Bovine Viral Diarrhea Virus (BVDV) Exposure in Dairy Cattle in Southern and Central Ethiopia and Potential Association with Reproductive Performance
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Date
2022
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Addis Ababa University
Abstract
Bovine viral diarrhea virus (BVDV) is an important viral pathogen of cattle with a worldwide distribution. Although infection with the virus is usually subclinical, it may cause wideranging clinical conditions in cattle. Its main economic significance results from its effect on reproductive performance of cattle. It causes embryonic mortality and absorption, abortion, stillbirth, fetal malformation and birth of weak calves depending on stage of pregnancy during infection. In cetain outbreaks it may cause severe morbidity and mortality in susceptible herds depending on the strain of the virus. Despite the economic importance of the virus in almost every major cattle producing countries of the world only few studies have so far been conducted in Ethiopia. Those few works were also mostly limited to serological studies in limited geographic areas. There is lack of reports regarding occurrence of active disease or outbreaks associating infection with clinical conditions and losses. There is also so far no published work on the genotype of the virus prevalent in the country. Therefore this study was designed with aims to estimate the seroprevalence, identify associated risk factors and assess association of BVDV serostatus with reproductive wastage in dairy cows in Ethiopia. The study also attempted to detect and characterize BVDV nucleic acid in samples collected from bovine abortions and sera collected from selected animals. Accordingly, sera were collected from 954 randomly selected cattle from 98 dairy herds in southern and central Ethiopia. These sera samples were tested for BVDV antibodies using a commercial ELISA. Fetal tissue samples and placenta from 30 bovine abortions and sera from 26 selected cattle were also collected for detection of BVDV nucleic acid using reverse transcription (RT)-PCR. Among screened sera samples 20.9% (95%CI, 18.4, 23.6) were tested positive to BVDV antibodies. The herd prevalence was 50% (95%CI, 40.1, 59.9) and the intra-herd prevalence ranged between 2.6% and 100% (mean = 31.4%) in positive herds. Geographic region, herd size and animal arrangement in the farm had significant association with serostatus (p <0.05). Cattle from southern Ethiopia and herds of large size had 2.8 (95%CI; 1.9, 4.2) and 2.6 (95%CI; 1.5, 4.6) times higher odds of being seropositive compared to their counterparts, respectively. Serostatus to BVDV was associated with history of anestrus, repeat breeding (RB), mastitis and extended calving interval (CI) (p <0.05). Animals with history of extended CI and mastitis were 1.7 (95%CI; 1.0, 2.7) and 2.2 (95%CI; 1.5, 3.2) times more likely to be seropositive compared with those with normal CI and no history of mastitis, respectively. On the other hand, animals with history of anestrus and RB were less likely to be seropositive to BVDV compared to cattle with no such history. All samples tested with RT-PCR were negative for BVDV nucleic acid. Our study highlights the association of BVDV infection with some important reproductive performance traits and potential risk factors. The study also demonstrated high occurrence of reproductive health problems in dairy cattle in Ethiopia and that the reproductive performance of dairy cattle in the study herds is suboptimal.
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Keywords
Bovine viral diarrhea virus, Dairy Cattle, Ethiopia, Reproductive Disorders, Reproductive Performance