Quote: phaedra rieff

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.

Load as in the number of HW that were injected into each dog. One of the theroies as to H/W preventative failure in parts of the south is that that the drug is insufficient to kill the high ammount of larve that the dog is being infected with.

The reason I'm wondering about dosage/size of dog is that with Heartgard and Interceptor the cut off weight for a dose is 25#. For Advantage Multi the cut off is 20#. Beagle size is generally in that 20-30# range. So theoretically many of them could have been been at the bottom end of the weight scale for the Advantage and the upper end for the other preventitives. So one group would be getting almost twice as much per # of dog as the others. Which could be significant if the strain of HW used was particularly virulent or the load was heavy.

 Quote: Lynne Barrows

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...

They give p-values of 0.0047 to 0.0030 for each treatment vs. control. I think that it's clear that treatment is beneficial; I'm not sure that the study is strong enough to show that one treatment is better than another. They probably should have done ANOVA, or at the very least, a Bonferroni correction for multiple pairwise comparisons.
PM me if you want a copy of the full article.

 Quote: Arik Kershenbaum

 Quote: Lynne Barrows

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...

They give p-values of 0.0047 to 0.0030 for each treatment vs. control. I think that it's clear that treatment is beneficial; I'm not sure that the study is strong enough to show that one treatment is better than another. They probably should have done ANOVA, or at the very least, a Bonferroni correction for multiple pairwise comparisons.
PM me if you want a copy of the full article.

Arik, thanks. Your assessment is good enough for me...
(and it's nice to know we have a 'go-to' person for statistical analysis... )

Thanks Arik. The speaker giving the lecture was very, very enthusiastic about the results. As you you from the full article it talks about how heartworm is becoming more and more resistant to treatment, and that reminded me of Bob Scott and the PSDs that were on preventative medication, but still got infected.
Obviously it's a small study, but promising. Much more research will be done on the topic I'm sure, as he mentioned in the webinar.

 Quote: Mara Jessup

 Quote: phaedra rieff

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.

Load as in the number of HW that were injected into each dog. One of the theroies as to H/W preventative failure in parts of the south is that that the drug is insufficient to kill the high ammount of larve that the dog is being infected with.

The reason I'm wondering about dosage/size of dog is that with Heartgard and Interceptor the cut off weight for a dose is 25#. For Advantage Multi the cut off is 20#. Beagle size is generally in that 20-30# range. So theoretically many of them could have been been at the bottom end of the weight scale for the Advantage and the upper end for the other preventitives. So one group would be getting almost twice as much per # of dog as the others. Which could be significant if the strain of HW used was particularly virulent or the load was heavy.

Great observation, Mara. Very interesting about the weight cutoff points, and something to consider if you have a dog that is close to the weight cut-off...

 Quote: Mara Jessup

Load as in the number of HW that were injected into each dog. One of the theroies as to H/W preventative failure in parts of the south is that that the drug is insufficient to kill the high ammount of larve that the dog is being infected with.

It was 100 larvae per dog. Anyone know if that's considered a heavy load?

I downloaded and read the whole paper, and (putting my professional biological scientist hat on) I have some comments. Not the statistics – I think their non-parametric analysis was OK. What got my attention was:

1 .The first three treatments, ivermectin/pyrantel (Heartguard), milbemycin oxime (Interceptor or Sentinel) and Selamectin (Revolution) are all supposed to be administered monthly, according to the manufacturers. In this study, the dogs in each treatment group were given just one dose at the beginning of the experiment, which then ran for another 5 months. So each of these heartworm preventatives was incorrectly administered–as the authors of the study admit. What I find interesting is that despite this, Heartguard, Interceptor and Revolution still reduced the final adult heartworm count significantly compared to the untreated controls (an average of just over 2 adult worms per treated dog compared to an average of almost 52 worms per untreated dog).

The fourth treatment, which consisted on one topical application of imidacloprid/moxidectin (Advantage Multi), was 100% effective, with no adult heartworms recovered from these dogs at the end of the experiment. So – when administered according to the manufacturer’s instructions, this stuff works. But it hardly seems a useful comparison when the other three heartworm treatments were not administered correctly.

2. It’s not clear whether the lab-cultured strain of heartworm the researchers used is representative of the various strains in the real world in terms of virulence and resistance. The loss of efficacy of some heartworm preventatives reported in parts of the country do indicate that some resistant strains of heartworm have evolved. The authors of the paper discuss this.

3. The research was funded by Bayer, the manufacturer of Advantage Multi. I’m not accusing the Auburn university researchers of anything fraudulent, although I think their failure to correctly dose the dogs in the first three treatment groups is a serious weakness in their experimental design. I’m just saying…..BTW way, Phaedra, who sponsors and produces your online webinars? And was the enthusiastic researcher a Bayer employee?

The take-home message for me from this study is that if you are looking for a single-dose heartworm preventative with long-term efficacy then Advantage Multi seems to work well, at least against this strain of heartworm. But this study does not show that other monthly heartworm preventatives are ineffective when used correctly.

The study you describe where the medication is not administered is really interesting to me. People often don't give medicine, they pay for it,take it home, and never use it. One of the reasons that sometimes a veterinarian will administer an injection of an antibiotic to a sick dog needing antibiotics along with dispensing oral medicine. My husband says people often don't take their medicine either.

Kind of peculiar, really.

In their discussion the researchers make the case that for dog owners who won't or can't administer a heartworm preventative each month, then the longer-term protection from a single dose of Advantage Multi is advantageous. It is a legitimate point - I guess in such cases the product could be applied in the vet's office, and then the issues you describe with owner follow-up could be avoided.

What annoyed me about the paper, though was the spin the authors put in their summary on the apparent superiority of Advantage Multi to other preventatives when only a single dose was given. You have to dig through the whole paper to realize that they were underdosing with the other products to get the results they did.

The paper does give the impression of being a little disingenuous (the third author is a Bayer man, BTW). One problem is that they don't do any explicit comparisons of the efficacy of the different treatments. Sure, it looks like Advantage is better (0/8 positive as compared to 21/24 positive, or 100% vs. 95.5% efficacy) but there's no indication of the statistical confidence. As you said, they should have pointed out in the conclusions that they didn't follow the recommended regime:

 Quote:

not all available heartworm preventive products are effective against the MP3 strain of D. immitis when applied as a single treatment ... Advantage Multi® for dogs was 100% effective

I don't think I'd have recommended accepting this for publication without revision.