Salmonellosis in dairy goat farming; development of an accreditation programme
Dijkstra E.1, Aalberts M.2, Snijders-van de Burgwal N.1, ter Bogt-Kappert C.1, van den Brom R.1
1Department of Small Ruminant Health, Royal GD, P.O. Box 9, 7400 AA Deventer, the Netherlands; e.dijkstra@gdanimalhealth.com (corresponding author)
2Department of Research and Development, Royal GD, P.O. Box 9, 7400 AA Deventer, the Netherlands. Royal GD (in collaboration with Wageningen University and Platform Melkgeitenhouderij)
Several outbreaks of high morbidity and mortality in neonatal dairy goat kids due to salmonellosis were observed since 2016. Predominantly, Salmonella enterica subsp. enterica serovar Typhimurium was found as causal agent. In case of two outbreaks, salmonellosis was also detected in some of the producers’ relatives, caused by the same MLVA-type of S. Typhimurium. In collaboration with the Dutch dairy goat industry, a comprehensive study was initiated to investigate the prevalence of salmonellosis within the dairy goat sector, to identify potential risk factors and ways to control salmonellosis on dairy goat farms.
Material & methods
All dairy goat farms in the Netherlands (n=403) were encouraged to participate in a prevalence study by taking repeated dust and faecal-contaminated bedding samples for culture of rearing facilities at week three and six of a kidding period in 2021. In addition, bedding samples were taken of trailers at the three largest small ruminant abattoirs after delivering young stock. Of 33 volunteering dairy goat farms of which the Salmonella spp. infection history was known, bulk milk samples from March, April, May, July and August 2023 were screened for the presence of antibodies against Salmonella spp. serotype B/D LPS, using an ELISA. In addition, with permission of milk processors, single bulk milk samples from April of 314 dairy goat farms were anonymously tested for antibodies.
Results
Of the approached farms, 52% (N=209) participated in the prevalence study, of which 148 farms delivered the requested two samples within a lambing period and 61 farms participated just once. Salmonella spp. were detected on seven farms. Positive Salmonella spp. cultures were found on all abattoirs in seven of 37 pooled samples. Samples from farms with (recent) salmonella infections or using an autovaccine had higher S/P-values in the antibody ELISA, compared to farms with no or unknown history of a salmonella infection (median test, P<0.001). Based on the participation of more than half of the Dutch dairy goat industry, a prevalence was found of 4%.
Conclusion
The prevalence of salmonellosis amongst dairy goat farms is similar to the prevalence of salmonellosis in Dutch dairy cattle. Apparently, presence of Salmonella spp. in goats does not necessarily lead to a clinical outbreak, so it is expected that Salmonella spp. are more common on farms than previously thought. In addition, we found that a Salmonella BD-ELISA can contribute to distinguish dairy goat farms with or without
salmonella infections. Nevertheless, further research on the antibody dynamics in goats after salmonella infection and the relation between individual antibody responses and bulk milk antibody levels will be necessary to refine the cut-off value and provide more insight into the implication of the ELISA for goat bulk milk in an accreditation scheme.
Distribution of S/P values of bulk milk samples from 347 dairy goat farms in April 2023, shown for farms with no or unknown (-) and a known recent history of salmonellosis and/or using autovaccination (+).