For a dog that receives a monthly heartworm preventative year round , the American Heartworm Society suggests that the interval between tests could be longer that one year. This is only if there were no missed or late doses of preventative. If a dose was missed or late, the dog should be tested on an annual basis. It is also recommended that a test be performed after the first year the dog has been on the preventative. The active ingredient in most daily preventatives is diethylcarbamazine.
Severe reactions can occur if diethylcarbamazine is given to a dog with adult heartworms.
Because of this, dogs receiving daily preventatives on a seasonal basis must be tested before the preventative is resumed in the spring or summer. Dogs receiving daily preventative all year round must be tested annually. The American Heartworm Society will be reviewing these recommendations on testing and preventatives in late 1998. We will keep you informed. Nursing Dams Treat concurrently with pups or kittens.