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Aims: To describe temporal trends in bulk milk antibody ELISA and PCR testing for bovine viral diarrhoea (BVD) in New Zealand pastoral dairy herds and to assess the use of historical accession data to predict herd-level BVD incursions. Methods: Data on all diagnostic testing of bulk milk for BVD performed by the Livestock Improvement Corporation (Hamilton, NZ) over eight lactation seasons from 1 June 2010 to 31 May 2018 were analysed. This included anonymised herd identification, geographic location, herd size, sample collection date, sample to positive (S/P) ratio for antibody ELISA results, and cycle threshold values for PCR detecting viral RNA. Multivariable logistic regression was used to explore the relationship between historical accession data and the risk of herds having at least one positive bulk milk PCR test result in the 2017 season. Results: There were 156,034 bulk milk BVD diagnostic testing accessions for 10,495 uniquely identified dairy herds over the 8-season period. The prevalence of tested herds with at least one positive bulk milk PCR test result decreased from 14.6% (407/2,786) in the 2010 season to 5.6% (355/6,309) in the 2017 season with similarly marked declines in S/P ratios. In the 2017 season, 2,961/6,309 (46.9%) herds had S/P ratios greater than the 0.75 cut-off value indicating recent or active BVD virus transmission within the herd while 1,422/6,309 (22.5%) herds were classified as having negative or low S/P ratios. Herds that cleared BVD from the milking herd experienced a mean decline in S/P ratio of 0.11 units per year (min 0.05; max 0.18). In the multivariable analysis, the overall incidence risk of herds experiencing a BVD incursion in the 2017 season was 3.8% (146/3,848) and there were three significant predictors in the final model: herd size, PCR status in the 2014 season, and change in S/P ratio between the 2014 and 2015 seasons. The area under the receiver operating curve for the final model was 0.695 indicating poor discrimination. Conclusions and clinical relevance: The prevalence of dairy herds in New Zealand with positive bulk milk PCR test results and high S/P ratios has decreased over time, suggesting fewer herds are actively infected with BVD and that herd immunity may also be declining. Although monitoring trends in bulk milk test results provides useful information on changes in individual herd status, it is difficult to accurately predict when new incursions will occur and farmers should continue to maintain good biosecurity. [ABSTRACT FROM AUTHOR]

To estimate animal-level seroprevalence of Leptospira interrogans serovar Copenhageni and L. borgpetersenii serovars Ballum and Tarassovi, in beef cattle, sheep and deer on New Zealand farms, and herd/flock-level seroprevalence of any serovar when existing same-sera data for serovars Hardjobovis and Pomona were included, and to determine associations between risk factors and animal-level seroprevalence. Banked sera from sheep (n = 82), beef (n = 54) and deer (n = 62) herds/flocks (n = 3,878 animals) from seven regions were analysed using the microscopic agglutination test. Titres of ≥48 were designated positive. Herds/flocks were considered positive if either ≥1, ≥2 or ≥3 animals were positive. Existing same-sera data for serovars Hardjobovis and Pomona were included to establish farm-level any-serovar seropositivity. Factors associated with serological status were analysed using generalised estimating equations. Animal-level seroprevalence for serovars Ballum, Copenhageni, and Tarassovi, respectively, was 13.7 (95% CI = 11.7–16.0)%, 12.6 (95% CI = 10.6–14.7)% and 18.0 (95% CI = 15.7–20.5)% for beef cattle, 10.5 (95% CI = 9.0–12.1)%, 16.7 (95% CI = 14.9–18.6)% and 14.0 (95% CI = 12.4–15.8)% for sheep and 6.6 (95% CI = 5.3–8.2)%, 15.5 (95% CI = 13.5–17.7)% and 3.6 (95% CI = 2.7–4.8)% for deer, respectively. Herd/flock-level seroprevalence for Ballum was 86.6, 52.4 and 39.0% for sheep, 85.2, 52.7 and 33.3% for beef cattle and 50.8, 27.9 and 21.3% for deer at definitions ≥1, ≥2 and ≥3 seropositive animals per species, respectively. For Copenhageni, corresponding data were 95.1, 73.2 and 56.1% for sheep, 68.5, 48.2 and 29.6% for beef cattle and 73.8, 57.4 and 41.0% for deer, and for Tarassovi, 80.5, 59.7 and 45.1% for sheep, 83.3, 68.5 and 61.1% for beef cattle, and 42.6, 16.4 and 4.9% for deer. Seropositivity to all serovars was observed from all regions, with some differences in seroprevalence observed between species and regions, but not between islands. Combining with Hardjobovis and Pomona data, herd/flock-level seropositivity for all animal species and all five Leptospira serovars was 100% at definition ≥1 animal positive, and 97.5 and 96.3% for sheep flocks, 87.8 and 97.8% for beef cattle herds, and 89.3 and 75% for deer herds at ≥2 and ≥3 animals positive, respectively. Seropositivity to serovars Ballum, Copenhageni and Tarassovi is common in sheep, beef cattle and deer New Zealand and most, or all farms have ≥1 livestock species seropositive to ≥1 serovar. Serovars Ballum, Tarassovi and Copenhageni should be considered when clinical or subclinical signs of leptospirosis are observed in sheep, beef cattle or deer. Livestock sector workers are potentially at risk of exposure. [ABSTRACT FROM AUTHOR]

Aims: To investigate the seroprevalence of infection with bovine viral diarrhoea (BVD) virus among 75 beef herds and seroconversion in cattle during early pregnancy, and to determine the practices and opinions of farmers towards BVD control and their association with real and perceived herd serological status. Methods: Blood samples were collected before mating in 75 beef herds across New Zealand from 15 unvaccinated heifers that had delivered their first calf that season. Serum samples were tested for BVD antibodies using ELISA individually, and after pooling samples for each farm. Animals that were antibody-negative were retested at either pregnancy diagnosis or weaning. Farmers were asked to complete a detailed survey about herd demographics, BVD testing and vaccination practices, and opinions towards national BVD control. Results: Based on the pooled serum antibody ELISA results, there were 28/75 (37%) negative herds, 15/75 (20%) suspect herds, and 32/75 (43%) positive herds. Of 1,117 animals sampled 729 (65.3%) tested negative for BVD virus antibodies; when retested, 47/589 (8.0%) animals from 13/55 (24%) herds had seroconverted. Among 71 famers providing survey responses 11 (15%) believed their herd was infected with BVD, 24 (34%) were unsure and 36 (51%) did not think their herd was infected. Only 19/71 (18%) farmers had performed any BVD testing within the past 5 years and 50/70 (71%) had not vaccinated any cattle for BVD. Support for national BVD eradication programme was strong in 51/71 (56%) respondents, but the biggest challenge to BVD control was considered to be famer compliance. Compared to farmers who did not think their herd was infected, more farmers who thought BVD was present in their herds had previously tested for BVD, would consider testing all replacement calves, and would support establishing a national BVD database; fewer would consider purchasing BVD tested or vaccinated cattle only. Conclusions and clinical relevance: Only 15% of the beef farmers in this study believed their herds were infected with BVD virus and few of them had undertaken BVD screening. Nevertheless many were supportive of implementing a national BVD control programme. It is likely that the lack of farmer awareness around BVD and the failure of farmers to recognise the potential impacts in their herds are hindering progress in controlling the disease in New Zealand. There are opportunities for New Zealand veterinarians to be more proactive in helping beef farmers explore BVD management options. [ABSTRACT FROM AUTHOR]

AIMS: To determine seroprevalence of Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona in beef cattle, sheep and deer in New Zealand and the association between farm-level risk factors and seroprevalence. METHODS: Between June 2009 and July 2010, 20 serum samples per flock or herd were collected from 162 sheep flocks, and 116 beef cattle and 99 deer herds from 238 farms, along with farm data by interview. Samples were tested for antibodies to serovars Hardjo and Pomona by microscopic agglutination testing, with a titre ≥48 being positive. Species-specific associations between herd-level seroprevalence (number of seropositive animals, for each serovar, divided by the number of animals tested) and herd-level risk factors were determined by multivariable logistic regression analysis. Vaccinated animals were excluded from seroprevalence estimates but included in multivariable analyses. RESULTS: For sheep (n=3,339), animal-level seroprevalence was 43.6 (95% CI=41.9-45.3)% for serovar Hardjo and 14.1 (95% CI=12.9-15.3)% for serovar Pomona; for beef cattle(n=1,886), it was 45.6 (95% CI=43.3-47.9)% for Hardjo and 19.6 (95% CI=17.9-21.5)% for Pomona; and for deer (n=1,870), it was 26.3 (95% CI=24.3-28.4)% for Hardjo, 8.8 (95% CI=7.6-10.2)% for Pomona. In sheep flocks (n=161), flock-level prevalence for Hardjo varied from 77.9-91.3%, and for Pomona from 40.4-73.9%, when ≥1, ≥2 or ≥3 animals were seropositive. In beef herds (n=95), herd-level prevalence for Hardjo varied from 79.0-90.5%, and for Pomona from 42.1-68.4%. In deer herds (n=93), herd-level prevalence for Hardjo varied from 45.2-59.1%, and for Pomona from 22.6-48.4%. For sheep flocks, herd-level seroprevalence for Hardjo was associated with flock size (OR=1.56) and number of dogs (OR=0.75), and for Pomona, seroprevalence varied with region. For beef cattle, herd-level seroprevalence for Hardjo was associated with herd size (OR=1.4), presence of dams (OR=0.6) and vaccination (OR=2.9), and for Pomona, co-grazing with deer (OR=0.4), vaccination (OR=3.22), presence of dams (OR=0.2) and streams (OR=2.7). For deer herds, seroprevalence for Hardjo or Pomona was associated with herd size (OR=1.6 and 1.8) and varied with region, and for Pomona seroprevalence varied with season (summer vs. winter: OR=4.8). CONCLUSIONS: Serovars Hardjo and Pomona were highly prevalent at herd and animal levels, with serovar Hardjo highest in all species. Larger herd size was the common risk factor for seroprevalence in all livestock species. [ABSTRACT FROM AUTHOR]

Summary: In the last decades, many regional and country‐wide control programmes for Johne's disease (JD) were developed due to associated economic losses, or because of a possible association with Crohn's disease. These control programmes were often not successful, partly because management protocols were not followed, including the introduction of infected replacement cattle, because tests to identify infected animals were unreliable, and uptake by farmers was not high enough because of a perceived low return on investment. In the absence of a cure or effective commercial vaccines, control of JD is currently primarily based on herd management strategies to avoid infection of cattle and restrict within‐farm and farm‐to‐farm transmission. Although JD control programmes have been implemented in most developed countries, lessons learned from JD prevention and control programmes are underreported. Also, JD control programmes are typically evaluated in a limited number of herds and the duration of the study is less than 5 year, making it difficult to adequately assess the efficacy of control programmes. In this manuscript, we identify the most important gaps in knowledge hampering JD prevention and control programmes, including vaccination and diagnostics. Secondly, we discuss directions that research should take to address those knowledge gaps. [ABSTRACT FROM AUTHOR]

This review summarises current control measures for clinical paratuberculosis (Johne’s disease; JD) in New Zealand pastoral livestock. Most New Zealand sheep, deer, beef and dairy cattle herds and flocks are infected byMycobacterium aviumssp.paratuberculosis(Map). Dairy cattle and deer are mostly infected with bovine (Type II), and sheep and beef cattle with ovine (Type I) strains. Control in all industries is voluntary. While control in sheep and beef cattle isad hoc, the dairy and deer industries have developed resources to assist development of farm-specific programmes. The primary target for all livestock is reduction of the incidence rate of clinical disease rather than bacterial eradicationper se. For dairy farms, a nationally instituted JD-specific programme provides guidelines for risk management, monitoring and testing clinically suspect animals. While there is no formal programme for sheep farms, for those with annual prevalences of clinical disease >2%, especially fine wool breeds, vaccination may be a cost effective control option. The deer industry proactively monitors infection by a national abattoir surveillance programme and farmers with an apparent high disease incidence are encouraged to engage with a national network of trained consultants for management and control advice. Evaluation of the biological and economic effectiveness of control in all industries remains to be undertaken. Nevertheless, opportunities exist for farmers, who perceive significant JD problems in their herds/flocks, to participate in systematic best-practice activities that are likely to reduce the number of clinical infections withMapon their farms, and therefore the overall prevalence of JD in New Zealand’s farming industries. [ABSTRACT FROM AUTHOR]

Leptospirosis is a global zoonosis that in New Zealand affects primarily people occupationally exposed to livestock. The objective of this study was to estimate the seroprevalence of five Leptospira serovars in farmers working on cattle, sheep and deer farms that had the serological status of animals previously assessed and to identify risk factors for farmer seropositivity. A total of 178 farmers from 127 properties participated in the study. Blood samples were tested using the microscopic agglutination test (MAT) for the presence of antibodies to Leptospira. Samples with a MAT titre ≥48 were considered seropositive. Using Bayesian statistical analysis, the median seroprevalence of Leptospira, all serovars combined, was estimated to be 6.6% (95% probability interval (PI) 3.6-10.9%). Risk factors associated with seropositivity were assisting deer or cattle calving, farming deer, having ≥25% of flat terrain and high abundance of wild deer on farm, while high possum abundance on farm was negatively associated with seropositivity. No association was observed between farmer serostatus and previously recorded livestock serology. Leptospira seropositivity was associated with influenza-like illness of farmers (RR = 1.7; 95% PI 1.0-2.5). Assuming a causal relationship, this suggested an annual risk of 1.3% (95% PI 0.0-3.0%) of influenza-like illnesses due to Leptospira infection in the population of farmers. The association between seropositivity and disease can be used to estimate the public health burden of leptospirosis in New Zealand. Identifying and understanding risk factors for Leptospira seropositivity can inform preventive measures, hence contributing to the reduction of leptospirosis incidence in farmers. [ABSTRACT FROM AUTHOR]

Objective To determine the influence of farm-level and animal-level factors on the seroprevalence of antibodies to Neospora caninum and associations between seropositivity and reproductive outcomes. Methods A questionnaire for a cross-sectional survey was posted to the 63 properties with a herd size ≥50 beef breeding cows that had participated in a previous seroprevalence study. Correspondence analysis, which does not appear to have been used previously in any Australian studies of livestock diseases, was used in conjunction with logistic regression to analyse the data. Results Geographic factors that increased the risk of seropositivity included higher rainfall North Coast location. Herd management factors that increased the risk of seropositivity included the use of Bos indicus genetics, cross-breeding and running several breeds in the one herd. Using fox control measures was found to be protective against infection with N. caninum. The risk of abortion was 12-fold greater in individual animals that were seropositive for N. caninum. Within a herd, the calving rate was 10.4% lower in herds with one or more N. caninum-positive animals (P = 0.03), but the difference in abortion rate was not significant between seropositive and seronegative herds (0.3% higher, P > 0.3). Conclusions This study confirmed previous observations of increased risks for N. caninum seropositivity with being located in the coastal subtropics, some styles of herd management and canid exposure. In addition, it suggested that cross-breeding and proximity to an urban area may increase the risk, and that having pet dogs may reduce the risk of seropositivity. [ABSTRACT FROM AUTHOR]