Tick Bite Paralysis in Dogs
Ticks act as carriers of various diseases in animals, including in dogs. Tick paralysis, or tick-bite paralysis, is caused by a potent toxin that is released through the saliva of certain species of female tick and which is injected into the blood of the dog as the tick infests the skin of the dog. The toxin directly affects the nervous system, leading to a group of nervous symptoms in the affected animal.
The toxins released by ticks cause lower motor neuron paralysis, which is defined as a loss of voluntary movement and which is caused by a disease of the nerves that connect the spinal cord and muscles. With lower motor neuron paralysis the muscles stay in an apparent state of relaxation.
An infestation of ticks is not necessary for a diseased state to occur. While multiple ticks are usually present on a dog that is showing symptoms of tick paralysis, tick-bite paralysis can take place after being bitten by only one tick. Conversely, not all animals, infested or not, will develop tick paralysis.
Symptoms usually begin to appear around 6-9 days after a tick has attached to the skin of the dog. This disease is somewhat seasonal and more prevalent in the summer time in certain areas of the U.S.. In areas where the seasonal temperatures are more consistently warm, such as in the southern states and northern Australia, ticks may be present throughout the year.
In the U.S., this disease is more commonly seen in dogs than in cats. In fact, cats in the U.S. appear to have a resistance to the tick toxin.
Symptoms and Types
There is history of a recent visit the dog has taken to a wooded area, or living in an area that is endemic to ticks. Symptoms are gradual in nature, including:
- High blood pressure
- Fast heart rate and rhythm (tachyarrhythmias)
- Weakness, especially in the hind limbs
- Partial loss of muscle movements (paresis)
- Complete loss of muscle movement (paralysis), commonly seen in advanced disease state
- Poor reflexes to complete loss of reflex
- Low muscle tone (hypotonia)
- Difficulty in eating
- Disorder of voice (dysphonia)
- Asphyxia due to respiratory muscle paralysis in severely affected animals
- Excessive drooling (sialosis)
- Megaesophagus (enlarged esophagus)
- Excessive dilatation of pupil in the eye (mydriasis)
- Tick infestation
You will need to give a thorough history of your dog's health, onset of symptoms, and possible incidents that might have preceded this condition. For example, your veterinarian will ask about any recent visits you and your dog have made to wooded areas, especially within the last several days and weeks.
Your veterinarian will conduct a complete physical examination, looking closely at your dog's skin for the presence of ticks or for recent evidence of ticks. If ticks are found to be present on the skin, your veterinarian will remove the tick and send it to the laboratory for a determination of its species. Routine laboratory tests will include a complete blood count, biochemistry profile, and urinalysis. However, the results of these tests are often normal if no other concurrent disease is present along with tick paralysis.
In patients with respiratory muscle paralysis, blood gases will need to be calculated to determine the severity of the respiratory compromise. If respiratory muscle paralysis is occurring, low oxygen and high levels of carbon dioxide will be present in the blood, as the dog will not be able to properly inhale oxygen and exhale carbon dioxide. A chest radiograph may reveal an enlarged esophagus due to the extra effort of trying to breath.
The most important step in the diagnosis is to search for and find the tick that bit your dog so that it can be identified and its ability to transmit disease determined. Your veterinarian will thoroughly search all areas of your dog’s skin to find any ticks so that this can be done.
In case of severe disease, your dog will need to be hospitalized for intensive care and nursing support. Respiratory paralysis is an emergency and needs immediate veterinary medical attention.
Identifying and detaching the ticks is the first step to preventing the further release of toxins and aggravating the symptoms. Even if no ticks are found, an insecticidal bath may be given to your dog to kill any ticks that may be hidden in the folds of the skin. In some cases, this is the only treatment required and the dog will soon start showing signs of recovery. However, in cases with respiratory paralysis, oxygen supplementation or some other form of artificial ventilation will be required to keep the dog breathing.
If the dog is dehydrated, intravenous fluids will be given, along with medications that can be used to counter the effects of the toxins on the nervous system, and to relax the muscles enough so that the dog can breathe.
Living and Management
For the best recovery, you will want to keep your dog in a quiet, cool environment. The affects of the toxins are temperature dependent and at high temperatures aggravation of symptoms may increase. Physical activity should also be temporarily avoided, as activity can increase body temperature and aggravate symptoms. Encourage your dog to relax as much as possible until a full recovery.
Some affected animals have problems with vomiting and loss of appetite and are unable to eat. In such cases, food should not be offered until these symptoms are properly managed. Your veterinarian will instruct you on the type of food supplements that should be fed to your dog, and the method you should use to feed your dog (which can be by syringe or tube, for example). Good home nursing care is important for a prompt and full recovery.
During hospitalization, a daily neurological assessment of your dog will be taken. The overall prognosis largely depends on the specie of tick that was found to have infested your dog, but as with any illness, your dog's recovery may also rest on its health condition and age previous to the tick acquired illness. In some cases, with particularly toxic reactions, death can occur even with the best treatment.