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Modeling the Effect of Bovine Viral Diarrhea Virus in Australian Beef Herds.

ABSTRACT: Bovine viral diarrhea virus (BVDV) is an economically important disease in Australian beef farming. The disease typically results in low-level production losses that can be difficult to detect for several years. Simulation modeling can be used to support the decision to control BVDV; however, current BVDV simulation models do not adequately reflect the extensive farming environment of Australian beef production. Therefore, the objective of this study was to develop a disease simulation model to explore the impact of BVDV on beef cattle production in south-east Australia. A dynamic, individual-based, stochastic, discrete-time simulation model was created to simulate within-herd transmission of BVDV in a seasonal, self-replacing beef herd. We used the model to simulate the effect of herd size and BVDV introduction time on disease transmission and assessed the short- and long-term impact of BVDV on production outputs that influence the economic performance of beef farms. We found that BVDV can become established in a herd after a single PI introduction in 60% of cases, most frequently associated with the breeding period. The initial impact of BVDV will be more severe in smaller herds, although self-elimination is more likely in small herds than in larger herds, in which there is a 23% chance that the virus can persist for >15 years following a single incursion in a herd with 800 breeders. The number and weight of steers sold was reduced in the presence of BVDV and the results demonstrated that repeat incursions exacerbate long-term production losses, even when annual losses appear marginal. This model reflects the short- and long-term production losses attributed to BVDV in beef herds in southeast Australia and provides a foundation from which the influence and economic utility of BVDV prevention in Australian beef herds can be assessed.

SUBMITTER: Fountain J

PROVIDER: S-EPMC8712561 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:More and more European countries have implemented a bovine viral diarrhea virus (BVDV) control program. The economic effects of such programs have been evaluated in simulations, but empirical studies are lacking, especially in the final stage of the program. We investigated the economic (gross margin) and production effects (milk yield, somatic cell count, and calving interval) of the herds obtaining BVDV-free certification based on longitudinal annual accounting and herd performance data from Dutch dairy herds between 2014 and 2019, the final stages of the Dutch national BVDV-free program. This study was designed as a case-control study: two types of case herds were defined for two analyses. The case herds in the first analysis are herds where the BVDV status changed from “BVDV not free” to “BVDV free” during the study period. The not-free status refers to a herd that participated in the BVDV-free program but had not yet obtained the BVDV-free certification. In the second analysis, the case herds started participating in the Dutch BVDV-free program during the study period and obtained the BVDV-free certification. Control herds in both analyses were BVDV-free during the entire study period. Potential bias between the covariates of the two herd groups was reduced by matching case and control herds using the propensity score matching method. To compare the differences between case and control herds before and after BVDV-free certification, we used the time-varying Difference-in-Differences estimation (DID) methodology. The results indicate that there was no significant change in milk yield, somatic cell count, calving interval, and gross margin upon BVDV-free certification. There are several possible explanations for the non-significant effects observed in our study, such as the final stage of the BVDV control program, not knowing the true BVDV infection situation in case herds and not knowing if control measures were implemented in case herds prior to participating in the BVDV-free program. In our study, the effects of BVDV-free certification might have been underestimated, given that the Dutch BVDV control program became mandatory during the study period, and some of the case herds might have never experienced any BVDV infection. The results of this study suggest that in the final stage of the BVDV control program, the program may no longer have a clear benefit to the herd performance of participating dairy herds. When designing national programs to eradicate BVDV, it is therefore important to include incentives for such farms to motivate them to join the program.

Project description:Background and aimTo meet domestic demand for meat, Indonesia imports live cattle from Australia, which have non-bovine viral diarrhea (BVD)-free status. The consequence of importing live cattle from Australia is potentially introducing a novel BVD variant to Indonesia. Therefore, detecting BVD early and determining the agent's characteristics and clinical symptoms are necessary. This study aimed to detect and characterize clinical symptoms of bovine viral diarrhea (BVD) and highlight the importance of farm management as a risk factor for the spread of BVD. This study aimed to provide information about the effectiveness of preventive measures against BVD in Australian-imported cattle at the Tanjung Priok Seaport Agricultural Quarantine. Bovine viral diarrhea is among the most common diarrheal diseases found in feedlots and is a severe health and economic problem in cattle.Materials and methodsAll cattle in a selected feedlot were examined for clinical symptoms on their first day of arrival. The sampling criteria included age, body weight, body temperature (BT), animal breath (AB), pulse (PL), conjunctivitis (CJ), hyperlacrimation (HL), hypersalivation (HS), DR, fever, limping leg (LL), emaciation, stomatitis (ST), weakness (WK), and coronitis (CR). In addition, 64 blood samples were taken from cattle that exhibited clinical symptoms of BVD. On the 3rd day of arrival, a blood sample showing positive clinical symptoms was examined using antigen (Ag)-capture enzyme-linked immunosorbent assay (ELISA). The data from these clinical symptoms were analyzed alongside the laboratory results using multidimensional scale analysis, heatmap distribution, and principal component analysis (PCA). Furthermore, the positive serum samples obtained from the Ag-capture ELISA underwent a nested multiplex polymerase chain reaction and molecular detection and genetic characterization of BVDV based on the 5' untranslated region of the viral genome, followed by sequence and phylogenetic tree analyses.ResultsUsing PCA, 12 clinical symptom characteristics of BVD were determined from 13 clinical symptoms synergized with five cattle positive for Ag-capture ELISA. The clinical symptoms included internal factors such as physiological conditions of CJ, HL, HS, DR, BT, LL, loss of appetite, ST, WK, CR, AB, and PL. The screening test showed that five samples tested positive for the BVD Ag, while 59 tested negative. Phylogenetic tree analysis using a 360-nucleotide portion of the NS5B gene showed that Sample B23F5R had a distinct path compared to the other two samples in the phylogenetic diagram. The profile of sample B23F5R was closely related to BVDV reference subgenotype 1-a group (NCBI, access no. LC068605), with a homology percentage of 92.36%. Furthermore, this sample was similar to the BVDV reference 1-a, Strain 12, identified in Japan. The other two samples, B13F5R and A13F5R, showed close resemblance to the BVDV reference subgenotype 1-a that had been previously identified in Indonesia (NCBI, access no. MK411755), with homology percentages of 97.81% and 97.75%, respectively.ConclusionThe BVDV-1a strain is the main subtype present in beef cattle imported from Australia to West Java, Indonesia. The characteristics of clinical symptoms associated with BVD infection comprised 12 symptoms synergized with the positive sample in the PCA. The present results can facilitate the development of preventive and control measures for BVD circulation in Indonesia.

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Modeling the Effect of Bovine Viral Diarrhea Virus in Australian Beef Herds.

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