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Canine
pythiosis presents as cutaneous or subcutaneous lesions, acquired through
open wounds on the skin, or gastrointestinal lesions which are acquired
when P. insidiosum contacts the mucous membranes. The fact
that dogs frequently drink stagnant water and eat grass that may contain
elements of P. insidiosum explains the high number of intestinal
pythiosis cases in canines.
The cutaneous and subcutaneous lesions are denuded of hair and perforated
by fistulous sinus tract, that discharge a serosanguineous exudate.
They are usually located on the dog’s tail, legs, thorax, and abdomen.
The hard stony masses (kunkers) observed in equine pythiosis are not
present in dogs with the disease. Microscopic examination shows multifocal
areas of necrosis with eosinophils and a moderate number of neutrophils
and macrophages. The hyphae of P. insidiosum are found in the
center of eosinophilic micro abscesses.
Canine
gastrointestinal pythiosis is characterized by vomiting, weight loss,
and sporadic diarrhea. Formation of hard gastrointestinal tumor-like
masses and areas of thickness and mucosal ulceration are common. The
organism can spread to adjacent tissue such as pancreas, uterus, and
mesenteric lymph nodes. Histopathologically, the mucosa shows ulceration,
atrophy, and hyperplasia. Eosinophils, plasma cells, macrophages, epithelial
cells and giant cells are detected in infected tissues. The hyphae of
P. insidiosum, however, are difficult to detect. Silver stain
or other special stains are required to visualize the hyphae of this
pathogen in the infected tissues.
TREATMENT: Because dog pythiosis is relatively a new
disease in this specie, most small animal veterinary practitioners are
not familiar with its clinical features. Most cases of cutaneous pythiosis
are initially diagnosed and treated as bacterial or parasitic infections,
whereas gastrointestinal pythiosis is often misdiagnosed as intestinal
tumor-like disease (neoplasia) and treated by surgical removal of the
tumor mass(s).
SURGERY: Because P. insidiosum lesions progress
rapidly a quick diagnosis is essential for animal survival. Once the
diagnosis of pythiosis have been established, wide surgical removal
of the infected tissues may be a successful treatment for cutaneous,
subcutaneous, and intestinal pythiosis. However if the P. insidiosum
is not completely removed the lesions will re establish.
DRUGS: Antifungal therapy using amphotericin B, itraconazole,
ketoconazole, or nistatin has been unsuccessful.
IMMUNOTHERAPY: Treatment with the therapeutic product
used to cure cases of equine pythiosis has shown only 35% success in
dogs with pythiosis. This may be due in part that all treated cases
were dogs with chronic pythiosis (infection >60 days). Immunotherapy
has demonstrated a lower rate of cure in chronic infections. This immunotherapeutic
product has show greater than 75% success in treating infections of
less than 30 days duration in Equines.
6/16/04
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