Welcome to our fifth case of the month! This month we have a dog with an unexplained cough. If you want to see other cases, scroll down to the bottom of the page.
 

HOME IS WHERE THE HEART IS

 

HISTORY

Bumpy was a young dog (about 9 months old in March) that had come from the local shelter last fall. He came to our clinic for his initial check-up and vaccinations, and had tested negative for intestinal worms. He had been given heartworm preventative to be used toward the end of the year (October and November), and had been healthy until early this year.

His owner started to notice some coughing, and Bumpy didn't seem to be as active as usual. When the cough seemed to be getting worse after several days, Bumpy's owner brought him in for an exam.

 

PHYSICAL FINDINGS

Bumpy's examination showed nothing remarkable except for some increased roughness in his lungs when he breathed. We were not able to make him cough, and his throat looked normal.

These are some things we think about with coughing:

We were able to narrow down or choices significantly because Bumpy was young (less worry of heart failure or asthma), had been tested for intestinal parasites, and had no exposure to other dogs (kennel cough). We actually diagnosed Bumpy's problem with one test, but ended up doing a couple of extras once we knew what was wrong (I'll explain why in a minute).


X-RAY RESULTS

First, I'll show you Bumpy's x-rays.


What's what?

 

Here's a close-up of the lungs:

If you look closely, you'll see some white fuzzy areas just to the right of Bumpy's heart. This suggests irritation of the lung tissue.

OTHER TESTING

Actually, the first test we ran was a heartworm test.

Bumpy was positive. In the past, veterinarians were forced to look for microscopic evidence of heartworms in an affected dog's blood, and missed a lot of infections. Current tests look for antibodies or evidence of heartworm protein in the blood, and are much better at detecting infection.

The x-rays followed, because heartworm disease often causes irritation of the lungs and changes in the heart and an x-ray can let us know how much damage has occurred. We also ran some blood tests, because Bumpy's owner wanted to treat him, and we had to be sure his liver and kidneys could handle the treatment (it can be pretty rough - see below).

TREATMENT

Bumpy's treatment occurred in multiple steps.

First, we had to kill the adult worms in his system. To do this we use a medication similar to arsenic. This is the most hazardous part of the treatment, and requires hospitalization for a couple of days. The treatment can also be hard on the kidneys and liver, so it helps to know how a pet's organs are functioning before treatement is even started. Bumpy did very well for the initial treatment.

The next step comes later, when a medication is given to kill any immature worms that might be in the bloodstream. This is less likely to result in any problems, so we usually keep patients for a few hours after the medication is given, and then send them home. Once again, Bumpy did fine.

After treatment we perform tests to look for heartworm over a period of a few months. We look for evidence of both immature and adult worms. And, where significant heart or lung damage has occurred, we often repeat x-rays to monitor healing. Bumpy is still only partway through the follow-up testing, but has looked good so far. In rare cases, the first treatment is not effective, and has to be repeated later.

 

DISCUSSION

Heartworm disease is a significant health concern for pets in our area. Both dogs and cats are susceptible (dogs much more at risk). Heartworm testing and prevention are a normal part of our preventative health program for dogs. Since cats are much less likely to be affected, we handle prevention in cats on an individual basis.

Heartworms are transmitted by mosquitoes. A mosquito picks up an immature heartworm and injects it into the next animal it bites. The immature worm goes through several molting stages before moving into the bloodstream and stopping in the heart.

Heartworms interfere with normal blood flow through the heart, and pieces of worms can break off and lodge in the lungs. Here are some signs of heartworm disease in dogs and cats:

DOGS

CATS

Heartworm disease can be prevented. Several types of medication are available which are given once a month and will prevent heartworm disease.

You may notice that Bumpy got heartworm disease even though he had been given heartworm preventative. This was a very unusual circumstance, which led us to have several discussions with the manufacturer of the preventative. What we think happened is that Bumpy was infected when he was very young, and had no health care until he ended up at the shelter. By then he may have had a life stage of the heartworm in his system that couldn't be affected by the preventative. Sound a little confusing? It was. In 8 years of practice, this was the first time we'd encountered this, and it's caused us to change how we administer the preventative in some cases.

I have an ulterior motive in presenting this case now. June through November is the time we consider to be heartworm season in Maine. Be sure your pet's protected!

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