In recent months, a common cause of illness in dairy calves has been garnering more attention among calf raisers, their veterinarians, and even health departments.
Salmonella infections can be some of the most severe causes of illness in calves less than one month of age. At the South Dakota Animal Disease Research and Diagnostic Lab in fiscal year 2016, Salmonella was the number one cause of bacterial septicemia (whole body infection) and was among the most common causes of diarrhea in calves. A wide variety of Salmonella serotypes exist. Many of these serotypes are considered common inhabitants of calves’ digestive systems. Some, however, are associated with severe clinical signs and mortality. In cattle, Salmonella dublin is the most common serotype isolated from sick animals; that serotype is considered relatively “host adapted” for cattle.
Calf Illness: Calf illness due to the virulent serotypes of Salmonella can be extremely frustrating to treat. Clinical signs can come on very quickly and consist of fever (104° - 105° F), diarrhea, lethargy, and refusal to drink. Mortality can be high in certain groups despite aggressive treatment efforts. Treatment attempts consist of oral or intravenous fluids and electrolytes, antibiotics, and anti-inflammatories. Salmonellosis most commonly affects calves from several days to several weeks of age.
Transmission: Virulent Salmonella serotypes are quite contagious and spread from the manure of infected animals (or the environment they have contaminated) to susceptible calves in a fecal-oral fashion. Dairy calves normally first become exposed to Salmonella at their farm of origin, as well as on transport vehicles, although they can become infected later as well.
A Salmonella serotype gaining recent notoriety is Salmonella heidelberg. While it is being found more commonly in calf diagnostic cases at the SDSU ADRDL, it is far from the most common serotype associated with calf illness. While Salmonella in general show resistance to many antibiotics, some of these S. heidelberg isolates are resistant to every antibiotic that’s practical for use in calves.
Because of the virulence and drug resistance of S. heidelberg and other Salmonella serotypes, prevention and control measures become critical. At the dairy of origin, strict sanitation of calving areas, calf hutches, and transport trailers is crucial. Once at the calf raising facility, sick calves should be isolated from others as soon as they are detected (although the speed of clinical signs in some affected calves may confound this). On farms with sick calves, a heightened level of cleaning and disinfection of feeding and treatment items, hutches, and other items that can spread germs from calf to calf should be implemented.
Biosecurity & Personal Safety
Calf raisers, veterinarians, and other visitors should pay close attention to biosecurity. Care should be taken to use boots and coveralls that stay in the calf area. Separate clothing is necessary when working with sick calves, and those animals should be worked with only after healthy calves are tended to.
While recent reports from the Centers for Disease Control and Prevention have linked the S. heidelberg serotype to human illnesses, all Salmonella serotypes – as well as other young calf pathogens such as Cryptosporidia) are potential causes of illness in people. Those working with calves – even healthy calves – should use protective coveralls, boots, and gloves that prevent germs from contacting the mouth or face. Those items should remain in the calf area or be disposed of after working with the calves.
The Bottom Line
Calf raisers or dairy producers suspicious of Salmonellosis or other illnesses in their animals should work with their local veterinarian to characterize the problem and institute plans for prevention, treatment, and containment. Health care providers should be contacted if a human illness associated with calf contact is suspected.