Heartworm disease is nearly impossible to detect in its earliest stages. There are few, if any, physical signs that indicate the point when a dog becomes infected. In order to offer a dog the best possible chance for a successful recovery, veterinarians rely on information gathered from diagnostic testing and treatment methods that have been developed to identify and combat heartworm disease.

Heartworm Testing Schedule

Remind your clients that getting an animal started on preventives before an infection occurs is imperative. The initial test for heartworm requires obtaining a small blood sample, which can be drawn during routine examination or preventive care visits. The following information offers a schedule guideline for drawing blood to test for possible heartworm infections:

• Puppies under 7 months of age
  • Preventive regimen can begin without completing a test
  • It is recommended to test 6 months after the preventives are started, then yearly afterward as long as testing indicates a negative result
• Adult dogs, animals over 7 months of age
  • Dogs not previously on preventives need to be tested prior to its start.
  • It is recommended to test 6 months after the preventives are started, then yearly afterwards as long as the test result remains negative.
• Adult dogs that test negative and have been kept on a year-round preventive program:
  • It is still recommended to test for heartworm yearly. This is done as an assurance that the preventive program is continuing to work.

It is very important that clients know that their dog is at risk of infection if the preventive is not provided as directed. Loss of protection can occur in ways, such as:

• Monthly dose is missed altogether
• Monthly dose is given late
• Animal spits up or vomits the dose
• Topical preventive dose is rubbed off or the animal is bathed too soon after application.

Heartworm Testing

Type of tests used:

• Antigen test
  • Simple blood test to detect the presence of female adult heartworms by checking for proteins released into the bloodstream
  • Done when the dog is over 5 months of age
• Microfilariae test
  • Blood test that detects heartworm larvae released by adult heartworm into the dog’s bloodstream
  • Able to detect the presence of heartworm at least 6 months after the animal becomes infected.

Confirmation of a Positive Diagnosis

If the test shows positive for the presence of heartworm, a second test will be given in order to validate the diagnosis. The treatment regimen for heartworm disease is complex and expensive. It is recommended to take the second test in order to absolutely rule out any chance of inaccurate test results before initiating treatment.

Before-Care Treatment

Clients may not realize that treating heartworm infections requires more than just giving the animal a pill or a shot. Before the animal receives treatment, it needs to be examined and determined to be strong and healthy enough to undergo the procedure. If the animal has severe heartworm or additional health issues, it may require additional care. A discussion may need to focus on the need for the following:

• Tests to check for underlying conditions that could cause a problem during heartworm treatment, for example:
  • Chest x-rays may be taken to check for signs of heart disease or lung damage
  • Blood tests to make sure that the animal has no kidney or liver problems that could keep its body from clearing out the treatment drug
• Physical restrictions
  • Physical exertion may increase the chance for damage to the dog’s heart and lungs
  • Normal physical activities may need to be restricted, even if the animal looks healthy and fit
  • If the dog shows clinical signs that indicate a severe case of heartworm disease, the activity level may need to be reduced even further.

Heartworm Treatment

Once the animal is ready, veterinarians should talk with clients to provide them with the following information: 

• The treatment to be used and the guidelines that will be followed
• Risks to the animal
• Complications that could arise
• Success rate
• Additional responsibilities of owner:
  • Follow-up heartworm test schedule to confirm the elimination of heartworm
  • Importance of following a preventive regimen schedule for the rest of the dog’s life.

After-Care Treatment

Following treatment, it takes roughly 4 weeks before adult heartworms are eliminated. Dying and/or dead worms can cause a blockage which could be harmful to the dog. Clients need to know that during this time, extra care should be taken to keep the animal from overly exerting itself.

Clients should know to watch for the following abnormal signs that indicate the need for immediate veterinarian contact:

• Coughing
• Vomiting
• Diarrhea
• Depression

Following veterinary guidelines for testing will help identify if an animal has become infected. The earlier the diagnosis, the better the results of the treatment.

Need more information about heartworm disease? Contact your Covetrus representative at: 855.724.3461.