A Comparative Meta-Analysis of Tick Paralysis in the United States and Australia.

CONTEXT: Tick paralysis is a neurotoxic envenoming that mimics polio and primarily afflicts children, especially in hyperendemic regions of the Western United States of America (US) and Eastern Australia.

OBJECTIVE

To compare the epidemiology, clinical and electrodiagnostic manifestations, and outcomes of tick paralysis in the US versus Australia.

METHODS

A comparative meta-analysis of the scientific literature was conducted using Internet search engines to identify confirmed cases of tick paralysis in the US and Australia. Continuous variables including age, time to tick removal, and duration of paralysis were analyzed for statistically significant differences by unpaired t-tests; and categorical variables including gender, regional distribution, tick vector, tick attachment site, and misdiagnosis were compared for statistically significant differences by chi-square or Fisher exact tests.

RESULTS

Tick paralysis following ixodid tick bites occurred seasonally and sporadically in individuals and in more clusters of children than in adults of both sexes in urban and rural locations in North America and Australia. The case fatality rate for tick paralysis was low, and the proportion of misdiagnoses of tick paralysis as Guillain-Barré syndrome (GBS) was greater in the US than in Australia. Although electrodiagnostic manifestations were similar, the neurotoxidromes differed significantly with prolonged weakness and even residual neuromuscular paralysis following tick removal in Australian cases compared with US cases.

DISCUSSION: Tick paralysis was a potentially lethal envenoming that occurred in children and adults in a seasonally and regionally predictable fashion. Tick paralysis was increasingly misdiagnosed as GBS during more recent reporting periods in the US. Such misdiagnoses often directed unnecessary therapies including central venous plasmapheresis with intravenous immunoglobulin G that delayed correct diagnosis and tick removal.

CONCLUSION

Tick paralysis should be added to and quickly excluded from the differential diagnoses of acute ataxia with ascending flaccid paralysis, especially in children living in tick paralysis-endemic regions worldwide.