Cryptosporidiosis in Snakes
Cryptosporidiosis is an increasingly diagnosed parasitic
infection in reptile collections, particularly in snakes.
The course of the disease is unusual since it tends to be
self-limiting in immunocompetent bovines, canines, felines,
and other species, but can be fatal in its reptilian host.
The infection is often insidious in onset, causing irreversible
pathological changes before physical signs develop. Clinically
healthy, intermittent shedders may become symptomatic
years after the parasite is first diagnosed in the animal.
Additionally, the affected animal may die acutely, or the
clinical disease may take up to two years before killing its
The life cycle of Cryptosporidium serpentis is thought
to be similar to that of Cryptosporidium parvum,muris,
and other species in mammals. Two types of infective stages
are produced. The first is a thick-walled oocyst which contains
four sporozoites. The oocysts are passed in the feces and
remain infective in the environment for months, where they
are extremely resistant to temperature extremes and disinfectants.
These oocysts are responsible for both infections in new hosts
as well as reinfection of the original host. The oocysts are
ingested, and the four sporozoites are released. The second
stage involves four sporozoites encased not in a thick wall,
but rather in a single, thin membrane. This membrane ruptures
after breaking out of a host cell, releasing the sporozoites
and immediately reinfecting the host animal. In both stages,
the sporozoites infect the microvillus border of the gastric
glands, and in snakes, lesions are usually localized to the
The classic presentation of Cryptosporidium serpentis
infection in the snake is an animal which regurgitates its
meal within four days or less of ingestion. This regurgitation
occurs because of decreased gastric lumen size and mucosal
irritation. Since the diameter of the stomach has often increased,
a noticeable swelling can be visualized and palpated in the
mid-body region. The snake may
or may not be anorexic, depending^n how far the disease has
progressed. Often, a mucoid diarrhea is noticed.
It is important to differentiate Cryptosporidiosis from other
causes of regurgitation and gastritis. Suboptimal temperatures,
inappropriate prey size, stress, and foreign body obstructions
are other potential causes of regurgitation. Hibernation
associated necrotizing gastroenteritis, parasitism from other
protozoa and nematodes, viruses, Salmonella and other
bacteria can all cause similar signs, but the gastric swelling
is pathognomonic for Cryptosporidiosis.
In the living animal, Cryptosporidiosis can be diagnosed
by gastric lavage,endoscopic gastric biopsy, fecal smears,
and smears of mucous adhered to regurgitated prey items. Since
oocysts are intermittently shed, it is recommended that multiple
samples be taken. It is important to note that a negative
result does not imply that the animal is not infected, only
that oocysts may not be present in the particular sample.
Acid fast staining is the preferred technique for cytology
and fecal preparations, and is easily performed.
Gross lesions include gastric hyperplasia and fibrosis, a
decreased diameter of the gastric lumen, and an increased
overall diameter of the stomach. Often, the gastric mucosa
will be edematous and the rugal folds thickened longitudinally.
Additionally, petechial hemorrhage and focal areas of necrosis
may be observed.
Histopathologically, the microvillus brush border becomes
disrupted as new oocysts burst out of their host cells. The
acid secreting cells that line the gastric pits become reduced
in number. Mucous secreting cells are hyperplastic, and the
mucosa atrophies while the submucosa and musculature becomes
fibrotic.Leukocytes may be present in response to the inflammatory
process, and the lamina propria may become edematous. The
organisms are microscopically visible attached to the epithelial
cells of the brush border microvilli. It is recommended that
multiple samples of gastric tissue, taken at necropsy, be
submitted for histopathology in order to improve the chances
of recognizing the organism.
Currently, there is no evidence that Cryptosporidium
serpentis is transmissible to humans or other mammals.
References available upon request.
-by David Kolins, Class of 1996
-Edited by M. Randy White, DVM,PhD