Almost all veterinarians agree on the necessity of heartworm preventive medication for every dog which spends time in an area where mosquitoes are present. In regards to heartworm testing:
- dogs are required to be tested for heartworms before starting on a monthly regimen of heartworm preventive medication for the first time, unless the dog is less than 6 months of age.
- annual heartworm testing is recommended for all dogs, even when receiving year-round heartworm preventive medication.
Why Do Veterinarians Recommend that Dogs Receiving Heartworm Preventive Medication be Tested Yearly for Heartworms?
Yearly tests for heartworms are endorsed by the American Heartworm Association and yearly testing is considered the "gold standard" of heartworm control. Thus, yearly tests are recommended by most veterinarians.
- Some veterinarians actually require that heartworm testing be performed before dispensing or prescribing additional heartworm preventive to the dog if the dog has not been tested within the past year.
- Other veterinarians are content simply to make the recommendation of an annual heartworm test to the dog's owner and let the owner make the decision regarding testing for heartworms.
These recommendations for yearly heartworm testing are based on the fact that heartworm infection can cause serious damage to a dog's heart and can do so in a fairly short period of time.
- Even though currently available heartworm preventive medications are very effective, there is truly no medication which is able to claim 100% effectiveness.
- In addition, there may have been lapses in the monthly heartworm preventive treatment protocal if the owner forgot to give the medications for a month or two and did not realize this was the case.
- Compliance issues can occur with dogs also and some dogs can be quite adept in pretending to swallow medications which they actually have not swallowed.
In effect, the yearly heartworm test is seen as a safety measure to protect the health of your dog and evaluate the efficacy of the heartworm preventive medication your dog is taking.
How is Testing for Heartworms Accomplished?
Testing for heartworms in dogs involves obtaining a small blood sample.
- The most common test done currently is the heartworm antigen test. This tests looks for evidence of the presence of adult heartworms.
- Testing for microfilariae (juvenile heartworms) in the blood was once a commonly performed test. It is now considered outdated for screening purposes, although it is sometimes used to help plan treatment programs for dogs which test positive for heartworms.
Annual Heartworm Tests for Dogs: Recommended vs Required
Among those veterinarians who require the heartworm test yearly for all dogs placed on heartworm preventive medication, the most commonly expressed reasons are:
- the amount of damage done to the heart in dogs testing positive for heartworms is too serious to not require the test.
- there is a possibility that some of the available heartworm preventive medications may not be entirely safe to administer to dogs harboring heartworms.
- there is the possibility of non-compliance by either the owner or the dog in respect to administering and taking heartworm preventive medication (i.e. the dog may not actually have received the medication each month as the owner believes). Heartworm preventive medications are much less effective if not given monthly as prescribed.
- there is a worry that without proper examination and testing, a valid client-patient relationship no longer exists. Prescription medications such as heartworm preventive medication cannot legally be prescribed without a valid client-patient relationship.
- there may be liability/malpractice issues involved with dispensing medication to an animal which may have existing medical problems such as damage done to the dog's heart by heartworm disease.
Those veterinarians who prefer to strongly recommend the heartworm test but not actually require it in order to fill a prescription request counter:
- the owner may elect to discontinue the heartworm preventive medication if a heartworm test is demanded prior to filling the prescription request. In this case, the dog is placed at additional risk by not being on heartworm preventive medication.
- if the owner declined the test, the responsibility for any complications lies with the owner. This may or not be true if challenged legally.
In summary, annual heartworm testing is recommended for all dogs, even when year-round heartworm preventive medication is administered. If your veterinarian requires a heartworm test for your dog each year before re-prescribing heartworm preventive medication, the veterinarian is simply looking out for the best interests of your dog.
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