Prevalence and significance of vomiting and regurgitation in dogs with tick paralysis caused by Ixodes holocylus.

Objective: To report the prevalence of vomiting and regurgitation in dogs with tick paralysis (TP) caused by Ixodes holocylus and investigate their association with respiratory dysfunction and survival.

Methods: Medical records at a single referral and emergency hospital in Sydney, between October 2021 and November 2024, were retrospectively reviewed. Dogs with clinical signs consistent with TP and with tick or tick crater found were included in the study. History of vomiting or regurgitation as well as the frequency before presentation and episodes in the first 24 h of hospitalisation were recorded and assessed for association with the outcomes. The primary outcomes of the study were the highest respiratory visual analogue scale (VAS) score representing the most severe respiratory dysfunction during the hospitalisation, deterioration of respiratory function and survival. The secondary outcomes of the study were the duration of hospitalisation, requirement of intubation and mechanical ventilation.

Results: The overall survival of the study was 79.3% (n = 138/174; 95% confidence interval [CI] 72.5-85.1). The overall prevalence of vomiting and regurgitation was 64.9% (n = 113/174; 95% CI 57.4-72), with 54.4% (n = 92/169; 95% CI 46.6-62.1) presenting with a history of vomiting or regurgitation. Vomiting and regurgitation for the first 24 h of hospitalisation were associated with a high respiratory VAS score, deterioration of respiratory function (odds ratio [OR] 4.01, 95% CI 2.06-7.83), aspiration pneumonia (OR 15.3, 95% CI 7.02-33.4), longer duration of hospitalisation (4 days, 1-17 vs 3 days, 1-10), intubation (OR 5.44, 95% CI 2.63-11.3), mechanical ventilation (OR 11.4, 95% CI 3.46-49.5) and lower survival (OR 0.23, 95% CI 0.10-0.49). In the multivariable analysis, age (OR 0.99, 95% CI 0.98-1), respiratory deterioration (OR 0.23, 95% CI 0.06-0.85), aspiration pneumonia (OR 0.19, 95% CI 0.04-0.96) and intubation (OR 0.13, 95% CI 0.03-0.53) were associated with lower survival.

Conclusions: The prevalence of vomiting and regurgitation was high in dogs with TP. Vomiting and regurgitation were associated with respiratory deterioration and lower survival indirectly by their association with aspiration pneumonia.