Diseases in dairy calves are commonly diarrhoea in the first month of life and Enzootic Calf Pneumonia, but features of this disease outbreak were:
- Very few signs of diarrhoea or respiratory disease
- Very high mortality. Most calves that became ill died.
- Some showed nervous signs typical of meningitis
- Most cases occurred in calves 3-6 months of age (when it is rare to experience acute disease).
Time and location: In March and April 2018 on the Atherton Tableland.
Case definition: Eighteen calves between 2 weeks and 6 months of age died in a 300-cow dairy herd that rears 200 calves annually. Healthy calves became lethargic, depressed and died within 2 -3 days. Most calves had already been weaned off milk and were grazing tropical pasture while being supplemented with a grain/ protein concentrate. Some calves showed nervous signs of recumbency, dog paddling and opisthotonus; others became depressed, lethargic and febrile.
Gross post mortem findings: 3 calves were autopsied. Few gross lesions were observed.
Laboratory findings: Salmonella dublin was cultured from various tissues in two of the calves but not from the faeces from live calves. Positive cultures came from the jejunum, mesenteric lymph nodes, liver, lungs and spleen.
Histological changes were consistent with septicaemic Salmonellosis. Lesions included meningitis, interstitial nephritis, paratyphoid nodules in the liver and interstitial pneumonia.
Animal / management / environment risk factors: A comprehensive calf rearing audit was conducted. Many aspects of management were investigated. Appropriate colostrum management was confirmed by a serum protein survey showing that 92% of calves had received transfer of passive immunity. Nutritional management was appropriate. Some shortcomings in stocking density, feeding hygiene and effluent management were observed.
Recommendations to the producer:
- Vaccinating calves with Bovilis S at 2 weeks and 6 weeks of age
- Improvements in feed utensil and pen cleaning
- Reducing calf density by moving older calves away from the calf rearing facility
- Avoiding use of paddocks that received effluent from the rearing facility.