Loudoun Wildlife Conservancy Habitat Restoration Chair Moni Burke, a Cascades resident, submitted a Lyme prevention article by invitation this month for her community association newsletter. We are pleased to share the full text here, and we welcome our members and friends to share it with their communities.
Lyme Prevention: Highest-Efficacy, Lowest-Cost, and Lowest-Toxicity Methods
Many of the methods for Lyme disease prevention which studies indicate to be most effective are low- or no cost, and carry low or no risk. The highest-efficacy, lowest-cost, lowest-toxicity Lyme prevention methods are tick checks and protective clothing. These personal measures and other effective landscape management methods for the homeowner are outlined below.
1. Personal Protective Measures
A. Tick checks and prompt removal
The definitive Tick Management Handbook states that “checking for ticks and prompt removal of attached ticks is probably the most important and effective method of preventing infection!” – and indeed, most scientific studies have supported this assertion.
B. Protective Clothing
The Tick Management Handbook recommends wearing long pants tucked into socks to make ticks easier to detect and keep them on the outside of the clothes. A 2008 Center for Disease Control (CDC) Connecticut study of nearly 2,000 individuals found protective clothing – defined as long pants and long-sleeved shirts to be 40% effective in preventing Lyme disease. Wearing this type of protective clothing is a risk-free prevention method.
2. Landscape Management
A. Tick-safe zones
According to a study referenced in the Tick Management Handbook, the nymphal blacklegged tick whose bite is the primary cause of Lyme disease in humans, is found mainly in densely wooded areas (67%) and in transitional edge ecotone habitat between woodlands and open areas (22%), which provide the relatively high humidity necessary for their survival. Fewer ticks are found in ornamental vegetation (9%) and lawn (2%).
The Tick Management Handbook, CDC and other sources recommend that families create tick-safe zones in lawns and play areas around their homes – isolating these zones from tick habitat with a wood chip or gravel barrier of approximately 3 feet, and then increasing exposure to sun and air in those zones. The Tick Management Handbook notes that acceptable alternatives to lawn include butterfly gardens, vegetable gardens, formal herb gardens, colonial style gardens, wildflower meadows and hardscapes.
These measures have been shown to reduce tick numbers on the subject property. However, a recent study showed them not to be significantly protective against Lyme disease – and the Tick Management Handbook concludes that “landscape management alone may not reduce disease incidence, as the undetected bite of only one infected tick is required for transmission of Borrelia burgdorferi.” Borrelia burgdorferi is the bacteria causing Lyme disease.
There is no real risk associated with this type of landscape management. The cost will vary depending on lot size and existing landscaping.
B. Replacing exotic invasives with native plants
Multiple studies have shown that controlling invasive plants, especially Japanese barberry, helps to reduce both total tick numbers and infected tick numbers. Two Maine Medical Center Research Institute studies, and the Tick Management Handbook, indicate that blacklegged ticks are significantly more abundant in areas dominated by exotic invasive plants, particularly Japanese barberry, than areas dominated by native shrubs. A 2010 Connecticut study indicates that control of Japanese barberry – either through cutting off the above-ground portion or using a flame treatment – “reduced the number of ticks infected with Borrelia burgdorferi by nearly 60% by reverting microclimatic conditions to those more typical of native northeastern forests.”
Invasive removal alone may in some cases be sufficient for native plants to return to the area without further effort or expense by the homeowner – though in some cases, there may be cost and labor associated with acquiring and planting new native shrubs.
Invasive plant removal carries no risk except for that associated with use of standard garden tools, and it carries many environmental benefits.
C. Promotion of vertebrate biodiversity
Recent research on Lyme disease mitigation points to a whole new paradigm, suggesting that we should focus not on culling or excluding one or two specific tick-carrying mammal species (such as deer or mice), but rather on fostering life for many diverse species of fish, amphibians, reptiles, birds, and mammals.
At the homeowner or property manager level, one way to promote vertebrate diversity is by replacing exotic invasive plants with native plants, as discussed in section 2B above, and by restoring habitat diversity, health, and complexity. As entomologist Douglas W. Tallamy writes, “because animals directly or indirectly depend on plants for their food, the diversity of animals in a particular habitat is very closely linked to the diversity of the plants in that habitat.”
Some research shows that at the community planning level, a key way to promote vertebrate diversity and thereby reduce Lyme disease risk is to discourage land-use practices that fragment our forests. This is because forest fragmentation tends to favor a small number of mammal species that are relatively likely to infect ticks with Lyme disease bacterium, while reducing populations of other species that are unlikely to be infected with Lyme disease bacterium.
Note on chemical spraying for ticks
The pesticides primarily used for tick spraying are bifenthrin and permethrin, both of which are a pyrethroid that is currently classified by the EPA as a Group C carcinogen (possible human carcinogen – cancer causing) and highly toxic to bees, fish, and aquatic invertebrates.
Read here for more information on Lyme disease mitigation.
Chair, Habitat Restoration
Loudoun Wildlife Conservancy