Clinic-based cross-sectional observational study of factors associated with canine parvovirus breakthrough infection among gastroenteritis cases in Nigeria.

Canine parvovirus (CPV) enteritis is a widespread infectious disease affecting dogs globally. While vaccination is an acceptable preventive measure, repeated cases of vaccination and immunization failures abound globally, posing a significant challenge to veterinary practice. Therefore, a clinic-based cross-sectional study of dogs presenting with acute gastroenteritis, aimed at identifying factors associated with CPV breakthrough infection in Nigeria was conducted. This study involved demographic with retrospective data of historical vaccination of gastroenteritis-presenting dogs from selected veterinary clinics. The dogs were sampled from 10 veterinary clinics from multiple locations in Nigeria, including Abeokuta, Abuja, Ibadan, Jos, Makurdi, Onitsha, and Warri. The cases were initially screened using an immunochromatographic assay and validated with polymerase chain reaction (PCR) assay. Data on signalment, vaccination history, and protocol compliance were collected from 158 cases between June 2016 and March 2018. Statistical associations were analyzed using Chi-square test and binary logistic regression to identify predictors of CPV-2 breakthrough infection. Result showed that among the gastroenteritis dogs, 93.7% (146/158) tested positive for CPV-2, with cases mostly affecting puppies aged 0-6 months (69.6%). Significant univariate predictors of infection included clinic location (p = .017) and vaccination status (p = .02). In vaccinated dogs, critical factors for breakthrough infection were the number of vaccine doses (p = .036), vaccination finish time (p = .002), and overall protocol compliance (p < .001). Logistic regression score test further identified breed (particularly Rottweilers, p < .001), age (p = .019), vaccine brand mixing within puppy primary series (p = .026), and the presence of concurrent infections (p = .026) as significant factors. However, due to quasi-complete separation and small effective sample size (n = 17), multivariable logistic regression results were unstable and are presented here for exploratory purposes only. Furthermore, clinical cases with single-, double-, triple-, and quadruple-dose protocol showed breakthrough infection rates in the following decreasing order, 31.0%, 17.1%, 12.0%, and 0.6%, respectively. This high rate of CPV-2 breakthrough infection suggests that vaccination protocols used in high-challenge environments may require review. Therefore, these findings show that completing the puppy primary vaccination series at or after 16 weeks of age was significantly associated with a lower rate of breakthrough infection compared to finishing earlier. Adherence to strict dosing intervals and consideration of breed-specific risks may be essential to reduce breakthrough infection rate in Nigeria. These results suggest potential gaps in vaccination timing and compliance and this may contribute to increased risk of CPV infection in Nigeria.