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Hours of Operation:

Monday: 8:30 a.m.-7 p.m.
Tuesday: 8:30 a.m.-7 p.m.
Wednesday: 8:30 a.m.-5 p.m.
Thursday: 8:30 a.m.-7 p.m.
Friday: 8:30 a.m.-7 p.m.
Saturday: 8:30 a.m.-2 p.m.
Sunday: 9:00 a.m-12 p.m.

Deer tick life cycle: how it transmits Lyme disease

Spring has sprung and those ticks are hungry and looking for hosts. Unfortunately, ticks can also transmit disease to us and our pets (primarily dogs) when they feed. Although there are different types of ticks and different diseases that they can carry (what are commonly called tick borne diseases in the veterinary community), the most common tick in our area is one called Ixodes scapularis, or the deer tick, and it carries Lyme disease. Therefore, today's article will concentrate on the deer tick's life cycle to learn to prevent Lyme disease. The second article, next month, will cover specific prevention techniques.

There are four stages to the deer tick life cycle: egg, larva, nymph and adult. Between each stage of the life cycle ticks must feed but they are very resilient. I can hardly make it from lunch to dinner without needing a snack but these guys are really incredible. Not only can these tick eggs postpone hatching in severe conditions, but they also have the ability to go dormant in any stage of their life cycle if the conditions are poor.

After feeding (usually in the spring and fall) adult female deer ticks will lay eggs in either the brush or the bedding of a host. A single female tick can lay up to 2,000 eggs and if the conditions are right, the eggs soon hatch into larva.

Now, when I hear the word larva I usually think of little wormy things that burrow around in the dirt but this is not true for deer ticks. The larva look very much like the adults except they are much smaller. They have six legs instead of eight but still have the same mouthparts and come out very hungry looking for a host.

How do larvae find their host? Since not all ticks have eyes they rely on their front legs to pick up on carbon dioxide, body odor, vibrations, temperature changes and other cues to find a host and feed. This is usually a smaller mammal such as a field mouse. Field mice can carry the bacteria that cause Lyme disease and the larval tick will pick up the organism when feeding.

After feeding the larva will go into a dormant stage (similar to a hibernation) and emerge the following spring as a nymph, or young adult. Nymphs have eight legs but their bodies are much smaller than adults. These guys also emerge very hungry and use the same techniques to find a host to feed. Unfortunately for our pets (mainly dogs), this is also when they can first transmit Lyme disease.

After feeding the ticks go again into a dormant stage and then emerge as adults. Adults look very similar to the nymph stage, only larger. One last time the ticks feed, mate and finish their life cycle. After feeding for a period of days the ticks fall off. The male ticks usually complete their life cycle (die), but the females still have work to do (as usual).

When ticks attach they do not insert their mouthparts directly into a blood vessel, but rather just insert them under the skin. This allows the ticks to obtain red blood cells (their primary source of nutrition), but they also swallow a lot of fluid. In order to relieve themselves of excess fluid as they feed the ticks have to regurgitate every so often. It is when these ticks regurgitate that they also pass along the bacteria that cause Lyme disease (or other diseases carried by ticks). My next article will focus on prevention of ticks and tick borne diseases.

Dr. Kearns has been in practice for 13 years and is pictured with his son Matthew, as well as the newest member of the family, Jasmine, a Labrador retriever.

Author: 
Matthew Kearns, DVM