Inclusion body disease

Inclusion body disease (IBD) is an infectious and invariably fatal viral disease affecting captive specimens of the boid family of snakes, particularly Boa constrictor. It has been recognized since the mid-1970s. It is so named because of the characteristic intracytoplasmic inclusion bodies that are observed in clinical examinations in epidermal cells, oral mucosal epithelial cells, visceral epithelial cells, and neurons. In the 1970s and 1980s, the disease was most commonly observed in Burmese pythons (Python bivittatus). From the 1980s on, it has been most commonly observed in boa constrictors. To date, no treatment for IBD is known, and snakes that are diagnosed with IBD should generally be euthanized to prevent suffering in the snake and to reduce the risk of further infections.

All boid snakes should be considered susceptible to the disease. Many zoos quarantine boas specifically as a result of the risk of IBD before introducing them into their permanent collections and breeding programs. While the disease has not been identified in non-boid snakes, non-boid snakes can harbour the virus. Mites are thought to be the primary vector of the virus, or at least to be a contributory factor.

Its distribution is worldwide, specifically in captive boid snakes. Its occurrence in the wild is unknown. The disease has only been identified in adult and subadult specimens, not neonates. Even so, all age groups are considered susceptible, and anecdotal reports of the infection in neonates have been made. A retro-like virus infection was suspected as the causative agent of IBD, but identification of highly divergent arenavirus sequences from boa constrictors with IBD suggested arenaviruses to be the etiological agent of IBD. Cell culture isolation of several arenaviruses from boid snakes with IBD further solidified, but did not yet confirm, the etiological relationship between IBD and arenaviruses.

In pythons and juvenile boas, the disease presents as an acute and severe neurological illness that is fatal in a few weeks. In adult boa constrictors, the disease assumes a milder, more chronic or, sometimes, even asymptomatic carrier form with a wide array of extremely variable manifestations that may or may not gradually progress to death over a course of months to years. Because they seem to tolerate infection so much better, boas are speculated to be the natural host of the virus, but this has not been confirmed.