AN UPDATE ON INCLUSION BODY DISEASE VIRUS IN BOID SNAKES

A disease characterized by the presence of intracytoplasmic inclusions in cutaneous and visceral epithelial cells, and neurons, has been reconized in members of the families Boidae and Phythonidae for over 20 years. This disease has been named inclusion body disease (IBD) of boid snakes. Starting i the late 1970s and extending into the mid 1980s, Burmese pythons (Python molurus bivittatus) were the most common boid snake diagnosed with this disease. In affected Burmese pythons, signs of central nervous system disease are typically seen. While also sen in boa contrictors (Boa constrictor) during this period of time, within the last 5 years more cases have been seen in boa contrictors as compared to Burmese pythons. The exact explanation for this shift is not known but may have to do with increased numbers of boa contrictors being bred for the pet trade and the ease in which these snakes are transported for breeding and sale. Initially, clinical signs in boa constrictors included regurgitation and signs of central nervous system disease. However, over the last few years a number of snakes with atypical clinical manifestations have been seen including stomatitis, pneumonia, and lymphoproliferative disorders. While a retro-like virus was identified in tissues of affected snakes and Koch's postulates were fulfilled using virus-positive tissue the original isolate was lost and never recovered. Recently, a virus has been isolated from an IBD-positive boa constrictor in our laboratory and the electron microscopic features and presence of reverse transciptase activity in infected cell cultures support this virus as being a member of the family Retroviridae. This isolate will be injected into clinically healthy captive-bred Burmese pythons to determine ist pathogenicity. We are in the process of purifying this virus for the production of specific antibodies in rabbits and the development of a virus-specific immunofluorescence assay. Currently, antemortem diagnosis is based upon the presencce of intracytoplasmic inclusions in esophageal, stomach, and liver biopsies, and the presence of elevated peripheral white blood cell counts (>30,00 cells/ul). The exact route of transmission is unknown. The snake mite, (Ophionyssus natricis), has been seen in multiple epizootics of IBD and may be involved in transmission. direct contact and venereal spread may be involved. some infected snakes may act as silent carriers, not exhibiting clinical signs for many years. Control centers around identification and elimination of known positive animals.

Acknowledgements: The author thanks Ms. Sylvia Tucker, Ms. Betty Hall, Dr. Bruce Homer, and Dr. Ayalew Meergia for their technical assistance.

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