IBD in boid snakes - new study

[Regius_049]

This is meant as something as a PSA for those who haven't seen it.

There is a new study on IBD (inclusion body disease) that was recently published in the Journal of Virology. The study was done to attempt to prove kochs postulates that the arenaviruses (specifically golden gate virus or GGV/GoGV) indeed cause IBD in boid snakes.

The authors followed both boa constrictors and ball pythons after they were inoculated with GoGV via cardiac injection and the two species were monitored for routes of viral shedding and disease progression.

The results were quite striking but no entirely out of line with previous information. One ball python was injected with only GoGV and the other with GoGV and a reptarenavirus isolated from a deceased boa constrictor that had died of IBD. Disease developed in both ball pythons after approximately 2 months time. Symptoms included lethargy, abnormal posture, paralysis, and failure to right themselves when placed on their back. In ball pythons the virus and viral proteins were only detected in the central nervous system (specifically within the brain) using PCR testing. Viral RNA in ball pythons was unable to be recovered from blood, liver, lung, and kidney tissue. Interestingly, no gross lesions or obvious inclusions were found in the diseased ball pythons, but increased CNS (central nervous system) inflammation was apparent. Using staining techniques, inclusion bodies were detected but only in nervous tissue and rarely in bile ducts.

In contrast, 8 boa constrictors were used for study. 5 of the first 6 boa constrictors submitted for testing were initially tested positive for viral RNA. 3 additional boa constrictors from a closed collection that initially tested negative were also inoculated using GoGV virus for study. Not a single boa constrictor developed IBD during the course of the 2 year study with behavior and weight gain being normal for all specimens. Prior to euthanasia, viral RNA was detected in liver tissue as well as fecal matter, shed skin, and urates. While viral RNA was able to be detected in these using PCR, attempts to isolate a usable virus were unsuccessful. After euthanasia, viral RNA was also detected more or less systemically throughout the specimen (liver, lung, trachea, tonsil, spleen, brain) despite no apparent signs of disease.

The authors note that boa constrictors may be natural reservoirs for arenaviruses and they evolved alongside rodent arenaviruses in the Americas, while ball pythons are native to africa. The authors are however careful to note that this is a small subset of reptarenaviruses and these results may not be indicative of all cases regarding the causative agent(s) for IBD. The "n" value for this study is also quite small.

The assertion that pythons succumb to IBD quickly compared to boas has been widespread and this study appears to generally support this notion, but other arenaviruses or a study with more subjects may have different results. Indeed there are anecotal reports of ball pythons and other python species seemingly living with IBD for much longer. Somewhat comforting is that ball pythons did not appear to shed the virus as easily as the boa constrictors and were more of a "dead end" as far as viral spread. However, this makes antemortem testing of IBD in ball pythons more difficult if this is correct. Boa constrictors appear to be prime candidate for IBD as a reservoir and for transmision based on this study and those preceeding it.

I will say that while enlightening, this is all quite limited information and more research is without question needed to address things with more certainty. For me personally, I would be interested to know in what percentage of IBD cases a boa constrictor snake was involved. It would be interesting to see if disease can spread from an IBD+ ball python to an IBD- ball python in a controlled setting.

If nothing else, I would like to make owners aware that a 30 day quarantine period is likely wholly insuffucient for IBD screening. It appears that IBD is quite prevalent in captive boa constrictors from most of the literature I have seen, but if this is the case, why is the disease so rare? Given the popularity of the boa constrictor, I would expect to hear about it more often. Either it is very difficult to transmit, fragile outside of a host body (indeed enveloped viruses of this nature usually are), or subclinial cases in non-boas are more common than this study suggests. It is also possible there is some element of truth to each postulate.

The paper is titled: "Differential Disease Susceptibilities in Experimentally Reptarenavirus-Infected Boa Constrictors and Ball Pythons" for those interested in reading it.

[bcr229]

This is listed as an "open access article" available at http://jvi.asm.org/content/91/15/e00...2-c255ccaa9fb0