A
New Approach to the Treatment and Resolution of Clinical Proventricular
Dilatation Disease (PDD) in Pet Birds.
By: R. D. Dahlhausen DVM, MS
Research Associates Laboratory, Inc.
This
report highlights important research advancements into Pro ventricular
Dilatation Disease (PDD, myenteric_ganglioneuritis, or macaw wasting disease) in
pet birds. The discovery of a suitable pharmacotherapy that allows for the
reversal and resolution of clinical signs is significant and
warrants its early dissemination. We have confirmed the effectiveness of this
treatment in eight well-
documented cases and have seen improvement in numerous other ongoing cases
under therapy. It is the author's intent that applied clinical use will further
define the guidelines for this approach and
immediately benefit those veterinarians managing clinically affected patients.
Proventricular
Dilatation Disease (PDD) is a most frequent fatal disease of pet birds.
Progressive weight loss and loss of body condition is accompanied by,
regurgitation, crop impaction, passage of undigested food, and secondary
bacterial and fungal infections of the digestive tract are commonly observed.
Neurological signs such as lack of coordination, ataxia, tremors, and seizures
can be seen when the disease involves the central nervous system, characterized
by a lymphocytic, plasmacytic inflammatory infiltrate of the central (CNS) and
peripheral nervous tissues. Nerve ganglia supplying the musculature of the
digestive tract are frequently affected, causing atrophy of the smooth muscles
of the crop, proventriculus, ventriculus, and/or small intestine resulting in
motility disorders and various degrees of dilatation. While supportive care may
help prolong the lives
of affected birds, there is no current treatment for this disease. Long-term
prognosis is grave, with the majority of birds succumbing after a period of
progressive debilitation and wasting.
PDD
is a disease of suspected viral etiology with a potentially long incubation
period of months to possibly years. Because the lesions of PDD are inflammatory
in nature, we speculated that diminishing this reaction might lead to clinical
improvement and resolution of clinical signs in affected birds.
Anti-inflammatory agents with significant activity in the CNS, peripheral
nervous system, and gastro intestinal tract that were safe for use in pet birds
were identified. Of these, the non-steroidal anti-inflammatory drugs (NSAIDs)
appeared most useful.
NSAIDs,
through inhibition of the cycloogenase (COX) enzyme, are effective for relief of
inflammatory processes. COX exists in at least two isoenzyme forms: COX-1 and
COX-2. COX-1 synthesizes prostaglandins that are involved in the regulation of
normal homeostatic cell
activity including gastrointestinal tract cytoprotection. COX-2 is an inducible
form that causes enhanced formation of prostaglandins involved in acute and
chronic inflammation. Conventional NSAIDs inhibit both COX-1 and COX-2. Their
use is tempered by the development of side effects from COX-1 inhibition, which
primarily involve platelet function, renal function, and the gastrointestinal
tract.
Celecoxib
(Celebrex, Pfizer), part of a new family of NSAIDs, is a potent and selective
inhibitor of the COX-2 isoenzyme. The specific inhibition of COX-2 has been
shown to effectively reduce man)*
parameters of inflammation, including edema, white blood cell infiltration, and
activation. At therapeutic levels, it does not inhibit COX-1 and has been shown
to be well tolerated and safe. The incidence of adverse events is similar to
placebos in most instances. In addition to its use in
osteoarthritis, celecoxib has potent anti-inflammatory and anti-neoplastic
activity in the gastrointestinal tract and has also been shown to inhibit
certain CNS viruses in vivo and in vitro.
We
have used celecoxib at 10 mg/kg orally once daily for the treatment of birds
with clinical FDD, Diagnosis was based on history, clinical exam, characteristic
radiographic changes, and crop biopsy) pathology. Treatment duration was for a
period of 6 to 12 weeks with the decision to cease medication based upon the
return to normal body weight, condition, and diet. Contrast radiograph)
was also used to monitor the progression of clinical improvement. Premature
cessation
of treatment can result in the recrudescence of clinical signs. In these
instances, clinical improvement resumed with additional medical therapy.
Supportive care to improve gastrointestinal transit (fluids, apple pectin),
nutritional support with easily digested hand-feeding formulas, an appropriate
therapy to eliminate bacterial (Clostridial) and fungal enteric infections were
utilized as needed.
Improvement in clinical condition is generally observed within the first week of
treatment with a gradual resolution of clinical signs and a return to normal
diet over the course of therapy.
Periodic
monitoring of clinical hematology and serum chemistry profiles have not
demonstrated and adverse side effects related to this extended therapy. No
adverse effects were observed clinically either during or after cessation of
treatment. The majority of birds treated demonstrated market
clinical improvement including those in advanced stages of the disease. Most
treated birds maintained their improved clinical status after treatment
cessation. The longest we have observed is a Blue & Gold Macaw that finished
therapy over 1.5 years ago.
We
are currently accumulating additional clinical data to further evaluate the
safety and efficacy of celecoxib use in
pet birds. Our experience has shown that it significantly improves the
functional status of PDD affected birds, and appears to be safe and well
tolerated in these species. Until such time when the particular agent that
causes PDD is identified and a suitable diagnostic assay developed to identify
infected individuals, the infectious status entreated/recovered individuals
remains unknown. A detailed report with clinical case summaries has been
submitted for presentation at the next AAV convention.
The
author acknowledges that support from the Midwest Avian Research Expo, Miami
Valley Bird Club, Central Indiana Caged Bird Club, and Kentuckiana Bird Club
made this research possible. The support and efforts of the individuals involved
in these organizations is greatly appreciated.
