West Nile virus warning system

In combating West Nile virus, information could be the ultimate repellant. In an effort to develop an early-warning system for potential West Nile virus outbreaks, Cornell University’s Northeast Regional Climate Center (NRCC) and the Department of Entomology will spend this summer collecting climate data in areas where disease-carrying mosquitoes are found.

The U.S. government-funded research, it is hoped, will result in the first Web-based, degree-day calculator that warns public health officials when, where and under which conditions infectious mosquitoes can either thrive or die. The information is expected to be on line by next summer.

“Scientists, whether they are climatologists or medical entomologists, have never fully examined the relationship between climate and the proliferation of the mosquitoes that carry West Nile virus,” says Arthur T. DeGaetano, Cornell associate professor of climatology and director of the NRCC, is one of the principal investigators on the project. “Cornell’s College of Agriculture and Life Sciences is unique in that collaborations like this are very possible. Interaction between climatologists and medical entomologists can be at a level where information — once it is gathered and processed — can be readily employed in vector management schemes,” he says.

The research, funded by the National Oceanic and Atmospheric Administration, will occur in four stages. First, climatologists and entomologists will gather climate data and synchronize this with mosquito habitat observations. These data then will be related to mosquito-count information through statistical analysis for mapping and graphing. From this information, indices will be developed for moisture surpluses, degree day-based mosquito development and killing freezes. Finally, all this data will be put on the Web for public health officials’ use.

Mosquitoes develop in microhabitats, according to Laura Harrington, Cornell assistant professor of entomology and a co-principal investigator on the project. The correlation of climate data with microhabitat information will provide scientific clues to how mosquito populations develop and age. Older mosquitoes are the carriers of West Nile virus, becoming contaminated when they feed on infected “reservoir” animals such as birds, and undergo an incubation period of the virus that can last 7-14 days. During subsequent blood meals after this incubation period, the mosquitoes inject the virus into humans and animals, where it can multiply and sometimes cause illness. It is outdoor temperatures that determine both the rate at which the virus replicates and the rate at which mosquitoes age.

While mosquitoes can live as long as three or four months in a laboratory, their life span in the wild is much shorter. Thanks to predators and pathogens, the longest a mosquito can live is probably three to four weeks, says Harrington. During the height of summer heat, a mosquito can age and become a full adult within seven to nine days.

The study also will gather information on early establishment and climate-influenced development of mosquitoes carrying West Nile virus in specialized habitats such as discarded tires and other types of containers that tend to be located close to human dwellings.

Catherine Westbrook, a Cornell graduate student in entomology, and Renee Anderson, a medical entomology extension associate, will monitor mosquito microhabitats in several Northeast locations this summer.

Contact: Blaine P. Friedlander Jr., bpf2@cornell.edu