In North America, some species of Dermacentor and Amblyomma cause tick paralysis due to a neurotoxin secreted in tick saliva. The toxin is not present in tick saliva during early stages of feeding, so paralysis occurs only when a tick has fed for several days or more. A single tick can cause paralysis, especially if it is attached to the back of the skull or near the spine.
Symptoms and signs include anorexia, lethargy, muscle weakness, impaired coordination, nystagmus, and ascending flaccid paralysis. Bulbar or respiratory paralysis may develop.
Diagnosis is based on clinical findings. Tick paralysis should be considered in North American patients with acute ascending flaccid paralysis or bulbar paralysis; ticks should be sought over the entire body surface and be removed. Differential diagnosis includes Guillain-Barré syndrome, botulism, myasthenia gravis, hypokalemia, and spinal cord tumor.
Tick paralysis can be fatal, but the paralysis is reversible with rapid removal of the tick or ticks. Paralysis usually begins to resolve in a few hours after tick removal, but paralysis may progress for 24 to 48 hours after tick removal. If breathing is impaired, oxygen therapy or respiratory assistance may be needed.