Weak positive on parvo fecal antigen ELISA can occur how long after a live vaccine?

• A. 4-8 days
• B. 1-2 weeks
• C. 2-3 weeks
• D. Several months

Answer: (A)

After a live attenuated canine parvovirus vaccine, the vaccine virus can replicate in the gut and be shed in the feces for a short period. Fecal antigen ELISAs detect parvovirus antigen from both wild-type and vaccine strains, so a weak positive can occur during vaccine shedding. This shedding typically happens about 4 to 8 days after vaccination, which is why that window is the best answer. Beyond this window, vaccine shedding is unlikely, so a positive result several weeks or months later is not due to the vaccine. If vaccine timing is involved and infection is still a concern, consider follow-up testing or more specific methods (like PCR) to distinguish vaccine strain from wild-type.