A Primer on IBD and Reptarenavirus

[WrongPython]

A Primer on IBD and Reptarenavirus

As written and shared by WrongPython, thanks to the work and help of the Reptile Health/Testing Friendly Community



What are IBD and reptarenavirus?

Inclusion body disease (IBD) is a disease in snakes caused by a type of virus called Reptarenavirus (AKA “arenavirus,” or just “arena;” Merck Vet Manual). Both IBD and reptarenavirus are typically associated with boas, as these are the snakes most typically affected by it in captivity. For this reason, IBD is also referred to as “boid inclusion body disease” (BIBD) in some circles. The reptarenaviruses that cause IBD in boas are also capable of infecting pythons (Hetzel et al. 2021, 2013). Reptarenavirus also appears capable of infecting colubrids, though it is not known whether this is the same type of reptarenavirus that causes IBD in boas or a different type altogether.


What are the symptoms of IBD and reptarenavirus infection? Does reptarenavirus always cause IBD?

A detailed description of IBD symptoms in boas and pythons may be found in the Merck Veterinary Manual (link here). Anecdotally, some keepers also report that reptarenavirus-infected boas develop respiratory infections (RI) or RI-like symptoms, as well as early-developing cancers.

It’s important to note that a significant number of reptarenavirus-infected boas will display no outward symptoms of their condition. They may eat, shed, and even breed normally for months or years. However, these boas are still infected and capable of spreading reptarenavirus to other snakes. After a period of time, these boas may develop the immunosuppressed condition roughly similar to AIDS in humans or IBD. Since the symptoms of reptarenavirus infection can be so varied, it is recommended that IBD and reptarenavirus should be considered in every sick boa (Merck Vet Manual).

Evidence suggests that boas with acute IBD may actually be simultaneously infected with two different strains of reptarenavirus (Heopjoki et al., 2015).


How does reptarenavirus spread?

Reptarenavirus can spread via contact with the body fluids from infected snakes. The transfer of body fluids can occur via mating, swapping of unclean cages and water bowls, and possibly mites.


How widespread are reptarenavirus and IBD?

That’s hard to say, as many keepers and breeders do not routinely test their snakes for the presence of reptarenavirus. One survey of 40 collections in Belgium found that 34% of boas tested were positive for IBD and 17% tested positive for reptarenavirus via a blood sample-based test (Simard et al., 2020). So, to err on the side of caution, it’s safer to assume that reptarenavirus is fairly widespread within the captive boa population and react accordingly.


How do I know if my snake has IBD or reptarenavirus?

The only way to definitively know if your living snake is infected with reptarenavirus is to have them tested for it. Diagnostic tests based on blood or oral swab samples are available through your veterinarian and (in the US) directly from testing companies for at-home sample collection.

If your snake has already passed away, request that your veterinarian perform a necropsy to check for the virus and the tell-tale inclusion bodies it leaves behind.


How can I get my snake tested for reptarenavirus?

Within the US, there are two main reptarenavirus testing options.

The University of Florida (link here) offers two types of reptarenavirus tests using blood samples: a standard PCR that simply tests for the presence of any strain of reptarenavirus, and a qPCR test that checks the viral load (ie. how many copies of the virus are in a snake’s blood) of a specific strain. To test through UF, set up an appointment with your vet and have them contact the lab, collect samples, and overnight them to UF. Note that UF will only work directly with veterinarians, ie. not private owners. Prices per test (before the associated vet fees) as of this writing are $135 for standard PCR and $65 for qPCR.

Research Associates Laboratory (RAL; link here) offers a simple PCR test for the presence of reptarenavirus using an oral swab sample. This swab may be collected at home or at your vet’s office. To test via RAL, order the quantity and size of swabs you need via their site, collect your samples, fill out the order form, and overnight the samples to RAL. Results are typically delivered by the end of the business day after the samples are received. Price per test (before the cost of swabs and mailing) are $25 for reptarenavirus only and $60 for a full boid panel that also included nidovirus/serpentovirus and paramyxovirus testing.

Keepers who have tested snakes through both labs report that their test results are in agreement with each other. Therefore, both labs can be trusted equally well. Use whatever lab is most feasible for you.


What should I do if my snake tests positive?

Reptarenavirus-positive snakes should be quarantined away from other snakes immediately and remain in said quarantine for the rest of their life.

There is no cure for reptarenavirus infection or IBD and no evidence to suggest that snakes can clear reptarenavirus infection on their own. Once a snake is infected, they are infected for life. Therefore, many owners opt to humanely euthanize their snakes once infection or IBD is confirmed.

It is extremely unethical to knowingly sell reptarenavirus-positive snakes and their offspring, particularly when doing so without disclosing their status. This sort of behavior has led to the pervasiveness of reptarenavirus within the hobby and the suffering of hundreds -- if not thousands -- of snakes. If you are a breeder and were notified that a snake you sold tested positive for reptarenavirus, immediately isolate and test that snake’s parents and littermates. If you offer a health guarantee and the buyer reported in a timely manner (ie. sample collection was conducted within under a week of receipt), offer a refund.

The ethics of rehoming a positive snake to a single snake-only home are dubious. As reptiles are stoic creatures that avoid displaying pain or discomfort, said snake may already be discomforted despite a lack of outward symptoms. Furthermore, this places the onus and costs of eventually euthanizing the snake on new owners.


I’ve heard about “false negatives” and “false positives” from IBD and reptarenavirus tests. What are those?

False negatives and positives stem from errors or hiccups in the PCR testing process.

False negatives occur when not enough copies of reptarenavirus are present in a sample to trigger a positive result. All diagnostic PCR tests a minimum number of copies of a virus to be present in a sample to yield a positive result. If the number of copies of virus in a sample (the “viral load”) is lower than this minimum, the PCR test will incorrectly return a negative result. While this is the more common of the two testing errors, it is still rare, and is typically only encountered when investigating reptarenavirus infection in its very early stages (ie. when the boa has not had enough time to build up a large viral load).

False positives occur when a snake without arenavirus is said to be positive. They may result from the accidental cross-contamination of samples or calibration/reading error within the PCR machine/process. This type of error is extremely rare. Prompt re-testing of a suspected false positive snake can quickly rectify this error.


How can I keep my snake from getting reptarenavirus?

As there is no cure for reptarenavirus infection or IBD, the only definitive way to keep reptarenavirus out of your reptile group is to follow proper quarantine procedure with and test all new arrivals.

Best practice quarantine procedure for new boas is reptarenavirus testing upon receipt, a one year quarantine period, and further testing before the boa is graduated from quarantine and introduced into the main group. At a minimum, new boas should be tested upon receipt, quarantined for a minimum of 90 days, and tested again before being graduated from quarantine. Ideally, you could obtain a pre-sale test from your new boa’s current owner as well, to prevent a positive individual from reaching your home/facility in the first place.

As pythons are much more sensitive to reptarenavirus, the 90 day minimum with testing is likely sufficient to catch any positive individuals.


Sources Cited

Divers, SJ. Viral Diseases of Reptiles - Exotic and Laboratory Animals. Merck Veterinary Manual. Available at:https://www.merckvetmanual.com/exotic-and-laboratory-animals/reptiles/viral-diseases-of-reptiles. Accessed November 7, 2021.

Hepojoki J, Salmenperä P, Sironen T, et al. Arenavirus Coinfections Are Common in Snakes with Boid Inclusion Body Disease. J Virol 2015;89:8657–8660.

Hetzel U, Korzyukov Y, Keller S, et al. Experimental Reptarenavirus Infection of Boa constrictor and Python regius. Journal of Virology 95:e01968-20.

Hetzel U, Sironen T, Laurinmäki P, et al. Isolation, Identification, and Characterization of Novel Arenaviruses, the Etiological Agents of Boid Inclusion Body Disease. Journal of Virology 2013;87:10918–10935.

Simard J, Marschang RE, Leineweber C, et al. Prevalence of inclusion body disease and associated comorbidity in captive collections of boid and pythonid snakes in Belgium. PLOS ONE 2020;15:e0229667.