| INCLUSION
BODY DISEASE - CASE STUDY
Case II - 165 or 96N165
(AFIP 2548995)
Armed Forces Institute of Pathology Conference,
September 11 1996
Conference Moderator: Jennifer A. Burris, Commander,
Public Health Service, Diplomate, ACVP
Food and Drug Administration
HFV-150, 750 Standish Place
Rockville, MD 20855
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Necrotizing enteritis and ulceration
in a red-tailed boa constrictor with zygomycosis
and concurrent boid inclusion disease. (HE,
40X,) |
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Pleomorphic fungal hyphae within
the ulcerated areas of the enteric mucosa
which have non-parallel walls, range up to
20 microns in diameter, are pauciseptate,
and stain well with HE - all characteristics
of a zygomycete. Further speciation is not
possible based on examination of this fungus
in tissue section. (HE, 400X) |
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Numerous round cytoplasmic inclusions
with enteric mucosal epithelial cells, which
are characteristic findings in boid inclusion
disease. Inclusions were also seen in lymphocytes
and cells of the myenteric plexus. (HE, 400X) |
Signalment:
3-year-old red-tailed boa constrictor (Boa
constrictor).
History:
This boa was part of a colony of over 40 exotic
snakes of various species. It had a 5 month history
of lethargy, intermittent anorexia, weight loss,
and fetid loose feces. On physical examination
it had dehydration and petechiation of its oral
mucosa and ventral scutes. It was treated with
fluids and antibiotics over a period of 2 months
without improvement.
Gross Pathology:
Marked coelomic and pericardial serous effusions.
Diffuse petechiation of fat bodies and subcutis.
Focal segment of distal small intestine with severe
edema and luminal accumulation of partially adherent
thick mucoid material.
Laboratory Results:
CBC (4 weeks ante-mortem): PCV = 21%, WBC
= 1500 cells/ul Intestinal contents, fungal culture:
Small numbers ofTrichosporon beigelii, Aspergillus
clavatus; Salmonella culture negative fecal floatation
negative IFA for Giardia and Cryptosporidium negative.
Contributor's Diagnosis and Comments:
- Necrotizing enteritis, heterophilic and granulomatous,
moderate, focal, with intra-lesional fungal
hyphae and yeast forms - presumptive etiology:
Aspergillus clavatus, Trichosporon beigelii.
- Intra-cytoplasmic eosinophilic inclusion
bodies in most cell types - Boid inclusion body
disease.
Inclusion body disease (IBD) affects various
species of boid snakes and usually manifests as
progressive debilitation, anorexia, weight loss,
regurgitation, and neurologic signs. The presence
of the typical, well-defined intracytoplasmic
eosinophilic inclusion bodies is often associated
with cellular degeneration in various tissues,
most commonly in the CNS, where a non-suppurative
encephalomyelitis can also be observed. Various
secondary infections are frequently associated
with IBD, such as pneumonia and nephritis. In
this boa, encephalitis was not noted, although
inclusions were numerous in the brain, and were
associated with degeneration. The animal also
had a mycotic enteritis affecting a focal segment
of distal small intestine. The morphology of the
fungal elements (pleomorphic hyphae, yeast forms)
was compatible with both the Aspergillus clavatus
and Trichosporon beigelii organisms obtained by
fungal culture of the intestinal contents. The
boa probably developed fungal enteritis from the
changes in gut flora induced by prolonged antibiotic
treatment; IBD may have been a predisposing factor.
Electron microscopy of liver tissue revealed that
the inclusions contained granular homogenous osmiophilic
material. Lined around the periphery, and occasionally
inside the inclusions were numerous clathrin-coated
pinocytotic vesicles. A few particles consistent
with type C retroviruses, measuring 95-110 nm,
were observed in the intercellular spaces, sometimes
budding from the cell membrane. The particles
were similar to those previously reported in snakes
with IBD (see reference).
AFIP Diagnosis:
Intestine: Enteritis, ulcerative, necrotizing,
granulomatous, multifocal, severe, with fungal
hyphae, red-tailed boa constrictor (Boa constrictor),
reptile, etiology consistent with a zygomycete.
Intestinal epithelium; lymphocytes; intestinal
ganglion cells of myenteric plexi: Eosinophilic
intracytoplasmic inclusion bodies.
Conference Note:
The inclusions in submitted tissues are eosinophilic
to amphophilic, range up to 10 microns in diameter,
and did not appear to be associated with degenerative
or inflammatory changes. The morphologic features
of the fungus are consistent with the those of
the Class Zygomycetes and not with Aspergillus
or Trichosporon spp. These features include broad,
thin-walled, infrequently septate, pleomorphic
hyphae that range from about 5 to 20 m in width
and irrgeular right angle branches. The fact that
the hyphae stain well with H&E is also characteristic
of a zygomycete.
Inclusion body disease of boid snakes has been
recognized for over 20 years in private and zoological
collections in the United States. The disease
affects only snakes of the Family Boidae including
both boa constrictors and pythons. The disease
is characterized by the formation of intracytoplasmic
inclusions in the epithelial cells of all major
organs and neurons in the central nervous system.
Clinical symptoms include head tremors, disorientation,
incoordination, and regurgitation. Ultrastructurally,
a type C retrovirus has been associated with the
lesions. The presence of a retrovirus is supported
by demonstration of reverse transcriptase activity
in the plasma and within the supernatant from
primary kidney cell cultures of affected snakes.
Major histologic lesions include a nonsuppurative
meningoencephalitis with neuronal degeneration,
gliosis, and demyelinization. Intracytoplasmic
inclusions are noted within degenerating neurons
of the gray matter and ependymal cells. Inflammation
in the central nervous system is more severe in
pythons; however, intracytoplasmic inclusions
are more numerous in boa constrictors. In the
experience of pathologists at the National Zoological
Park, Washington D.C., inclusion body disease
has been found not only as a primary disease but
also in association with secondary infections
or as an incidental finding. In fact, many lesions
within visceral organs of affected snakes have
been attributed to secondary infections.
Contributor:
Dept of Veterinary Pathology, Microbiology
& Immunology School of Veterinary Medicine,
University of California, Davis, CA 95616.
Reference:
- Schumacher J, Jacobson ER, Homer BL, Gaskin
JM. Inclusion body disease in boid snakes, J
Zoo and Wildlife Med 25(4):511-24, 1994.
- AFIP. 1996. AFIP Wednesday Slide Conference
- No. 2 September 11 1996 Extract.
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