![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
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.
Acknowledgements
A special thanks to all farmers who took their time to gather their animals and to take part in the interview, and to the 28 veterinary practices involved for their time and collaboration.
We gratefully acknowledge the Johne’s Disease Research Consortium (JDRC) for permitting survey data and samples collected for Johne’s Disease research to be used for this project, the Alma Baker Trust Fund, the Swiss National Science Foundation (SNF) and Rural Women New Zealand (RWNZ) for other research costs and PhD candidate support.
We thank New Zealand Veterinary Pathology (NZVP) for their support in sample processing and storage. A very special thanks to N. Haack for all the lab work and also to S. Prickaerts, P. Guzman, D. Tapia, R. Pearson, T. Delaune, M. Turlin, L. Stringer, J. Manuel Sanhueza, P. Moono, J. Job, R. Gregory, A. Kurian, G. Anakkaramadathil, S. Jacob, P. Jaros and S. Moore for technical assistance with sample management and analyses.