Low prevalence of Salmonella in Swedish dairy herds highlight differences between serotypes

•All Swedish dairy herds were screened for salmonella using two bulk milk tests.•Only 3% of the herds were test positive in any test.•The tests discriminated S. Dublin positive herds from herds with other serotypes.•Association to region and herd size differed between S. Dublin and other serotypes....

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Veröffentlicht in:Preventive veterinary medicine 2016-03, Vol.125, p.38-45
Hauptverfasser: Ågren, Estelle C.C., Sternberg Lewerin, Susanna, Wahlström, Helene, Emanuelson, Ulf, Frössling, Jenny
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Sprache:eng
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Zusammenfassung:•All Swedish dairy herds were screened for salmonella using two bulk milk tests.•Only 3% of the herds were test positive in any test.•The tests discriminated S. Dublin positive herds from herds with other serotypes.•Association to region and herd size differed between S. Dublin and other serotypes. Legislated Salmonella control in Sweden has been in place since the 1960s. The purpose of this study was to investigate presence of Salmonella antibodies in dairy cattle herds and to provide a basis for decisions on how surveillance and control can be improved. Bulk milk samples from all Swedish dairy herds (n=4 683) were analysed with two different ELISAs; one detecting antibodies against Salmonella Dublin (Dublin ELISA), and one detecting antibodies against several of the serotypes causing bovine salmonellosis including S. Dublin (Bovine ELISA). Information about herds, i.e. geographical location, local animal density, number of test positive herds within 5km, animal trade and herd size, was based on register data. The results confirm a very low prevalence of Salmonella in Swedish dairy herds throughout the country with the exception of an island in the southeast. The test positive herds split into two groups; 41 herds (1%) positive in the Dublin ELISA, and 101 herds (2%) positive in the Bovine ELISA but negative in the Dublin ELISA. Geographical location of positive herds, and comparison of the results of the screening with serotypes previously isolated from some of the herds, indicated that the first group represents herds presently or previously infected with S. Dublin while the second group represents herds presently or previously infected with other serotypes. Differences in serological status between herds in different regions, of different size, with different animal purchase patterns et cetera, were tested using logistic regression. Presence of positive herds within 5km was significantly associated to testing positive. For herds testing positive in the Dublin ELISA, significant associations were also seen with herd size. Purchase of animals during the last year was not significantly associated with the outcome in the final models. We conclude that for future surveillance, the Bovine ELISA can be used to help in identifying infected herds, and the Dublin ELISA can be used to distinguish herds with S. Dublin infections. The geographical clustering of test positive herds could facilitate future surveillance and disease control interventions. The results h
ISSN:0167-5877
1873-1716
1873-1716
DOI:10.1016/j.prevetmed.2015.12.015