Circulating heartworm antigen appears in the blood as early as five months post-infection in a small percentage of dogs, but most dogs are not antigen positive until seven months post-infection. Yes, contrary to popular belief, a dog infected six months previously can be negative on an antigen test.
How soon after infection can heartworm be detected?
The earliest that the heartworm proteins can be detected in a dog's bloodstream is about 5 months after it is bitten by an infected mosquito.
How long before a dog tests positive for heartworm?
It takes at least 6-7 months for heartworm disease to show up on a test.
How soon after heartworm treatment will a dog test negative?
While 100% of adult worms might be dead at the 6-month point, residual heartworm antigen in circulation is detectable for a time and could lead to an invalid test result. Waiting an additional 3 months allows time for the antigen to be cleared from the dog.
How long can heartworms go undetected?
Dogs are typically heartworm tested prior to transport, but due to the life cycle of the heartworm, there is a window where dogs may test negative but still have heartworms. Heartworm in these dogs may go undetected for several months or more, allowing them to serve as a source of infection for other dogs.
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