Unexplained, Progressive Paralysis May Result From Tick Bite

If tick paralysis is confused with similar neurologic conditions, the only effective treatment – tick removal – won’t be utilized, according to Dr. Michael W. Felz, family medicine physician at MCG and principal author of the study published in the Jan. 13 edition of the New England Journal of Medicine.

"This is not a well-known syndrome, but it should be because of the potential for disaster if it is not considered in the differential diagnosis," Dr. Felz said of the condition that can begin with tingling extremities and, over several hours to days, hinder walking and breathing. Children are especially vulnerable, probably because of their smaller size, to the potentially lethal nerve toxin produced by a pregnant, feeding tick.

Dr. Felz; Dr. Carrie Davis Smith, a pediatrician in Toccoa, Ga.; and Dr. Thomas R. Swift, chairman of the MCG Department of Neurology, authored the study which profiles the case of a 6-year-old child from neighboring South Carolina who came to MCG in June 1998 unable to walk without support.

The child’s problems began some 30 hours earlier with a tingling in her fingers and progressed over the next day to leg weakness and difficulty walking. Her initial workup, including X-rays, spinal tap, sensory and cranial nerve testing, laboratory studies and a toxicology screen, yielded no explanation for her weakness. Doctors suspected Guillain-Barre Syndrome, an autoimmune response to a viral or bacterial infection for which there is no definitive diagnostic test. As time passed, the weakness worsened. "She had paralysis in her legs, then in her arms, then her swallowing, speech and breathing weakened," Dr. Felz said.

Dr. Smith, then a second-year pediatrics resident at MCG, was at the child’s bedside in the pediatric intensive care unit while others were inserting a femoral line to begin treatment for Guillain-Barre, a filtration of the blood called plasmapheresis. She remembered a similar scenario from her days as a medical student; a resident – aware of the similarities between Guillain-Barre and tick paralysis – began looking through a paralyzed child’s hair for a tick. That resident didn’t find one, but when Dr. Smith used a fine-tooth comb to examine this child’s long, blond hair she found a large, flesh-colored tick near the back of her scalp. Remembering Dr. Felz’s numerous studies of ticks and tick-related disease, she called him immediately.

"I removed that tick and identified it as a Dermacentor variabilis, the most common cause of tick paralysis in the United States," Dr. Felz said. The female tick was engorged after feeding for several days and was pregnant.

"It is known that female ticks do not fully engorge unless fertilized," he said. When the eggs of a female tick mature, the female’s salivary glands produce a toxin that interrupts the electrical transmission of nerve impulses and can kill the host.

The host may recover from paralysis without medical intervention if the tick completes feeding and drops off before the patient’s ability to breathe is lost. The child whose case is reported by the MCG doctors experienced rapid recovery after tick removal and was discharged from the hospital 32 hours later with a normal neurological examination.

"We postulate that there are probably cases believed to be Guillain-Barre Syndrome that don’t respond to treatment, but actually were due to ticks that were never detected," Dr. Felz said. Reviewing medical literature in this country, the investigators found numerous reports of tick paralysis in humans in several states. "We also found, to our horror, reports of a few people who had died years ago from unexplained paralysis on whom the undertakers found engorged ticks," Dr. Felz said.

"The conclusion for patients and physicians is that a diagnosis of Guillain-Barre Syndrome requires a careful body search to exclude a hidden, engorged tick," he said.