Lyme disease is caused by the bacterium Borrelia burgdorferi. It is primarily transmitted by deer ticks. Deer ticks can also harbor other potentially serious diseases including Anaplasmosis and Ehrlichiosis.
Deer ticks, Ixodes scapularis, are much smaller than the dog tick, Dermacentor variabilis. The adult female is about the size of a sesame seed while the nymph is merely the size of a poppy seed. Eggs hatch into larvae that then feed on the white-footed mouse. This is when most ticks become infected with Lyme. The larvae drop off after ingesting blood and enter a resting state for winter. The following spring the larvae molt into nymphs. Infection that is acquired by a larval tick is carried through the molt to the next life stage. Nymphs prefer to feed on mice, but can feed on a variety of mammals including dogs and humans. By feeding on mice, nymphs have a second opportunity to become infected. In the fall of the second year nymphs turn into adults. The white tailed deer is the preferred host of the adult tick on which they feed from late fall to early winter. Adult ticks remain active as long as the temperatures are above 35 degrees. The adult ticks mate on the host. Females drop off after about a week and over winter to complete their two year life cycle by laying their eggs the following spring. New studies have shown that adult ticks that do not find a host that fall can over winter and continue their life cycle in the spring.
In summary, the deer tick’s life cycle requires three hosts and takes two years, making them difficult to control and allowing them multiple opportunities to become infected the organism that can cause Lyme disease. Both the nymph and adult can transmit Lyme disease to our dogs who, according to researchers, are at most risk of exposure in the early spring and late fall.
Deer ticks can be differentiated from the dog tick based on size, body markings, and mouth parts. The adult deer tick is considerably smaller, measuring only 2-3.5 mm, while the dog tick is around 5 mm. The dog tick’s body has mottled brown and white markings. The female deer tick has a reddish brown hind part of its body while the male is solid dark brown. Deer ticks can also be identified by their long mouth parts.
After a tick attaches to a dog it quickly begins to feed. Its long mouthparts and ingredients in its saliva allow it to burrow deeply into the skin. After attachment the bacterium that can cause Lyme Disease migrates from the midgut to the salivary glands. The longer the tick is attached the great chance it has to transmit the organism. It used to be believed that it took 48 hours of attachment before Lyme could be transmitted but more recent information suggests that transmission can happen much sooner.
Ticks and Lyme Disease are a real and increasing threat to us in the Burlington area. The most recent figures from the CDC identified Vermont as having the second highest incidence of Lyme Disease in the United States. Preventing tick attachment is vital in our defense against Lyme Disease. Tick exposure is greatest in early spring and late fall. As soon as the melting snow exposes shrubs and temperatures are above 35 degrees ticks return with vengeance. Starting prevention early and maintaining it late into the fall is vital. Tick checks every evening after venturing into tick environments remains one of the best ways to prevent Lyme Disease. Topical (spot on and collars) or oral preventatives are also extremely important in our fight against lyme disease. Many options are available. Numerous factors go into which preventative is best for your family. It is best to consult River Cove Animal Hospital to discuss your options. Changes in lifestyle to avoid ticks would be beneficial but is often unrealistic.
Several canine vaccinations are available to prevent Lyme Disease. At this point, we do not feel it is a core vaccine for all dogs. It is important to evaluate each individual’s risk of exposure and to critically weigh the benefits of the vaccination. All dogs should be tested prior to vaccination as there seems to be no benefit to vaccinating dogs that have already been exposed. If the vaccine is appropriate for your pet, it is important to remember that it is merely another layer of protection. It does not replace frequent tick checks and preventative medications.
If you find a tick on your dog, it is best to remove it as soon as possible. Please use tweezers to grab the tick as close to the skin as possible. Remove it by pulling straight out without twisting or crushing the tick. You should wash your hands after removal to limit potential exposure to yourself.
Please stay tuned for our next article on clinical lyme disease and testing.