Page 513 - Small Animal Internal Medicine, 6th Edition

CHAPTER 31 Disorders of the Intestinal Tract 485

ALIMENTARY TRACT PARASITES

VetBooks.ir WHIPWORMS

Etiology
Trichuris vulpis is principally found in the eastern United
States. Animals acquire the infection by ingesting ova; the
adults burrow into the colonic and cecal mucosa and cause
inflammation, bleeding, and/or intestinal protein loss.

Clinical Features
Dogs and rarely cats acquire whipworms, which produce a
wide spectrum of mild to severe colonic disease that can
include hematochezia and protein-losing enteropathy. Severe
trichuriasis may cause severe hyponatremia and hyperkale-
mia, mimicking hypoadrenocorticism. Marked hyponatre-
mia might be responsible for CNS signs (e.g., seizures).
Whipworms generally do not affect cats as severely as dogs.
FIG 31.3
Cytologic preparation of a colonic mucosal scraping Diagnosis
demonstrating Prototheca spp. Note the bean-shaped T. vulpis should always be sought in dogs with large bowel
structures that have a granular internal structure and appear diarrhea. Diagnosis is primarily made through finding ova
to have a halo (arrows) (Wright-Giemsa stain; ×1000). (Fig. 31.4) in the feces. Ova are relatively dense and float
(Courtesy Dr. Alice Wolf, Texas A&M University.) only in properly prepared flotation solutions. However,
they are shed intermittently and sometimes are found only
if multiple fecal examinations are performed. Adults can
be seen at colonoscopy (mild infestations may only affect
the cecum).

W

T

i

FIG 31.4
Photomicrograph of a fecal flotation analysis from a dog, demonstrating characteristic ova
from whipworms (W), Toxocara canis (T), and Isospora spp. (i). The remaining ova are
those of an unusual tapeworm, Spirometra spp. (×250). (Courtesy Dr. Tom Craig, Texas
A&M University.)