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Heartworms are parasites that invade a pet’s circulatory system and heart. The adult heartworms produce offspring called microfilariae, which circulate in the infected pet’s blood. Mosquitoes feed on an infected pet, serve as a host while the microfilariae mature for approximately two weeks, then transfer infective heartworm larvae when they bite healthy pets. These heartworm larvae migrate through the pet’s tissues and circulatory system and reach the heart in five to six months, where they arrive as small worms about two inches in length. Once they are in the heart, the adult worms reproduce and grow. They may reach a length of twelve or more inches and may stay in a pet’s heart for several years.

The worms grow and multiply, infesting the chambers on the right side of the heart and the arteries in the lungs. They can also lodge in the veins of the liver and the veins entering the heart. The first sign of heartworm infestation may not manifest for a year after infection, and even then the soft cough that increases with exercise may be dismissed as unimportant by the owner. But the cough worsens and the dog may actually faint from exertion; he tires easily, is weak and listless, loses weight and condition, and may cough up blood. Breathing becomes more difficult as the disease progresses. The progression is traumatic: the dog’s quality of life diminishes drastically and he can no longer retrieve a Frisbee or take a long walk in the park without respiratory distress. Congestive heart failure ensues, and the once-active, outgoing pet is in grave danger.

If you live in Montana year round, we recommend giving your dogs heartworm prevention tablets (Iverhart Max, Heartguard Plus, or Interceptor*) once a month from May through October. If you travel outside the state with your pet or live in a warmer climate for part of the year, you may need to extend your heartworm prevention program beyond those six months, and screen for heartworm on a more frequent basis. 

A heartworm screen is required every other year before a veterinarian can dispense the preventatives. This involves taking a 3-drop blood sample from your pet & running an 8-minute test. The screen ensures that we become aware of infected pets in the area, since it takes up to 7 months from the time of infection for the worms to mature enough to show up as positive on the test. It is especially important to screen your pet because giving the preventative to a dog already infected with heartworm can be life threatening. Please call today to schedule a heartworm screen or to order preventatives.
Intestinal Parasites


Just about every pet is susceptible to intestinal parasites, in fact, kittens and puppies can become infected with worms when they are still in their mother’s womb.  Very young pets are the most vulnerable, however, animals of any age can contract parasites that live and grow in their intestines, and they can pass them to other pets easily.  The most common types of these parasitic worms are Roundworms and Hookworms, though we also see many instances of Tapeworms and Giardia. Once an animal is infected, they can contaminate their surroundings by passing eggs or larvae in their feces (waste). Because pets will pass feces anywhere, they may contaminate a large area quickly. These eggs and larvae are resilient and can survive in areas such as parks, playgrounds, and yards – even inside homes. 

People are susceptible to these worms as well, through direct contact with infected feces. This usually happens by chance ingestion of contaminated soil, sand or plant life.  So take care to wash your hands thoroughly after petting your animal, and avoid letting them lick your face. Children are more vulnerable to infection than adults, so supervise them closely and teach them to wash their hands after handling their pet.

 Most pets will not show any sign of infection. However, some do. Signs may include vomiting, loss of appetite, or severe weight loss. Heavy infections in young puppies and kittens may be fatal. A Fecal testing is how we determine whether there are any parasites present in the intestines.  We recommend fecal testing at least once a year, during your pet’s annual wellness visit. You may bring in a stool sample from home (it needs to be recent), or we can collect a sample while your pet is at the office.

We recommend strategic deworming for all new kittens and puppies. This begins with an initial dose of deworming medicine, and a subsequent dose of medication in 2 weeks, followed by a fecal test to ensure complete deworming.  Strategic deworming can be effective health care for adult pets as well, especially if you think that your pet has access to rotting animal carcasses and/or fecal matter. We currently carry a topical dewormer for cats that is applied to the back of the neck and treats/prevents intestinal worms (tapeworms, roundworms, & hookworms) in just one application.