The 1997-1998 classical swine fever epidemic in The Netherlands - A survival analysis

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)235-248
Journal / PublicationPreventive Veterinary Medicine
Volume42
Issue number3–4
Online published2 Dec 1999
Publication statusPublished - Dec 1999
Externally publishedYes

Abstract

The aim of this analysis was to characterise the temporal pattern of infection during the 1997/98 classical swine fever (CSF) epidemic in The Netherlands and hence identify and quantify risk factors for infection in different enterprise types and areas. Survival analysis and Cox proportional hazards regression were used to describe the epidemic. Substantial differences in temporal survival patterns (herd breakdown rate) were found between areas where different control policies operated. Factors with a significant influence on the infection hazard of individual herds included: sow numbers as a percentage of total sows and fatteners (HR = 3.38 for mixed herds (0.1-60% sows) vs. fattening herds (0% sows) and HR = 2.74 for breeding herds (60-100% sows) vs. fattening herds), the number of 'transport contacts per month' (>0.3 vs. 2) in the area (HR1000 pigs 1.48) and herd size (HR100 pigs = 1.01).
Pre-emptive slaughter in an area appeared to be associated with lower subsequent disease levels. Higher frequency of transport contacts for welfare slaughter during the epidemic, however, well regulated and controlled, was associated with a substantially higher risk of becoming infected. The positive association of a higher pig density with CSF indicates the potential importance of local spread as a factor in disease transmission and emphasizes that dilution of the pig population can contribute to reduction in CSF occurrence. This analysis suggests however, that if pre-emptive slaughter can promptly be applied effectively in an area after initial diagnosis, pig density is then not a significant factor. Mixed and breeding herds had a higher probability of becoming infected than fattening herds, possibly due to different types and frequencies of inter-herd contacts. These contacts continue to some extent during the epidemic, despite the standstill of animal movements.
© 1999 Elsevier Science B.V. All rights reserved.

Research Area(s)

  • Classical swine fever, Cox proportional hazards regression, Risk factors, Survival analysis, Temporal pattern, The Netherlands

Citation Format(s)

The 1997-1998 classical swine fever epidemic in The Netherlands - A survival analysis. / Benard, H. J.; Stark, K.D.C.; Morris, R.S. et al.
In: Preventive Veterinary Medicine, Vol. 42, No. 3–4, 12.1999, p. 235-248.

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review