Cats can show symptoms with as few as one to three adult heartworms living in the heart. These signs include coughing, difficulty breathing, vomiting, lethargy, anorexia (decreased appetite), and weight loss. There can also be acute episodes of shock and respiratory distress, as well as sudden death. On physical exam, there can sometimes be a heart murmur noted.
Diagnosis in cats is difficult when compared to dogs as the standard in-hospital testing (antigen test) that is used for dogs is not always accurate in cats. This is because cats tend to have only a few worms. A send-out test to the reference laboratory (antibody test) may be more useful, but a negative result still does not rule out heartworms. Other helpful diagnostics include radiographs (x-rays), echocardiogram (an ultrasound of the heart), complete blood count (CBC), internal organ function testing (chemistry), and fecal exam (to rule out parasites that can live in the lungs and cause coughing).
Prevention is the same as that used in dogs and includes monthly oral medications such as heartgard or trifexis, or topical solutions such as advantage multi or revolution. A six month injection called Proheart is available in dogs, but a similar product is not available in cats at this time.
Though dogs can undergo risky heartworm treatment (a series of two to three injections of a drug called immiticide to kill the heartworms in the span of a month or two), no such treatment is available in cats. Treatment is limited to monthly use of preventive medications to prevent further infestation and shorten the life of the heartworm. Supportive care includes bronchodilators to help pets breathe easier and steroids to reduce inflammation.
Written by Dr. Laura Theobald
Lap of Love Veterinary Hospice