Debre Birhan Agricultural Research Centre, Debre Birhan, Ethiopia.
University of Gondar, College of Veterinary Medicine and Animal Sciences, Gondar, Ethiopia.
BMC Vet Res. 2021 Feb 19;17(1):87. doi: 10.1186/s12917-021-02798-w.
Bovine Viral Diarrhea virus (BVDV) is one of important diseases of cattle worldwide causing economic losses to the cattle industry primarily due to increased premature culling and decreased reproductive performance. The virus can cross the placenta during early pregnancy and result in the birth of persistently infected (PI) calves that are efficient transmitters of BVDV and serving as the primary reservoirs for BVDV. Relatively few studies have focused on understanding BVDV seroprevalence, virus detection, genotyping and its distribution in Africa. Most BVDV research in Ethiopia has involved serologic surveys in adult cattle, rather than the identification of PI calves, despite their role in viral shedding and recurring infections. A cross-sectional study was undertaken in three different livestock production systems of Ethiopia with the objective to estimate the prevalence of bovine abortion, calf mortality, and BVDV persistently infected calves.
Ear notch samples (882) collected from calves in 349 households were tested for BVDV antigen using antigen capture enzyme-linked immunosorbent assay (ACE). All samples tested were negative for BVDV antigen. The overall animal level crude abortion and calf mortality prevalence were 4.0% (95% CI: 2.9-5.2) and 9.2% (95% CI: 7.7-11.0) respectively. The lower BVDV PI prevalence may be due to a lower effective contact rate between cattle reared in small-scale extensive production systems in Ethiopia.
This is the first report of BVDV Ag test in Ethiopia and no PI was detected in calves in the study areas. Since BVDV is a disease of great economic importance, this study finding must be interpreted with care since absence of evidence is not evidence of absence and even a single BVDV infected animal can serve as source of infection and contribute to the persistent spread of the virus. Greater attention needs to be given to screening for PI animals through testing large number of animals and culling positive animals. Hence, future research should focus on regions and production systems with high BVDV seroprevalence followed by antigen ELISA or BVDV real-time PCR to detect persistently infected and acutely viremic animals.
牛病毒性腹泻病毒（BVDV）是全球范围内重要的牛病之一，主要导致牛群提前淘汰和繁殖性能下降，给牛业造成经济损失。该病毒可在妊娠早期穿过胎盘，导致持续感染（PI）的小牛出生，这些小牛是 BVDV 的有效传播者，并成为 BVDV 的主要储主。相对较少的研究关注了解 BVDV 的血清流行率、病毒检测、基因分型及其在非洲的分布。在埃塞俄比亚，大多数 BVDV 研究都涉及成年牛的血清学调查，而不是 PI 小牛的鉴定，尽管它们在病毒脱落和反复感染中起作用。本研究在埃塞俄比亚三种不同的畜牧业生产系统中进行了横断面研究，目的是估计牛流产、犊牛死亡率和 BVDV 持续感染牛的流行率。
从 349 户家庭的犊牛耳缺样本（882 份）中采集样本，使用抗原捕获酶联免疫吸附试验（ACE）检测 BVDV 抗原。所有测试样本均为 BVDV 抗原阴性。动物水平的总流产和犊牛死亡率流行率分别为 4.0%（95%CI：2.9-5.2）和 9.2%（95%CI：7.7-11.0）。较低的 BVDV PI 流行率可能是由于埃塞俄比亚小规模粗放生产系统中饲养的牛之间的有效接触率较低所致。
这是埃塞俄比亚首次报道 BVDV Ag 检测，研究地区未检测到 PI 犊牛。由于 BVDV 是一种具有重大经济重要性的疾病，因此必须谨慎解释本研究结果，因为缺乏证据并不等于不存在证据，即使只有一头 BVDV 感染动物也可以作为感染源，并有助于病毒的持续传播。需要更加关注通过大量动物检测和淘汰阳性动物来筛选 PI 动物。因此，未来的研究应集中在 BVDV 血清阳性率较高的地区和生产系统，然后进行抗原 ELISA 或 BVDV 实时 PCR 检测，以检测持续感染和急性病毒血症的动物。
