Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) are vector-borne orbiviruses that pose an emerging threat to livestock, including cattle and sheep. This review summarizes the global distribution, genetic diversity, and key factors driving their spread along with the existing knowledge gaps and recommendations to mitigate their impact. Both viruses cause hemorrhagic disease in susceptible ruminants and are commonly reported in tropical and subtropical regions including North America, Asia, Africa, Oceania, and some parts of Europe. The geographical distribution of these viruses, encompassing 27 BTV and 7 EHDV serotypes, has shifted, particularly with the recent invasion of BTV-3, 4, and 8 and EHDV-8 serotypes in Europe. Several factors contribute to the recent spread of these viruses such as the distribution of virulent strains by the movement of temperature-dependent Culicoides vectors into new areas due to rapid climate change, the reassortment of viral strains during mixed infections, and unrestricted global trade. These diseases cause significant economic impacts including morbidity, mortality, reduced production, high management costs, and the disruption of international trade. Effective prevention and control strategies are paramount and rely on vaccination, vector control using insecticides, and the destruction of breeding sites, husbandry practices including the isolation and quarantine of infected hosts, restriction of animal movement, prompt diagnosis and identification of circulating strains, and effective surveillance and monitoring plans such as the pre-export and post-import screening of semen used for artificial insemination. However, challenges remain with intercontinental virus spread, live vaccines, and the failure of inactivated vaccines to produce protective immunity against dissimilar strains. Significant knowledge gaps highlight the need for a better scientific understanding and a strategic plan to ensure healthy livestock and global food security.

The bovine viral diarrhea virus (BVDV) infects a wide range of domestic and wild mammals. This review hypothesized that there might be cross-species transmission of BVDV. Therefore, the aim was to explore the BVDV-5′ UTR and N-pro sequence-based evidence to understand host plasticity among different animals. A total of 146 unique BVDV sequences retrieved from GenBank, originating from 12 distinct mammalian species that are submitted from 55 countries, were analyzed. The phylogenetic analysis revealed that all three BVDV species exhibited genetic relatedness infecting diverse animal species. BVDV-1 sequences obtained from cattle, buffalo, and pigs and BVDV-2 and HoBi-like pestivirus sequences from cattle, goats, and sheep showed a genetic resemblance. Surprisingly, cattle and buffalo in China, cattle and yak in Mongolia, cattle and wild boar in Serbia, cattle and deer in Mexico, cattle and alpacas in Canada, goats and pigs in the USA, and sheep and buffalo in Argentina were infected with BVDV-1 within the same county and strongly positioned in the same cluster, indicating potential spillover with host tropism. Moreover, BVDV sequences isolated from various neighboring countries clustered closely, suggesting potential cross-border transmission events. Based on genomic evidence, the BVDV transmission cycle could be depicted, where cattle act as a primary source of infection, while other domestic and wild animals maintain the infection ecology within their habitat due to virus tropism.

Bovine viral diarrhea virus (BVDV) is globally endemic, with the ability to establish persistent infection (PI) being central to its complex epidemiology. Currently the genetic variability of BVDV in Bangladesh remains poorly understood. This study involved a survey in commercial dairy herds in the south-eastern part of Bangladesh in 2024/2025. A total of 373 blood samples were collected from cattle in 24 dairy herds. Serum and buffy coat samples were analyzed using antibody-ELISA and RT-qPCR targeting the 5'-UTR region, followed by sequencing. The MDBK cell line was used for virus isolation and biotyping. Herd and animal-level seroprevalences were 83.3% and 15.3%, respectively, while the corresponding viremic rates were 79.2% and 11.0%. Analysis of 41 sequences identified nine distinct BVDV-1 subgenotypes (1a, 1b, 1c, 1d, 1e, 1 k, 1p, 1o, and 1v), with BVDV-1b (41.5%) and BVDV-2a (14.6%) predominating. Additionally, five HoBiPeV-a pestiviruses were detected. Among antigen-positive cattle, 38 (92.68%) were identified as transiently infected and 3 (7.3%) were confirmed as PI. Six (14.6%) and 27 (65.9%) were identified as cytopathic and non-cytopathic biotypes, respectively. Risk factors for BVDV seropositivity included: female sex (OR: 3.0), clinical disease in the past three months (OR: 2.4), crowding (OR: 2.9), and lack of dedicated clothing for farm workers (OR: 5.7). Active infection was associated with calves (OR: 6.2), heifers (OR: 2.3), stunted growth (OR: 3.0), technician-performed artificial insemination (OR: 10.4), and frequent neighboring farm visits (OR: 3.1). This study has provided data crucial for formulating prevention and control strategies against BVDV to safeguard the Bangladeshi dairy industry.

Interspecies transmission and co-circulation of BVDV among bovines occur frequently, contributing to complex epidemiological dynamics in mixed-herd environments. A cross-sectional study was conducted in mixed bovine herds in the southern region of Bangladesh. A total of 219 blood samples were collected from cattle and water-buffalo across 12 mixed herds. Serum samples were tested for BVDV-specific antibodies using Ab-ELISA, while RT-qPCR on blood to detect seropositivity and active infection, respectively. PCR-positive samples were then subjected to 5'-UTR-based sequencing to identify circulating species and subgenotypes. Biotyping was conducted using the MDBK cell line. At the herd level, the prevalence of BVDV seropositivity and active infection were 75.0% and 66.7%, respectively. At the animal level, seropositivity was 15.9% in cattle and 14.0% in buffalo, while active infection was detected at 9.5% and 7.5%, respectively. Among infected animals,18 (94.7%) were transiently infected (TI), and one calf was persistently infected (PI). Of the 19 isolates, 12 (63.2%) were classified as BVDV-1, representing eight subgenotypes (BVDV-1a, 1b, 1c, 1d, 1j, 1k, 1o, and 1p) detected in both species, indicating co-circulation and high nucleotide identity (93-100%). All BVDV-2 and HoBi-like isolates belonged to subgenotypes BVDV-2a and HoBiPeV-a, respectively. Ten isolates (10/15; 66.7%) were non-cytopathic, and five (5/15; 33.3%) were cytopathic. Stunted growth (p = 0.036) and a history of clinical diarrhoea (p = 0.032) were associated with BVDV seropositivity. At the farm level, close proximity between farms (p = 0.001), larger farm size (p = 0.034), and introduction of recently purchased animal (p = 0.034) were significantly associated with seropositivity. The co-circulation of diverse BVDV genotypes at the cattle-water buffalo interface presents challenges for control and eradication in mixed-farming systems.

Bovine viral diarrhea virus (BVDV) remains a neglected viral disease in water buffalo despite its significant economic impact in production systems. Although limited epidemiological studies have been reported worldwide, the serostatus and active infection in buffalo have not been systematically reviewed. A systematic review and meta-analysis were conducted to estimate BVDV prevalence in water buffalo and identify associated epidemiological factors. Relevant studies published up to January 31, 2026, were retrieved from five electronic databases. A total of 49 studies were identified from 15 different countries were found for inclusion. A random-effects model was used to estimate pooled-prevalence and assess heterogeneity among studies. A meta-analysis of 37 studies (9270 buffalo) estimated a pooled BVDV seroprevalence of 30.5%, while analysis of 16 studies (7189 animals) indicated an antigen prevalence of 16.5%. Continent-wise analysis revealed the highest BVDV seroprevalence in South-America (44.0%), while antigen prevalence was highest in Africa (21.2%) followed by Asia at 12.2%, and no BVDV data reported from North-America. Among the different countries, the highest BVDV seroprevalence was detected in Turkey (61.6%) and Argentina (59.0%), while antigen prevalence was highest in Egypt (21.2%), with lower estimates in Brazil (11.8%) and Iraq (11.3%). Notably, high heterogeneity (I² > 90%) was observed in the all-pooled estimates, indicating variations in sampling period, age, sex, sample source and types, diagnostic methods, production-system, and study quality. These findings demonstrate the widespread presence of BVDV in water buffalo populations and indicate the need for targeted control strategies to mitigate its impact on health and productivity.