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Pet Wellness

The Realities of Heartworm Disease


dog in grass

Heartworm disease is found in many areas of the world, including the United States. It is a serious disease that can be fatal, even with treatment. It is caused by worms that can grow up to a foot long, and live in the heart, lungs, and associated blood vessels of affected animals. Over time, the worms will cause severe lung disease, heart failure, and damage to other organs, such as the kidneys. Dogs and other species such as wolves, coyotes, and foxes are the primary hosts of heartworms. Since coyotes and foxes are often found in urban and suburban areas, they serve as a potential reservoir of infection for pet dogs. Cats can also be infected by heartworms, though they are affected differently than dogs.

Unlike many other common parasites, heartworms require two separate hosts to reach maturity. Immature heartworms are carried between dogs by mosquitoes. When an infected mosquito bites a dog, the larval stages are left on the skin of the dog and enter the dog’s body through the wound left by the mosquito. It takes 6 months for the larvae to mature into adult heartworms if untreated. Adult worms typically live from 5 to 7 years in dogs and 2 to 3 years in cats. As female worms reproduce, the number of worms will increase with time, then there will be more worms to spread the disease to other animals if an infected animal is not treated.

Even though Minnesota’s climate does not support a year-round population of mosquitoes, we are seeing more cases of heartworm disease in the last several years. There are likely many reasons for this. Dogs travel with their owners more now than ever before, and many will join their owners in warmer climates during the winter months. Local animal shelters often will bring in dogs and cats from the south, where many shelters cannot accommodate them. Dogs are typically heartworm tested prior to transport, but due to the life cycle of the heartworm, there is a window where dogs may test negative but still have heartworms. Heartworm in these dogs may go undetected for several months or more, allowing them to serve as a source of infection for other dogs. Still another cause is inadequate prevention. Many pet owners believe that heartworm prevention only needs to be given during the summer months, leaving their pet vulnerable during the late spring and early fall. While mosquitoes may not be as numerous during those times, they are still active.

Heartworm disease is diagnosed through a blood test, and can be easily prevented in dogs by administration of monthly preventive medication, such as Heartgard Plus. Dogs typically enjoy the chewable, flavored medication and most will readily eat it. We recommend administering preventive medications year-round for a few reasons. The medication will protect against the common intestinal parasites roundworms and hookworms. Year-round administration will insure dogs are protected if we have an early spring or warm fall weather, and will also protect “snowbird” dogs that travel with their owners.  It will also help prevent resistance to the preventative.

Treatment of heartworm disease is possible, but is much more expensive and risky than the monthly preventive medication, and requires strict rest for several months during the treatment period, which is typically not easy with young, active dogs.

Has your dog been heartworm tested in the last year? If not, please contact us to discuss testing and protecting your dog against this serious but preventable disease.


What Symptoms Do Infected Animals Exhibit?


Most dogs infected with heartworms do not show any signs for a long time.  Eventually, as the disease progresses, the animal may exhibit such signs as coughing, weakness, shortness of breath, and exercise intolerance.  The signs depend on the number of adult heartworms present, the location of the worms, and the length of time the worms have been present. Infected cats may be asymptomatic or may exhibit signs of respiratory distress, such as coughing or wheezing.


How Is Heartworm Disease Diagnosed And Prevented?


Heartworm disease is diagnosed with a blood test that detects antibodies to the parasite in cats and antigen produced by the worms in dogs. We recommend testing all dogs once a year, and using healthy and heartworm preventative once a month all year. We recommend testing cats that go outside, and any cats that show signs of respiratory distress or coughing.


Feline Leukemia Virus Infection


General information

Feline leukemia virus (FeLV) is one of the most common and destructive of all cat viruses. It is highly contagious and is spread primarily by saliva during catfights, grooming or mating. The virus may also be spread by blood, urine and feces. Kittens may become infected while still in the womb, at birth, or during nursing.

Currently, there is no effective treatment for cats infected with FeLV. Of the cats persistently infected, about 25% will die within one year, and 75% will die within three years. Some may live longer, but tend to have various chronic illnesses.


There are no signs specific for FeLV infection, because it can affect any organ system. The main effect of the virus is to disrupt the cat’s immune system. While anemia is the most common disorder caused by the virus, cancer and various other diseases are common. Some disorders commonly associated with FeLV include: chronic GI or respiratory disease; chronic infection of the mouth, gums and tongue; chronic eye disease; frequent or chronic skin disease and frequent or chronic urinary tract infections.


Outdoor cats (ie those exposed to other cats) are at risk for developing FeLV infection. Testing and vaccination before exposure to the virus is the best means of preventing FeLV infection. The vaccination protocol is two initial vaccines one month apart, followed by yearly boosters. Without vaccination, isolation from other cats is the only means of prevention.


How Is Heartworm Disease Treated?


Dogs that test positive for heartworm disease are treated with a series of injections that kill heartworms. The immature heartworms are killed with an oral dose of Ivermectin. During the treatment, owners are advised to keep the dog very quiet, with no strenuous exercise, which could hinder recovery and exacerbate the clinical signs of illness. We prescribe an antibiotic and prednisone to decrease inflammation as well to treat Wohlbachia, a parasite that often accompanies adult heartworms. Other medications are prescribed based on the degree of damage to the heart and blood vessels sustained as a result of infection. Cats are generally treated with a combination of prednisone, and a bronchodilator.