We had a "webinar" (an online seminar) about a recent study into 5 top heartworm medications - among them were Interceptor, Revolution and Advantage Multi (the other 2 escape me at the moment, but I'll post them).

The study was done on about 120 colony beagles, all infected with heartworm strain MP3, all treated once (except the control group) with the medication. At the end of the study, of course the dogs were humanely euthanized and the worms retrieved and counted.

In most of the groups, 7/8 dogs were infected, but the kill rate was about 90-95%. Except in the Advantage Multi group, where they did not find ONE SINGLE HEARTWORM!

Keep in mind, this was a totally blind study, and the "infectors" had no idea which dogs were being treated, or with what, neither did the "collectors" of the worms. They checked and rechecked the results.

Also keep in mind that this is only one strain of heartworm, but they picked a virulent one. I thought that I would post this, as I know some of you have had problems with heartworm.

I am trying to get a printout of the results.

Interesting. I'd very be interested in knowing the protocols that were used for the test.

My biggest questions would be what kind of h/w load and what dose of meds were used (were the dogs close to the upper end of the dose? or not?)

The meds were dosed as per on label instructions for normal use. As for the h/w load, I'm not sure what you mean.

I believe the entire trial was 90 days, but I could be wrong on that. I know that they were very strict, even taking the control group 1 by 1 into the treatment room, closing the door, mocking treatment. Then everyday, examining them exactly the same way.

I know that the heartworm was injected into the medial thigh.

Phaedra... can you give us a link? or was it contained within the webinar?

It's not online that I know of. We have these online CE lectures once a week from with various guest speakers at various Veterinary Schools around North America. They are live, and we normally don't get paperwork, we see a powerpoint presentation and try to take notes. I'm going to try and get some text from this one, because it's useful info for the clinic, whereas sometimes it's just medically interesting topics.

ETA - the study was also supervised every step of the way by the FDA, as they have strict requirements on how to collect and count the worms, etc.

It sounds like this paper just published, although the numbers are slightly different.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TD7-51XH9F1-F&_user=1464331&_coverDate=03%2F10%2F2011&_rdoc=16&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info(%23toc%235191%232011%23998239997%232924781%23FLA%23display%23Volume)&_cdi=5191&_sort=d&_docanchor=&view=c&_ct=29&_acct=C000052817&_version=1&_urlVersion=0&_userid=1464331&md5=e4bfc024c12d74a2a3de860478053850&searchtype=a
(that's Veterinary Parasitology Volume 176, Issues 2-3, 10 March 2011, Pages 189-194, in case the link doesn't work)


Edited by Arik Kershenbaum (04/22/2011 01:16 AM)
Edit reason: added plain text link

Yes, that is it. I think maybe they started with 120 beagles and only ended up using 40, which would make sense for the groups of 8. So the other meds were all around 95% effective - for anyone not interested in reading the link. And they were:
"Group 1 were treated orally with ivermectin/pyrantel pamoate chewable tablets, Group 2 dogs were treated orally with milbemycin oxime flavored tablets, Group 3 dogs were treated with selamectin topical solution, and Group 4 dogs were treated with imidacloprid/moxidectin topical solution. Group 5 dogs remained nontreated"

Forgive my ignorance,
Is one study significant? Or does it suggest something of interest that should be looked into farther?

And I must be confusing some use of terms; in your opening post you said the kill rate was about 95% in all but one group, does this refer to the amount of worms still virulent and deadly thereby a killer to the dogs? Or does it refer to the kill rate of the worms? Because your last post says all the meds were 95% effective.

As you may have guessed I'm confused about what this all means.
I thought I understood it, until I didn't.

I would like to see a larger double blind study. 40 dogs is not much.

 Quote: randy allen

Forgive my ignorance,
Is one study significant? Or does it suggest something of interest that should be looked into farther?

And I must be confusing some use of terms; in your opening post you said the kill rate was about 95% in all but one group, does this refer to the amount of worms still virulent and deadly thereby a killer to the dogs? Or does it refer to the kill rate of the worms? Because your last post says all the meds were 95% effective.

As you may have guessed I'm confused about what this all means.
I thought I understood it, until I didn't.

Randy, 3 meds were 95% effective, the 4th was 100% effective (no worms found at necropsy). All animals in the control group were infected...
This study is quite small, I agree. And the abstract does not list the confidence intervals (the likelihood that the results were chance and not a result of the meds given)...
The full study probably does, but I can't access it...

The other point that bears mentioning is that, from what I can tell from the abstract, the h/w meds were given on day 1, then nothing was given for 90 days following the initial treatment. I don't recall enough about the life cycle of heartworms, but under normal circumstances h/w meds would be given every 30 days. I wonder if the results would have been the same if the meds were given on a more normal schedule.

Phaedra, if I'm misinterpreting that info, please correct me!