The saliva of several types of ticks contains substances that have a toxic effect on the nervous system of dogs. When the tick bites the dog, the saliva enters the body, and the highly potent toxins in it cause motor paralysis which progresses rapidly, usually ending in death if the tick remains attached to the body.
Not only dogs, but other animals and humans, particularly children, are susceptible to tick paralysis. Mainly ticks belonging to the 3 genera, namely, Ixodes, Amblyomma and Dermacentor are responsible for tick paralysis in humans. They occur inAustralia, South Africa, Europe and North America. Besides these, a few others such as Argas, Otobius, Haemaphysalis, and Rhipicephalus can cause paralysis in dogs and other animals.
The earliest symptoms of tick paralysis in dogs are change of voice, coughing, gagging and vomiting. The breathing may be rapid and labored, and the pupils may be dilated. Lack of coordination, weakness in the limbs, and loss of voice are other symptoms that appear early.
Sudden appearance of weakness in the limbs and breathing difficulty may lead to diagnosis of tick paralysis, and spotting a tick on the dog’s body confirms it. If the tick has become detached, the tell-tale signs of tick bite, such as a ‘tick crater’, or a hole with a red and raised area around it, may be proof enough. The symptoms of tick paralysis may be similar to many other diseases affecting dogs, but in any area with a prevalence of ticks, they are the first suspects, especially if the dog has been in a place or activity (such as parks and hunting) where the possibility of exposure is high. The veterinarian takes these factors into consideration to quickly diagnose the cause of paralysis, as immediate measures taken to treat this potentially fatal condition can help save the dog’s life.
The ticks should be removed as soon as possible. The dogs affected by tick paralysis in North America are known to show signs of improvement within a day of removing the tick. If that does not happen, the dog should be searched thoroughly for the presence of more ticks. Other possible reasons for paralysis should be explored too.
Tick paralysis found in Australia is different in some respects. The paralysis may continue to progress in spite of removing the source of toxin and even after treating the dog for respiratory and motor symptoms.
While the dog is recovering from a tick paralysis, it should be kept free of stress as much as possible. There may be a worsening of symptoms immediately after the ticks are removed, and the trend may continue for the next 24 hours, but an improvement may be seen afterwards. The dog should be hospitalized during this period and kept calm and quiet, while the search for more ticks should continue, particularly in dogs with thick and long fur.
Even after the dog has recovered from the disorder, it should be looked after well, taking special care to avoid stress and too much physical activity. Strenuous exercise should be avoided for at least two months after complete recovery.
Despite giving the best of medical and treatment, not all dogs survive tick paralysis. Fatality rate is about 5%, the risk being higher for older and weaker dogs and in advanced cases where the paralysis has already become widespread. A tick antiserum which is also called Canine tick hyperimmune serum has been developed specifically for treating the tick paralysis due to Ixodes holocyclus, as no vaccine is effective against the tick toxin of this species.