Epidemiological Study of Bovine Parainfluenza 3 Virus in Sheep: Seroprevalence, Risk Factors, and Distribution in Two Regions of Algeria

Respiratory viral diseases, including the bovine parainfluenza 3 virus, cause significant economic losses in ruminants. There is no available data regarding the epidemiological situation of this virus in Algeria.  The present study aims to determine the seroprevalence and the associated risk factors of bovine parainfluenza 3 virus (BPI3V) in sheep in two different climatic regions of Algeria.  A total of 108 serum samples were collected from sheep at different ages and tested for antibodies against BPI3V using an indirect enzyme-linked immunosorbent assay (ELISA). A real-time polymerase chain reaction (PCR) test was also performed on nasal swabs to detect the viral genome.  At the animal level, out of 108 sera tested, 82 (75.93%, 95% CI, 66.75%, 83.63%) showed antibodies against BPI3V. At the herd level, all 23 herds tested (100%) had at least one animal with BPI3V antibodies. Our results showed no association between the presence of BPI3V antibodies and the region (P=0.72). However, at the herd level, risk factors such as flock size and predisposing factors like climate change, feed deficit, postpartum stress, and dust were identified. At the animal level, a highly significant association was found between BPI3V seroprevalence and the age of the animals (P<0.0001). Notably, the sheep group over 3 years was more susceptible than other age groups. Furthermore, a significant difference in BPI3V seroprevalence based on sex was observed (P<0.003). All collected nasal swabs were negative for BPI3V genome detection using real-time PCR.  This study is the first serological survey on BPI3V in Algeria, confirming its presence in sheep from two regions. The high serum prevalence of BPI3V observed in the study population highlights addressing this viral disease to mitigate economic losses in ruminants.