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Tick paralysis

Daniel J Sexton, MD
Section Editor
Stephen B Calderwood, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Ticks transmit a number of infections to humans and other animals. However, the toxins of various ticks can also cause a disease known as tick paralysis, which can be confused with both infectious and noninfectious conditions.

Tick paralysis was first described by explorers in the Australian outback in 1824 [1]. Eighty-eight years later, the disease was recognized to occur in western Canada [2]. Tick paralysis has subsequently been found to affect humans and domestic and wild animals worldwide, although most cases occur in Australia and North America. Although it is a rare disease in humans, tick paralysis is important to recognize because it can be fatal or nearly fatal [3]. However, if diagnosed promptly, this illness can be cured with the combination of tick removal and supportive care.


There is no national surveillance system for tick paralysis and reliable information on incidence does not exist. However, the disease appears to be uncommon based upon available literature and clinical experience. As an example, only 33 cases were reported in Washington State in the 50 years between 1946 and 1996, even though tick paralysis was a reportable disease in this state until 1998 [4]. Most cases in North America occur in the western regions of the United States and Canada, but the illness has also been seen in the eastern, southeastern, and south central United States. In addition, cases have been reported in Argentina [5], and in urban areas in travelers returning from endemic areas [6,7].

Four cases of tick paralysis were reported in patients from north central Colorado in 2006 [8]. The clustering of these cases was unusual because in previous years, on average, only one case per year was reported from Colorado. Another unusual characteristic of this cluster was the age distribution of cases: only one of four cases occurred in a child. Previous case reports noted that tick paralysis was more likely to occur in children under the age of 10 years because tick toxins are more likely to cause symptoms in individuals with a smaller body mass.

Females are affected more often than males, possibly because ticks are more likely to remain undetected following attachment to individuals with long hair. As with other tick-borne diseases, most cases occur in the spring and early summer months [9].

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Literature review current through: Nov 2017. | This topic last updated: Feb 02, 2016.
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