WildLife Group
of the SAVA
Demonstration of oocysts in fecal smears with modified
Ziehl-Neelsen stains, fecal flotation techniques and
polymerase chain reaction (PCR), must be correlated
to the clinical signs and other pathogen/s isolated.
The mere detection of Cryptosporidium does not
necessarily mean this protozoan is the cause of the
disease process. Rapid immunochromatographic tests,
ELISA and fluorescent antibody techniques (FAT) have
not been validated in wildlife species.
Histological examination of formalin-fixed intestinal
sections (jejunum, ileum, cecum, colon) still provides
the most reliable means of diagnosis. The diagnostic
power of histopathology is that the presence of
Cryptosporidium can be directly correlated to the
severity of the villous pathology and therefore,
whether the infection is likely to be related to clinical
disease (figure 5 and figure 6). However, the diagnostic
success of histopathology relies almost entirely on the
correct formalin fixation procedure (figure 7 and figure
8).
Figure 6. Small intestine- higher magnification revealing spherical
cryptosporidia colonizing the surface villous epithelium (arrows)
Post mortally it is imperative that both fresh samples
for culture as well as formalin fixed tissue samples for
histopathology are collected. Many other important
enteric pathogens can complicate cryptosporidiosis
and these need to be identified to formulate the most
relevant control program for a particular outbreak.
In many instances the Escherishia coli and Salmonella
involved are opportunistic or low pathogenic strains,
which have been potentiated by the pathology
caused by the cryptosporidium. Therefore, before any Figure 7. Small intestine- poor fixation with extensive mucosal auto
digestive change with fragmentation of the mucosa.
Figure 5. Small intestine- marked villous atrophy with flattening and
doming of the stubby villi. Heavy colonization of the surface villous
epithelium by myriad spherical cryptosporidia (arrow) Figure 8. Small intestine- higher magnification of poor fixation demon-
strating the fragmented sections of villous epithelium which severely
complicate histological examination..jpg
6