Page 511 - Small Animal Internal Medicine, 6th Edition

CHAPTER 31 Disorders of the Intestinal Tract 483

Clinical Features is believed due to these bacteria, then appropriate antibiotics
Patients are classically smaller breed dogs (e.g., Yorkshire as determined by culture and sensitivity are used. The pre-
VetBooks.ir Terriers, Schnauzers, Miniature Pinschers, Maltese). Many ferred length of antibiotic therapy is uncertain but should
probably be continued for 1 to 3 days beyond clinical remis-
(not all) initially vomit (may be bloody or not). Hemorrhagic
sion (except for histiocytic ulcerative colitis— see page 495).
diarrhea quickly ensues.
Diagnosis Prognosis
Diagnosis is by exclusion of other causes. Most patients have The prognosis is usually good.
an increased PCV.
Public Health Concerns
Treatment/Prognosis Public health concerns are currently undetermined.
Timely fluid therapy is associated with an excellent progno-
sis. Antimicrobial therapy has not been found beneficial. HISTOPLASMOSIS

MISCELLANEOUS BACTERIA Etiology
Caused by Histoplasma capsulatum, histoplasmosis is a
Etiology mycotic infection that may affect the GI, respiratory, and/or
Escherichia coli is of major importance as a cause of diarrhea reticuloendothelial systems, as well as the bones and eyes.
in most mammalian species, and the subject is beyond the Classically considered in animals from the Mississippi and
scope of this text. There are several different strains that Ohio River valleys, it has been diagnosed in patients that
produce different syndromes (e.g., enterotoxigenic E. coli have always lived in nonendemic areas.
associated with acute canine and feline diarrhea; adherent-
invasive E. coli [AIEC] associated with histiocytic ulcerative Clinical Features
colitis, especially in Boxers and French Bulldogs, etc.). Yer- Alimentary tract involvement is primarily found in dogs;
sinia enterocolitica, Aeromonas hydrophila, and Plesiomonas diarrhea (with or without blood or mucus) and weight loss
shigelloides may cause acute or chronic enterocolitis in dogs are common. Lungs, liver, spleen, lymph nodes, bone
and/or cats as well as in people. However, these bacteria marrow, bones, and/or eyes may also be affected. Cats more
(especially the latter two) are uncommonly diagnosed in the commonly have respiratory dysfunction (e.g., dyspnea,
United States. Y. enterocolitica is primarily found in cold cough), fever, and/or weight loss, but they occasionally have
environments and in pigs, which may serve as a reservoir. It alimentary involvement.
is also a cause of food poisoning because of its ability to grow In GI histoplasmosis, the colon is often the most severely
in cold temperatures. affected segment. Diffuse, severe, granulomatous, ulcerative
mucosal disease can produce bloody stool, intestinal protein
Clinical Features loss, intermittent fever, and/or weight loss. Small intestinal
All of these bacteria may cause small bowel diarrhea. Select involvement occasionally occurs. The disease may smolder
E. coli and Y. enterocolitica produce chronic large bowel for long periods of time, causing mild to moderate nonpro-
diarrhea. gressive signs. Occasionally, histoplasmosis causes focal
colonic granulomas or is present in grossly normal-appearing
Diagnosis colonic mucosa.
E. coli can be cultured from the feces of almost all mammals.
With the exception of histiocytic ulcerative colitis, it is Diagnosis
extremely difficult to associate an E. coli isolate with intesti- Definitive diagnosis requires finding the yeast (Fig. 31.2).
nal disease in a particular patient. If it is necessary to try to There is an ELISA for antigen shed in urine that appears to
determine whether or not a particular E. coli is responsible have good sensitivity/specificity. Serologic tests for antibody
for disease, then virulence factor testing is needed (but not to H. capsulatum are poorly sensitive/specific. Dogs from
necessarily sufficient by itself). Animals with persistent endemic areas with chronic large bowel diarrhea are espe-
colitis, especially those that are in contact with pigs, may cially suspect. Protein-losing enteropathy (PLE) is common
reasonably be cultured for Y. enterocolitica. in dogs with severe alimentary histoplasmosis, and PLE in a
dog with large bowel disease is a strong indication to check
Treatment for histoplasmosis.
With the exception of E. coli–associated histiocytic ulcerative Rectal examination sometimes reveals thickened rectal
colitis, therapy is supportive. The affected animal should be mucosa. Cytologic preparations from rectal mucosal scrap-
isolated from other animals. People in contact with the ings sometimes reveal the yeast. Colonic biopsy is usually
animal and/or its environment and wastes should wear pro- diagnostic, but special stains may be necessary. Mesen-
tective clothing and clean themselves with disinfectants. teric lymph node samples or repeated colonic biopsy is
Antibiotic therapy generally has not shortened duration of rarely required. Fundic examination occasionally reveals
acute diarrhea caused by these bacteria. If chronic diarrhea active chorioretinitis. Abdominal imaging often shows