Pneumonia Outbreaks - is it Salmonella Dublin?
A review of our VIDA diagnostic data for submissions where a diagnosis of Salmonella Dublin was made revealed a few interesting findings:
- The majority of Salmonella Dublin associated disease is diagnosed in dairy cows and calves
- 53% of calf and 66% of adult cow diagnoses presented with clinical signs of diarrhoea
- 17% of calf diagnoses presented with respiratory signs.
- Other clinical presentations included abortion, milk drop, ill thrift, sudden death and more rarely arthritis, osteomyelitis and gangrene.
Prior to turn out is an excellent time to consider convalescent single sample serology in groups of calves that have experienced pneumonia.
This is a well used and simple technique for the common respiratory viruses and Mycoplasma bovis.
For groups of dairy calves in particular, we would recommend including Salmonella Dublin serology in the suite of tests carried out.
Important facts to note when using the Salmonella Dublin serology are:
- Peak antibody titres are reached 5-6 weeks after infection (slower in calves; faster in adult cattle)
- Maternally derived antibody persists up to 3 months of age
- Sensitivity and specificity varies with age of animal sampled. The test performs best in animals of 3-10 months of age, where sensitivity and specificity are 94%
- Serology provides a more sensitive assessment of herd status than culture-based techniques, particularly if there are no acute, symptomatic cases
- Sampling calves between 3 and 6 months of age can be a useful compromise between cost and sensitivity. The herd size and structure will determine how many need to be sampled.
The test costs £7.50 per sample and, unlike positive culture results we are not required to report any seropositive results to APHA. We would still recommend culture and PM examination as the best means of diagnosing potential acute disease due to Salmonellosis.
If you are interested in more details on Salmonella Dublin control, please refer to a recent In Practice article at the link below written by vets from the Dumfries centre.