On atopy fleas and food allergy
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One of the founding fathers of the European College of Veterinary Dermatology,
Richard Haliwell (Edinburgh, UK) has become a household name in veterinary
dermatology and allergology. A regular speaker at European and International
conferences and courses, he also lectures here in Granada the right occasion
to ask him a few questions. |
What got you interested in allergic diseases to begin with?
When I graduated from veterinary school, I entered small animal practice
in London. I was often presented with dogs with skin problems, and found
the lack of knowledge most frustrating. After 5 years, I went to the University
of Pennsylvania on a visiting fellowship under Robert Schwartzman, who
was very interested in canine atopic dermatitis. This really stimulated
my interest, and I was fortunate enough to have the opportunity to return
to Cambridge to undertake PhD studies under Robin Coombs.
Was this the Robin Coombs of the Coombs test fame?
Yes, it was indeed. And what is not generally known is that Coombs
is a veterinarian, and was always proud to be a member of our profession.
What was the topic of your PhD studies?
I worked on the characterisation and purification and purification
of canine IgE the antibody with a major role in allergic diseases. This
was a very exciting period, in that it coincided with major work being
undertaken at the same time on human IgE.
What next?
I returned to the University of Pennsylvania and carried on working
in the field of allergy. Amongst other work, with the help of Gail Kunkle,
we developed the first in vitro test, the radioallergosorbent test for
the serological diagnosis of IgE mediated allergic diseases in dogs.
So when did your work on fleas start?
When I moved to the University of Florida, the whole State was overrun
with fleas. One had to either love them or hate them! I grew to love them,
and quickly realised how little we knew about the pathogenesis of flea
allergy dermatitis. We had always assumed that the work done in guinea
pigs by Benjamini and colleagues in the 1960s could be extrapolated to
dogs. From this work it was believed that the flea allergen was a low molecular
weight hapten, which was only antigenic upon combination with dermal collagen.
We showed that there were in fact a number of protein allergens. We also
showed that all dogs could be made allergic to fleas, and that intermittent
exposure favoured the development of allergy, whereas continual exposure
tended to be protective by inducing immunological tolerance. We also showed
that in addition to immediate and delayed hypersensitivity, cutaneous basophil
hypersensitivity was also involved.
What then?
In 1989 I moved to the University of Edinburgh. In Scotland there are
very few fleas and so the work on fleas had to stop. However, little
work had been done on feline allergies. So when Sophie Gilbert from Belgium
came to do PhD studies, and told me that she loved cats this was an obvious
opportunity to do similar studies on feline allergies. Sophie did some
very nice studies characterising feline IgE, and inducing IgE antibodies
in normal cats both to food allergens and to house dust mite allergen.
Did this make the cats suffer from clinical allergies?
No, actually it did not. This raises the fascinating possibility that
there may be more than one type of IgE both in dogs and cats. This is
one of the challenges for future work.
What about food allergies - one of your lectures during this congress?
The serological response to foods is very interesting and we are
currently undertaking studies on this. It seems that most dogs make IgG
antibodies to a great number of good antigens. However, contrary to what
has appeared in the literature, it seems that the incidence of IgE antibodies
to food antigens in normal dogs is very low. There is a greater incidence
in atopic dogs, with by far the highest incidence in dogs with proven adverse
food reactions.
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Does this mean that undertaking serological
tests for the diagnosis of food allergy may be of value diagnostically?
The only definitive test to confirm an adverse food reaction is clearly
to show an improvement upon removal of the food from the diet, and a relapse
upon re-feeding the original diet. However, our work, which is being done
in conjunction with Drs Regina Wagner and Christa Horvath from Vienna,
suggests that serological tests may help in the selection of an appropriate
hypoallergenic diet, and also in indicating a possible role for food hypersensitivity
in difficult, complex cases.
Over 100 Presentations from meetings and seminars went online.
Please visit www.VetContact.com.
No 100 is from Dr. Otto Fischer, Vienna. It shows the efficacy of a
Nitenpyram/Lufenuron combination in the treatment and long term control
of flea allergy dermatitis).
This interview reflects the achievements of his work.
What is the incidence rate of allergic reactions in dogs infested
with fleas?
Flea bite hypersensitivity or flea allergy dermatitis (FAD) is the
most common hypersensitivity skin disorder where fleas are endemic. In
a study in the UK fleas were found in 5 - 20 % of dogs, depending on area.
The corresponding prevalence of FAD was 2 - 11 %. This suggests that
about half of the dogs with fleas develop flea bite hypersensitivity, although
to a variable degree.
What gave you the idea for this study?
In the veterinary community it is assumed that dogs with flea
bite hypersensitivity need flea control remedies acting before fleas get
a chance to bite. As this does not seem to be the case with most products
- fleas bite within minutes after getting on a host - , the idea was to
evaluate the role of the allergen-load needed to induce clinical disease.
Our hypothesis was that a systemic treatment with a compound that has ultra
fast onset of action would minimise the allergen exposure of the dog and
provide allergy control despite the fact the flea has to bite to be killed.
Why did you choose CAPSTAR and PROGRAM?
Nitenpyram (CAPSTAR) is a newly developed compound with ultra fast
action. It kills fleas within minutes of the blood meal and leads
to 100 % elimination within three hours. Thus the allergen exposure
of the skin is minimal. The combination with Lufenuron was chosen
to gradually eliminate the fleas from the dogs' environment. This reduces
also the frequency of the Nitenpyram application needed from daily
to once a week and minimizes the risk of resistance development.
Where there any side-effects of the therapy?
No, there were no side- effects seen or reported by the owners. Nitenpyram
is a new insect specific neonicotinoid which acts as an agonist on the
postsynaptic acetylcholine receptors. It has a very short half life which
prevents accumulation. Lufenuron has been used for a long time and
is proven to have a good safety profile.
Would you recommend this therapy to veterinarians for their clients
with FAD dogs?
The results suggest that I do: The therapy used has proven to be very
effective. In 96 % of dogs included in this study good or excellent
clinical efficacy was achieved. Long term management in phase
two of our study resulted in 75 % excellent and 25 % good clinical
efficacy. For the dermatologist this therapy has the big advantage
that topical treatments like medicated shampoos can be used on a regular
basis without interfering with insecticide efficacy. For some clients it
will be an attractive treatment, as there is no insecticide exposure of
people in contact with the animal.
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