Tick Paralysis

Tick paralysis is a rare form of paralysis in animals and humans caused by a toxin released by certain ticks. This paralysis is reversed upon tick removal. The species causing the most cases of human tick paralysis in Canada are Dermacentor andersoni (the Rocky Mountain wood tick) and Dermacentor variabilis (the American dog tick). Dermacentor andersoni is found throughout British Columbia (BC), and are most common in interior BC. Other ticks such as Ixodes spp also can cause tick paralysis but this is very rare.

The disease is not reportable and official counts are not available. The BCCDC Public Health Laboratory receives consultations on tick paralysis in 0-2 human cases per year in BC. Most cases occur in the BC Interior region in the spring and summer. Children are more often affected than adults.

Causes

Tick paralysis is caused by a toxin released by certain species of ticks which can lead to paralysis in animals and rarely in humans. This paralysis is reversed upon tick removal. Prolonged attachment of a tick (primarily Dermacentor ticks) to an animal or human can cause tick paralysis. The tick releases a toxin which disrupts the function of nerves. The toxin is found in its saliva and is transmitted during tick feeding.

Symptoms

Symptoms begin after a female tick attaches to the skin and has fed for 5-7 days. Symptoms may include:

Numbness and tingling in the face and limbs
Fatigue
Weakness
Irritability
Restlessness or muscle pains

Over several hours or days, this can progress to unsteady balance and then complete paralysis (affecting the whole body) starting from the legs and moving upwards, or partial paralysis (affecting only one body part, e.g. an arm or leg). Other features include double vision and difficulty swallowing and speaking.

Although less common, illness can progress and cause: respiratory difficulties and death due to respiratory muscle paralysis can rarely occur if the tick is not removed rapidly.

Diagnosis

If this diagnosis is suspected, a meticulous examination should be done to look for a tick on the body, with special attention paid to the scalp, neck, ears, and the spaces between the fingers. Hair should be sifted through with a fine toothcomb. If a tick is found in an accessible location, then it should be extracted carefully using proper methods (see "How to remove a tick" on the tick-borne diseases page). If a tick is found in a location where proper removal can be difficult, then seek medical attention for removal. Rapid improvement once an attached tick is properly removed is diagnostic. The diagnosis can be delayed due to the rarity of the condition.

Treatment

The treatment for tick paralysis is tick removal. Most patients with tick paralysis will recover or substantially improve within a few hours following tick removal.

Prevention

Find more information about prevention of tick paralysis on the main tick-borne diseases page.