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Subject: search.filters.subject.Bovine viral diarrhoea

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    Bovine viral diarrhoea viruses from New Zealand belong predominantly to the BVDV-1a genotype.
    (Taylor and Francis Group, 2024-03-01) Dunowska M; Lal R; Dissanayake SD; Bond SD; Burrows E; Moffat J; Howe L
    AIM: To determine which genotypes of bovine viral diarrhoea virus (BVDV) circulate among cattle in New Zealand. METHODS: Samples comprised BVDV-1-positive sera sourced from submissions to veterinary diagnostic laboratories in 2019 (n = 25), 2020 (n = 59) and 2022 (n = 74) from both beef and dairy herds, as well as archival BVDV-1 isolates (n = 5). Fragments of the 5' untranslated region (5' UTR) and glycoprotein E2 coding sequence of the BVDV genome were amplified and sequenced. The sequences were aligned to each other and to international BVDV-1 sequences to determine their similarities and phylogenetic relationships. The 5' UTR sequences were also used to create genetic haplotype networks to determine if they were correlated with selected traits (location, type of farm, and year of collection). RESULTS: The 5' UTR sequences from New Zealand BVDV were closely related to each other, with pairwise identities between 89% and 100%. All clustered together and were designated as BVDV-1a (n = 144) or BVDV-1c (n = 5). There was no evidence of a correlation between the 5' UTR sequence and the geographical origin within the country, year of collection or the type of farm. Partial E2 sequences from New Zealand BVDV (n = 76) showed 74-100% identity to each other and clustered in two main groups. The subtype assignment based on the E2 sequence was the same as based on the 5' UTR analysis. This is the first comprehensive analysis of genomic variability of contemporary New Zealand BVDV based on the analysis of the non-coding (5' UTR) and coding (E2) sequences. CONCLUSIONS AND CLINICAL RELEVANCE: Knowledge of the diversity of the viruses circulating in the country is a prerequisite for the development of effective control strategies, including a selection of suitable vaccines. The data presented suggest that New Zealand BVDV are relatively homogeneous, which should facilitate eradication efforts including selection or development of the most suitable vaccines.
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    Epidemiology of BVD in New Zealand dairy herds : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Epidemiology at Massey University, Manawatu, New Zealand
    (Massey University, 2016) Weir, Andrew Muir
    The objective of this thesis was to determine the prevalence and incidence of bovine viral diarrhoea (BVD) virus at cow and herd level, define risk factors for new infection and to quantify the impact at cow level of seroconversion during the seasonal breeding programme under the seasonal calving, pasture grazed systems in New Zealand. A questionnaire and bulk tank milk (BTM) BVD PCR and antibody ELISA test was completed for 402 New Zealand dairy herds, and repeated in the subsequent lactation. North Island herds had a high turnover rate with 67% of virus positive herds clearing infection each lactation and being replaced with newly infected herds, while the larger South Island herds rarely cleared infection naturally (14% per lactation) and maintained a higher prevalence (32% compared to 8.5% for North Island herds). Transmission pathways associated with bulk tank BVD status were purchasing cows, neighbour's stock, and stock movements off-farm. The other factors associated with bulk tank BVD status were herd size, herd BVD vaccination, and herd ownership structure. In 10 BTM PCR positive herds, all lactating cows (n=3,793) were tested for BVD antibody at the start of the seasonal breeding programme (planned start of mating; PSM), and again 125 days later, to identify cows that seroconverted during the observation period. Improved cutoff values were derived for the IDEXX milk antibody ELISA. There were few (3.8%) susceptible lactating cows at PSM in herds with a lactating persistently infected cow (PI), but most of these susceptible cows (82%) seroconverted. This required 4.6 contacts per PI each day. There were more susceptible (31%), and a smaller proportion of susceptible cows seroconverted (32%) in herds without a lactating PI. Seroconversion was associated with 13% longer PSM to conception (3.2 days), 4% lower pregnancy rate, 6% lower conception to AI, and $11.97 (1.9 times) greater cost of clinical disease. The average cost per transient infection was $91.08. These results contributed to voluntary BVD control efforts in New Zealand and will be essential for developing a comprehensive cost-benefit model to estimate the average total cost of BVD, and assessing the benefit of various control strategies. Keywords: Bovine Viral Diarrhoea; BVD; BVDV; virus; diarrhea; pestivirus; Flaviviridae; veterinary; epidemiology; New Zealand; dairy; prevalence; incidence; herd; cow; reproduction; disease; transient infection; immune suppression; PI; PCR; ELISA; antibody; milk; economic; cost; seasonal; pasture-based; observational study; longitudinal; cross-section; risk factor; risk; probability; proportion; rate; mastitis; lactation; seroconversion; regression; generalised estimating equation; GEE; Hurdle model; accelerated failure time; AFT; questionnaire; survey; sharemilker; cow behaviour; herd management; model