Monday, November 6, 2017

Tick Paralysis in British Columbia


Tick paralysis results from exposure to a neurotoxin released by tick salivary glands during a blood meal; it is the only tick-borne disease not caused by an infectious agent. The toxin appears to be produced exclusively by female, egg-laden ticks. It is most commonly seen in children under 16, and within this population affects girls more than boys, probably because ticks are harder to detect under longer hair. Among adults, men are disproportionately affected.
Worldwide, over 40 tick species have been associated with tick paralysis, but in North America the most common culprits are Dermacentor variabilis (American dog tick) and Dermacentor andersoni (Rocky Mountain wood tick). Bites from Amblyomma and Ixodes ticks can also cause tick paralysis. In the United States, tick paralysis is most common in the Pacific Northwest, Rocky Mountain states and southeastern part of the country. It occurs most frequently in the spring months, from April through June.

(Since ticks often carry more than one infectious microbe, a person could also contract other diseases along with Tick paralysis)

From 1993 to 2016, there were 56 cases of suspected tick paralysis with at least one tick specimen submitted for testing at the BCCDC PHL. Humans and animals were involved in 43% and 57% of cases, respectively. The majority of cases involved a Dermacentor andersoni tick (48 cases or 86%) and occurred between the months of April and June (49 cases or 88%). Among known locations of tick acquisition, the Interior region of BC was disproportionately affected, with 25 cases (69%) of tick bites occurring in that area.

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