Seroepidemiology of Infectious Bovine Rhinotracheitis and Bovine Brucellosis, and Major Reproductive Problems in Commercial and Smallholder Dairy Farms in North Shewa, Central Highlands of Ethiopia
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Date
2023
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Addis Abeba University
Abstract
A cross-sectional study was conducted from November 2022 to May 2023 to determine the seroprevalence of infectious bovine rhinotracheitis and bovine brucellosis, and to identify the major reproductive problems and potential risk factors in commercial and smallholder dairy farms in North Shewa, the central highlands of Ethiopia. Stratified random sampling technique was employed to sample animals from the respective farm types. A total of 511 blood samples
were collected from crossbred and local cattle from 142 herds. The serological investigations were conducted using competitive gE-ELISA for IBR, RBPT and CFT for bovine brucellosis. The overall seroprevalence of IBR was 61.84% (95% CI: 57.53-65.97%) at animal level and 85.21% (95% CI: 78.28-90.21%) at the herd level; while the prevalence of bovine brucellosis was 0.98% (95% CI: 0.41-2.34%) at animal level and 3.52% (95% CI: 1.46-8.26%) in the herds based on combined RBPT and CFT tests. The univariable logistic regression analysis revealed that age, breed, parity, history of abortion, retained fetal membrane and ocular/nasal discharges were significantly associated with IBR seropositivity. The final adjusted model for potential risk factors indicated that animals above 6 years old were 9.16 (95% CI: 3.09-27.16; p = 0.000) times at higher risk, while animals with abortion were 4.51 (95% CI: 1.23-16.53; p
= 0.019) times and nasal discharges were nearly 3 (95% CI: 1.86-9.31; p = 0.030) times more at risk for IBR seropositivity. The univariable firth’s bias reduced logistic regression analysis indicated that district, age, breed, parity, history of abortion, retained placenta and dystocia were found to be significant factors for bovine brucellosis seropositivity in dairy cattle. The odds of brucellosis were higher in animals above 6 years old (OR = 3.82; 95% CI: 1.71-7.97; p = 0.004), local breeds (OR = 6.2; 95% CI: 2.08-8.21; p = 0.016), and aborted cows (OR = 22.35; 95% CI: 3.90-107.91; p = 0.002). Semi-structured questionnaire was administered to 120 respondents to determine major reproductive problems, and assess the knowledge, attitude and practices of farmers. The most common reproductive problems in dairy herds were repeat breeding (47.5%), anoestrus (44.17%), retained placenta (40%), abortion (32.5%) and dystocia (22.5%). Most of the farmers (55.83%) reported assisting a cow during parturition and 75% of them did not use protective glove or personal protection. The practices of raw milk (26.67%) and raw meat (64.17%) consumption were reported. However, only 14.17% of the respondents were found to have the awareness on zoonotic transmission of brucellosis. In conclusion, the results of the present study showed that IBR was widely distributed in commercial and smallholder dairy farms; whereas, the prevalence of bovine brucellosis was found to be very low among dairy cattle. Therefore, the initiation of vaccination for Bovine Herpes Virus-1 with marker vaccines in Ethiopia, regular herd testing, isolation of animal with predictive signs, and implementation of strict farm biosecurity measures are forwarded to minimize impacts of the diseases on the growing dairy industry, and public health impact of brucellosis.