History
Inclusion
body disease of boid snakes has been recognized since the mid 1970's. It is named
for the characteristic intracytoplasmic inclusions which are seen in epidermal
cells, oral mucosal epithelial cells, visceral epithelial cells, and neurons.
In the 1970's, through the late 1980's, this disease was most commonly seen in
Burmese pythons, Python molusus bivittatus. Starting in the late 1980's until
present, it has been seen most commonly in boa constrictors, Boa constrictor.
All boid snakes should
be considered susceptible. While the disease has not been identified in non-boid
snakes, it is unknown whether nonboid snakes can harbor the virus. The primary
host of this virus has not been identified. Distribution
Worldwide
in captive boid snakes. Its occurrence in the wild is unknown. Ages
Affected
Has been identified primarily in adult snakes. However, all age
groups should be considered susceptible. There are anecdotal reports of infection
in neonates. Etiologic
Agent
A retro-like virus has been incriminated as the causative agent of
IBD (Figure 1). We have an isolate from a boa constrictor that will be used in
a transmission study to fulfill Koch's postulates and determine if it is the causative
agent. reverse transcriptase activity has been demonstrated in supernatant from
viper heart cells infected with this virus. This virus is currently being purified
for biochemical characterization and production of polyclonal antibodies in rabbits. Clinical
Signs History
Inclusion body disease of boid snakes has been recognized
since the mid 1970's. It is named for the characteristic intracytoplasmic inclusions
which are seen in epidermal cells, oral mucosal epithelial cells, visceral epithelial
cells, and neurons. In the 1970's, through the late 1980's, this disease was most
commonly seen in Burmese pythons, Python molusus bivittatus. Starting in the late
1980's until present, it has been seen most commonly in boa constrictors, Boa
constrictor. Host
All
boid snakes should be considered susceptible. While the disease has not been identified
in non-boid snakes, it is unknown whether nonboid snakes can harbor the virus.
The primary host of this virus has not been identified. Distribution
Worldwide
in captive boid snakes. Its occurrence in the wild is unknown. Ages
Affected
Has been identified primarily in adult snakes. However, all age
groups should be considered susceptible. There are anecdotal reports of infection
in neonates. Etiologic
Agent
A retro-like virus has been incriminated as the causative agent of
IBD (Figure 1). We have an isolate from a boa constrictor that will be used in
a transmission study to fulfill Koch's postulates and determine if it is the causative
agent. reverse transcriptase activity has been demonstrated in supernatant from
viper heart cells infected with this virus. This virus is currently being purified
for biochemical characterization and production of polyclonal antibodies in rabbits. Clinical
Signs
Clinical signs are quite variable. Regurgitation and signs of central
nervous system disease (Figure 2; Figure 3; Figure 4A and Figure 4B) are commonly
seen in boa constrictors. Stomatitis, pneumonia, undifferentiated cutaneous sarcomas
(Figure 5), lymphoproliferative disorders, and leukemia have all been seen. Burmese
pythons generally show signs of central nervous system disease without manifesting
any other clincal signs; regurgitation is not seen in Burmese pythons. Pathology
By
light microscopy, in hematoxlin and eosin stained tissues sections of a wide variety
of epithelial and neuronal cells, characteristic intracytoplasmic inclusions are
seen. Several snakes have been seen with proliferative pneumonia (Figure 6). While
inclusions are commonly seen in the liver, kidney, and pancreas (Figure 7; Figure
8; Figure 9), we have seen cases where there are very few inclusions. In a few
snakes with signs of central nervous sytem disease, and with a severe encephalitis,
no inclusions have been seen in any cells. While the presence of chracteristic
inclusions is diagnostic for the disease, the absence of inclusions does not necessarily
mean the snake is disease or IBD virus free. While cells having inclusions may
show mild degeneratve changes, inflammation is rarely seen in visceral tissues.
In the brain, mild to severe encephalitis, with lymphocytic perivascular cuffing
may be seen. Several snakes with lymphoproliferative disorders have been identified
with lymphoid infiltrates in multiple organs. Transmission
Exact
route of transmission has not been identified. Possibly by: 1) direct contact;
2) intrauterine transmission to developing embryos in viviparous species and eggs
in oviparaous species; 3) veneral transmission. The snake mite, Ophionyssus natricis
has been implicated as a vector for the virus since mite intestations are commonly
seen in epizootics of IBD. Diagnosis
Currently
there is no serologic assay available for determining exposure. We are working
toward developing an immunoflourescence assay. At the University of Florida College
of Veterinary Medicine, we perform complete blood counts on suspect snakes. Infected
snakes commonly have white blood cells counts > 30,000/ul. Intracytoplasmic
inclusions are occasionally seen in peripheral lymphocytes (Figure 10). We also
take esophageal, gastric, and liver bopsies. If inclusions are identified in any
cells, euthanasia is recommended. Control
Identify
infected snakes and euthanatize. All new snakes should be quarantined for minimally
90 days before introduction into an established collection. Recommendations for
boas is 6 month quarantine period. Mite control and elimination is essential.
Fibroglass cages of infected snakes should be cleaned with chlorox and left out
in the sun to dry before being used for other snakes. Wooden cages, unless sealed
with urethane or some other sealeant should be discarded. Current
and Future Research - Isolation
and purification of the causative agent.
- Development
of a serodiagnostic test.
References - Schumacher,
J., Jacobson, E.R.; Homer, B.L.; Gaskin, J.M. 1994. Inclusion body disease in
boid snakes. J. of Zoo and Wildlife Med. 25(4):511-524.
- Axthelm,
M.K. 1985. Viral encephalitis of boid snakes. Int. Colloq. Pathol. Reptiles Amphib.
3:25. (Abstract)
For More Information Contact:
Dr.
Elliott Jacobson
Box 100126
Department of Small Animal Clinical Sciences
College
of Veterinary Medicine
University of Florida
Gainesville, Florida 32610 Dr.
Juergen Schumacher
Box 100126
College of Veterinary Medicine
University
of Florida
Gainesville, Florida 32610 | 