Cluster of Tick Paralysis Cases --- Colorado, 2006

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September 1, 2006 / 55(34);933-935

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5534a1.htm?s_cid=mm5534a1_e%0A

Cluster of Tick Paralysis Cases --- Colorado, 2006

Tick paralysis is a rare disease characterized by acute, ascending,

flaccid paralysis that is often confused with other acute neurologic

disorders or diseases (e.g., Guillain-Barré syndrome or botulism).

Tick paralysis is thought to be caused by a toxin in tick saliva; the

paralysis usually resolves within 24 hours after tick removal. During

May 26--31, 2006, the Colorado Department of Public Health and

Environment received reports of four recent cases of tick paralysis.

The four patients lived (or had visited someone) within 20 miles of

each other in the mountains of north central Colorado. This report

summarizes the four cases and emphasizes the need to increase

awareness of tick paralysis among health-care providers and persons in

tick-infested areas.

Case 1. On May 15, a girl aged 6 years from Weld County awoke with

symptoms of bilateral lower extremity weakness. She attended school as

usual but needed assistance from a friend to walk outside for recess,

where she fell down and was unable to get up. Her mother took her to

an outpatient clinic, and a neurology appointment was arranged for the

next day. She awoke the next day with a tingling sensation in her

hands and feet, an inability to sit or stand on her own, and

difficulty swallowing. She was taken to a local emergency department

(ED) and transferred to a regional children's hospital. A physical

examination revealed ophthalmoplegia (i.e., paralysis of muscles

controlling eye movement), dysarthria (i.e., slurred or abnormal

speech), and areflexia (i.e., absence of neurologic reflexes); nerve

conduction studies indicated decreased velocities. The girl was

admitted to the intensive-care unit on May 16 with a presumed

diagnosis of Guillain-Barré syndrome and subsequently required

intubation. On the evening of May 17, a nurse who was bathing the girl

found a tick along her hairline. Investigators later learned that the

tick had been visible on magnetic resonance imaging of the girl's head

earlier that day. The tick was removed immediately, and the girl's

symptoms improved; she was discharged home 1 week later. The tick was

identified as a female Dermacentor andersoni. The girl often had

visited her grandmother in the mountains in Larimer County and

frequently hiked in the area. Seven days before symptom onset, the

girl had visited her grandmother and played outside in the yard.

Case 2. On May 22, a man aged 86 years from the mountains in Larimer

County began to have increased difficulty standing and transferring to

and from his motorized scooter. The man was homebound as a result of

chronic polyneuropathy and weakness from spinal stenosis. The next

morning, his weakness worsened, and he was unable to walk or grasp

objects. He called for emergency services and was admitted to the

local hospital with a diagnosis of progressive worsening of his

chronic neuropathy. Physical examination revealed normal cranial nerve

function but generalized weakness; deep-tendon reflexes were absent.

On the evening of May 23, a nurse who was changing the man's gown

noticed a tick on his back. After tick removal, his symptoms improved

during the next 4 days, and he was discharged home on May 27, although

2 weeks later he did not feel he had yet recovered to his baseline

condition. The man did not report any recent travel or spending any

time outdoors, with the exception of daily visits to his mailbox using

his scooter. He owned a dog that was often outside, and he believed

this was the likely source of the tick; the dog had no signs of tick

paralysis.

Case 3. On May 22, a woman aged 78 years from the mountains in Grand

County had generalized weakness and difficulty walking. During the

next few days, her signs and symptoms progressed to facial weakness,

slurred speech, decreased taste, and confusion. While the woman was

preparing to go to the ED on May 25, her roommate noticed a tick on

the back of the woman's neck below the hairline. Physical examination

in the ED revealed normal cranial nerve function and no appreciable

weakness, but the patient did have decreased deep-tendon reflexes. The

ED physician removed the tick by cutting the surrounding tissue with a

scalpel. The patient was discharged home to recover. The patient

subsequently reported that within 24 hours her weakness, alteration in

taste, and confusion were resolved; however, 3 weeks after discharge,

she still became tired easily. The woman reported that she hiked or

walked outside daily.

Case 4. A man aged 58 years from Larimer County with a history of

chronic renal failure traveled to southern Texas on April 20. On April

24, he had a tingling sensation in his hands and perioral numbness.

Three days later, he collapsed while trying to stand and was unable to

get up. While helping him off the floor, his wife discovered a tick on

the man's back. She removed the tick before transporting him to a

local ED. He was transferred and admitted to an intensive-care unit

but did not require intubation. Several hours later, he began to

regain feeling in his hands and was able to walk with assistance. He

was discharged home on May 5, but 6 weeks later he still reported

residual subjective weakness. The patient reported that he frequently

performed yard work and various outdoor recreational activities.

Reported by: WJ Pape, K Gershman, MD, Colorado Dept of Public Health

and Environment. WM Bamberg, MD, EIS Officer, CDC.

Editorial Note:

The four cases described in this report illustrate the importance of

considering tick paralysis in the differential diagnosis of persons

with ascending paralysis who live in or visit tick-endemic regions.

Diagnosis is confirmed by finding a tick embedded in the skin and

observing for signs of improvement after tick removal; no other test

exists for confirming tick paralysis. Although rare, cases of tick

paralysis have been identified worldwide; most cases in North America

occur in the western regions of Canada and the United States. The

species most often associated with tick paralysis in the United States

and Canada are the Rocky Mountain wood tick (D. andersoni) and the

American dog tick (Dermacentor variabilis); however, 43 tick species

have been implicated in human disease around the world (1). Most North

American cases of tick paralysis occur during April--June, when adult

Dermacentor ticks emerge from hibernation and actively seek hosts (2).

Tick paralysis is thought to be caused by a toxin secreted in tick

saliva during feeding that reduces motor neuron action potentials and

the action of acetylcholine, depending on the species of tick (1,3).

Symptom onset usually occurs after 4--7 days of tick feeding.

Ascending flaccid paralysis progresses over several hours or days;

sensory loss does not usually occur, and pain is absent (4,5).

Resolution of symptoms usually occurs within 24 hours of tick removal.

When the tick is not removed, the mortality rate resulting from

respiratory paralysis is approximately 10% (6,7).

Although tick paralysis is not a reportable disease in the state, the

Colorado Department of Public Health and Environment receives, on

average, a report of one case per year. The geographic and temporal

clustering of cases described in this report is unusual. No

explanation exists to account for this clustering; the risk for

acquiring tick paralysis has been widespread in the western United

States and Canada.

The cases described in this report also differ in other respects from

previous reports. For example, the majority of patients have been

children, particularly girls (2,7). However, in this cluster, only one

patient was a child, and two patients were aged >70 years. The ticks

removed from all four patients were on the neck or back; in previously

reported tick paralysis cases, ticks were predominantly on the head

and neck (7). Although outdoor exposure, such as hiking or camping in

wooded areas, is usually associated with tick paralysis, one of the

four patients was homebound with limited outdoor exposure.

Health-care workers discovered the ticks incidentally on two of the

patients whose conditions had received alternative diagnoses.

Health-care providers should consider a diagnosis of tick paralysis in

any patient living in or visiting a tick-endemic area who has acute,

symmetric paralysis and should perform a complete examination for

ticks, particularly on the head, neck, and back. Ticks should be

removed by grasping the tick close to the patient's skin with forceps

and pulling with a steady, even pressure (8). Persons in tick-endemic

areas should be educated regarding tick-borne diseases and should

perform routine checks for ticks after possible exposures. Insect

repellents should be applied to skin, and permethrin-containing

acaricides should be sprayed on clothing to help prevent tick bites.

Additional information regarding prevention of tick-borne diseases is

available at http://www.cdc.gov/ncidod/ticktips2005.

Acknowledgments

This report is based, in part, on contributions by S Rubaii, MD,

Granby Medical Center, Granby; AC Nyquist, MD, The Children's

Hospital, Denver; V Lambiase, Estes Park Medical Center, Estes Park;

and R Grossmann, Larimer County Dept of Health and Environment, Fort

, Colorado.

References

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2. Dworkin MS, Shoemaker PC, D. Tick paralysis: 33 human

cases in Washington state, 1946--1996. Clin Infect Dis

1999;29:1435--9.

3. Felz MW, CD, Swift TR. A six-year-old girl with tick

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4. Spach DH, Liles WC, GL, Quick RE, DE Jr, Fritsche

TR. Tick-borne diseases in the United States. N Engl J Med

1993;329:936--47.

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(Dermacentor variabilis Say) paralysis in Virginia: with a summary of

all the cases reported in the Eastern United States. Pediatrics

1948;1:174--80.

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

7. Schmitt N, Bowmer EJ, Gregson JD. Tick paralysis in British

Columbia. Can Med Assoc J 1969;100:417--21.

8. Needham GR. Evaluation of five popular methods for tick removal.

Pediatrics 1985;75:997--1002.