What is a heartworm?

A heartworm is a thin “spaghetti-shaped” worm of length varying from 6 to 14 inches that lives within the heart of dogs. Heartworms live in the chambers of the heart where blood is pumped through and the heart valves must work. Their presence interferes with blood flow and the function of the heart valves, resulting in heart failure.

How Does a Dog Get Heartworm?

The large worms within the heart produce thousands of tiny worms (larvae) that are very abundant in all circulating blood. Mosquitoes  ingest the larvae when taking a blood meal. Upon biting another dog these worms will gain entrance into the new host. After approximately 4 months these tiny worms make their way to the heart. In another 2 months they grow to adult size and begin to reproduce.

What are the Signs of Heartworm Infection?

In cases where a dog may have very few worms there may be no clinical symptoms. Diagnostic tests performed by your Veterinarian will detect this type of infection.
In cases where there are many worms interfering with heart function, clinical signs relate to those of heart failure. Signs may be coughing, shortness of breath, and lack of exercise tolerance. As with other forms of heart disease, that related to heartworm is very serious and can result in death.

Can Heartworm Disease be Treated?

There are treatments to eliminate worms from infected dogs. These treatments are involved, dangerous, and expensive.  Furthermore, a heart that has been damaged by the worms will not return to its normal health. Prevention of the infection is thus much more practical and important.

Can I Prevent Heartworm Infection?

Heartworm infection can be prevented. A prevention program involves regular testing to ensure that the pet is free of adult worms. The pet is then placed on a monthly medication to kill the immature worm before they cause disease.  Recent research has indicated that yearly testing may not be necessary depending on the prevalence of  heartworm disease in various areas.  Pet owners would best be advised to consult with their veterinarians to find out more about optimal heartworm prevention programs in their area.

Should my Dog be on Heartworm Prevention?

Heartworm disease is a real threat to the well being of our dogs. Because of the lack of early clinical signs and the complexity and poor response to treatment.  We feel that preventative care is the only real alternative.  In Southwestern Ontario, heartworm prevention is typically given from June through to November.  In warmer climates however year round protection may be required.  Once again,  concerned pet owners would best be advised to discuss the prevalence and risks of heartworm in their specific geographical location.