Tick Paralysis

How tick paralysis happens

Certain hard ticks produce a toxin in their saliva that blocks the release of acetylcholine at nerve endings, the chemical signal that makes muscles contract. The toxin builds up as the tick feeds, so symptoms usually begin after the tick has been attached for 4 to 7 days, when it is engorged. Only one attached tick is needed.

In North America the main culprits are the Rocky Mountain wood tick (Dermacentor andersoni) in the western US and Canada and the American dog tick (Dermacentor variabilis) in the east. Cases cluster in the Pacific Northwest and Rocky Mountain regions, and in British Columbia. In Australia, the Ixodes holocyclus tick produces a more potent toxin, and paralysis may even worsen for a day or two after removal.

Symptoms

Symptoms develop over hours to a few days:

1. Early: tiredness, irritability, tingling or numbness in the legs, muscle aches.
2. Unsteady walking (ataxia): often the first obvious sign. Children may stumble, fall or refuse to walk.
3. Ascending weakness: both legs become weak, then the weakness spreads upward to the trunk, arms and face over 12 to 36 hours.
4. Loss of reflexes in the affected limbs.
5. Facial and throat weakness: drooping face, double vision, slurred speech, difficulty swallowing.
6. Breathing muscle weakness: shallow breathing and, eventually, respiratory failure.

Fever is typically absent, and the person is alert and thinking clearly. Sensation is mostly normal. Sometimes the weakness affects only one arm or leg near the bite site, or mainly causes imbalance.

Tick paralysis vs Guillain-Barre syndrome and other causes

Tick paralysis is often first misdiagnosed as Guillain-Barre syndrome. Every child with sudden weakness or unsteadiness should have a full skin check for ticks.

Diagnosis: finding the tick

The diagnosis is made by finding an attached, engorged tick in someone with typical symptoms. Ticks are easily missed:

• part long hair section by section and check the whole scalp, including behind the ears and the nape of the neck
• check inside and around the ears, in skin folds, the armpits, groin, between the buttocks, behind the knees, between toes and under the waistband
• look for more than one tick

Tests such as nerve conduction studies may show reduced nerve signals but are not needed if a tick is found. Spinal fluid and MRI are normal, which helps rule out other causes if the tick is not found at first.

Treatment

Remove the tick

1. Use fine-tipped tweezers to grasp the tick as close to the skin as possible.
2. Pull upward with steady, even pressure. Do not twist, jerk, crush or squeeze the body.
3. If mouthparts remain, remove them if easy. Otherwise leave them and let the skin heal.
4. Clean the area and your hands with soap and water or rubbing alcohol.

Do not use petroleum jelly, nail polish, heat or matches, which delay removal and may cause the tick to release more saliva. In Australia, local advice is to kill the tick in place with a freezing spray before removal.

Medical care

People with significant weakness should be monitored in hospital. Breathing tests check whether the breathing muscles are weakening. A small number need temporary oxygen or a breathing machine until the toxin wears off. Antitoxin is available in Australia for Ixodes holocyclus but rarely used.

Antibiotics are not used for tick paralysis itself, because it is caused by a toxin, not an infection.

Recovery and outlook

With North American ticks, improvement often starts within hours of removing the tick, and most people recover fully within 24 to 48 hours. Recovery after Australian tick paralysis is slower and can take days. Death is rare and occurs when the tick is not found and breathing fails. Having tick paralysis does not give immunity.

Prevention

• Use insect repellents with DEET, picaridin or oil of lemon eucalyptus on skin, and permethrin on clothing and gear.
• Wear long sleeves and trousers tucked into socks in woods and tall grass.
• Do a full-body tick check, including the scalp, after being outdoors, and shower within 2 hours.
• Check pets, which can bring ticks into the home.
• Tie back or braid long hair during outdoor activities.

Frequently asked questions

What are the symptoms of tick paralysis?

It usually starts with unsteady walking and leg weakness, then the weakness climbs to the arms, face and breathing muscles over hours to a day or two. There is usually no fever, and the person remains alert. Reflexes are reduced or absent.

How long does tick paralysis last?

After removing a North American tick, symptoms usually start improving within hours, and most people recover fully within 1 to 2 days. With the Australian paralysis tick, symptoms may worsen for a day or two before recovering over several days.

Can adults get tick paralysis?

Yes, though it is less common than in children. Adults working or hiking in tick-infested areas can be affected. In adults, the tick may be found on the scalp, behind the ears, in the groin or other hidden areas.

Is tick paralysis the same as Lyme disease?

No. Tick paralysis is caused by a toxin in the saliva of certain ticks and resolves quickly once the tick is removed. Lyme disease is a bacterial infection spread by deer ticks that causes rash, fever and joint or nerve problems weeks later, and is treated with antibiotics.