Canine Heartworm Disease - Get Ready For Spring

Heartworm disease is caused by a parasite (Dirofilaria immitis).

While dogs are considered the primary host for heartworms, Dirofilaria immitis can infect more than 30 species of animals including cats and people.

Heartworm Disease is widely distributed throughout the United States and has been found in all 50 states. All dogs and cats regardless of breed, sex, age or habitat are susceptible to heartworm infection. Eight out of one hundred unprotected dogs will get heartworm disease in the next 12 months in Chester, PA.

Transmission:

Heartworms can only be transmitted from one animal to the other by mosquitoes. Adult worms in an infected animal will produce offspring called microfilaria which circulate in the blood stream. A mosquito will feed on the infected animal and ingest blood containing the microfilaria. The microfilaria develops in the mosquito to an “infective larval stage”.

A mosquito carrying infective heartworm larvae will bite a dog or cat and transmit the larvae. The larvae then grow, develop and migrate in the body over a period of several months and then mature into adult worms. Those adult worms live in the heart, lungs and associated blood vessels.

Location:

If there is a dog and a mosquito in a location, there will be heartworm disease.

Infection:

Adult heartworms ranging from 4 to 12 inches in length reside in the heart, lungs and associated blood vessels. Their life span in dogs appears to be at least 5 to 7 years.

The number of worms infecting a dog is usually high and can range from 1 to approximately 350.

Stages and Clinical Signs of Heartworm disease:

1. 
   
   Early Infection             No Abnormal clinical signs observed
   
   


2. 
   
   Mild Disease                Cough
   
   


3. 
   
   Moderate Disease      Cough, exercise intolerance, abnormal lung sounds
   
   


4. 
   
   Severe Disease           Cough, exercise intolerance, difficulty breathing, abnormal  lung sounds, enlargement of the liver, fainting, fluid accumulation in the abdominal cavity, abnormal heart sounds, followed by death.
   
   

Diagnosis:

Heartworm is relatively easy to diagnose with a blood antigen test. A blood test can be performed at our hospital in less than 10 minutes.

Prevention:

Prevention of heartworm disease is much safer and more economical than treating an infection once it occurs. This is usually done with a chewable treat given orally once a month.

Why Test?

The heartworm prevention medication may be vomited or spit out by your dog without your knowledge, thereby, exposing your dog to heartworm disease.

Either by accident or oversight, you may forget to give the monthly prevention (or may give it late).

None of the routine heartworm tests are able to detect immature or early heartworm infestation. Your dog may have had an undetectable infection at the time of his/her last heartworm test, and therefore, could have a dangerous infection.

Treatment of heartworm disease in dogs is much safer and more effective if the disease is caught early in its course.

Dogs may show no outward symptoms. Thus, it can be next to impossible to know if a dog is infected without doing the blood test.

Recommendations:

Providence Veterinary Hospital recommends giving heartworm preventative to dogs every month. In addition, dogs should be tested once annually for heartworm disease. Only use medication provided by your veterinarian. Do not buy medication for prevention of heartworm disease on-line or over the counter.

The Providence Veterinary Hospital Blog is a publication of  Peter Herman, VMD, at the Providence Veterinary Hospital, 2400 Providence Ave. in Chester, PA.  Contact Dr. Herman at 610-872-4000 or visit us at http://www.providencevet.com/.