Risk factors associated with seropositivity to porcine respiratory coronavirus in Danish swine herds

Abstract

Serolo,Eical screening of swine herds in 1984indicated that porcine respiratory coronavirus (PRCV) had been introduced into Denmark. To determine risk factors associated with the introduction of PRCV, a cross-sectional study of 408 Danish swine herds was carried out between May 1985 and June 1986. The association between herd-PRCV serological status and possible risk factors, obtained from a field questionnaire, was assessed by unconditional maximum likelihood logistic regression. An increasing herd size, location in the Jutland peninsula (compared with location on the island of Funen) (OR = 7.9 in a multivariable logistic regression model not including interaction terms), the presence of a slurry system (i.e. pigs living on a slatted floor) (OR=4.6) and purchase of pigs (OR= 1.7) were significantly (P < 0.05) associated with seropositivity. Two significant interactions, both involving herd s#ize, were subsequently identified.The PF!CV serological status of neighbouring herds was found to be related, and closeness of a seropositive herd was associated with an increased risk of a herd being serologically positive.The re.sults of this study indicate that herd size may be an important determinant of airborne transmission of PRCV infection, and that herd size may modify the effect of other risk factors.*Corresponding author. 0167-5877/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI016?-5877(95)00498-X s2 J. Flori et al. /Preventive Veterinnry Medicine 25 (1995) 5142

Effect of husbandry methods on seropositivity to African swine fever virus in Sardinian swine herds

“…The natural logarithm of the number of tested pigs per visit in a farm was associated with an increased ASFV seropositivity (Table 2). However, a logistic regression coefficient for ln(NTEST) p = 1 suggested that the risk of infection for a single animal was not affected by herd size (Willeberg et al, 1994;Flori et al, 1995).…”

Empirical and theoretical evidence for herd size as a risk factor for swine diseases

“…Even for herds not introducing pigs and with limited contacts with other herds, there is empirical evidence that large swine herds are at increased risk of airborne introduction of viral diseases. For example, for infections such as PRCV and PRV (for which airborne transmission in Denmark has been reported), an increased risk of infection was evident in large herds (Henningsen et al, 1988;Christensen et al, 1990;Flori et al, 1995). In addition, the authors of these three studies found that a natural logarithmic transformation of herd size was the best formulation of the independent effect of herd size on the odds of positive PRCV or PRV status.…”

“…A discussion of herd size measures would be incomplete without reference either to herd (and pig) density in an area, which might also be positively correlated with herd size, or to pig stocking density within herds. Greater herd (and pig) density may be confounded with larger herd size at least in some countries, such as Denmark (Flori et al, 1995), and therefore might in part explain the reported herd-size effects. The importance of considering the density of infected herds or pig density on an area basis in addition to herd size as risk factors for pseudorabies was recognized in at least five studies (Austin et al, 1993;Leontides et al, 1994aLeontides et al, , 1995Boelaert et al, 1999;Maes et al, 2000).…”

The importance of straw for pig and cattle welfare: A review

“…But, unless the upper layer of the straw bedding is kept fresh and dry, the strength of the horn will decrease because of the higher water content (Kroneman et al, 1993). Furthermore, slatted floors may be more stressful to pigs and indirectly, through a reduction in resistance, lead to an increased infection risk (Straw, 1986;Flori et al, 1995). This hypothesis may explain the lower risk for influenza A infections (Ewald et al, 1994) and stomach and intestine disorders (Christensen et al, 1995;Smith and McOrist, 1998) found in straw systems compared to slatted floors.…”