The most effective method for eliminating mouse hepatitis virus is cesarean or embryo transfer rederivation.

• A. True
• B. False
• C. Not proven
• D. Depends on strain

Answer: (A)

The most reliable way to eliminate mouse hepatitis virus from a line is rederivation through cesarean delivery or embryo transfer because these techniques remove the pups from the dam’s infectious environment entirely. MHV is transmitted from dam to offspring through birth materials and nursing, so simply cleaning facilities or isolating animals can miss persistent transmission from the dam and milk. By performing a cesarean, the pups bypass exposure during birth, and by embryo transfer into virus-free recipient dams, the offspring begin life free of maternal-associated virus. If embryos are sourced from or tested for MHV and transferred into clean surrogates, the resulting pups are practically free of the virus, provided proper testing confirms absence. While environmental controls help, they don’t guarantee elimination due to potential undetected vertical or horizontal transmission within a colony, making rederivation the most effective approach. This method is effective across strains, so the statement holds true.