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This study aimed to investigate the current epidemiology and genetic evolution of bovine viral diarrhea virus (BVDV) on cattle farms in Gansu Province, China, between 2021 and 2025. A total of 749 samples from 62 farms across 14 cities and prefectures in Gansu were tested. The overall BVDV positivity rate was 19.89%, determined by amplification of the 5′-UTR and Npro regions. Seven subtypes were identified: BVDV-1a, -1b, -1d, -1m, -1v, -1u, and -2a. BVDV-1u was the predominant subtype (59.06%), followed by BVDV-1v (13.42%). The greatest subtype diversity was observed in Jinchang City and Gannan Tibetan Autonomous Prefecture. A non-cytopathic BVDV-1v strain, designated YC-2025-Gansu2 (GenBank accession no. PV945812.1), was isolated. This study expands the BVDV subtype database for Gansu and supports the development of subtype-specific prevention strategies in the region.

Bovine viral diarrhea virus (BVDV) is a major pathogen affecting livestock health in China. However, the current epidemiological status in yaks ( ), particularly in Qinghai Province, remains insufficiently understood. In the present study, a comprehensive serological and molecular investigation of BVDV in yaks was conducted across broad geographic areas of eight administrative regions including Yushu, Guoluo, Huangnan, Hainan, Haidong, Haixi, Haibei, and Xining in Qinghai Province. The results revealed widespread BVDV exposure in Qinghai yak, with an overall antibody prevalence of 84.52% (1158/1370) and substantial herd variation (12.00~98.07%). Active infections were confirmed through antigen detection, revealing prevalence ranging from 0.34% (Haixi) to 4.90% (Huangnan). Genetic characterization identified two circulating subgenotypes: BVDV-1a (n=3) and the predominant BVDV-1u (n=30), with the latter dominating across all regions. These results highlight the endemic circulation of BVDV in Qinghai yak populations and uncover unexpected genetic diversity, emphasizing the need for control measures to mitigate the adverse impacts of BVDV infection in yaks in high-altitude pastoral systems.

Bovine viral diarrhea (BVD), caused by bovine viral diarrhea virus (BVDV), has a significant economic impact on affected farms worldwide. For effective disease control, it is crucial to select an appropriate vaccine based on the specific genotype of BVDV. Therefore, developing a rapid and reliable assay to detect and genotype BVDV is imperative for controlling the spread of disease. In this study, we developed a TaqMan assay to detect and genotype BVDV types 1 and 2 directly in bovine serum without extraction of RNA. The direct BVDV TaqMan assay effectively detected both BVDV1 and BVDV2 with confirmed specificity and showed no cross-reactivity with any of the other viruses tested, including bovine respiratory syncytial virus, bovine coronavirus, Akabane virus, bovine herpesvirus 1, bovine parainfluenza virus 3, bovine immunodeficiency virus, and bovine leukemia virus. The assay could detect the virus in serum samples with a titer as low as 102 TCID50/mL in two out of three trials for BVDV1 and all three trials for BVDV2, indicating that its sensitivity is equivalent to that of virus isolation. Our findings represent a significant advancement in BVDV detection and typing directly from bovine serum.

Bovine viral diarrhea virus (BVDV) causes ongoing economic losses to cattle industries, directly through reduced herd performance or indirectly through control program costs. ELISA assays, one of the most widely used techniques due to their ease of implementation, have been a valuable tool for mass surveillance and detection of BVDV. In this study, we developed a new indirect ELISA (rE2-ELISA) for serologic detection of BVDV. The assay considers three recombinant E2 protein subtypes as antigens, allowing serologic diagnosis of BVDV-1b (high prevalence worldwide), BVDV-1d and 1e (high prevalence in southern Chile) sub-genotypes. Recombinant E2 (rE2) proteins were successfully expressed in stably transfected CHO cells. Conditions for rE2 ELISAs were established after determining appropriate concentrations of antigen, blocking agent, secondary antibody, and serum dilutions to achieve maximum discrimination between positive and negative serum samples. The developed rE2-ELISA showed a sensitivity of 92.86% and a specificity of 98.33%. Clinical testing of 180 serum samples from herds in southern Chile showed high accuracy (kappa > 0.8) compared to the commercial BVDV Total Ab kit (IDEXX), with 95.37% positive and 87.5% negative predictive value. In addition, the rE2 ELISA has shown the capability to detect anti-BVDV antibodies from naturally infected animals with sub-genotypes 1b, 1e, or undetermined. These results indicate that the developed indirect ELISA could serve as a valid, and efficient alternative for identifying BVDV-infected animals, thus contributing to the success of disease control and eradication programs.

Bovine respiratory disease (BRD) is a common global health problem in dairy cattle. The definitive diagnosis of BRD is complex because its etiology involves several predisposing and determining factors. This report describes the etiology of a BRD outbreak in a dairy herd in the mesoregion of Central Eastern Paraná, which simultaneously affected young (calves and heifers) and adult (cows) Holstein-Friesian cattle. Nine biological samples, consisting of five lung samples from two cows and three suckling calves, and four nasal swab samples from heifers, were used for etiological diagnosis. The nucleic acids extracted from lung fragments and nasal swabs were subjected to PCR and RT-PCR assays for partial amplification of the genes of five viruses [bovine viral diarrhea virus (BVDV), bovine alphaherpesvirus 1 (BoAHV1), bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (BPIV-3), and bovine coronavirus (BCoV)] and four bacteria (Mycoplasma bovis , Mannheimia haemolytica , Pasteurella multocida , and Histophilus somni ) involved in the etiology of BRD. All nine biological samples from the animals with BRD tested negative for BoAHV1, BRSV, BPIV-3, BCoV, and H. somni . Therefore, the involvement of these microorganisms in the etiology of BRD outbreak can be ruled out. It was possible to identify the presence of BVDV and M. bovis in singular and mixed infections of the lower respiratory tract in cattle. BVDV was also identified in two nasal swabs: one as a single etiological agent and the other in association with two bacteria ( P. multocida and M. haemolytica ). The phylogenetic analysis conducted in the nucleotide sequence of the 5’UTR region and N pro gene of the BVDV amplicons demonstrated that the BVDV field strains of this BRD outbreak belong to subgenotype 2b. To the best of our knowledge, this is the first report of BVDV-2b involvement in the etiology of BRD in Brazil. Finally, it is necessary to highlight that the cattle were obtained from an open dairy herd with biannual vaccinations for BVDV-1a and - 2a.

Background The reproductive problem is an animal health-related bottleneck that constrains livestock genetic improvement efforts in tropical countries such as Ethiopia. The infectious causes of reproductive disorders are one cause of decreased reproductive efficiency. This study aimed to determine the seroprevalence to Bovine Herpesvirus-1 (BHV1), Bovine Viral Diarrhea Virus ( BVDV), Neospora caninum ( N . caninum) and C. burnetii (C. burnetii) exposures in dairy cows with reproductive disorders in selected areas of Ethiopia. Overall, 164 serum samples were collected from October 2018 to May 2019 from animals with a history of reproductive disorders. The collected sera were tested for antibody titers to Brucella species, N. caninum , BVDV, BHV1, C. burnetii and Chlamydophila abortus (C. abortus ) using Rose Bengal and ELISA. Results The apparent seroprevalence of BHV1, BVDV, N. caninum and C. burnetii were 61%, 33.5%, 4.9% and 0.6%, respectively. Among the selected study areas, the mean apparent seroprevalence was significantly greater in Bishoftu (35.9%), Holeta (34.2%) and Adaberga (28.6%) than in Mekelle (9.9%) and Ambo (16.2%). Among the specific seroprevalence in specific areas, BHV1 was the most common in Adaberga, with an apparent seroprevalence of 92.9%. Similarly, the seroprevalence of BVDV was the highest in Holeta, with an apparent seroprevalence of 73.3%. On the other hand, no seropositive animal to Brucella spp. or C. abortus was found in these study areas. Conclusion BVDV and BHV1 seroprevalence was higher in dairy cattle with a history of reproductive disorder in Ethiopia as compared to the seroprevalence of N. caninum and C. burnetii .

Bovine Pestiviruses A and B, formerly known as bovine viral diarrhoea viruses (BVDV)-1 and 2, respectively, are important pathogens of cattle worldwide, responsible for significant economic losses. Bovine viral diarrhoea control programmes are in effect in several high-income countries but less so in low- and middle-income countries where bovine pestiviruses are not considered in disease control programmes. However, bovine pestiviruses are genetically and antigenically diverse, which affects the efficiency of the control programmes. The emergence of atypical ruminant pestiviruses (Pestivirus H or BVDV-3) from various parts of the world and the detection of Pestivirus D (border disease virus) in cattle highlights the challenge that pestiviruses continue to pose to control measures including the development of vaccines with improved cross-protective potential and enhanced diagnostics. This review examines the effect of bovine pestivirus diversity and emergence of atypical pestiviruses in disease control by vaccination and diagnosis.

Bovine viral diarrhea virus (BVDV) is classified into two species, namely, Bovine viral diarrhea virus 1 and Bovine viral diarrhea virus 2 , and affects cattle worldwide, resulting in significant economic loss. The prevalence of BVDV-1 and BVDV-2 infections and its genotypes in Mongolian animals has not been studied. In this study, we surveyed BVDV infection in dairy cattle and yaks from Bornuur and Bulgan counties by RT-PCR, and the average infection rate in the sampling sites was 15.8 % and 20.0 %, respectively. In addition, molecular features of the 5’-UTR region of the BVDV genome in Mongolian cattle and yaks were identified as belonging to the subtypes BVDV-1a and BVDV-2a, respectively. Determining the prevalence, geographical distribution, and molecular diversity of BVDV-1 and BVDV-2 in various host species in Mongolia is important for further studies and process control programs.

Bovine viral diarrhea virus causes a wide range of clinical manifestation with subsequent economic losses in dairy production worldwide. Our study of a population of dairy cattle in Thailand based on 933 bulk tank milk samples from nine public milk collection centers aimed to monitor infective status and to evaluate the effect of the infection in cows as well as to examine the reproductive performance of heifers to provide effective recommendations for disease control in Thailand. The results showed a moderate antibody-positive prevalence in the herd (62.5 %), with the proportion of class-3 herd, actively infected stage, being 17.3 %. Fourteen persistently infected (PI) animals were identified among 1196 young animals from the class-3 herds. Most of the identified PI animals, 11/14, were born in one sub-area where bovine viral diarrhea virus (BVDV) investigation has not been performed to date. With respect to reproductive performance, class-3 herds also showed higher median values of reproductive indices than those of class-0 herds. Cows and heifers in class-3 herds had higher odds ratio of calving interval (CI) and age at first service (AFS) above the median, respectively, compared to class-0 herds (OR = 1.29; P  = 0.02 and OR = 1.63; P  = 0.02). Our study showed that PI animals were still in the area that was previously studied. Furthermore, a newly studied area had a high prevalence of BVDV infection and the infection affected the reproductive performance of cows and heifers. Although 37.5 % of the population was free of BVDV, the lack of official disease prevention and less awareness of herd biosecurity may have resulted in continuing viral spread and silent economic losses have potentially occurred due to BVDV. We found that BVDV is still circulating in the region and, hence, a national control program is required.

Exposure to animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) results in immunomodulation of cohorts that may have health and growth consequences; however, effects may differ in low-risk, preconditioned (PC) vs. high-risk, auction market (AM) beef cattle. Our objective was to compare health and performance of PC or AM management systems with (PI) or without (CON) presence of a PI-BVDV pen mate using a 2 x 2 factorial arrangement. Four shipment blocks of crossbred PC steers (n = 236) from 3 ranch-origins were weaned, dewormed, vaccinated, tested for PI-BVDV, and kept on the ranch for ≥42 d. Subsequently, PC steers were transported to a stocker receiving unit (RU), weighed (251 ± 2 kg), blood sampled, stratified by d –1 BW, and assigned randomly to treatment (PCPI or PCCON) with no additional processing. Simultaneously, 4 blocks of crossbred AM calves (n = 292) were assembled from regional auction markets and transported to the RU ± 36 h from PC arrival. The AM calves were weighed (245 ± 1.3 kg), stratified by gender and d –1 BW, processed under the same regimen used for PC steers at their origin ranch except bull calves were castrated, and then assigned randomly to treatment (AMPI or AMCON). Treatment pens (0.45 ha) were arranged spatially such that PI did not have fence-line or water source contact with CON. Calves were fed identically and followed the same antibiotic treatment protocol. Daily BW gain for the entire 42-d receiving trial was greater (P < 0.001) for PC (1.2 kg) compared with AM (0.85 kg). There was an exposure effect (P = 0.002) on ADG from d 28 to 42; CON gained 1.12 kg vs. 0.90 kg BW for PI cohort. Morbidity was markedly greater (P < 0.001) in AM (70%) vs. PC (7%), resulting in (P < 0.001) an antibiotic treatment cost of $20.52 and $2.48/animal, respectively. Treatment with a third antibiotic occurred more often (P = 0.04) for PI cohort, and the percentage of chronically ill cattle was greatest (P = 0.06) for AMPI. Upon arrival, BVDV type 1a, 1b, and 2a titers were greater for PC (treatment x day, P < 0.001), and the percentage seropositive to BVDV type 1a on d 0 was 100% for PC vs. 23% in AM. Platelets increased transiently (P < 0.001) with greater platelets observed in AM (P < 0.001). Results indicate that PC calves gain faster and require fewer antibiotic treatments during the receiving period. Exposure to PI reduced BW gain from d 28 to 42, increased the number of calves treated thrice, and increased chronically ill cattle for AM.