Evans, Charlotte M. , Medley, Graham and Green, Laura E. (2008) Porcine reproductive and respiratory syndrome virus (PRRSV) in GB pig herds : farm characteristics associated with heterogeneity in seroprevalence. BMC Veterinary Research, Vol.4 (No.48). doi:10.1186/1746-6148-4-48 ISSN 1746-6148.

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Abstract

Background: The between- and within-herd variability of porcine reproductive and respiratory syndrome virus (PRRSV) antibodies were investigated in a cross-sectional study of 103 British pig herds conducted 2003–2004. Fifty pigs from each farm were tested for anti-PRRSV antibodies using
ELISA. A binomial logistic model was used to investigate management risks for farms with and without pigs with PRRSV antibodies and multilevel statistical models were used to investigate variability in pigs' log ELISA IRPC (relative index × 100) in positive herds.
Results: Thirty-five herds (34.0%) were seronegative, 41 (39.8%) were seropositive and 27 (26.2%) were vaccinated. Herds were more likely to be seronegative if they had < 250 sows (OR 3.86 (95% CI 1.46, 10.19)) and if the nearest pig herd was ≥ 2 miles away (OR 3.42 (95% CI 1.29, 9.12)). The
mean log IRPC in seropositive herds was 3.02 (range, 0.83 – 5.58). Sixteen seropositive herds had only seropositive adult pigs. In these herds, pigs had -0.06 (95% CI -0.10, -0.01) lower log IRPC for every mile increase in distance to the nearest pig unit, and -0.56 (95% CI -1.02, -0.10) lower log IRPC when quarantine facilities were present. For 25 herds with seropositive young stock and adults, lower log IRPC were associated with isolating purchased stock for ≥ 6 days (coefficient - 0.46, 95% CI -0.81, -0.11), requesting ≥ 48 hours 'pig-free time' from humans (coefficient -0.44, 95% CI -0.79, -0.10) and purchasing gilts (coefficient -0.61, 95% CI -0.92, -0.29).
Conclusion: These patterns are consistent with PRRSV failing to persist indefinitely on some infected farms, with fadeout more likely in smaller herds with little/no reintroduction of infectious stock. Persistence of infection may be associated with large herds in pig-dense regions with repeated reintroduction.

Item Type:	Journal Article
Subjects:	S Agriculture > SF Animal culture Q Science > QL Zoology
Divisions:	Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) > Biological Sciences ( -2010)
Library of Congress Subject Headings (LCSH):	Porcine reproductive and respiratory syndrome, Swine -- Diseases -- Great Britain, Swine -- Infections -- Great Britain
Journal or Publication Title:	BMC Veterinary Research
Publisher:	BioMed Central Ltd.
ISSN:	1746-6148
Official Date:	28 November 2008
Dates:	Date Event 28 November 2008 Published
Volume:	Vol.4
Number:	No.48
DOI:	10.1186/1746-6148-4-48
Status:	Peer Reviewed
Access rights to Published version:	Open Access (Creative Commons)

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