundance.

Couret is also studying the epidemiology of the dengue virus to see how weather and climate affect disease transmission over time. Working in collaboration with Entomology Professor Howard Ginsberg, Civil Engineering Assistant Professor Ali Akanda, and Computer Science Assistant Professor Gavino Puggioni, she is using dengue fever in Puerto Rico as a case study.

“Dengue is now endemic in Puerto Rico, with cases every year, and occasionally there is a major outbreak,” she said. “But we don’t really understand why in some years there are fewer cases and in other years there are many cases. Using knowledge of the mosquito vector’s response to different environmental conditions, we’re looking to use modeling to predict what aspects of weather and climate will relate to the incidence of dengue.”

She hopes to identify climate-related data that that can predict the outbreak of disease and then apply that information to other parts of the world with a similar urban environment.

“There are a lot more mosquitoes in city slums that don’t have adequate sanitation,” Couret said. “And since there is no vaccine for dengue and Zika, control of the diseases depends on management of mosquitoes and understanding the ecology of the mosquitoes.” 

She notes that it takes a massive, global effort to eradicate mosquito-borne diseases, but the recent drop in malaria cases gives her hope.

“What we learned from the Ebola crisis is that when you have these urgent public health crises, the whole community pulls together,” Couret concluded. “With Zika, until we can get the mosquito populations under control, it’s difficult to imagine that it will just go away. It will continue to spread. But in the vast majority of cases it’s not a deadly disease, and once you’re immune you’re immune, so it should eventually run its course.”