I'm not an expect on the subject, but I think it's very important to share awareness about this disease. It can be hard to find information about it, and sometimes when you find something, it's just much and complicated the things you find. So I have just tried my best to gather information from the internet, facebook groups and breeders and then written it together simple (as good as I can).

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Arena virus / IBD

Arena virus / IBD is a widespread disease among boas. The disease is among constrictor snakes, though it's not seen so much with Colubridae, most commonly seen at boas (Boidae) and pythons (Pythonidae).

The virus goes into the immune system, where it eventually goes to the brain and nerves.

Arena virus / IBD is as with e.g. HIV / AIDS. The arena virus develops into IBD. 

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Affected snakes usually die from secondary infections, such as bacterial (salmonellosis), fungal (aspergillosis), protozoal (amoebiasis), and blood infections that take over due to a weakened immune system. These infections cause diseases of the brain, lungs (pneumonia), liver, stomach, intestine, bones, and cancers of the blood (lymphoma). This is probably a consequence of immunosuppression since both red and white blood cells, as well as the cells of the bone marrow, also develop the typical inclusion bodies that probably impair the function of these cells.

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Quarantine

It's always a good standard to have new snakes quarantined. E.g. 3 months. This can be done by keeping the snake in a box on a paper towel or newspaper, and place the box in a room away from your other snakes. Hand sanitizer are always used before and after handling.

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Symptoms

The case with boas ​is the disease outcome varies; affected animals either die within weeks or months or become healthy-looking carriers of the disease. They can be infected, but go on for years without showing any symptoms, but in that time infect others, which is why it's a widespread disease. It is estimated that approximately 20% of captive boa constrictors are infected with the virus.

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The best thing to do when you get a new boa home, is to have it checked as soon as possible for the virus.

On the other hand, pythons, if infected, generally develop severe fatal neurological symptoms within a few weeks, so that would be discovered already in the quarantine.

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As I mentioned, there are many healthy carriers of the infection, and those who haven't developed IBD yet. However, they can have symptoms that aren't very alarming. Since the disease affects the immune system, it can cause problems with 'common' things like colds, aggressiveness, they stop eating or dehydration before it breaks out.

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When it develop from arena to IBD breaks out, it has gone into the brain and into the nervous system. The symptoms will most likely be evident. They will toss, turn and twist.

In the video below you can see the typical symptoms. It shows how the snake has difficulty turning themself up again when layed on their backs. A healthy snake would do it quickly. At the end of the video you can also see how the snake turns and twist.

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Inclusion Body Disease (video not by me, credit to the youtuber)

 

Spread

The disease transmits through liquids and isn't airborne. So that means it can transmit, for example, if they drink from the same water bowl or if two snakes are paired. Another example, if a female has the disease and gets paired up and gets offspring, it will result in both the male and all the offspring now having the virus.

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Another way it quickly spread in the collection, is if you get/have snake mites (Ophionyssus matrices) infestation.

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Diagnoses

The exact cause of IBD is unknown, but nevertheless a test has been developed. It's found that infected snakes have a unique protein in their cells, and this is why it can be tested. The test started to be developed in 2014, where it started to be tested with a blood test and sent to a laboratory abroad. At that time, IBD and arena virus were not known to be linked, but genetic similarities were found between the unique protein and the protein in the arena virus. 

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Subsequently, a month swap test has been developed.

When a snake is affected it takes 3 months from infection, before a test can track the virus.

False negative tests (which says the snake does not have IBD but really does) are unfortunately possible, however. The test is about 90% sure, so it may be an good idea to test new snakes again after a every few months, so you can be all sure the snake is not infected. In contrast, if the test is positive, you are 100% sure that the animal is infected.

 

Specially as a breeder it's a good idea to test the entire collection before mating season begins, so you are sure all animals are still healthy and therefore don't breed a lot of affected babys. 

 

Treatment

There is no treatment or vaccine for arena virus / IBD.

The best thing to do to prevent IBD in your collection, is quarantine, good hygiene and always test new snakes.

 

If a snake is affected and tested positive for the virus, or if you have an untested snake that begins to show neurological symptoms (= IBD), humanely euthanized is the only thing to do. As there's no treatment, it's better just to ends its sufferings, and keeping it alive is only a risk of transmitting the disease to your other snakes.

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