Heartworm disease is a serious and potentially fatal disease seen mostly in dogs due to the bite of an infected mosquito. These worms live in the heart, lungs, and blood vessels of the pets they infect and cause damage to the heart, lungs, and other vital organs. Heartworm disease can be seen in cats where it causes heartworm associated respiratory disease (HARD).

Signs of heartworm disease in dogs may include a persistent cough, decrease in exercise, more frequent fatigue, decreased appetite, and weight loss. If these symptoms persists and are left untreated, dogs may develop heart failure and ascites (fluid in the abdomen). End stage signs of heartworm disease occur when a large number of worms block blood flow to the heart causing life-threatening cardiovascular collapse (caval syndrome).

Heartworm associated respiratory disease (HARD) in cats typically shows very subtle signs including a low grade cough, asthmatic type episodes, occasional vomiting, weight loss, or a decrease in appetite. Severe signs may include ataxia (difficulty walking), fainting, seizures, or ascites. Unfortunately, the most common sign associated with heartworm associated respiratory disease in cats is sudden death.

Testing for canine heartworm disease requires a small blood sample. If your puppy is started on a heartworm preventative prior to 6 months of age, no test is required. Puppies over 6 months of age should have a negative test before starting prevention along with a follow-up test in 6 months to confirm the negative test. This is due to a risk of an adverse reaction that may occur if a preventative is given to a dog with heartworm disease. After your dog is started on heartworm prevention, a yearly screening test is recommended to ensure that the medication is effective. Testing in cats is much more difficult due to the smaller number of worms likely seen in cats. Blood tests may be used, but other diagnostics such as x-rays and ultrasound may be required. Because of the difficulty in testing and the lack of an approved treatment for heartworms in cats, prevention is critical.

Heartworm disease is prevented with the use of a monthly oral medication that is used to kill immature worms before they can cause damage, or with the use of an injectable medication that works similarly for 6 months with each injection. Prevention in cats involves a topical medication used monthly to prevent injection. Due to the difficulty in testing and the lack of an approved treatment for heartworm in cats, prevention is crucial to decrease the likelihood of an infection.

If the screening test for your dog is positive several steps are taken to ensure the best treatment possible. The screening test will be confirmed via testing from an outside laboratory. We recommend that you begin restricting exercise in an effort to decrease the damage done by the circulating heartworms. Once your dog’s condition is stabile, a treatment protocol will be instituted consistent with guidelines set forth by the American Heartworm Society. Six months after the completion of treatment, a heartworm test will need to be performed to confirm a negative test before beginning heartworm prevention.

If your cat tests positive for heartworms additional diagnostics will need to be performed. Circulating heartworms in cats can affect multiple organ systems and not just the lungs and cardiovascular system. Additional diagnostics may include an x-ray, complete blood count, and possibly additional blood test and/or an ultrasound. Unfortunately, there are no approved treatments for heartworm disease in cats but vigilant monitoring and supportive veterinary and lessen potential complications. Prevention is key in cats, especially if your cats has symptoms related to heartworm disease.

If you have any questions or concerns about your pet, do no hesitate to give us a call. More information can be found at the American Heartworm Society website at www.heartwormsociety.org