Page 510 - Small Animal Internal Medicine, 6th Edition

482 PART III Digestive System Disorders

after resolution of clinical signs. Individuals in contact with check for toxin A and B is the best approach. However, com-
clinically ill animals, their environment, and their waste mercially available toxin assays for C. difficile toxin have not
VetBooks.ir should wear protective clothing and wash with disinfectants been validated for the dog or cat. Elimination of other causes
of diarrhea plus resolution of signs when treated appropri-
such as phenolic compounds or diluted bleach (1 : 32 dilu-
tion). Although the risk of zoonotic transmission from dogs
ism and/or toxin is typically the basis for presumptive
and cats to people seems small, it appears possible (but is not ately (see next paragraph) in addition to finding the organ-
true typhoid fever). diagnosis of C. difficile–induced disease.
CLOSTRIDIAL DISEASES, Treatment
INCLUDING ACUTE HEMORRHAGIC If C. perfringens disease besides acute hemorrhagic diarrheal
DIARRHEAL SYNDROME syndrome (AHDS) is suspected, tylosin (10-20 mg/kg PO
q24h or divided q12h) or amoxicillin (22 mg/kg PO q12h)
Etiology are typically effective in patients that are systemically ill or
Clostridium perfringens and Clostridium difficile can be that have chronic disease. If the diagnosis is correct, response
found in clinically normal dogs. For C. perfringens to produce is expected within 2 to 5 days. Metronidazole is not as con-
disease, environmental conditions must be appropriate for sistently effective as tylosin or amoxicillin. Antibiotic treat-
the bacteria to produce toxin. ment by itself often fails to permanently cure patients with
chronic diarrhea attributed to C. perfringens, but if a high-
Clinical Features fiber diet is fed concurrently with administration of tylosin,
Infection with C. perfringens seemingly may produce various the patient can often be maintained on diet alone once it is
syndromes: an acute, bloody, self-limiting nosocomial diar- in remission. Animals that reliably respond to tylosin or
rhea; acute hemorrhagic diarrheal syndrome (used to be amoxicillin but which relapse every time the antibacterial is
called hemorrhagic gastroenteritis); or chronic large bowel withdrawn (despite remaining on a high-fiber diet) can be
diarrhea. These clostridial diseases are primarily recognized treated indefinitely with the drug (undesirable due to con-
in dogs. Acute hemorrhagic diarrheal syndrome is discussed cerns with promotion of antibacterial resistance) or one can
in detail separately. Disease associated with C. difficile is consider fecal transplantation or probiotic therapy. In con-
poorly characterized in small animals but might include trast, if AHDS is suspected, then fluids are the most impor-
large bowel diarrhea, especially after antibiotic therapy. tant therapy.
If disease caused by C. difficile is suspected, supportive
Diagnosis fluid and electrolyte therapy may be necessary depending on
Finding spore-forming bacteria on fecal smears (Fig. 31.1), the severity of signs. Metronidazole should be effective in
culturing the bacteria from the feces, and detecting C. per- killing this bacterium, but one must be sure to use a suffi-
fringens enterotoxin are neither sensitive nor specific for ciently high dose to achieve adequate metronidazole concen-
disease due to C. perfringens. Finding C. difficile toxin in the trations in the feces. Oral vancomycin is often used to treat
feces, although useful in people, is of uncertain value in dogs people with this disease, but it has generally been unneces-
and cats. If toxin will be sought, then using ELISA to first sary in dogs or cats, and this drug should be avoided in
check for bacterial antigen and, if positive, then ELISA to veterinary medicine as it is a “drug of last resort” in human
medicine.
Prognosis
The prognosis is excellent in dogs with diarrhea caused by
C. perfringens but uncertain for those cases caused by C.
difficile.

Public Health Concerns
There is no obvious public health risk from dogs or cats
shedding C. perfringens despite anecdotal evidence of trans-
mission between people and dogs. Dogs occasionally shed
strains of C. difficile that are found in people but do not
appear to be a risk factor for human infection or disease.

ACUTE HEMORRHAGIC
DIARRHEAL SYNDROME

FIG 31.1 Etiology
Photomicrograph of air-dried canine feces stained with
Diff-Quik. Numerous spores are seen as clear vacuoles in This disease used to be called “Hemorrhagic Gastroenteritis.”
darkly stained rods (×1000). Cause is uncertain but believed to involve C. perfringens.