Annual Heartworm Prevention & Testing

Treat year ‘round with once monthly chewables.



We moved 6 months ago and our vet there didn’t heartworm test our dog after he was 9 months old because the dog was on the heartworm preventive year ’round. Our new vet says that the dog needs to be blood tested every year. Why? It’s so expensive and I’m a senior citizen on a limited income.


Dr. Nichol:

You have raised an important question. Here are the basic facts that you must know to protect your dog. There are two types of heartworm preventive tablets. One is give daily, the other monthly. Both are safe and effective. The cost on a per month basis is about the same. Niether is perfect. Like all medications, they are not 100% effective. This means that to be sure that your dog is not infected with heartworms, he or she needs a blood test annually.


What can happen if you don’t? Consider this: If your dog is feeling fine but found heartworm positive on an annual heartworm test, treatment to kill the parasites can usually be done safely. Your dog would suffer no long term effects. On the other hand, if you skip the annual test and your dog gets heartworm, you would have no way of knowing until he started coughing (possibly coughing up blood), losing weight, and becoming inactive. In this case he could also be treated for heartworm infection but with symptoms like these, the risk is high for complications or death. Long term, he may have scarring in his lungs from the dead heartworms that can cause exercise intolerance. The bottom line is that it is much safer to test annually.


The last question that we often hear is why is it important to give the preventive tablets year ’round if we don’t have mosquitoes in the winter? This year ’round recommendation comes from the American Heartworm Society. Research has shown that mosquitoes are becoming a better adapted parasite. This means that they have learned to survive indoors in closets, sheds, and garages even during the winter. The heartworm risk to your dog is somewhat less in the winter but he is still vulnerable unless the preventive is given nonstop. You are right that all of this can get expensive. But it’s still a lot cheaper that the cost of treatment.





Heartworm Risk Factors


I understand that many veterinarians in Albuquerque do not recommend heartworm tablets for dogs. Some do. Please comment.


Dr. Nichol:

If you live in a wet area your dog is at higher risk of getting heartworm because the mosquitoes that carry the disease need moisture. Rainfall varies in New Mexico but that’s no reason to gamble. The preventative medications are both highly effective and safe.


Preventatives can be given to dogs in tablet form monthly or by injection every 6 months. The American Heartworm Society recommends year ’round protection because mosquitoes can move indoors during the winter and put your dog at risk. We don’t gamble with the Nichol family dog. Peter Rabbit gets a tasty pill every month and a blood test once a year. He’s special.




More on Heartworm Risk Factors


We have a malamute and a Border collie mix. We live on the west side. Is it prudent to get the dogs tested for heartworm and on medication? Our vet says he has only seen about 6 cases in 18 years here. Also, what is your view on getting the dogs shaved over the summer?


Dr. Nichol:

The necessity for heartworm prevention is all about where you live plus your risk tolerance. Without preventatives dogs living in the southeastern part of the country are almost guaranteed to play host to a big mop of spaghetti-like worms clogging their hearts and pulmonary arteries. Living on a desert mesa means fewer carrier mosquitoes and thus a somewhat lower heartworm risk.


Mosquitoes are nasty little disease vectors and they’re getting worse. Nowadays they can even live in sheds, garages, and in closets through the winter months. But the number of canine heartworm infections varies from year to year because of differences in rainfall and mosquito populations. There will always be a reservoir of heartworm larvae because there will always be a persistent level of infection in wild animals. Your dogs will be at greater risk of they travel with you. Fortunately heartworm preventatives are safe, effective, and relatively cheap. Your veterinarian can blood test your dogs and supply them with monthly chewable tablets or a spot-on treatment called Revolution.


Regarding shaving your dogs, I think it’s great as long as their hair is at least a half inch long to prevent sunburn. Short hair will help keep them cool and they’ll look pretty dapper too. Come to think if it, I may do the same for myself.