Quick Review

What Is Heartworm Disease?

Canine heartworm disease is a potentially deadly infection,caused by worms (Dirofilaria immitis) that may grow to be 14-inch-longadults. These worms live in the right side of the heart andarteries of the lungs. Dogs of any age and breed are susceptible toinfection. Heartworm infection can cause potentially serious damageto these arteries, eventually leading to heart failure, and insevere cases, damage other organs such as the liver and kidneys. Inextreme cases, a dog can be infected with several hundredheartworms. Cats are also susceptible to the disease.

Coinciding with mosquito season, heartworm disease is spread bymosquitoes that become infected with microfilariae while taking a blood meal from an infected dog.The microfilariae mature into the infective larval stage within themosquito. When the mosquito then bites another dog, cat, orsusceptible animal, it then passes the larvae into the animal’s blood stream through the bite wound,resulting in heartworm infection. It then takes approximately sixmonths for the infective larvae to mature into adult worms that can live for five toseven years in the dog.

What Are the Signs of Heartworm Disease?

For both dogs and cats, clinical signs of heartworm disease maynot be recognized in the early stages, as heartworms tend toaccumulate gradually over a period of months and sometimes yearsand after repeated mosquito bites.

In dogs, recently infected animals may exhibit no signs of thedisease, while heavily infected animals may eventually showclinical signs, including mild, persistent cough, reluctance tomove or exercise, tiredness after only moderate exercise, reducedappetite, and weight loss.

Cats may exhibit clinical signs that are very non-specific,mimicking many other feline diseases. Chronic clinical signsinclude vomiting, gagging, difficulty breathing or rapid breathing,lethargy and weight loss.

How Do You Detect Heartworm Disease?

Detection of heartworm infection in apparently healthy animalsis usually made with blood tests for microfilariae or a heartworm substance called an “”antigen,”” although neither test is consistently positive untilabout seven months after infection has occurred.

Heartworm infection may also be detected through x-ray and/orultrasound images of the heart and lungs, although these tests areusually used in animals that are known to be infected.

How Can I Prevent Heartworm Disease?

Because heartworm disease is completely preventable, the AHSrecommends that pet owners take steps now to talk to theirveterinarian about how to best protect their pets from thisdangerous disease. According to the AHS, heartworm prevention issafe, easy and inexpensive compared to treating a dog or cat afterworms have matured into adults. While treatment for heartwormdisease is possible, it is a complicated and expensive process,taking weeks for infected animals to recover.

There are a variety of options for the prevention of heartworminfection for dogs, including daily and monthly tablets andchewables, or monthly topicals. For cats there are monthly tabletsor a topical solution. All of these methods are extremely effectiveand when administered properly on a timely schedule, heartworminfection can be completely prevented.

What Is the Treatment for Heartworm Disease?

In dogs, most cases of heartworm disease can be successfullytreated with a drug called an adulticide that is injected into the muscle. A series ofinjections are given to dogs who have received a thoroughexamination to assess the risk of the treatment. Hospitalization isusually recommended during treatment, but treatment can also beperformed on an outpatient basis. During the duration of therecovery period lasting one to two months, it is recommended thatexercise for the pet be limited to leash walking, decreasing therisk of partial or complete blockage of blood flow through thelungs by dead worms.

Dogs in heart failure and those with cavalsyndrome (a form of liver failure) require special attention.Reinfection is prevented by administering a heartworm preventative.Some preventatives also eliminate the microfilariae if they are present.

Currently, there are no products in the United States approvedfor the treatment of heartworm infection in cats. Cats have provento be more resistant hosts to heartworm than dogs, and often appearto be able to rid themselves of infection spontaneously. In severecases of the disease, veterinarians will treat an infected cat withsupportive therapy measures.

This is intended as a short summary. Please refer to the canineand feline section information, or glossaryfor more detailed information.


Comments are closed.