In horses, Salmonella infection can present with a range of signs. Which statement best describes this range?

• A. It always presents as mild disease
• B. It can range from inapparent to acute diarrhea; adults may have fever and depression; foals may develop septicemia
• C. It never causes diarrhea
• D. It only causes respiratory disease

Answer: (B)

Salmonella infections in horses show a wide range of clinical presentations, shaped by the horse’s age, immune status, and the virulence of the strain. This breadth is best captured by recognizing that many infections are inapparent, with shedding but no signs. When disease does appear, it often manifests as an enteric illness with fever and depression, and in foals the infection can become septicemic, spreading through the bloodstream and causing systemic signs. In other words, the same pathogen can stay subclinical in some horses, cause acute diarrhea in others, and lead to life-threatening septicemia in young foals. This spectrum reflects how host factors and disease progression influence presentation. The other statements are too narrow: diarrhea isn’t the only possible sign, respiratory disease isn’t the exclusive manifestation, and subclinical infections do occur, all of which the chosen description incorporates.