Heartworms are transmitted to dogs and cats by mosquitoes. Heartworm disease develops when a dog or cat is bitten by a mosquito carrying microscopic heartworm larvae (juvenile worms) of a parasite called Dirofilaria immitis. As a mosquito feeds, these larvae are deposited on the pet’s skin and quickly penetrate the skin to begin their migration into the pet’s bloodstream. The larvae migrate through the bloodstream and tissues, eventually reaching the heart and lungs. Adult heartworms can grow 10 to 12 inches in length and make their home in the right side of the heart and pulmonary (lung) arteries, often causing lung disease and heart failure.
Heartworm disease is a major health problem for dogs living in the United States and throughout the temperate and tropical regions of the world. Once thought to be only a disease of dogs and other wild canids (foxes, wolves, and coyotes), recent studies indicate that heartworm infection in cats is more common then ever believed. Without the protection of a heartworm preventive, your pet couldget heartworm disease – a potentially deadly illness of the heart and lungs. While there is treatment available for dogs that get infected with heartworms, treatment can be expensive, difficult and can lead to serious side effects. However, there is no approved treatment for feline heartworm infection. Therefore, heartworm prevention given to your pet once monthly year-round is strongly advised to protect your pet from contracting this potentially fatal disease.
The good news is that heartworm disease is essentially 100% preventable! Various heartworm preventives are available, including monthly oral and topical formulations. Heartworm preventives are effective when given properly and on a timely schedule. All heartworm preventive medications work by killing heartworm larvae acquired during the previous month and do not continue to protect pets from future infection. This is why it is important to administer heartworm preventives to your pet once every month year-round. All approved heartworm preventives are highly effective, safe, easy to use, relatively inexpensive, and often provide treatment for additional parasites. Please remember, it is your responsibility to faithfully maintain the preventive program you have selected in consultation with your veterinarian. The best way to eliminate the risk of heartworm infection in your pet is to institute a year-round prevention program. Prevention is always more safe and affordable than treating dogs with adult heartworm infections.
Clinical signs of heartworm disease in dogs and cats can vary. Recently infected dogs may show no signs of the disease. Some common signs of heartworm infection in dogs include coughing, difficulty breathing, exercise intolerance, decreased appetite, weight loss and lethargy. Left untreated, heartworm disease may be fatal to your dog as it can cause “caval syndrome”, a sudden obstruction of blood flow through the heart and lungs, or development of heart failure. Signs of heartworm disease in cats range tremendously, from mild and subtle in appearance to severe and life threatening. Symptoms of feline Heartworm Associated Respiratory Disease (HARD) can mimic many common diseases of cats such as hairballs, asthma, or pneumonia. Signs of disease may include loss of appetite, sluggishness, intermittent vomiting (not associated with eating), coughing, wheezing, and respiratory distress. The presence of just one heartworm may result in permanent damage – or even death – to a cat or kitten. In fact, sudden death may be the first and only sign of heartworm infection in some cats.
Detecting heartworm disease in both dogs and cats involve simple blood tests; however, heartworm disease in dogs and cats do have some differences. Numerous blood tests are available for detecting heartworm infections in dogs, and your veterinarian will perform the test most appropriate for your dog. Tests cannot consistently detect infection until heartworms are at least six to seven months old. Moreover, tests are unable to detect infections if only male worms are present or if there are only one or two female worms. All dogs more than six months of age should be tested for heartworm infection before starting a preventive program. Annual heartworm testing is recommended for monitoring the success of any heartworm prevention program in dogs. If your dog tests positive for heartworm disease, then your veterinarian will need to perform a thorough physical examination, blood tests (e.g. a CBC and chemistry profile), and radiographs to assess your dog’s level of risk and stage of disease. To reduce complications, your veterinarian will educate you in great detail before beginning treatment. While the heartworm medication melarsomine dihydrochloride (Immiticide) is extremely effective in eliminating adult worms, some dogs will not be completely cleared with a single course of treatment. Testing is recommended six months after treatment to ensure all heartworms were killed. If tests are positive, additional adulticidal treatment may be indicated.
For the feline population, two blood tests are currently available to assist in diagnosing heartworms in cats. Unfortunately, test results do not always produce clear answers, even with professional interpretation. Positive tests indicate heartworms were present, but do not necessarily mean the pet is still infected. Moreover, since tests cannot diagnose very early infection or those infections cause by only one or two worms, negative test results are not always accurate. Even when heartworm disease is highly suspected, confirming a diagnosis through testing in the cat can be difficult. Multiple blood tests along with chest x-rays and ultrasound imaging of the heart and lungs are often needed to make a diagnosis. Since no safe treatment exists for the elimination of heartworms in cats, the best option is the routine use of heartworm preventives to inhibit development of infection.
All dogs are at risk for heartworm disease no matter where they live. Cats are at risk wherever dogs are at risk. The prevalence of heartworm disease has increased steadily since it was first identified. It now affects dogs in all 50 states. Even indoor cats can get heartworm disease. Some people think that indoor cats are safe from heartworm disease, but mosquitoes can get indoors, and cats can get out. Please visit the website of the American Heartworm Society (www.heartwormsociety.org) for more in-depth information regarding prevention, diagnosis, and treatment of heartworm disease.
We strongly recommend heartworm preventives for your pet once monthly year-round. Here at Hope Animal Medical Center, we carry a variety of products that can help you and your pet. Below is a brief explanation of the different products we have available.
Heartgard = Ivermectin/Pyrantel pamoate, oral heartworm prevention plus intestinal parasite control (hookworms and roundworms), lasts 1 month
Trifexis = Spinosad/Milbemycin Oxime, oral flea control plus heartworm prevention, intestinal parasite control (hookworms, roundworms, and whipworms), lasts 1 month (DOGS ONLY)
Iverhart Plus = Ivermectin/Pyrantel pamoate, oral heartworm prevention plus intestinal parasite control (hookworms and roundworms), lasts 1 month (DOGS ONLY)
Revolution = Selamectin, topical flea/tick control plus heartworm prevention, lasts 1 month
Advantage Multi = Imidacloprid/Moxidectin, topical flea control plus heartworm prevention, intestinal parasite control (hookworms and roundworms), and earmite treatment/prevention, lasts 1 month
Revolution = Selamectin, topical flea control plus heartworm prevention, intestinal parasite control (hookworms and roundworms), and earmite treatment/prevention, lasts 1 month.
Heartgard = Ivermectin, oral heartworm prevention plus hookworm intestinal parasite control, lasts 1 month