Typical Scenario-1
- Newly assembled herd, animals from unknown source, or from a dealer
- High morbidity ( at least 40 - 60% in the herd infected)
- Drop in milk production, ~ 10 %, high risk of bulk tank milk contamination
- Typically observed with S. Typhimurium, last 2-4 weeks
- Samples taken during outbreak show extensive herd contamination
- Samples collected 4-6 weeks later, most of which test negative
- Subsequent outbreaks or infections may be sporadic, or may go unnoticed