Broad-based vaccination of wild mice could help reduce lyme disease risk...( mph from transmitting the disease. ...),Health

After immunizing roughly 55 percent of the mouse population over the course of the two studies, researchers saw an overall reduction of 16 percent in the prevalence of nymphal infection at locations in which mice had been given vaccine versus placebo. This translates to a possible reduction of 27 percent in nymphal infection had all the mice been vaccinated.

In addition, the researchers concluded that other animals, such as chipmunks and shrews, may play a larger role in the spread of Lyme disease than was previously thought. For example, the researchers discovered that the success of the vaccine in curbing the infection of nymphal ticks depended largely on mouse density. In sites where mouse densities were high, the numbers of infected nymphs in corresponding control sites were also high, indicating the important role mice played in nymphal infection prevalence in those sites. It was in these areas where the vaccine worked best in preventing nymphal infection the following year. In contrast, where mouse densities were lower, the vaccine was less effective in reducing the prevalence of nymphal infection, suggesting that other animals probably played a role in disease transmission. Also, the researchers found that certain strains of B. burgdorferi were less likely than other strains to be passed from a mouse to a tick; these strains were most prevalent in nymphs in one study site in which infection prevalence did not change following mouse immunization, again indicating the contribution of other animal reservoirs.

Which animals help spread Lyme disease, and, more specifically, which ones transmit the more virulent strains, needs further study, the researchers contend, to determine how best to implement a broad-based vaccination program. Also, study sites need to be monitored for strains that are not susceptible to the vaccine. Lastly, experiments will be conducted in which the vaccine is administered orally
'"/>

Contact: Jennifer Wenger
jwenger@niaid.nih.gov
301-402-1663
NIH/National Institute of Allergy and Infectious Diseases
13-Dec-2004