Risk factors for respiratory diseases in New Zealand pig herds

Aims. A survey of lung lesions and risk factors for respiratory diseases was conducted in order to estimate the prevalence of respiratory diseases in the New Zealand pig population and to identify influential management practices. Methods. Eighty-nine New Zealand pig farms with a minimum herd size of 50 sows participated in the survey, and risk factor data were collected using a mailed questionnaire. Abattoir data were recorded once in winter 1995 and once in summer 1996. A total of 6887 lungs was inspected. Results. The prevalence of enzootic pneumonia, pleuropneumonia and pleurisy in winter was 63,4%, 2.7% and 19.1%, respectively. Enzootic pneumonia was significantly less frequent in summer. Pleuropneumonia/pleurisy was found to be more prevalent in the South Island. The univariate risk factor analysis was consistent with earlier published evidence on the importance of environmental factors related to housing and management of the farm. The multivariate models for enzootic pneumonia and pleuropneumonia or pleurisy had a reasonable good predictive power of 81-91% for farms with high disease prevalence. Conclusion. the results are useful to model the disease process on high-risk farms, which account for a considerable proportion of the New Zealand pig population.