For many years, a mysterious disease in boa constrictors and pythons called Inclusion Body Disease (IBD) has been the scourge of aquariums, breeders, and pet snake owners. The disease is ultimately fatal, and until now, its cause was unknown. Using the latest methods in ultra deep sequencing and de novo sequence assembly, the DeRisi lab, in collaboration with the California Academy of Science and local veterinarians, has identified a novel snake arenavirus that is closely linked to the disease. The paper describing this discovery is published in ASM's new open-access journal mBio.

Frequently Asked Questions:

Snake Inclusion Body Disease (IBD) and Snake Arenaviruses

1. What is inclusion body disease (IBD)?
IBD is an infectious disease of snakes that is named after the inclusions that are apparent in cells of infected animals. IBD is believed to be a progressive and ultimately fatal disease. Snakes with IBD may display characteristic neurological symptoms such as “stargazing” and may refuse to eat or regurgitate their meals. IBD has been reported to affect a number of snake species, but it has best characterized in boas and pythons. Although it was known that IBD can be transmitted from snake to snake, no infectious agent has been definitively linked to the disease.

2. How is IBD diagnosed?
If a veterinarian suspects IBD he or she will collect a blood sample or perform a liver biopsy. These samples will be sent to a pathologist, who will use a microscope to look for large unusual bodies (inclusions) in cells.

3. Is there any treatment or cure for IBD?
There have been no treatments or cures for IBD. Because of this, euthanasia is recommended if there is a risk of exposure to other snakes or if the snake is displaying neurological symptoms (e.g., stargazing).

4. How is IBD transmitted?
This is unknown. Previous studies and our recent work suggest that IBD might result from a viral infection. Anecdotal reports suggest that snake mites might act as vectors but there is no published data to support this possibility. Additional studies will be required to understand the route of transmission.

5. What are snake arenaviruses and how are they related to IBD?
The snake arenaviruses are several new members of the arenavirus family of viruses. Arenaviruses have previously been known to infect mammals. Their natural hosts are rodents and infection in rodents is typically asymptomatic. Occasionally humans become infected after exposure to secretions of infected rodents. Arenavirus infection in humans can lead to severe or fatal disease. We have established a correlation between the detection of snake arenaviruses and IBD diagnosis and have shown that the inclusions in infected animals contain viral protein.

6. Do snake arenaviruses cause IBD?
Although we have compelling evidence that suggests that these viruses might cause this disease we have not formally demonstrated causation. Additional experiments designed to demonstrate causality will be necessary to formally establish the link between viral infection and disease.

7. How were snake arenaviruses discovered?
Researchers at UCSF, in collaboration with veterinarians Chris Sanders (Wildwood Veterinary Hospitals, Portola Valley, CA), Freeland Dunker (California Academy of Sciences, San Francisco, CA), and Drury Reavill (Zoo/Exotic Pathology Services, Sacramento, CA), analyzed the tissues of snakes with and without IBD. The researchers used the latest DNA sequencing technology to sequence all of the nucleic acid in these samples. The hypothesis was that if a virus caused IBD then its DNA (or RNA) would be evident in the infected tissue. This advanced diagnostic technology has the ability to detect known viruses and to discovery new viruses.

8. Are there any treatments, vaccines, or cures for arenavirus infection?
There are drugs (e.g., Ribavarin) that have been shown to reduce the severity of disease associated with arenavirus infection in humans. There is also a vaccine against Junin virus (an arenavirus) that has been demonstrated to be protective in humans. It remains to be determined whether any of these could be effective in treating or preventing snake inclusion body disease.

9. Can people get IBD/get infected with snake arenaviruses from their snakes?
There is no evidence that snake arenaviruses can infect humans.

10. My pet has been diagnosed with IBD, how can I get it tested for snake arenavirus?
We are interested in working with commercial diagnostic labs to establish and validate such a test. (We have no plans to patent or attempt to profit from the testing, but we lack the capacity of a commercial diagnostic operation). If you are a commercial company interested in working with us, please contact our Logistics Manager, Tara Christiansen at

11. My pet has been diagnosed with IBD, how can I participate in further IBD research?
If you would like to participate in ongoing research efforts. Please send an e-mail to our Logistics Manager, Tara Christiansen at

12. Where can I find the paper describing the discovery of snake arenaviruses?