The more dense a population, the easier it is to transmit disease. During calving time when animals are sometimes brought together in closer quarters, especially in poor weather conditions, Salmonella spp. can flourish. “Bacterial infections are still a ‘numbers game’,” says Russ Daly, DVM, Dipl. ACVPM, South Dakota State University. “Anytime you can drop the numbers of bugs the cattle can contact, the risk of infection and clinical disease usually drops as well. Even if we can’t completely prevent infection, we might be able to prevent disease by implementing some management practices.”
In a Salmonella enterica serotype Newport case Daly was involved with, three herds in separate pastures all were positive for S. Newport, even though only one of the herds showed clinical signs. “We don’t know exactly how the S. Newport got distributed to all the groups, but the same equipment was used in all three pastures (tractor, bale feeder, pickups, fourwheelers). In addition, the farm dog was positive for S. Newport. Although its clinical signs showed up after those in the cattle, it could have been a potential ‘vector’ as well.”
Salmonellae are so hardy; it’s not unthinkable that anything in contact with a sick or carrier animal (but especially a sick animal) can serve as a means of transmission. Daly says to focus on anything that is contaminated by manure or by oral fluids of the affected animal. Work on sick groups last and if working with individual animals (doctoring sick calves), work with them last and use dedicated clothes and boots. Largeticket equipment items are trickier, such as tractors and feeders, etc. in contact with cattle and manure out in the pastures. Fenceline feeding and feeding off the ground are things to consider if feasible.
It’s always a good idea to quarantine new animals, and if they are about to go clinical with a Salmonella spp. infection following transport to a new operation, Daly expects that clinical disease would show up well within a normal 30-day quarantine period. “If that happens, though, I would worry about the animal being a long-term carrier even if they recover from the disease.”