Q. I have a 5-year-old Labrador Retriever mix, and she has never been treated with any kind of heartworm medication or preventive. Is it necessary to start her on something and if so, how should I go about it?
A. Until you have actually seen a dog's heart full of spaghetti-sized worms, writhing and wiggling, you cannot appreciate the significance of heartworm disease.
Heartworm disease is a life-threatening risk to dogs anywhere there are mosquitoes. It is spread when mosquitoes bite an infected dog that has microscopic worms (microfilaria) in his bloodstream. When the mosquito bites another dog, the microfilaria are injected into the bloodstream, where they develop into large adult worms and migrate to the heart, where they live. There, they wreak havoc with the heart and lungs, causing problems from coughing to blood clots to severe allergic reactions.
Thankfully, humans cannot get this disease.
Once a dog is infected with heartworms, he requires treatment with a powerful medication with potentially serious side effects to treat the disease. This assumes that diagnosis comes before the dog is seriously sick.
To prevent heartworms entirely, dogs can be put on a monthly medication that kills any of the microfilaria before they develop into adult worms. The preventive does not kill adult worms. All dogs in areas with mosquitoes should be on this preventive medication.
Before dogs are put on heartworm preventive, they should be tested to make sure they are not already infected. Puppies can be put on heartworm preventive without testing.
One major benefit of heartworm preventive is that it also kills other intestinal parasites such as roundworms and hookworms. For this reason, I recommend it for all dogs, even in areas where there are minimal mosquitoes.
Go to your vet, get your dog tested, and get started on the preventive medication. It is one of the great medications of all time for dogs.
Best,
Jon Geller, DVM
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