Prevalence of Mycobacterium avium subsp. paratuberculosis in farmed red deer (Cervus elaphus) with grossly normal mesenteric lymph nodes

Abstract

AIM: To estimate the prevalence of Mycobacterium avium subsp. paratuberculosis (Map) in farmed deer with no gross post-mortem evidence of Map infection slaughtered in New Zealand, and to assess predictors of infection.

METHODS: Mesenteric lymph node (MLN) samples (n = 251) were collected from 60 lines of deer presented at two slaughterhouses in the North and two in the South Island of New Zealand between October 2008 and January 2009 and cultured for Map. Estimates of individual animal prevalence for each island were adjusted to account for the clustering of individual observations within herds. The national herd prevalence estimate was calculated as a weighted mean, with weights being the proportion of herds from which deer were slaughtered at North and South Island slaughterhouses among all herds slaughtering deer throughout New Zealand. Age, gender, and the presence of other carcasses with enlarged and/or granulomatous MLN in the same line (line status) were assessed as predictors of infection using multivariable logistic regression.

RESULTS: A national cluster-adjusted individual animal prevalence of 45 (95% CI = 30–60)% was estimated, with North and South Island prevalences of 29 (95% CI = 16–45)% and 51 (95% CI = 36–66)%, respectively. Line status was a strong predictor of infection in young deer (OR 7.1, 95% CI = 2.4–21.5), but not in older deer. Herd-level prevalence was 44 (95% CI = 24–64)% in the North Island and 67 (95% CI = 49–85)% in the South Island. Weighted adjustment resulted in a national herd-level prevalence estimate of 59 (95% CI = 41–78)%.

CONCLUSIONS: This study has provided a national baseline prevalence estimate for Map infection at the individual and herd-level, showing a contrast between the North and South Islands. More research to investigate the factors contributing to the difference in infection prevalence seen between the islands may help to identify suitable control measures for Map in deer herds.

Keywords:

• Deer
• Cervus elaphus
• paratuberculosis
• Johne's disease
• Mycobacterium avium subsp. paratuberculosis
• mesenteric lymph node
• BACTEC culture
• prevalence

Acknowledgements

This study was funded by the Johne's Research Group in association with DEEResearch Ltd, the Foundation for Research, Science and Technology and supported by Massey University and New Zealand Government International Doctoral Research Scholarships. The authors would like to thank veterinary students Helena van der Heide and Jorien Druijf from the University of Utrecht in the Netherlands for assistance with sample collection; the meat inspectors, managers and kill floor staff at the DSP involved and all staff at AgResearch, Centre for Biosecurity and Infectious Disease, Wallaceville, Upper Hutt for diagnostic support.

Notes

¹ JC Hunnam, Anexa Animal health Centre, Morrinsville, New Zealand

*Non-peer-reviewed

Additional information

Notes on contributors

L A Stringer

Current address: Anexa Animal health Centre, Morrinsville, New Zealand.