The clinical signs of Salmonella are easy to identify — sudden weight loss, weakness, fever, diarrhea and dehydration. While these symptoms signal clinical Salmonella on your clients’ dairies, they are only the tip of the iceberg.

The majority of Salmonella infections in herds are sneaky and often can go undetected for long periods of time in the form of subclinical salmonellosis. These cases show no visible clinical signs of disease, so they are difficult to identify yet reduce a herd’s productivity. What’s worse, Salmonella pathogens can spread from animal to animal throughout an operation for months without detection.

“USDA data tells us that nearly half of all dairies are infected with Salmonella, and in herds over 500 cows, that number jumps to 61%,” explains Gary Neubauer, DVM, Pfizer Animal Health. “Most of those infections are subclinical, resulting in decreased milk production and cattle that are more susceptible to other diseases, especially right after calving.”

A subclinical case of salmonellosis can develop as a result of exposure to three different types of pathogen carriers:
• Active carriers that shed the Salmonella organism in manure and/or milk
• Symptom-free carriers that infrequently shed organisms
• Dormant carriers that harbor Salmonella but do not shed bacteria

Neubauer points out that cattle can often move among these carrier states. For example, a dormant carrier may become an active carrier and vice versa. Carriers can infect the rest of the herd through fecal-oral contamination of bacteria shed during periods of stress. Neubauer recommends taking these steps as part of a Salmonella control plan:
• MAINTAIN CLEAN FACILITIES Evaluate fresh cow, transition and calving pens. Apply fresh bedding on a consistent schedule and remove all manure from the facilities.
• SANITATION IS KEY Feeding equipment and loaders should not be used for manure handling. Help reduce the spread of bacteria by using chlorhexidine to clean calf-feeding utilities and oral treatment equipment, on a regular basis.
• ENFORCE BIOSECURITY MEASURES Insist that all visitors, including veterinarians, wear clean boots and clothing. Wash boots regularly with orthophenylphenol and launder work clothes daily. Ideally, work attire should be left at the dairy.

Work with clients to develop a Salmonella control program. Discuss the role that vaccination can play. For more information on ways to reduce the risk of Salmonella visit