Sissy’s Heartworm Saga

SAMSUNG CAMERA PICTURESSissy is a 2 1/2 year old Blue Tick Hound.  She had been kept outside in a dog house since adopted as a pup.  Since she wasn’t getting the attention she deserved, the original owners gave her up to another family.

Sissy was brought to Four Lakes Veterinary Clinic for an exam and to be spayed.  She was a sweet girl and was getting along very well with her new owner’s other dog.

Sissy’s ovariohysterectomy (spay surgery) went well, with no complications.  She was examined, vaccinated, and blood was sent off to check for heartworms and exposure to tick-borne diseases (like Lyme).

Heartworm-mapHeartworms aren’t terribly common in Wisconsin, especially when compared to warm, southern states.  So we were surprised when her test came back positive.  In addition, a stool sample showed she was infected with 3 other types of intestinal worms: roundworms, hookworms, and whipworms.  Poor Sissy!

She was treated for the intestinal worms with a deworming medication and started on heartworm preventative and an antibiotic prior to starting heartworm treatment in 1-2 months time.  Heartworms are often infected with a bacteria called Wolbachia that can make the body react more strongly to the heartworms.  The antibiotic kills the Wolbachia in the adult worms,  so the lungs have less of an inflammatory response to the heartworms being killed by the Immiticide.

whipworm-adultsInitially Sissy was prescribed Heartgard to start killing the microfilaria (“baby” heartworms), but because that medication doesn’t control whipworms, we decided to give her Sentinel Spectrum instead.  Whipworm eggs, passed in the feces, are very hardy and can stay in the soil a long time, even through harsh winters and hot summers.  Once there are whipworm eggs in the environment, a dog is always at risk of contracting them again.  So giving a monthly preventative that controls them is very worthwhile.

The owner gave the first dose of Sentinel Spectrum and over the next several days Sissy started vomiting and not eating.  It turned out the vomiting was really coughing, so chest x-rays and bloodwork were performed to try and determine what was going on.


Her bloodwork was normal, but we did find microfilaria in her blood.

Thsissylate x-ray showed a lot of inflammation in the lungs, likely heartworm pneumonitis.The most likely scenario was that the high dose of milbemycin in the Sentinel Spectrum killed off a large number of microfilariae quickly. They then got filtered out in the lungs, caused severe inflammation, which then led to the forceful coughing and lethargy.

Sissy was immediately started on steroids, which decreased the inflammation and stopped the coughing, making her feel much better within 24 hours.  Until her heartworm treatment is done and she no longer has microfilaria in her blood, she will take Heartgard monthly.

Sissy took the prednisone, for about 2 weeks.  The amount given was decreased every 4 days.  Near the end of the medication, she developed diarrhea.  We first just treated it like “normal” diarrhea–withholding food for 24 hours then feeding a bland diet.  This didn’t help, so we examined a sample of the diarrhea and were suspicious of a Giardia infection.  She was prescribed metronidazole, which can kill Giardia and is also helpful for other causes of diarrhea.  It didn’t help Sissy at all.  She started defecating fresh blood and not much stool at all.

When I examined her, she had lost weight, her gums were quite pale, and she had fresh blood on the rectal exam.  A complete blood count (CBC) was done and it showed she was anemic and had virtually no platelets, which aid in clotting blood.  Because of all her clinical signs (anemia, low platelets, weight loss, coughing, lethargy, and because she lived outdoors, I started wondering if she might have a fungal infection of Histoplasmosis.  Histoplasmosis isn’t common in Wisconsin, but she did live in other states, where the risk is higher.  The best test for histoplasmosis is through urine, so the owner’s brought in a urine sample the next day.  It took a couple days for the lab to get results, so I also started her back on high doses of steroids, in case her very low platelets were due to destruction by her immune system.

Thankfully, her histoplasmosis test was negative.  Fungal infections can be very difficult to treat.  But the high doses of steroids I started her on were causing her to be extremely ravenous.  She broke out of two very sturdy cages and destroyed the house, eating brillo pads and anything that was in her path.  The owner was ready to relinquish her to the shelter because of the behavior!  It was touch and go for Sissy for that first week.

The high doses of steroids suppressed her immune system, allowing her platelets to rebound.  The blood and diarrhea stopped and she was much more energetic.  As her platelets stayed in the normal range, we started decreasing the steroid dose, which helped with her behavior.  At least she stopped breaking out of kennels!

Now that her platelets are holding steady and in the normal range, she is almost ready for her heartworm treatment!  The plan is to take another chest x-ray to make sure her lungs are all normal, taper the steroid dose a little more, and give the first Immiticide injection.

To be continued…