Which statement is true of mouse hepatitis virus?

• A. It affects the immune system of asymptomatic mice.
• B. It mainly causes diarrhea in adult mice.
• C. It is easily identified because of clear clinical signs.
• D. The only method which can be used to eliminate this virus is embryo rederivation.

Answer: (A)

Mouse hepatitis virus often causes subclinical infections in adult mice, yet it can modulate immune function even when there are no obvious signs. This means animals can look healthy while their immune responses are affected, which can influence experimental outcomes, vaccine responses, and susceptibility to other infections. That subclinical immunomodulation is what makes the statement about affecting the immune system of asymptomatic mice the best description of the virus’s impact.

Diarrhea is not the typical or reliable sign for this virus, and many infections are not readily identifiable by clear clinical signs. Embryo rederivation is a method to produce MHV-free lines but is not the only way to eliminate the virus; barrier housing, quarantine, testing, and other strategies are also used depending on the situation.