Salmonella bacteria can be found on virtually all dairies, regardless of region. Whether it starts as an undetected presence or causes a major disease outbreak depends greatly upon the exposure level of Salmonella organisms to animals.
“Healthy animals can tolerate low doses of Salmonella exposure,” says Bhushan Jayarao, DVM, Extension veterinarian with Pennsylvania State University, University Park, Pa. “But it becomes a much more serious concern when they ingest very large doses of the organism.”
Salmonella infections can cause dairy cattle of all ages to become severely ill. In young calves, it typically shows up as scours, often accompanied by fever. In older animals, it can cause a dramatic drop in milk production, along with fever, diarrhea, bloody stools, dehydration, weight loss, rapid breathing, and/or sloughing of skin from the extremities. Infections can be fast-acting and fatal, or can exist at a subclinical level, with no outward signs of illness.
It is these subclinical or “carrier” cows that can be a major source of disease transmission in a herd, says Gary Neubauer, DVM, senior manager, Dairy Veterinary Operations, Pfizer Animal Health. “Because those infected animals can silently shed Salmonella organisms in their feces, urine and/or milk, they become a reservoir of infection that can easily spread the disease to the rest of the herd,” he says.
“The main source of Salmonella infections on dairies is transmission of the bacteria from feces of infected animals to mouths of susceptible animals,” Jayarao says. “This makes it extremely important to help prevent fecal contamination of feedstuffs, feeding surfaces and water troughs.”
Salmonellosis is a pervasive disease that is hard to keep out of a dairy operation. Once it is in the herd, it can be devastating to cattle health and performance. As the figure below shows, there are many routes Salmonella transmission can take. Dr. Jayarao and Dr. Neubauer offer these tips on helping reduce disease exposure.
- Make sure loaders and other feeding equipment are not used simultaneously to handle manure.
- Pasteurize waste milk and colostrum fed to calves.
- Maintain sanitary calving facilities to avoid infecting newborns.
- Keep populations of rodents, feral cats and birds low in feed storage and animal housing areas.
- Control flies throughout the dairy with common fly control methods.
- Restrict visitors and insist on biosecurity measures (such as clean boots and clothing) by all who enter the facility, including the herd veterinarian.
- Clean calf feeding utensils and oral treatment equipment with chlorhexidine (3 ounces per gallon).
- Wash boots regularly with orthophenylphenol (e.g., 1-Stroke Environ), and change and launder work clothes daily. Ideally, boots and work clothing should be left on the dairy.
- Thoroughly sanitize transport trailers, particularly when hauling young calves.
Neubauer notes that many strains of Salmonella can infect humans. Thus, it is imperative to maintain good personal hygiene when working with animals of all ages on the dairy, and to never drink raw milk.
“It is true that Salmonella is a very common bacterium on dairies, but that doesn’t mean we have to surrender to it,” Jayarao says. “There are many practices that can help to limit animals’ exposure to it and, thus, keep them healthy and productive.”
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Source: Pfizer Animal Health