Strategies for reducing the risk of Lyme borreliosis in North America

The incidence of Lyme borreliosis continues to increase in the United States. In 1991, when Lyme borreliosis first became a nationally reportable disease to the Centers for Disease Control and Prevention (CDC), a total of 9470 cases were reported; in contrast, by 2002 a total of 23,763 cases were reported, >2.5x the total in 1991. Area-wide acaricides can be highly effective in killing nymphal Ixodes scapularis, with >95% of nymphs killed in studies using cyfluthrin, deltamethrin, or carbaryl. The majority of residents living in households within the area hyperendemic for Lyme borreliosis will not, however, consider the use of area-wide acaricides. A survey of communities in 4 states (Connecticut, Massachusetts, New Jersey, New York) demonstrated that <25% of the populace have used area-wide acaricides on their own property. In searching for alternative methods of reducing Lyme borreliosis risk, host-targeted methods have been proven to be effective. Newly developed methods include the use of acaricides applied to deer feeder stations. This method is called the 4-poster method and has been shown in trials to reduce populations of nymphal I. scapularis by ⩾69%. In addition, rodent-targeted bait boxes containing fipronil have been shown to eliminate ticks on mice and negatively impact the population of questing I. scapularis and reduce the proportion of these ticks infected with Borrelia burgdorferi sensu stricto. Host eradication can also be utilized. On Monhegan Island, Maine, white-tailed deer were totally eradicated from the island from 1999 to 2000. By 2004, no immature I. scapularis could be found on rodents on Monhegan Island. Landscape management practices can also be utilized to reduce the risk of Lyme borreliosis as can personal protection procedures including regular tick checks. These practices have been nicely summarized in a new Tick Management Handbook produced by Dr. Kirby C. Stafford III with the Connecticut Agricultural Experiment Station. Although there is no magic bullet available to completely eliminate the risk of Lyme borreliosis from large geographic areas, the use of Integrated Pest Management (IPM) practices holds the prospect for reducing and managing Lyme borreliosis risk in the future.