Lyme Disease Prevention Programs
Plant Science Day 2001 Short Talk
Kirby C. Stafford III, Ph.D.
Department of Forestry and Horticulture
The Connecticut Agricultural Experiment Station
123 Huntington Street, P.O. Box 1106
New Haven, CT 06504
Phone: (203) 974-8485
Fax: (203) 974-8502
Lyme disease is one of three tick-associated diseases in Connecticut and other northeastern states associated with the bite of the blacklegged tick, Ixodes scapularis (commonly known as the deer tick). The other two diseases are human granulocytic ehrlichiosis (HGE) and human babesiosis. Lyme disease is a multi-symptom illness of people and animals caused by the spirochete, Borrelia burgdorferi. Most Lyme disease is contracted during the summer months following the bite of the nymphal stage of the tick. The number of Lyme disease cases in Connecticut reported to the Connecticut Department of Public Health has steadily increased from a few hundred in the mid-to late 1980s to 3,772 cases for 2000, a rate of 110.8 cases per 100,000 people. This is a new state record. Over one-third of the cases in 2000 were reported from Fairfield County. The highest incidence in disease by age group is in children 5 to 10 years old and 40 to 50 year old adults.
While the incidence of Lyme disease is increasing, it is or could be a preventable disease. I find that personal protection measures, such as long pants and a permethrin-based tick repellent, and conducting tick checks to be effective at preventing tick bite or infection. Only a proportion of I. scapularis nymphal ticks are infected (generally about 20%) and it takes over 24 hours for an attached, infected tick to transmit Lyme disease spirochetes. In a recent study, only 12.5% of mice exposed to field collected infected ticks for 48 hours became infected, while 78.9% and 93.8% became infected after 72 and 96 hours of attachment, respectively. The risk of Lyme disease from a recognized tick bite in various studies of the prophylactic use of antibiotics for tick bite has been less than 5.0%. The problem is that the majority of Lyme disease patients never detect the tick that infects them and many people do not protect themselves from ticks on a regular basis. For example, while 96% of the residents in Westport and Weston indicated in a survey that they use some form of personal protection against ticks, only 65.6% reported they practiced such measures regularly or most of the time. The management of Lyme disease has relied heavily on personal protection and early diagnosis and treatment of Lyme disease.
Approaches that reduce the tick population or prevalence of infection in the ticks should lower the risk of infection and therefore, the incidence of disease. The Centers for Disease Control and Prevention (CDC) has shifted the focus of their grant program from basic research and surveillance towards community or other population based interventions to prevent Lyme disease and the development of novel strategies for the prevention of Lyme disease, with the objective of reducing the incidence of disease in the target populations or, at least, determining what approaches do and do not work. A successful community prevention program will depend upon extensive education and awareness, increased use of various residential strategies for tick bite prevention and tick management by individual homeowners, use of the Lyme disease vaccine, and community-level host-targeted control measures.
In 1999, Connecticut received the first community-based project award for the prevention of Lyme disease from the CDC. This project, called Target Lyme Disease, involves primarily the Westport Weston Health Department (WWHD), the Connecticut Department of Public Health (DPH), and the Connecticut Agricultural Experiment Station (CAES). This year the CDC has expanded the Lyme disease prevention initiatives with additional project awards in New Jersey, New York, Massachusetts, and Connecticut. In Connecticut, the program will include the Ledge Light Health District in Groton and 3 towns in the Torrington Health District in Litchfield County. The CDC and project participants got together at a recent meeting at CAES to discuss approaches to managing ticks and conducting community-based programs. For today’s program, I will highlight the Target Lyme Disease project in Westport and Weston.
The objective of Target Lyme Disease is to teach and get residents to practice Lyme disease prevention. Program elements include the development and implementation of a population-based strategy to prevent Lyme disease, a survey of people’s knowledge, attitudes, and behaviors related to Lyme disease, obtaining data on current practices to control ticks, conducting training workshops for commercial companies that offer tick control services, surveying the deer population, establishing active Lyme disease surveillance, and collecting and analyzing data on tick abundance and infection rates. Among other activities, the health district established an advisory board consisting of homeowners, municipal agencies, civic groups, business leaders, educators and other concerned residents, created a self-guided demonstration site at the Weston historical site on Route 57 to illustrate landscape management techniques for tick control, and conducted a community-wide consumer education campaign on Lyme disease this past spring.
According to the random digit-dialed telephone survey of Westport and Weston residents at the beginning of the project, 79% felt Lyme disease was a serious problem and 76% desired more information on protection from getting Lyme disease. However, only 54% reported using tick management practices to control ticks and acceptance of chemicals for tick control was low (22.5%). Most (75.6%) of those that did use insecticides, however, hired a commercial company to apply the pesticide. Consequently, I have surveyed commercial applicators operating in Fairfield County on various issues related to tick control and conducted tick management workshops for the commercial pesticide applicators. From my survey, I discovered that 71% of the companies in Fairfield County saw an increase in their tick control business in the past 4 years and 64% reported business in Westport and Weston had increased.
Based on the surveys, the major thrust of the health district and Experiment Station has been to teach people how to create a tick safe zone around the home, primarily communicating landscape management approaches to reducing tick abundance around the home and, secondarily, teaching residents on the proper use of pesticides for tick control. Integrated tick management involves landscape management to reduce environmental suitability for ticks, host management, host-targeted pesticides, and selective use of least-toxic pesticides to the highest-risk areas. Ironically, the proper use of an insecticide for tick control may actually decrease overall usage by proper timing and targeted applications to high-risk areas around the home. In past studies, I have recovered 82% of I. scapularis nymphs on the lawn within 3 meters of the woods and stonewalls. My studies have also shown that clearing leaves and using a wood chip or mulch barrier between the lawns and woods can reduce tick numbers on the lawn by over 50% and a pyrethroid-based insecticide will provide 85% or better suppression of blacklegged (deer) ticks. The pyrethroid insecticide cyflurthrin was reported the major chemical used by slightly over half the companies in the applicator survey.
Another important element of a community-based approach is host-targeted methods for tick control, aimed either at white-tailed deer, Odocoileus virginianus, or the white-footed mouse, Peromyscus leucopus. White-tailed deer are the preferred host for adult I. scapularis and numerous studies have linked the number of deer with the abundance of this tick. White-footed mice are an important reservoir for Lyme disease bacteria; ticks that feed on infected mice become infected with the Lyme disease spirochetes. A USDA-funded regional tick project evalulating the topical application of pesticides to white-tailed deer for the control of ticks at sites in 5 states is completing its 4th year. Deer are treated with a patented device called a 4-poster, which has a paint roller on each corner to apply the pesticide as deer obtain corn from one of two troughs. Over the course of the project, deer usage of the devices has generally been high (> 90%), although most sites had periods of high acorn production when the 4-posters were little used. Control of ticks on deer has been high (about 90%) and we are starting to document reductions of around 70% in the tick population. The treatment of deer is the only potential approach that could impact the tick population community wide without the direct active involvement of most residents.
The CDC has developed a new rodent bait box approach for tick control using fipronil, the same material in the flea and tick control product Frontline®. The CDC with support from CAES evaluated the use of fipronil on the mice on Mason’s Island in Mystic, Connecticut in 1999 and 2000. Use of fipronil has resulted in virtually 100% control of ticks on the mice and substantial reductions in the number of ticks around treated homes. I started expanded trials this year of the fipronil bait box in neighborhoods in Groton, Westport, and Weston, Connecticut using a prototype box (patent pending) from Aventis Environmental Science. This bait box could potentially become an important tool in community-based Lyme disease prevention efforts. We will be monitoring tick abundance in these communities over the next three years to evaluate the bait boxes.
In conclusion, Lyme is an increasing, but preventable disease. As long as deer remain abundant and this tick continues to spread, the incidence of disease will increase in the absence of an effective Lyme disease program or wider acceptance of the Lyme disease vaccine. Public health initiatives to reduce Lyme disease in selected, targeted communities are an important step in that direction. The reduction of Lyme disease and other tick-associated diseases will require a multifaceted approach utilizing a variety of tick management and Lyme disease prevention measures by many individual homeowners and the community.