Tick Paralysis in Dogs

Summary

Tick paralysis, or tick toxicity, is a quick acting, progressive disease that can cause extreme harm to a dog (and humans). Beginning two to seven days after a tick starts feeding on a host, the paralysis starts in the dog’s lower extremities and moves to the upper extremities. The paralysis usually involves both legs symmetrically. Other initial signs include changes to the dog’s bark, trouble with coordination in the hind legs, change in rate or effort of breathing, and effort, gagging or coughing, vomiting, and dilated pupils. If the tick isn’t removed from the dog’s skin, suffocation may occur. Fortunately, if the tick is promptly removed, the dog will likely recover in days. If the tick is not removed, the paralysis can be fatal. 

This form of motor paralysis is caused by the neurotoxins in the saliva of female ticks of certain species. These ticks are found in humid climates in the USA and Australia. 

Note: Not all tick bites or infestations lead to paralysis, as the toxin is not produced by all females and species of ticks. Protect the dog from tick paralysis and other tick related diseases by using appropriate prevention products to repel ticks and to kill any ticks that bite. Always consult a veterinarian before choosing a tick control product as there are many products on the market which are neither safe nor effective for use.

Risk Factors

While rare, tick paralysis in dogs can be life-threatening. Dogs showing symptoms of paralysis need emergency medical care, regardless of any known tick exposure. Rapid identification and removal of all ticks on a dog with symptoms of tick paralysis is critical for recovery. 

In North America, tick paralysis is most prevalent in the southeastern and northwestern regions. Most cases of paralysis occur from May to June, but tick paralysis has been reported year round.

Possible Causes

Tick paralysis is caused by the bites of certain species of ticks. In North America there are six species whose females are thought to carry the neurotoxin:

• Dermacentor andersoni (the Rocky Mountain wood tick) • Dermacentor variabilis (the American dog tick)

• Amblyomma americanum (the lone star tick) • Amblyomma maculatum (the Gulf Coast tick)

• Ixodes scapularis (the black-legged tick) • Ixodes pacificus (the western black-legged tick)

Dogs who are not on tick prevention medications have a higher risk, as do dogs who spend time where ticks live (woodlands and grassy areas), even if they take medication. There is no difference in reported cases of  tick paralysis based on age, breed, or sex.

Most tick paralysis cases occur in the spring and early summer when ticks are most active.

Main Symptoms

The most prevalent early symptom of tick paralysis is weakness in the hind legs. This progresses towards the front legs, affecting the whole body as it moves forward. Other symptoms of tick paralysis include:  

• Weakness • Ataxia (trouble walking) • Paralysis • Coughing • Difficulty breathing (dyspnea)

• Difficulty swallowing (dysphagia) • Vomiting

Detailed Characterization

Symptoms initially appear mild as weakness limited to the rear of the body. As the disease progresses, symptoms move in an ascending fashion towards the front of the body and become more severe as weakness develops into full-fledged paralysis.

Secondary symptoms include a decrease in 

• Jaw tone and eye reflexes • Ability to breathe • Muscle tone • Changes in bark quality and volume

Symptoms typically appear 3 - 9 days after a tick bites. The paralysis worsens if the tick is not removed. 

Each dog reacts to the stress of the toxins differently. Puppies, older dogs, small dogs, and dogs with other illnesses (comorbidities) tend to suffer more.

Testing and Diagnosis

The first priority for a dog with tick paralysis is to find and remove all ticks. In reported cases, 10% of dogs have more than one tick, so a thorough examination is critical.  To ensure all ticks are found, shaving long or matted hair is often necessary. If the dog is anxious, sedation may be used to facilitate shaving and reduce stress. Acaricides (pesticides that specifically target ticks) are used in an effort to kill any remaining ticks that escape detection.

Even if no ticks are found, the presence of a tick bite on the skin can suggest that a dog’s sudden paralysis is the result of a tick exposure.Tick bites have a characteristic crater-like sore with raised, red edges surrounded by scabby debris and a small dark hole at the center. 

If the symptoms lessen within a couple of hours following the removal of ticks and/or use of an acaricide, a diagnosis of tick paralysis is confirmed. 

Hospitalization is necessary for dogs with severe symptoms. The use of tick antiserum (canine tick hyperimmune serum) to neutralize the salivary toxin shows promise as treatment.   The other diseases that have similar symptoms are:

• Acute polyradiculoneuritis • Botulism • Myasthenia gravis (crisis form)

Steps to Recovery

90 to 95% of dogs recover from tick paralysis. Afflicted dogs  are expected to improve within hours of having all the ticks removed or killed. Most symptoms resolve within one to three days. Muscle strength may not fully return for months, but most dogs recover completely when treated appropriately. Exercise restriction is advised for 1-2 months for dogs recovering from tick paralysis. 

If untreated, the dog can die from paralysis of the respiratory muscles.

Prevention

Tick paralysis itself is not contagious. No vaccine is available for tick paralysis. Tick antiserum (canine tick hyperimmune serum) shows promise as a form of treatment for tick paralysis and investigation into it is ongoing. 

Tick paralysis can only result from direct exposure to toxic tick saliva. Almost all warm-blooded land animals can be affected by tick paralysis, including humans.  The best way to prevent tick paralysis is to use year-round tick control products. Prescription preventatives are the safest and most effective options. Additional ways to minimize risk check for ticks any time dogs have been in an area where ticks are prevalent.

Is Tick Paralysis Common in Dogs?

Tick paralysis is not commonly reported in dogs.

Typical Treatment

• Removal of ticks • Acaricidal treatment • Supportive and nursing care as typically required for paralysis • IV fluids

• Assistance with eating • Parenteral nutrition • Bladder and bowel assistance • Supplemental oxygen

• Mechanical ventilation