Heartworm—Canine

Heartworm is transmitted to dogs by the bite of an infected mosquito. Dogs typically do not have clinical signs in the early stages of infection, but if infection remains undiagnosed, heartworm infection can cause severe illness and in some situations can be fatal. Therefore, prevention and routine screening for heartworm infection are critical components of the canine health plan.

 

 
Heartworm—Canine
In the early stages, heartworm has no clinical signs and it may not be detectable via laboratory tests for up to six months.

 

Clinical signs and physical examination findings that can develop include:

  • Persistent cough
  • Exercise intolerance
  • Dyspnea
  • Abnormal lung sounds
  • Hepatomegaly
  • Syncope
  • Ascites
  • Abnormal heart sounds
  • Death

 

After the prepatent period, the adult stage of the infection can be determine by detecting heartworm antigen in the blood. A less sensitive means of diagnosis is to identify microfilariae in the dog’s blood.

 

Radiography of the chest and electro- or echocardiography may also be helpful in making a diagnosis, and may indicate the severity of the infection.

 

 

 

View/print the Canine heartworm algorithm (PDF)

The best approach to heartworm infection is to avoid infections.  This can be achieved by using one of the numerous, highly efficacious heartworm preventatives on the market.

 

The goal of adulticide treatment is to eliminate any adult heartworms and circulating microfilariae, while minimizing any negative side effects of the therapy. 

 

To confirm the treatment efficacy, re-check for the heartworm antigen after six to twelve months.

 

For more details, see the American Heartworm Society or the Companion Animal Parasite Council.