Tick Paralysis -- Washington, 1995

Tick paralysis (tick toxicosis) -- one of the eight most common tickborne diseases in the United States (1) -- is an acute, ascending, flaccid motor paralysis that can be confused with Guillain-Barre syndrome, botulism, and myasthenia gravis. This report summarizes the results of the investigation of a case of tick paralysis in Washington.

On April 10, 1995, a 2-year-old girl who resided in Asotin County, Washington, was taken to the emergency department of a regional hospital because of a 2-day history of unsteady gait, difficulty standing, and reluctance to walk. Other than a recent history of cough, she had been healthy and had not been injured. On physical examination, she was afebrile, alert, and active but could stand only briefly before requiring assistance. Cranial nerve function was intact. However, she exhibited marked extremity and mild truncal ataxia, and deep tendon reflexes were absent. She was admitted with a tentative diagnosis of either Guillain-Barre syndrome or postinfectious polyradiculopathy.

Within several hours of hospitalization, she had onset of drooling and tachypnea. A nurse incidentally detected an engorged tick on the girl's hairline by an ear and removed the tick. Within 7 hours after tick removal, tachypnea subsided and reflexes were present but diminished. The patient recovered fully and was discharged on April 11. The tick species was not identified.

Reported by: E Haas, D Anderson, R Neu, Asotin County Health Dept, Clarkston, Washington. N Berkheiser, MD, Saint Joseph Regional Medical Center, Lewiston, Idaho. J Grendon, DVM, P Shoemaker, J Kobayashi, MD, P Stehr-Green, DrPH, State Epidemiologist, Washington State Dept of Health. Div of Field Epidemiology, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Tick paralysis occurs worldwide and is caused by the introduction of a neurotoxin elaborated into humans during attachment of and feeding by the female of several tick species. In North America, tick paralysis occurs most commonly in the Rocky Mountain and northwestern regions of the United States and in western Canada. Most cases have been reported among girls aged less than 10 years during April-June, when nymphs and mature wood ticks are most prevalent (2). Although tick paralysis is a reportable disease in Washington, surveillance is passive, and only 10 cases were reported during 1987-1995.

In the United States, this disease is associated with Dermacentor andersoni (Rocky Mountain wood tick), D. variabilis (American dog tick), Amblyomma americanum (Lone Star tick), A. maculatum, Ixodes scapularis (black-legged tick), and I. pacificus (western black-legged tick) (3,4). Onset of symptoms usually occurs after a tick has fed for several days. The pathogenesis of tick paralysis has not been fully elucidated, and pathologic and clinical effects vary depending on the tick species (4). However, motor neurons probably are affected by the toxin, which diminishes release of acetylcholine (5). In addition, experimental studies indicate that the toxin may produce a substantial decrease in maximal motor-nerve conduction velocities while simultaneously increasing the stimulating current potential necessary to elicit a response (5).

If unrecognized, tick paralysis can progress to respiratory failure and may be fatal in approximately 10% of cases (6). Prompt removal of the feeding tick usually is followed by complete recovery. Ticks can be attached to the scalp or neck and concealed by hair and can be removed using forceps or tweezers to grasp the tick as closely as possible to the point of attachment (7). Removal requires the application of even pressure to avoid breaking off the body and leaving the mouth parts imbedded in the host. Gloves should be worn if a tick must be removed by hand; hands should be promptly washed with soap and hot water after removal of a tick.

The risk for tick paralysis may be greatest for children in rural areas, especially in the Northwest, during the spring and may be reduced by the use of repellants on skin and permethrin-containing acaricides on clothing. Paralysis can be prevented by careful examination of potentially exposed persons for ticks and prompt removal of ticks. Health-care providers should consider tick paralysis in persons who reside or have recently visited tick-endemic areas during the spring or early summer and who present with symmetrical paralysis.

References

1. Spach DH, Liles WC, Campbell GL, Quick RE, Anderson DE, Fritsche TR. Tick-borne diseases in the United States. N Engl J Med 1993;329:936-47.

2. CDC. Tick paralysis -- Wisconsin. MMWR 1981;30:217-8.

3. CDC. Tick paralysis -- Georgia. MMWR 1977;26:311.

4. Gothe R, Kunze K, Hoogstraal H. The mechanisms of pathogenicity in the tick paralyses. J Med Entomol 1979;16:357-69.

5. Kocan AA. Tick paralysis. J Am Vet Med Assoc 1988;192:1498-500.

6. Schmitt N, Bowmer EJ, Gregson JD. Tick paralysis in British Columbia. Can Med Assoc J 1969;100:417-21.

7. Needham GR. Evaluation of five popular methods for tick removal. Pediatrics 1985;75:997-1002.

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