Serology tests can detect heartworm in the dog's blood:

• A. Immediately after becoming infected
• B. Several days after becoming infected
• C. Several weeks after becoming infected
• D. Several months after becoming infected

Answer: (D)

Serology tests for heartworm detect signals produced by adult worms, not by the early larval stages. After a dog is bitten by an infected mosquito, it takes time for larvae to mature into adult worms that release detectable antigen. In dogs, the period from infection to when adult female worms are present and producing measurable antigen is typically around five to seven months. Because of this, serology tests generally become positive only several months after infection, not immediately or within days or weeks. While antibody tests can sometimes indicate exposure earlier, standard antigen-based serology relies on mature worms, which is why several months is the expected window for detection.