More than 20 species of ticks across the US are reported to be able to inflict tick paralysis. It occurs mainly in dogs and humans (especially children), but only occasionally in cats, which seem to be relatively immune to the condition.

Tick paralysis is thought to be due to a potent neurotoxin produced in the saliva of female ticks, which is injected into hosts while feeding. Pets with tick paralysis cannot transmit the disease to humans.

The ticks mainly involved in the US are the American Dog Tick (Dermacentor variabilis), found in the eastern two-thirds of the country plus California and Oregon, the Wood Tick (D. andersoni) found from the Cascades to the Rocky Mountains, and another related species, D. occidentalis. The Lone Star Tick (Amblyomma americanum) has been known to spread the disease from Texas and Missouri to the Atlantic coast, as has the Gulf Coast Tick (A. maculatum) on the Atlantic and Gulf of Mexico seaboards.

Tick paralysis occurs most commonly in the Rocky Mountain and northwestern regions of the United States. Most cases are reported between April and June when nymphs and mature ticks, the stages during which ticks most commonly bite dogs and humans, are most prevalent.

Motor neurons (nerves which cause muscle movement) are thought to be affected by this neurotoxin, which diminishes the body's release of acetylcholine (a substance which transmits nerve impulses). This means that muscles do not receive the signals to move, causing a flaccid paralysis which starts in the lower body and moves up.

If untreated, tick paralysis can progress to paralysis of the respiratory muscles and to eventual respiratory failure. The disease is fatal in up to 10 per cent of human cases, with young animals appearing to be more susceptible than older ones.

In humans, the disease is most common in girls under 10. Disease prevalence is linked to increased tick activity in spring and early summer. Generally, individuals who live or walk pets in areas surrounded by tick-infested woods or long grasses are at a greater risk of tick paralysis.

The clinical effects of tick paralysis vary, depending on the species. The incubation period is between five to nine days from the time of tick attachment, so daily checks for, and prompt removal of ticks is essential.

Unlike most tick-related diseases, the temperature of the infected pet usually remains normal. Initially, the animal experiences discomfort and often vomiting and difficulty swallowing, with a reduced tone in the jaw muscles. Reduced reflexes in all four legs and an unsteady gait and weakness quickly follow, with this progressing to an ascending paralysis.

The patient loses the ability to stand in one to three days, however the ability to feel pain, consciousness and continence are retained. As the disease progresses, the animal loses the ability to move and finds difficulty breathing, as the respiratory muscles become progessively more paralyzed. Death may ensue several hours later if ticks are not removed.

However, if ticks are removed in time, the disease has an excellent prognosis and recovery takes from one to three days. Diagnosis is based on the progressive paralysis and the presence of a tick. There are no observable lesions, and blood and fluid values in affected animals are normal.

There is no specific treatment other than the prompt removal of ticks. Animals can be bathed in insecticidal baths to try to kill the offending ticks if they cannot be found. Supportive care, including providing warmth, oxygen (if there are breathing problems) and fluids may help speed recovery.

Efforts should be made to reduce exposure to ticks and to remove them when they are discovered. The use of tick prevention products such as Frontline, collars or dips containing amitraz, or permethrin-based products is recommended during the tick season, as well as daily inspections. Your veterinarian can recommend an appropriate product for your pet.

If you or your pet have a tick, it should be removed immediately. Do not touch the tick with your fingers,and ensure the it is pulled out gently backwards, grasping the tick as closely as possible to the mouth parts to avoid leaving the head embedded in the skin.

It is a good idea to keep the tick in a glass jar to assist the veterinarian's diagnosis in the event that tick paralysis is suspected.

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