Heartworm disease is an important pet-health issue in the United States. This disease has been reported in all fifty states, including Alaska. Since mosquitoes transmit heartworm disease, pets living in warm, wet environments, like Florida, have an increased likelihood of contracting the disease. These free-floating parasitic worms, about the size of thin spaghetti, invade the right ventricle of the heart and the nearby pulmonary blood vessels. Mosquitoes can infect dogs with hundreds of heartworms, while cats usually develop only one or two. Typically, symptoms of heartworm disease develop several years after the pet is infected, and signs of heartworm disease in dogs include coughing, difficulty breathing, exercise intolerance and a distended abdomen from heart failure. Cats infected with heartworms most commonly present with signs of chronic coughing and difficulty breathing, making it difficult to differentiate from Feline Asthma.
Your veterinarian can use several tests to detect heartworms in dogs and cats. In dogs, the most frequently used test is an occult heartworm test; this highly accurate blood test detects pieces of the adult heartworm, referred to as antigens, which circulate in the blood. Because it takes six months for an adult heartworm to develop, the test cannot detect heartworm infection in dogs younger than six months old. Therefore, only dogs seven months and older are tested for heartworm disease. Dogs should have an occult heartworm test on an annual basis to detect a heartworm infection in its earliest stage. Early detection is the key to a successful heartworm treatment.
Unfortunately, heartworm disease in cats is more difficult to diagnose than in dogs. Because cats are infected with only one or two adult heartworms and have very little heartworm antigen in their blood, the occult blood test is usually not able to detect a heartworm infection. Identifying heartworm disease in cats often requires performing chest X rays, cardiac ultrasound and heartworm antibody blood tests.
The good news is that heartworm disease is preventable by giving your pet(s) a monthly oral or topical heartworm preventative. Monthly heartworm preventatives work by destroying larval forms of the heartworm that are deposited into the pet’s blood when the mosquito bites the pet. If larvae mature in the pet’s blood stream, they will develop into adult heartworms in six to seven months. By destroying the heartworm larvae within the first month of their maturation cycle, the heartworm prevention stops adult heartworms from developing. Heartworm preventatives are extremely effective in keeping your pets heartworm-free, but owner compliance is critical to prevent this deadly disease. Owners must give their pets heartworm preventatives every month of the year. Inconsistent dosing schedules, using the wrong dosage or inadequately applying topical preventatives can result in a heartworm infection.
Dogs should start heartworm preventative medication at eight weeks old, and dogs over seven months should be tested for heartworms before administering any heartworm preventative. Dogs that have heartworms should never be given a heartworm preventative unless under the direct supervision of your veterinarian. Heartworm-positive dogs can have a life threatening anaphylactic reaction to the heartworm prevention. Cats should also start heartworm prevention at eight weeks old. Since cats are not at risk for an anaphylactic reaction to the preventatives, it is not necessary to test for heartworms before starting prevention.
In the unfortunate situation that your dog becomes infected with heartworms, treatment is available. Heartworm treatment involves a series of two or three intramuscular injections in a one or two stage therapy using a medication called Melarsamine. Common side effects of the treatment include pain and swelling at the injection site and coughing. Strict confinement and exercise restriction are required for one to two months following the administration of the heartworm treatment because fatal complications, such as pulmonary thromboembolism, may result from lack of appropriate confinement. Consult your veterinarian to determine which treatment plan is most appropriate for your dog. Unfortunately, cats cannot be safely treated for heartworms. Cats with heartworm disease are treated symptomatically to control their respiratory signs. Therapy usually involves treatment with corticosteroids, but may also require bronchodilators, oxygen therapy, cardiovascular drugs and hospitalization in more severely affected patients.
Preventative health care is the key to ensure that your pet lives a long and healthy life. Along with year-round heartworm prevention, regular wellness visits are critical to your pet’s health and welfare. Wellness exams and diagnostic laboratory tests allow your veterinarian to detect a health concern in its earliest stage, before your pet’s quality of life is compromised. To protect your pet and prevent dangerous and costly diseases, be sure to have your pet visit your veterinarian regularly.
Gainesville Animal Hospital (East and West) 2838 NW 6th St., 372 -5366; 7615 W. Newberry Rd. 332-5366, Archer Animal Hospital, 1605 SW Archer Rd. 495-2910; or visit their websites at http://gainesvillevet.com and http://archeranimalhospital.com
