Question Answer Session

Question and Answer Session Q: Dosages for topical treatment with

Q: How was the itching/pruritus measured

imidacloprid are usually calculated according to body weight. On the other hand, the surface area (i.e., hair and skin) as well as species, age, body weight and sex have a major impact on how the drug is distributed. Please comment on this regarding the ferret studies.

in the cat FAD study?

A:

For topically applied and active compounds, the surface area is of more importance than the body weight. There is a difference in body weight and surface area between the smaller females and the larger male ferrets. Certainly, this is an area that could be investigated further, as we have seen real differences between the two sexes. For example, in the U.S. study, where the animals were treated with 1 pipette (0.4 ml) of imidacloprid per animal, the calculated dosage was only 36.4 to 47.05 mg/kg in the heavier males compared to 57.1 to 66.6 mg/kg in the lighter females. This had an impact on the duration of flea efficacy in this study.

Q: How do you think these observations relate to the rabbit study that compared hair surface area to skin surface area?

A:

The difference between rabbits and ferrets is that rabbits, by and large, have a similar body conformation to cats. We can extrapolate within limits between one and the other, but the ferret shape is very different. Physiologists look at rabbits and cats as more or less spherical for calculating the ratio of surface area to volume and weight, whereas ferrets are viewed as cylindrical. Of course, that alters all of the arithmetic considerably. You can extrapolate from cats to rabbits within reason, but you can’t extrapolate from cats to ferrets. Furthermore, the skin structure and the amount of body fat on the outer surface of the skin is quite different if you compare dogs with cats and then rabbits and ferrets.

Suppl Compend Contin Educ Pract Vet Vol. 23, No. 4(A), 2001

A:

The owners were asked to evaluate it by observing the cats during a specific time period each day to see if they could tell how much change had occurred. We extrapolated from the decrease in clinical signs that were reported.

Q: Is it possible to use imidacloprid (Advantage ) ®

in other small animal species, like guinea pigs or hamsters?

A:

There is quite a lot of anecdotal information available that imidacloprid has been used effectively to treat flea infestations in a large variety of small domestic animals. We believe that this publication contains valid data demonstrating that it is possible to control flea infestations in rabbits and ferrets.

Q: What about flea infestations in hedgehogs? A:

Hedgehogs carry a lot of ectoparasites. However, we know that we can control fleas in hedgehogs with imidacloprid without concern. We have also used imidacloprid on California ground squirrels to control sylvatic plague. We found that it had a high level of therapeutic efficacy, but the duration of efficacy was variable because of the nature of the ground squirrel and its hair and skin structure. Bear in mind that we are not treating cat fleas on ground squirrels. The fleas found on ground squirrels are a different flea species with a distinct biology. Again, the coat condition affects the efficacy of imidacloprid and the surface area of the skin is very important.

Second International Flea Control Symposium

Q: What prompted the Susceptibility Monitoring Initiative?

A:

The main reason for the initiative was to monitor susceptibility of populations of fleas on animals that had been treated. Those of us who work with fleas know that historically there is a long list of compounds to which the cat flea has become resistant. We are in the process of collating and analyzing data and establishing appropriate parameters. If we do encounter a response suggestive of resistance in the field, we will immediately clone the isolate and

TNAVC, January 2001

amplify it on cats so that we can characterize it by dosage titration. We’ll also work with the veterinarian to develop a suggested means of control, if needed. At this point, however, we don’t have any reason to suspect or to predict the existence of strains that behave any differently than the field or laboratory strains that we’ve encountered. The Advantage® International Flea Susceptibility Monitoring Initiative is the first of its kind and will establish unique and detailed methodologies that will be available to all who have an interest in the field. That alone, we think, will be a tremendous benefit and we owe a debt of gratitude to Bayer for their generous support.

Suppl Compend Contin Educ Pract Vet Vol. 23, No. 4(A), 2001