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ABSTRACT: Bovine viral diarrhea virus (BVDV) is a productive and reproductive virus with a high global economic impact on dairy production systems. We investigated the prevalence of BVDV at the herd and individual levels in most dairy-producing regions of Brazil. The frequency of BVDV at the herd level was investigated using quantitative reverse transcription polymerase chain reaction (RT-qPCR) in bulk milk tanks monitored at 289 dairy farms between August 2020 and January 2022. Among these farms, 68 production systems were selected to investigate the prevalence of persistently infected (PI) animals using two antigen-enzyme-linked immunosorbent assays (Ag-ELISAs), at 21-d intervals, from ear-notch samples. In total, 2,902 RT-qPCR and 23,466 Ag-ELISAs were performed. At the herd level, 23.87% (69/289) of dairy farms were considered infected, presenting at least one qPCR test positive. At the individual level, 41.2% (28/68) of the subgroup of selected farms had at least one animal positive in the Ag-ELISA test. Association between tests allowed the classification of farms into the following four categories: level 0, negative for both tests (41.2%, 28/68); level 1, RT-qPCR positive and Ag-ELISA negative (17.6%, 12/68); level 2, RT-qPCR negative and Ag-ELISA positive (13.2%, 9/68); and level 3, positive for both tests (27.9%, 19/68). Multiple correspondence analysis (MCA) suggested a possible association between BVDV positivity and large farms, average daily milk production (herd), breed, and somatic cell counts. The confinement and intensification of animals from different categories, and use of artificial bedding are associated with BVDV infection. Using waste or bulk tank milk to fed calves was also a risk factor for BVDV positivity in RT-qPCR and Ag-ELISA. Despite the use of reproductive vaccines by most producers, their use seems to be associated with BVDV-positive farms. This study presented the epidemiological frequencies of BVDV at the individual and herd levels in the Campos Gerais Paranaense region. The region ranks among the top milk-producing areas in Brazil. Additionally, the association between BVDV tests and farm characteristics indicated the farm risk for BVDV and guides specific control programs.

ABSTRACT: This study determined the association between biosecurity practices and the status of bovine viral diarrhea virus (BVDV) in dairy production systems. Approximately 280 herds were screened for BVDV virus detection. Following the screening, 68 herds were selected to identify individual BVDV PI animals using an ear notch biopsy and ELISA-antigen. All offspring of the last generation were tested, and the maternal lineage of positive cases was examined. A questionnaire on BVDV biological risk assessment was completed. A multiple correspondence analysis (MCA) was conducted to determine the association between herds with or without BVDV circulation and biosecurity practices. The MCA revealed that farms with virus circulation lacked knowledge about the disease and wrongly perceived their herds as protected, while farms without virus circulation were aware of the disease but considered their herds unprotected. Vaccination practices differed between positive and negative herds, with positive herds using vaccines only for reproductive diseases and negative herds vaccinating for respiratory and reproductive issues. Biosecurity practices such as frequent visitation, contact between animals of different ages, and annual introduction of new animals were linked to viral circulation, while virus-free herds implemented measures like controlled visitation, no contact between different age groups, and quarantine. Lastly, herds with virus circulation acquired pregnant females without prior testing. This study emphasized the crucial role of biosecurity practices in controlling BVDV in dairy herds. It highlighted the sharper risk perception and better application of biosecurity practices in negative herds compared to BVDV-positive herds.

ABSTRACT: This study aimed to evaluate the effect of bovine leukemia virus (BLV) on the systemic profile of naturally infected dairy heifers during the transition period. Pregnant Holstein and Jersey heifers (n=24) were distributed in pairs into two experimental groups: (BLV+) and (BLV-). Animals in the BLV+ group were divided into two subgroups based on the median BLV proviral load (high and low). The animals were then assessed at weeks -3, -2, -1, calving time (0), +1, +2, and +3. Blood samples were obtained for hematological and biochemical analyses, as well as haptoglobin measurements. Farm BLV screening revealed a herd BLV prevalence of 57.25% and heifer BLV prevalence of 38.7%. Mean corpuscular hemoglobin concentration was the only hematological variable for which group interaction was observed, with BLV+ cattle having higher values (33.29 ± 3.39%) than BLV- cattle (31.08 ± 2.31%). Aspartate aminotransferase activity was higher in the BLV+ heifers. The BLV+ group had greater incidence of inflammation (haptoglobin ≥ 2.0 mg/dL). Fibrinogen concentrations were also higher at weeks 0 and +1 in BLV+ heifers than in BLV- heifers. A high proviral load affected total leukocyte and lymphocyte count; however, this profile was not observed in the low proviral load and paired BLV- heifers. To our knowledge, this is the first study to report the impact of BLV infection on the health of dairy heifers during the transition period, demonstrating the effect of proviral load on white blood cell changes and early inflammation in infected animals.

ABSTRACT: This study evaluated the vaccine-induced serological response after administering four commercial formulations containing Bovine Viral Diarrhea Virus (BVDV) type-1, BVDV-2, and Bovine Herpesvirus type 1 (BoHV-1) to young heifers with circulating maternal antibody titers. The study also determined the anamnestic response to vaccinations after the complete metabolization of maternal antibodies when the calves reached six months. Eighty-seven Holstein heifers were selected and randomly distributed into four experimental groups based on the vaccine administered. The four vaccine-based experimental groups were as follows: vaccine A (n = 22), vaccine B (n = 22), vaccine C (n = 24), and vaccine D (n = 19), given on the 60th, 90th, and 180th day of life, respectively. Virus-neutralization (VN) tests were performed at baseline (day 60) and 30 days after administering the second (day 120) and third doses (day 210). We analyzed the effect of vaccine group (P ≤ 0.001), day of vaccination (P ≤ 0.001), and group versus vaccine day interaction (P ≤ 0.001) for antibody titers produced against BVDV-1, BVDV-2, and BoHV-1 using the PROC MIXED method (Statistical Analysis System -SAS 9.4). Antibody titers against BVDV-1, BVDV-2, and BoHV-1 were similar at baseline and on day 60 of life. The mean antibody titers were constant and persisted against BVDV-1 in heifers immunized with vaccines A and C. Heifers immunized with vaccine A alone had a similar effect against BVDV-2. Regarding BoHV-1, the antibody titers decreased between days 60 and 210 in groups B, C, and D. The antibody titer for heifers in group A also decreased between days 60 and day 120, and an intense increase in titers was observed on day 210. After being immunized with formulations B, C, and D, the frequency of animals with titers above protective levels for BVDV-1, BVDV-2, and BoHV-1 was very low or null. Indicators of anamnestic response were observed in heifers vaccinated with formulation A only. Therefore, it can be concluded that passive immunity negatively interferes with antibody production after vaccination.

ABSTRACT: We evaluated some indicators of innate and humoral immune response in persistently infected (PI) Holstein calves and cows from 1 to 36 months of age matched with controls from the same herd. The effects were cataloged by grouping animals into the following age groups:

O presente estudo objetivou avaliar a correlação entre a contagem de células somáticas (CCS) automática e a CCS microscópica direta por diferentes colorações no leite de ovelhas da raça Santa Inês. Avaliou-se a CCS automática por citometria de fluxo, e a CCS microscópica foi realizada por esfregaços lácteos corados com as colorações de Broadhurst-Paley (BP), Hematoxilina-eosina (HE) e Rosenfeld. Os valores logarítmicos da CCS microscópica pela coloração de BP e Rosenfeld foram superiores aos valores logarítmicos da CCS automática e a CCS microscópica pela coloração de HE (PThe present study was designed to assess the correlation among the automatic somatic cell count and the microscopic somatic cell count using the Broadhurst-Paley (BP), Hematoxilin-eosin (HE) and Rosenfeld dyes. The milk smears were stained with BP, HE and Rosenfeld and the automatic cell count was performed by flow cytometry. The mean logarithmic microscopic SCC by BP and Rosenfeld was higher than the values from automatic SCC and microscopic SCC by HE (P