With the approach of spring and warm weather, the Chicago Veterinary Medical Association (CVMA) is alerting dog and cat owners about the importance of heartworm disease prevention. Heartworm, a serious disease that is spread by mosquitoes, is far better to prevent than to treat.

Heartworm can be found in both dogs and cats, but is most common in dogs. As its name implies, heartworms live in the dog or cat’s heart and adjacent blood vessels. Adult heartworms produce offspring – microfilariae – which circulate in the infected animal’s blood. When a mosquito bites an infected animal, it obtains and carries blood with microfilariae. These microfilariae mature within the body of the mosquito to become infective larvae – the necessary evolutionary step in transmitting heartworm. When these larvae infected mosquito bites another cat or dog, the infection is transmitted.

Preventative drugs are available to pet owners as part of their routine care. The drugs are available in a variety of formats and when administered monthly prevent the larvae from developing into adult heartworms. Advances in veterinary research have created medications and procedures that have greatly improved the treatment of heartworm disease, but only in dogs. Prompt detection and early treatment are essential to successfully cure the disease.

The American Heartworm Society recommends an annual blood test to screen for heartworm disease prior to administering year-round preventive medication. Severe or even fatal reactions may occur if preventative drugs are given to dogs already infected with heartworm, so testing first is imperative. Radiographs, x-ray films and other, sophisticated laboratory tests may also be used to detect heartworm disease. Pet owners should also be aware of the following symptoms which may indicate their dog is suffering from heartworm: difficulty breathing, coughing, listlessness/lethargy, weight loss, and a rough haircoat. If not detected and properly treated, heartworm will lead to congestive heart failure and death.

While seen less frequently in cats, heartworm poses a much greater danger of sudden death. Currently, there are no medications approved to treat feline heartworm. Attempts have been made to use canine medications, but they resulted in serious side effects including lung failure and death. Currently, the approach is to treat the disease’s symptoms, in the hopes that the animal will outlive the life cycle of the worms (which is about two years in a feline). Symptoms of feline heartworm include: coughing, rapid breathing, weight loss and vomiting. However, these symptoms are very similar to, and often mistaken for feline asthma. Diagnosis of feline heartworm is difficult, and requires outside laboratory tests, radiographs and ultrasound studies.

Cat owners should be aware that, like dogs, there are monthly heartworm prevention drugs available in both topical and tablet form for felines. They are recommended for both indoor and outdoor cats and are available through your veterinarian.

The Chicago Veterinary Medical Association (CVMA) is an association of more than 1000 veterinarians and 4000 support staff who lovingly assist Chicago area pets and their families. Since 1896, the CVMA has been dedicated to the health and well-being of animals; providing its members with nationally recognized continuing education and professional services; and the community at large with public awareness and educational programming regarding the importance of appropriate pet care.