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Heartworms

Keep your dogs on heartworm preventative year round. Heartworm prevention is available in pill format and is prescribed by your vet.

Heartworm disease is a serious and potentially fatal condition caused by parasitic worms living in the arteries of the lungs and occasionally in the right side of the heart of dogs. Heartworm infection in apparently healthy animals is usually detected with blood tests for a heartworm substance called an "antigen" or microfilariae.

Heart-Healthy Tips for All Dogs

  1. If you have not already, have your dog tested for heartworms. If he tests positive, have him treated immediately. Heartworms will not go away by themselves.
  2. When you are certain your dogs are heartworm-negative, make sure they are all on a recommended heartworm preventative. Make it a “first of the month” routine to administer their preventative.
  3. Don’t put off your vet’s annual exam reminder; schedule an appointment for a checkup every year. As with humans, many potential issues, including the detection of heartworms, can be “nipped in the bud” at that annual exam. Your vet will probably want to re-test your dog for heartworms annually, even if he is on a preventative.
  4. Keep your dog at a healthy weight. Feed her a premium dog food that’s wheat and corn-free (she doesn’t need those extra carbs either), resist the temptation to over-treat, and limit her consumption of “people food”.
  5. For most dogs, the words “Want to go for a walk?” are the greatest in the world. Don’t cheat your dog out of this wonderful exercise, for his sake as well as yours. Proper leash walking is as mentally exhausting to a dog as it is physically exhausting, and a tired dog is a good dog! Cesar Millan recommends a 45-minute power walk first thing in the morning.

Everything You Wanted to Know (or Not!) About Heartworms. Yuck. Take Our Quiz.

  • True or False: Heartworms are contracted through flea bites.

False. The only way for a dog to contract heartworms is through the bite of an infected mosquito. Unfortunately, there’s no way to tell whether a mosquito is infected, which is why prevention is critical. How likely is your dog to contract heartworms if he’s not on preventatives? C’mon! We live in Texas, Mosquito Capital of the World. Your dog is at risk. Period.

  • True or False: Puppies can’t get heartworms. 

True and False. Typically, young puppies are at lower risk for heartworms, primarily because the incubation period for heartworms is about as long as true puppyhood. However, as we all know, puppies grow up fast – and if you are adopting a puppy from a shelter or rescue organization, the puppy’s age may just be an educated guess. Best course of action: Put your pup on heartworm preventative right away – she can start taking it as early as 4 or 5 months old.

  • True or False: If my dog has heartworms, he can pass them to my other dogs. 

False. Remember the mosquito thing – that’s the only way heartworms can be contracted.

  • True or False: Heartworms mature quickly and it will be easy to tell when my dog has contracted them. 

False. Once a dog has been bitten by an infected mosquito, it takes about seven months for the larvae to mature into adult heartworms. They then lodge in the heart, lungs, and surrounding blood vessels and begin reproducing. Adult worms can grow up to 12 inches long, can live 5-7 years, and a dog can have as many as 250 worms in his system. They are insidious because often there will be no symptoms. Other times a dog may develop a cough and will have difficulty exercising; he will become winded more easily. If the heartworms are left untreated, most dogs will die. Bottom line: Don’t guess. Get your dog tested.

  • True or False: Heartworm treatment includes up to several months of crate rest. 

True. Heartworm treatment actually entails injecting a poison (arsenic-based) into the dog’s blood stream to kill the worms that are encircling the heart and lungs. After treatment, the worms begin to die, and as they die, they break up into pieces, which can cause a blockage of the pulmonary vessels and even death. Yeah, how gross is that? A dog in treatment has to be kept quiet during the treatment and for several weeks afterward so that the worms that have died and broken up can filter through the blood vessels.

  • True or False: Heartworm preventative is expensive. 

False. Heartworm treatment is expensive – sometimes running into the $1,000 range. But for the cost of two lattes at Starbucks, you can arm your dog monthly with an ivermectin-based product and keep those nasty parasites away.

  • True or False: Once my dog has been treated for heartworms, he is immune to them. 

False. If your dog has undergone treatment for heartworms, he must immediately begin taking a heartworm preventative and stay on it for the rest of his life – unless you happen to live on the moon, or some other place that doesn’t have mosquitos.

  • True or False: It’s okay to skip the preventative in the colder months. 

False. The American Heartworm Society (bet you didn’t see that one coming!) recommends year-round heartworm prevention. Miss even one or two months and your dog could become infected. Another reason not to stop is that many of the preventatives today also include an intestinal parasite control for roundworms, whipworms, or tapeworms – an added bonus!

Excerpted from Heartworms in Dogs: Facts and Myths by Sandy Eckstein, with help from Sheldon Rubin, 2007-2010 president of the American Heartworm Society.