Durland Fish, professor of epidemiology in the Division of Epidemiology of Microbial Diseases at Yale School of Medicine, has received a $2.9 million, four-year grant from the Centers for Disease Control and Prevention (CDC) to develop a detailed surface map of the eastern United States depicting human risk of infection from the spirochetal bacteria that causes Lyme disease.
The map created by Fish and his colleagues will standardize a large geographic area, and will represent an improvement over current risk models based on localized, smaller studies and reports of tick findings. In addition, the research will provide information about the genetic strains of bacteria found during the time of year when the risk of contracting Lyme disease is highest.
Fish and his colleagues will study deer ticks (Ixodes scapularis), which occur east of the Great Plains. Lyme disease is caused by bites from ticks that are infected by the spirochetal bacterium Borrelia burgdorferi.
Lyme disease was first recognized in the U.S. in Lyme, Connecticut, in the mid-1970s after the appearance of a cluster of cases of what doctors at first thought was arthritis. The disease is a public health problem in those places where ticks come into contact with people. The number of cases in the U.S. is rising steadily: according to the CDC, the number of cases reported annually has more than doubled since 1991, and annual Lyme disease incidence increased 40 percent between 2001 and 2002. Fish's grant is one of 10 for Lyme disease research that CDC recently awarded in response to these data.
Fish and his colleagues will study ticks in the second of their three life stages. Ticks in their nymphal stage of life have high prevalence of Borrelia infection and are of greatest risk to humans because of their small size. The field research will take place at 95 sites, from Maine to Texas, chosen for the high levels of deer ticks.
"This is the largest field study ever conducted on Lyme disease," said Fish, whose team will estimate the population density of host-seeking deer ticks and the extent of Borrelia infection among them at each site. Those data analyzed will include information about variables in climate and vegetation throughout the U.S. using geographic information system (GIS) software. This will allow the researchers to examine the relationships between the variables and assist them in generating a continuous map of human risk for infection for Lyme disease in the eastern U.S. The results will be used by the CDC and local public health officials to focus education efforts on Lyme disease prevention.