The Sweetest “Caution” Dog Ever Who Just Happens to Have Heartworms (Dirofilaria immitis)

Pitbull - Kim

Image via Wikipedia

The perks of working at a vet hospital when you have a science based blog, is that it’s really hard to run out of material. At the moment, we have a pit bull waiting for adoption who is reported to be dog and cat aggressive and is also heartworm positive. He’s probably the sweetest dog ever (imagine the dog in the picture, only black), he just doesn’t seem to know how strong he is, which he displayed this morning by jumping all over me.

I’m sure most people have heard about heartworms and that they’re dangerous to our pet’s health but people may not know just how much.

– Scientific Classification –

Dirofilaria immitis is the canine form of heartworm, with other definitive hosts being wild canids and ferrets. Cats are an abnormal host. The worms are long and thin and the females can reach 28 cm. Adult worms are found mostly in pulmonary arteries and also in the righthand portion of the heart. There is a 6 month prepatent period with a minimum of 2 weeks inside the mosquito (who serves as the vector). Adult worms can live for 5 years.

Some cases of heartworms can be asymptomatic. Mild to moderate disease can result in a chronic cough and decreased exercise tolerance. Moderate to severe cases can lead to syncope (fainting), hemoptysis (coughing up blood), pulmonary hypertension, right heart enlargement and failure.

Diagnosis is based on an antigen test (for adult females), which is the most sensitive option. A dog can be tested after the 6 month prepatent period or just prescribed a preventative. Preventatives that can be prescribed are macrolides and are a monthly product. They kill heartworms acquired in the previous month.


The pit bull in our care doesn’t seem too bothered by his disease as of late. Hopefully he gets adopted by someone who can handle him soon!

Also, an update on the Old English Sheepdog :: she wasn’t in the treatment room when I worked today so hopefully she went home and is feeling better!

:: Information from this post is from my notes from an Introductory Parasitology class taught by Dr. Zajac at Virginia Tech ::

Parasite Terminology

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