Heartworm Testing

Preventive medications come in several forms, including topical applications, 6-month injectables, and once-a-month oral treatments.

Dogs six months and older are required to be tested for heartworms before starting them on any regular heartworm prevention. We check for the presence of heartworm infection by collecting a small blood sample from your pet and using a SNAP test.

If your dog’s test results come back negative, our veterinarians will start him or her on a preventive treatment that you will need to administer year-round for the rest of the animal’s life. 

A heartworm test should be scheduled annually to ensure your pet remains heartworm free. Any gap in coverage may require another heartworm test prior to restarting on a preventative.

If your dog's test results come back positive, then we will offer treatment to potentially clear your dog of heartworm disease, however, it is a lengthy and costly process.

Your pet will need to be kept calm for 30 days in order to avoid putting stress on the heart and lungs.

Cats should be put on a preventive treatment and tested as recommended by our veterinarians. Cats are not a natural host for heartworms.

However, just a few can make a cat very ill. Prevention in cats is critical because there is no approved drug treatment for heartworm infection in cats. 

When your cat receives a Feline Leukemia Virus/Feline Immunodeficiency Virus/Heartworm antigen combination test, he or she will be tested for heartworms.

If your cat tests positive for heartworms, he or she can be helped with good veterinary care and a long-term management plan.

Mosquitoes pick up larval heartworms (microfilaria) and transmit this potentially deadly parasite. Heartworms circulate in the bloodstream of infected animals, causing disease and potentially life-threatening complications. 

The heartworm in dogs that's prevalent in the United States is known as Dirofilaria immitis. Dogs, coyotes, wolves and foxes are considered to be primary heartworm hosts, but other mammals including cats and ferrets can be infected. 

Symptoms of heartworms in dogs and cats may differ. Dogs may show few or no symptoms in the early stages of disease. 

Signs of heartworm disease in dogs can include

• Mild but persistent cough
• Fatigue after moderate activity
• Decreased appetite 
• Reluctance to exercise
• Weight loss 

Signs of heartworm disease in cats can be very subtle or pronounced and may include:

• Asthma-like attacks
• Lack of appetite 
• Periodic vomiting
• Weight loss
• Coughing

In addition to the symptoms mentioned in the question above, your pet may experience complications as heartworm disease progresses. 

Pets may develop:

• Heart failure 
• Fainting
• Seizures
• Lung disease
• Appearance of a swollen belly due to excess fluid in the abdomen 
• Sudden blockages of blood flow leading to life-threatening cardiovascular collapse (in dogs)

Sadly, sometimes the first sign of heartworm disease is sudden collapse or sudden death. 

This can be avoided, simply and cost-efficiently through annual testing and preventative treatments that we provide at Marcello Veterinary Hospital.

Prevention is the best tool we have in protecting your pet's health against heartworms and heartworm disease, and it is much more cost-effective (and less stressful) than bringing your pet in for medical care after an infection has developed. 

Annual heartworm testing is also a critical aspect of your pet's healthcare and will help them to stay healthy and heartworm-free, not to mention offer you peace of mind. 

Testing for heartworm disease is designed to detect the condition in an animal before outward symptoms are identified.

The purpose of heartworm testing is to detect pre-clinical infections. In addition, giving a pet with high numbers of heartworm larvae in their bloodstream preventative medications can be dangerous as killing off large numbers of larvae can cause allergic-like reactions in some pets. 

While monthly preventatives are safe, they do not kill adult heartworms. Pets with heartworms will need further diagnostics and monitoring. 

We recommend starting puppies and kittens on heartworm prevention no later than eight weeks of age.

Dogs should typically be tested for heartworms annually. This can be done during a routine visit. 

Cats should be tested before being put on prevention and re-tested as your veterinarian advises. 

Your cat or dog may need to be tested depending on whether they've previously had preventive medication, their age, whether preventative medication doses were missed, etc. Ask your veterinarian for their guidance.

It's rare for heartworm tests to return either false positive or false negative results. 

False positive test results happen when an animal has tested positive but does not have adult heartworms in his or her body at the time of testing. Your veterinarian will likely retest your pet or perform a different test if a single test reveals a positive result.

False negative test results occur when a dog or cat is infected with adult heartworms and the test fails to detect their presence. This could be due to early infestations, very low numbers of parasites and infestation with mostly male worms.