Salmonellosis

Salmonella infections are important because of the potential of transmission to humans. Salmonella Dublin usually causes salmonellosis in calves and older cattle. Cattle can also carry Salmonella Typhimurium, a common cause of disease in humans.

Etiology

Salmonella are gram negative, facultative intracellular, enteric bacteria. A few serotypes are host specific, most are non-specific. Salmonella Dublin is host specific for cattle. It is the main cause of salmonellosis in calves as well as older cattle.

Epidemiology

Intensive, especially crowded, management systems and high protein diets
Predispose cattle to salmonella infections.

In some herds salmonellosis may be endemic in neonatal calves, especially if S. Dublin is involved. Disease is maintained by carrier animals shedding bacteria in their faeces or milk, infected calves, rodents or a contaminated environment.

Clinical signs

The incubation period of salmonellosis is 1-4 days. The most common clinical signs are fever and diarrhea. Neonates as well as adult animals may be affected.

Diarrhea varies from watery to mucoid with fibrin and blood. The presence of plasma proteins associated with inflammatory bowel disease gives the diarrhea a putrid odour. Bacteraemia and subsequent septicaemia may be seen in neonatal calves. In neonatal diarrhea, concurrent infections with other pathogens are common.

Salmonella Dublin may cause respiratory symptoms and sudden death in young calves. In adult cattle diarrhea or abortion occurs.

Salmonella colony growing on blood agar.