Heartworm Q for my roommate's dog

[Emily]

I have a question about heartworm, regarding my roommate's dog, which would be this sexy beast right here:

IMG_0673 by Traveling Koolie, on Flickr

Ok, so Balto was pulled from a high kill shelter in May of 2011 and treated for heartworm with Immiticide on July 8-9. I don't know what his worm load was like. He's been on Heartgard ever since his treatment.

Flash forward to today, and he just got a heartworm test. His old vet who ran the rescue he came from said that he would likely test positive up to a year following his treatment, but my vet today gave my roommate the impression that he would be concerned if it did, indeed, come back positive. I believe his exact language was, "The treatment can fail and if the test comes back positive, we'll have to confront that."

So, what do you guys know? I trust this vet, but I'm confused by the contradictory information between him and Balto's old vet. I'm asking this for my roommate so she doesn't find scary information on the internet and work herself up over nothing.

 

[Greenmagick]

I double checked with my friend who runs a rescue and has treated MANY HW+ dogs...she said expect to see postive results for 18-24 months. Adding a couple rounds of doxy can help clear it faster

 

[Saeleofu]

We usually do 3 injections of immiticide, first one then a few weeks later two back to back (separated by a day). I think. Ivermectin comes before immiticide, along with doxy and pred. We start them on heartworm preventative as soon as it's safe to do so (usually that means a month after the first ivermectin injection). With that treatment, a dog should NOT test positive when treatment is finished.

I'm thinking with the immiticide treatment, there should not be a positive. If it was JUST the heartgard then possibly a positive, but more likely a false negative (still have an infection, but all the females have been sterilized and are no longer producing microfilaria).

 

[Greenmagick]

I assumed they were doing slow kill, somehow missed the immiticide being given.

 

[Emily]

And he's NEGATIVE! Hooray!!! We're ecstatic over here.

Yeah, they did Immiticide and I'm really not sure why he old vet thought he would continue to test positive.

 

[Bigpoodleperson]

Agreed that a dog should not test positive after treatment. We test them again a couple months after treatment, and expect a negative result. Glad his test came back clean!