VAIL, Colo. - Tick paralysis is often misdiagnosed - with potentially dire consequences - as one of the other diseases that cause an acute ascending paralysis with preserved mental status.
The arthropod-inflicted paralysis is most often confused with Guillain-Barre syndrome. Other causes of an acute ascending paralysis with preserved mental status include spinal cord tumors and acute poliomyelitis. Botulism, in contrast, causes a descending paralysis with preserved mental status, Dr. Sean O’Leary said at the annual conference on pediatric infectious diseases, which was sponsored by the Children’s Hospital, Denver.
Photo Courtesy of James Gathany/CDC
A dorsal view of a male Rocky Mountain wood tick, Dermacentor andersoni.
Conducting a thorough search for an embedded tick is essential in a patient with an acute ascending paralysis with preserved sensorium, particularly when there is a history consistent with potential tick exposure. Treatment of tick paralysis is simple: remove the tick. Clinical improvement will follow within hours.
In unrecognized and untreated cases of tick paralysis, however, the fatality rate is about 10%, with death typically occurring just 18-30 hours after symptom onset, according to Dr. O’Leary of the Children’s Hospital and the University of Colorado, both in Denver.
Tick paralysis is more common in children than adults. The highest-risk group is young girls with long hair that can readily hide an engorged tick that’s had a blood meal. At 3 days after attachment, the tick (usually a female) begins secreting the neurotoxin that causes the paralysis. Symptoms appear 4-7 days after attachment. The peak time for tick paralysis is tick mating season: April through June.
The clinical scenario typically begins with loss of appetite and voice, followed by gait instability, ascending flaccid paralysis, excessive salivation, eye irritation, pupil asymmetry, and vomiting. Death usually is from respiratory failure. For more than half a century, there have been postmortem reports of ticks being found embedded in the skin of people who died suddenly of unexplained paralytic illnesses.
About 8% of the 870 named tick species have been associated with intoxication syndromes. The species that cause the most cases of human, dog, and livestock paralysis in North America are Dermacentor andersoni and D. variabilis, both of which are vectors for the rickettsial disease Rocky Mountain spotted fever. In the United States, tick paralysis occurs most often in the Pacific Northwest and Rocky Mountain states.
The tick toxin’s pathogenic mechanism isn’t fully understood. Australian investigators have reported that the toxin inhibits acetylcholine release at the neuromuscular synapse, but tick paralysis there is caused by Ixodes species, and it’s not clear that the same mechanism is at work in the paralysis caused by Dermacentor species, Dr. O’Leary said.
How to Remove a Tick
The proper way to remove a tick is to grab it with blunt forceps as close to the skin as possible and pull it straight out with steady pressure, according to Dr. O’Leary.
Don’t apply a hot nail or blown-out match to the critter’s backside. Don’t use tweezers or sharp forceps. Avoid using a twisting or corkscrew motion in removing the tick. Don’t crush or squeeze the tick’s body, as that can cause the tick to release more of the infectious organism or toxin.
Don’t handle the tick barehanded. “There have been documented cases of disease transmission” in people who did that, said Dr. O’Leary.
And although in bygone days it was a popular practice to apply gasoline, lidocaine, petroleum jelly, or other substances to the embedded tick to encourage it to back out, the current thinking is, don’t do it.
“There are horror stories about the use of those things,” he said.
Dr. O’Leary declared having no relevant financial relationships.