Conventional diagnostic approaches emphasize the search for an underlying systemic disorder that would explain the recurrences. Unfortunately, in many cases there is no identifiable underlying disease present, despite exhaustive diagnostic evaluation.
A variety of explanations have been set forth as to the underlying mechanisms at work in such patients. One hypothesis holds that development of bacterial hypersensitivity is responsible for the severe clinical signs and recurrent nature of at least a subgroup of dogs with chronic staphylococcal infection.
The disease is invariably quite antibiotic-responsive, with relief of itching often noted within 2 or 3 days after antibiotics are started and with a return to normal after 3 to 6 weeks of such treatment.
The problem arises when antibiotic treatment is stopped, for typically the disease can relapse within 1 to 3 weeks following cessation of antibiotics.
Experimental evidence, clinical appearance, and parallels with a similar syndrome in humans has led to the theory that in dogs, the antibody response to staphylococcal infection may be detrimental in some individuals and result in hypersensitivity and recurrent pyoderma.
Ideally, the antibiotic should be chosen based on a culture and sensitivity test.
Other factors to consider in selection of an antibiotic for initial treatment include cost and the possibility of adverse drug effects.
Initial treatment of superficial pyoderma should last for 1 to 2 weeks past complete clinical resolution. Typically, this will entail 3 to 6 weeks of antibiotic treatment.
Recurrent pyoderma is frequently a lifelong disease that can be satisfactorily controlled, but not often cured, and some trial and error will be necessary to find the best long-term control regimen for each patient.
Because relapse after initial treatment is the expected
result, additional treatment aimed at preventing such relapse
should be initiated at the same time as antibiotics. Such treatment
may be in the form of:
Adjunct topical treatment with antibacterial shampoos
is aimed at long-term reduction in the bacterial antigen load
present on the skin surface, which will in theory reduce the degree
of hypersensitivity reaction. In order to be effective for long-term
control of recurrent superficial pyoderma, shampooing must be
done frequently -- twice weekly at first, then usually at least
once weekly long-term after resolution of the active episode.
Useful products include shampoos containing 0.5% chlorhexidine,
or 2% benzoyl peroxide with a moisturizing additive (various manufacturers).
Immunomodulatory bacterins are an aid in long-term
management of recurrent pyoderma, including "staphylococcal
hypersensitivity." Bacterins are not used to cure an active
infection -- their major use lies in prevention of recurrence
once the initial infection is cleared by antibiotics. It is clear
that staphylococcal bacterins are effective for some dogs with
recurrent pyoderma, perhaps 50% or more of carefully-selected
cases (i.e., those cases where there is not a definable underlying
cause for recurrence). Commercial products that are licensed for
dogs and which have been subjected to study include SPL (Staphylococcus
Phage Lysate, Delmont Laboratories), and ImmunoRegulin (Propionibacterium
acnes bacterin, ImmunoVet). Bacterin treatment, if effective,
is usually less expensive than chronic antibiotic use and will
lessen the chance of developing antibiotic-resistant bacterial
strains. This treatment generally should be considered a lifetime
therapy, though some animals are apparently cured after 18-24
months of treatment and the injections can be stopped. Treatment
is undertaken by giving injections twice weekly for two weeks,
then once weekly until improved then start giving them at greater
intervals (every three weeks, then once monthly, etc.).
We hope that you will find this information helpful in your quest for better pet care. If you have any questions or comments, please call your veterinarian's office, or feel free to e-mail us.
David E. Hammett, DVM
and the Staff of All Creatures Veterinary Clinic, PC
