Do Deer Spread Lyme Disease?

photo 2007 Allan Hack | more info (via: Wylio)Although I miss the snow, I must confess that I am delighted spring has come to the...

Dr. Eric Barchas  |  May 6th 2011


Western Fence Lizardphoto 2007 Allan Hack | more info (via: Wylio)
Although I miss the snow, I must confess that I am delighted spring has come to the northern hemisphere.

Every spring, clients begin to enquire about Lyme disease (or, as many people incorrectly call it, Lymes disease or Lyme’s disease). Frequently they express concern that large numbers of deer in their areas place their dogs at great risk for the disease.

Lyme disease, also known as borreliosis, is caused by a type of bacteria called a spirochete (the specific spirochete under discussion is Borrelia burgdorferi). Or, rather, the symptoms of Lyme disease in dogs (which may include lethargy, joint problems, and kidney problems) are caused by the immune system’s response to the spirochetes.

Lyme disease is spread by ticks. The genus of tick that most commonly spreads the disease is Ixodes, which is known colloquially as the deer tick. Many people therefore assume, wrongly, that deer are the main reservoir for Lyme disease.

The prevalence of Lyme disease, in fact, is not terribly dependent upon deer populations. Deer are extremely ubiquitous in wooded and suburban areas, but Lyme disease incidence varies significantly from place to place.

The likelihood that any given tick will carry the spirochete depends more greatly on the populations of two different animals: the White Footed Mouse, and the Western Fence Lizard.

The White Footed Mouse is nature’s main reservoir for Lyme disease. Their populations help to keep Lyme disease going. The Western Fence Lizard is a preferred food source for certain life stages of Ixodes ticks in many areas, including California. Conveniently for dogs and people, the blood of the Western Fence Lizard seems to inactivate or kill the spirochete when ticks feed on the reptiles. This results in low Lyme disease prevalence rates in areas with healthy lizard populations. Next time you see a lizard sitting on a fence, be sure to tip your hat to the gentle soul who is unknowingly protecting you and your pet.

The best way to prevent Lyme disease is to prevent tick infestation. Frontline Plus is the tick preventative with the longest and, in my experience, best safety record as a tick preventative. K9 Advantix also has a good safety and efficacy profile (although it’s not safe for cats). No tick preventative is 100% effective, so be sure to search your dog, and comb or brush him, after any outdoor adventure.

The vaccine for Lyme disease is controversial. The vaccine works by stimulating the immune system. The spirochete, as you will recall, causes symptoms by stimulating the immune system. I have met a couple of experts who expressed concern (and claimed to have data to back up their concern) that the vaccine might do as much harm as good. Although I have never seen that data, I generally do not recommend the vaccine for my patients unless they are at very high risk for the disease.

My pal Buster goes hiking all of the time, and he has never received a Lyme vaccine. He does, however, receive Frontline Plus. And he lives in a state that is blessed with plenty of Fence Lizards.

Photo: unwitting protector.