Heartworm testing: What dog owners need to know

Your dog is your best friend, and you take good care of him, making sure he gets quality food and exercise, immunizations and heartworm medication. Why, then, does your veterinarian also insist on a yearly heartworm test?

Chances are, your veterinarian is following the advice of the American Heartworm Society (AHS), whose mission it is to lead the veterinary profession and the public in the understanding of heartworm disease.

“The AHS recommends annual testing for all dogs,” explains veterinary parasitologist and AHS board member Dr. Patricia Payne. “Heartworm is a devastating disease. It is preventable and can be treated in dogs, but early detection is essential.”

Unprotected Dogs are at Risk

Along with testing, the AHS recommends year-round administration of heartworm preventives. Unfortunately, says Dr. Payne, far too many dogs do not receive this measure of care.

Almost two-thirds of dogs in the U.S. that are seen by veterinarians are given no preventives at all, according to studies conducted by heartworm medication manufacturers.

Among those on prevention medication, far too many are only given medication in spring, summer and fall, when the mosquitoes that transmit heartworm larvae are active. Because weather is unpredictable and hardy mosquitoes can survive indoors as well as outdoors in protected areas, so-called “seasonal” usage creates ample opportunity for animals to unintentionally become infected.

Mistakes Can Happen

Another factor is human — and animal — error. “Pet owners who give heartworm medications year-round and on time are to be commended,” says Dr. Payne. “Even so, it is still possible for heartworm infection to occur.

The following are three scenarios that make heartworm testing a necessity for all dogs:

Even the most diligent owner can forget a dose now and then. “If you have medication left when your veterinarian reminds you that it’s time to purchase more preventive, it’s a pretty clear sign that you missed a dose or two,” says Dr. Payne.

Not all pills are swallowed, and not all topical medications are properly applied. If your dog vomits or spits out a pill when you aren’t looking — or if a topical medication isn’t absorbed completely — a pet may be less protected than you think.

Heartworm resistance is rare but real. “Owners can rest assured that heartworm medications are highly effective, but a few cases of heartworm strains that are resistant to common preventives have been documented,” explains Dr. Payne, adding that the issue is being studied by the AHS.

Test Annually

The good news for owners is that heartworm testing is simple and inexpensive. “Your veterinarian can easily conduct this simple blood test during a dog’s annual or semiannual wellness visit,” assures Dr. Payne. “If your dog tests positive, treatment can begin. With a negative test result, an owner has the peace of mind of knowing that his or her pet has been protected for another year.”