IV. Tyzzer's Disease

IV. Tyzzer's Disease





A. Etiology:


Clostridium piliforme, an obligate intracellular
bacterium, is a Gram-negative, pleomorphic, filamentous organism that can
produce spores.







B. Transmission:



The disease is spread by spore ingestion (fecal-oral).
Spores can remain viable at moderate to freezing temperatures for extended
periods of time (> 1 year).


The disease is perpetuated in breeding
colonies by the infection of bunnies born into the colony. The incidence
of disease is moderate.





C. Clinical Signs:


Usually rabbits are affected shortly after weaning
when passive immunity, if present, has waned.

Acute, profuse watery
to mucoid diarrhea, dehydration and death within 12 to 48 hours after onset
of diarrhea are typical.

The mortality rate is high. Exposure
of naive adult rabbits may cause little to no clinical disease.




D. Pathology:



Lesions in weanling rabbits include edema and hemorrhage
of mucosa, submucosa, and musculature of intestinal tract (A.).






It is unusual
to see an enlarged liver with multifocal tan to yellow foci of necrosis
or hemorrhage of the myocardium as is described in the literature.





Extensive mucosal necrosis with a granulomatous cellular mucosal infiltrate
may occur in the ileum, cecum, and proximal colon.






Visualization of the
bacterium is enhanced with use of silver stains.




Argyrophilic intracellular
bacteria in clusters or "pick-up-sticks" or haystack clumps are present
in viable enterocytes in areas of granulomatous enteritis (B.), and if
heaptic necrosis is observed, in hepatocytes adjacent to an area of necrosis.






E. Diagnosis:


Histopathological examination of liver or cecum
stained with silver will be diagnostic if intracellular bacterial rods
are observed.


PCR of feces, intestinal tissue or liver can be used
to document the presence of the bacterium.


An ELISA is useful to
detect antibody in recovered or asymptomatically infected rabbits.



F. Treatment:

No therapy has been uniformly successful.

Supportive therapy
may help when the enteric disease is mild and the rabbit is still eating.



G. Control:


Prevent overcrowding and use good sanitation techniques.


Stresses such as weaning and high environmental temperature may precipitate
an outbreak.






To minimize the stress of weaning, let the bunnies stay
in the original cage and remove the doe.





Work to prevent temperature
fluctuations and keep the rabbits well-ventilated in high temperatures
with fans. The spores are resistant to many disinfectants.






A 1% bleach solution will inactivate spores that remain after the fecal
material has been washed off soiled cages.





Temperatures of water
used to clean cages may also inactivate spores if the cages and supplies
are allowed to contact 180^oF water for no less than 15 minutes.