Tick Paralysis in Dogs

Tick paralysis is a rapidly progressive motor paralysis caused by a toxin in the tick's saliva that attacks the nervous system. Certain species of ticks are known to cause tick paralysis. People (especially children) and many other animals may be affected. Human cases of tick paralysis caused by the genera Ixodes, Dermacentor, and Amblyomma have been reported in Australia, North America, Europe, and South Africa. These 3 genera plus Rhipicephalus, Haemaphysalis, Otobius, and Argas have been associated with paralysis in animals.

Early signs in affected dogs include change or loss of voice, lack of coordination of the hind legs, change in breathing rate and effort, gagging or coughing, vomiting, and dilated pupils. Signs occur 3–5 or 5–9 days after the tick attaches, depending on the type of tick involved.

The presence of a tick along with the sudden (within 12 to 24 hours) appearance of leg weakness and/or difficulty breathing is diagnostic. If the tick is not still attached, the presence of a tick “crater” (a small hole surrounded by a slightly raised and red area) can help confirm diagnosis. Other diseases and disorders have the same signs as tick paralysis, but in areas where ticks are prevalent, tick paralysis is a strong possibility.

Removal of the tick(s) is necessary. In North America, the animal usually improves greatly within 24 hours of the tick being removed. If the animal does not recover, more ticks may still be attached, or the signs may be due to another condition. In Australia, the disease tends to progress even after removal of the tick and treatment of the motor and respiratory signs. All ticks must be removed, or death can occur due to paralysis of the muscles responsible for breathing.

Canine tick hyperimmune serum, also called tick antiserum (TAS), is the specific treatment for the toxin that causes tick paralysis..

Stress should be kept at a minimum. Affected animals may worsen for the first 24 hours after tick removal, and then recover. During this time, animals should be kept quiet under observation at a veterinary hospital. Animals, especially if long-haired, should be examined carefully for the presence of more ticks, and antiparasitic medications should be applied to kill any remaining ticks. Dogs with trouble breathing may require additional therapy, such as oxygen and breathing assistance under anesthesia. Other organs affected by the toxin may also require additional treatments. About 5% of animals are likely to die, despite treatment, especially if the stages of paralysis are advanced, if the ability to breathe is significantly impaired, or if the animal is very young or old. For animals that do recover, the owner should continue searching for ticks and avoid stressing or strenuously exercising the animal for the next 1-2 months.

Tick control products are available. However, owners should not rely only on chemical control to prevent ticks. Additional measures include keeping the hair short and routinely checking for ticks when dogs have been outdoors in an area where ticks are prevalent. There is no vaccine against the Ixodes holocyclus toxin.