Clinical presentations, treatments and risk factors for mortality in cats with tick paralysis caused by Ixodes holocyclus: 2077 cases (2008–2016)

Abstract

Objectives The objective of this study was to describe seasonality, demographics, presentations, treatments, complications and outcomes for cats with Ixodes holocyclus causing tick paralysis, and to identify risk factors for mortality. Methods This was a retrospective single cohort study with 2077 cases occurring between 2008 and 2016, and presenting to one of four emergency clinics in south-eastern Queensland, Australia. Case mortality at 5 days post-presentation could be determined for 1742 cases, and potential risk factors for mortality were assessed using random-effects logistic regression. Results Cases occurred all year round, but there was a marked seasonal pattern with more cases presenting in spring than any other season. Overall, 54/1742 cases (3%) died by 5 days after presentation. Five day mortality incidence for cases that received polyclonal canine tick antitoxin serum (TAS) and recommended treatment was 28/1410 (2%) vs 4/52 (8%) for cases that did not receive TAS ( P <0.001). Mechanical ventilation was recommended for 131/2077 cases (6%). Where mechanical ventilation was recommended but not implemented, mortality incidence was 15/17 (88%), whereas 4/22 cases (18%) that received mechanical ventilation died by day 5. From multivariable analyses, initial gait score (overall P = 0.047) and body temperature on presentation (overall P <0.001) were independently associated with mortality; cases with higher gait scores and those with body temperatures <35°C were at greater risk of death. Cases that had an adverse reaction to TAS were also more likely to die ( P = 0.002). Additional ticks were detected at coat clipping for 80/872 (9%) the cases that were clipped, and coat clipping was associated with a reduced risk of mortality ( P = 0.020). Risk of mortality did not differ significantly by time of year, clinic location, breed, sex, neuter status, age, weight, coat length or number of ticks found. Conclusions and relevance The overall mortality risk for cats treated for tick paralysis caused by I holocyclus is low. Risk factors for mortality include advanced gait and respiratory scores, and hypothermia at presentation. Coat clipping and TAS reduce the risk of mortality, whereas the occurrence of a TAS reaction increases the risk. Mechanical ventilation reduces mortality risk in cats with respiratory failure due to tick paralysis.

Tick paralysis in dogs and cats in Australia: treatment and prevention deliverables from 100 years of research

“…The problem with canine tick antiserum administration to cats was recognised as more serious, frequently fatal and primarily anaphylactic . Canine tick antiserum has been demonstrated to improve survival in cats but at the expense of some unexpected adverse reactions including death …”

“…Prophylactic broad spectrum antibiotics are currently considered essential for the management of dogs with evidence of aspiration, or deteriorating respiratory signs . Cats with advanced gait scores demonstrate a higher risk of mortality and should be closely monitored for hypoventilation and/or respiratory muscle fatigue . Advances in diagnostic imaging techniques such as digital radiography (Figure ) and computed tomography now provide a means of early detection of pulmonary pathology.…”

“…Cats express tick paralysis slightly differently to dogs and have a better overall prognosis for recovery than dogs …”

Diagnosis and Treatment of Lower Motor Neuron Disease in Australian Dogs and Cats

“…Cases of tick paralysis show a very strong geographical and seasonal distribution. The Ixodes ticks are distributed along the east and Southeastern coasts of Queensland, New South Wales, and Victoria, and roughly follow the native habitat of their preferred bandicoot and possum hosts [ 7 , 15 , 17 , 60 – 63 ]. Only the female tick has long enough mouthparts to pierce and hold fast.…”

“…When tick paralysis is a likely differential, it is advised to clip all hair on the body and perform a thorough search for embedded ticks. Particular attention must be paid to the head and neck, thorax, areas of skin folds (axilla, vulva, and groin), and the interdigital spaces [ 63 ]. Successful treatment and a positive outcome are impossible unless all ticks attached to the patient are identified and removed.…”