Eight-Legged Beasts

Warmer weather has arrived!  Bringing with it the picnics, the cookouts, the gardening….and the ticks. Yes, people aren’t the only species more active when the temperatures rise.

Ticks and Deer

Ticks are the most important ectoparasites infesting white-tailed deer in North America.  Eighteen species have been reported from white-tailed deer in the United States.  For deer, tick infestation and/or complications can include local irritation, anemia, secondary infections, and disease transmission. However, most deer show no signs of adverse effects nor do they exhibit serious health impacts from the unwanted hitchhikers. Those that are affected almost always are from populations that are malnourished and have high levels of internal parasites.

Disease Transmission

Ticks play a major role in disease transmission. Lyme disease is the most commonly reported tick-borne disease and probably the most well know but there are many other diseases that ticks can transmit like babesiosis, ehrlichiosis, anaplasmosis, and Rock Mountain Spotted Fever. Tick-borne diseases and their transmission are complex. While deer play a role, there are many factors involved in a diseases’ persistence in tick populations and its transmission to people. To learn more about the relationship between Lyme disease and deer check out Lyme Disease & Deer: Revelation or Red Herring, found on the deer page.

Life Cycle

Ticks have a multiyear life cycle and tick density varies significantly from year to year. These fluctuations depend on acorn and small mammal abundance. Acorns support small rodents and small rodents are essential to the tick life cycle especially the larval and nymph stages.  Adult ticks, most active in the fall, feed and mate on large animals, like deer, to complete their life cycle.

People are most likely to contract Lyme disease and other tick-borne diseases from the bite of an infected nymph-stage tick. Woodland rodents, especially white-footed mice, are most likely to infect larval and nymph stages of blacklegged ticks with the bacteria that causes Lyme disease.

Deer do not become ill with Lyme disease. And as the final host, deer do not infect ticks with the bacteria that cause Lyme disease. If a tick found on a deer is carrying Lyme disease, it likely was infected in an earlier life stage by a small rodent.

Rodent Hosts

Abundance of rodent hosts (i.e., mice and chipmunks) and acorns (rodent food supply) were the most important factors affecting the risk of Lyme disease in a 13-year study. While a 3-fold change in deer abundance did not affect risk of Lyme disease.

Related Links

More information on the tick life cycle and Lyme disease can be found in the Game Commission’s Wildlife Disease Reference Library – Lyme Disease, CDC website, or the Lyme Disease fact sheet from PennState. Connecticut also has a fact sheet – Managing Ticks of Your Property – that may be helpful at keeping those 8-legged beasts at bay.

By: J. T. Fleegle

Wildlife Biologist, Deer & Elk Section

Pennsylvania Game Commission

Management/Prevention
People should take certain precautions to reduce the risk of contracting Lyme disease. When spending time outdoors in potential tick habitats, long pants tucked into socks or boots, and insect repellant are recommended. Each day spent in tick habitat should be followed by a thorough “tick check”. Ticks found on people or pets should be removed promptly and completely. Veterinarian recommended tick control products should be used on pets that spend time outdoors. Lyme disease vaccines are no longer available for humans, but vaccines are available for pets.

-Excerpt from the Pennsylvania Game Commission Wildlife Reference Library-Lyme Disease