A loss of muscle function or sensation in humans or certain animals following the prolonged feeding of female ticks. Paralysis, of Landry's type, usually begins in the legs and spreads upward to involve the arms and other parts of the body. Evidence suggests that paralysis is due to a neurotoxin formed by the feeding ticks rather than the result of infection with microorganisms.

The disease has been reported in North America, Australia, South Africa, and occasionally in some European countries and is caused by appropriate species of indigenous ticks. In Australia, Ixodes holocyclus causes frequent cases in dogs, and occasional cases in humans, and paralysis has been known to progress even after removal of ticks. Ixodes cubicundus is associated with the disease in South Africa.