Salmonellosis is a significant disease of cattle. It is also a zoonotic disease that can be spread from cattle to humans through direct contact or consumption of contaminated food. The incidence of Salmonellosis in both beef and dairy herds appears to be increasing and an increasing rate of antibiotic resistance has added to the concern. Treatment of Salmonellosis can be costly, impractical, and ineffective. A key to controlling Salmonella in any cattle herd is recognizing the disease early. Do you know if you have Salmonella in your herd?

Clinical Presentation Salmonellosis is caused by the bacteria Salmonella. There are many different species or strains of Salmonella, all of which have the potential to cause disease in cattle. Some of the more important strains of Salmonella that affect cattle are Salmonella typhimurium, Salmonella newport, and Salmonella dublin.

Salmonellosis often infects young calves and most often occurs in the gastrointestinal tract. Salmonella infections are most commonly acquired by ingesting the bacteria. Contaminated feedstuffs, water sources, or environments are common sources of exposure. The most common signs of Salmonellosis are fever and diarrhea. The diarrhea often has a foul, putrid odor, and may be bloody. Other clinical signs include dehydration, weight loss, rapid breathing, skin sloughing from extremities, abortion, and sudden death.
 
Cattle may also be carriers of Salmonella. These carriers have Salmonella in their gastrointestinal tract and can shed the bacteria into the environment, while showing no signs of disease. These cattle are of particular importance because of their unique ability to quietly transmit the disease to other cattle or farms while showing no outward signs of disease.

Another emerging issue is the increase in antimicrobial resistance of Salmonella. In recent years multiple strains of Salmonella have developed a level of resistance to many traditional antibiotics including Ampicillin, Ceftiofur, and Sulfas. Therefore, bacterial culture and sensitivity is essential for choosing the correct antibiotic to treat Salmonella in your herd.

Prevention of Salmonellosis involves implementing measures both on the farm and in the home. The risk of transmission can be reduced on the farm through good hygiene and the implementation of strict biosecurity. In the home, the risk of Salmonella contamination can be reduced by properly preparing food and maintaining a sanitary kitchen.

Diagnostic Testing The most common way Salmonella is diagnosed is by culturing the organism from the feces of infected animals or from tissues collected from dead animals during necropsy. Isolation of Salmonella from cattle displaying clinical signs of Salmonellosis suggests a relationship between the organism and the disease process. Salmonella can be shed intermittently by cattle, leading to the possibility of false negative results. To determine if Salmonella is part of a disease outbreak in your herd, there are two main testing strategies. One strategy involves testing multiple cattle once on a given day and the other strategy involves collecting multiple samples from a sick animal over a 3 to 4 day period. Other methods are available for diagnosing Salmonella, but they tend to be more expensive, less sensitive and do not provide as much useful information as culture.

So what is the best course of action if you suspect Salmonella in your herd? If you believe that Salmonella is in your herd you should use the following steps as a guide for diagnosing the disease:
• If you observe clinical signs of disease described above, contact your veterinarian
• Collect fecal samples from cattle showing clinical signs of Salmonellosis for culturing
o Collect samples from multiple clinically affected animals or collect multiple samples from the same animal(s) over several days

• If a positive culture is found:
o Treat cattle with the appropriate antibiotics recommended by your veterinarian and based on culture sensitivity
o Consult with your veterinarian to devise a strategy for prevention and control of Salmonella in your herd

• If no positive cultures are found:
o Consult with your veterinarian to devise a strategy for prevention of Salmonella introduction into your herd

Salmonellosis is a serious disease that is significant in both animals and humans. Make sure you take the appropriate steps to diagnose and control it in your herd.

Source: Dr. Erik Corbett, Graduate Student, Dept. of Large Animal Clinical Sciences, Michigan State University