The Inclusion Body Disease (IBD)

What is IBD?

Relatively little is known about the inclusion body disease at this point. Naturally, this has lead to a number of rumors, half-truths, assumptions, and exaggerations being spread.

Therefore we are inclined to answer to the question "What is IBD?" polemically as follows: IBD is the favorite topic to slobber over in the reptile forums on the internet, relished by ignorant talkers who have no idea. With terms like "boa aids" these trolls are creating panic where sober facts would be appropriate.

But polemic doesn't help in this matter therefore we would like to contribute the following chapter to this topic, and thank Dr. rer. nat., Dr. med. vet. Udo Hetzel, University of Liverpool (UK), Department Of Veterinary Pathology for reviewing the medical-science part of our chapter on the inclusion body disease (IBD). Furthermore we thank Dr. med. vet Wolfgang Heuberger and Dr. med. vet Katharina Heuberger, specialists for reptiles diseases with a reptile surgery in Bavaria/Germany.

This report reflects the most recent knowledge about this disease.

What is the inclusion body disease (IBD)?

It is believed that the inclusion body disease (IBD) is a viral disease. The pathogen appears to be a retrovirus (as it is the case with AIDS). It produces Inclusion bodies that are found in the epithelial cells of the respiratory and digestive tracts, as well as in the liver, pancreas, spleen, kidneys, ovaries, testicles, marrow and nerve cells. This results in abnormal changes of the tissue in the retina, brain, spinal cord, peripheral nerves and organs.

1. Which boas and pythons are susceptible to the inclusion body disease (IBD)?

Boas and pythons are equally susceptible to the inclusion body disease (IBD). While there are minor differences in the clinical symptomatic, the disease is – once erupted – invariably fatal in both boas and pythons. Most cases have thus far been diagnosed in the U.S., but Europe has already had a few cases as well.

Boa constrictor is known for being a potential long-term carrier of the virus, without displaying any symptoms. However, such animals are able to infect other boas and pythons with this. Among the Boa constrictor in Germany, the inclusion body disease (IBD) has been confirmed most often in crossbreed specimens. This is not surprising, as these comprise the vast majority of the boas here. Of course, pure-bred Boa constrictor can obviously acquire the inclusion body disease (IBD) as well, if they are infected by sick specimens.

It is not yet known whether the inclusion body disease occurs in wild boas and pythons as well, or if it is a disease that is exclusive to captive specimens (the current experiences indicate the latter). the inclusion body disease (IBD) is usually found in juvenile to adult animals, but even neonates may be affected by it.

2. What are the clinical symptoms of the inclusion body disease (IBD)?

The most common and best known sign of the inclusion body disease (IBD) is the so-called “stargazing”. It manifests by the snake no longer being able to coordinate its movements, and uncontrollably tilting its head back. Due to these coordination problems, the reptile is no longer able to strike or swallow prey. The sick snake is also no longer able to shed its skin. Further described symptoms include paralysis and head twitching, as well as the inability of the sick snake to upright itself if placed on its back.


Most of the cases of such coordination disorders  ("stargazing") are not caused by IBD but by 

  • pathogenic germs who overcame the blood-brain-barrier and led to an infection of the central nervous system
  • side effects of medicaments, mainly Metronidazol
  • Poisoning (e. g. agents for getting rid of mites)
  • overheating of the snake

It is to criticize that many snake keepers and our ignorant trolls in the reptile forums consider the presence of a coordination disorder as a proof of IBD, Although the causes mentioned above are much more frequently responsible for "stargazing"  as the Inclusion Body Disease. What makes things even worse is that we have already heard of veterinarians who are acting similar. Apart from these neurological abnormalities, a broad array of other clinical symptoms of the inclusion body disease (IBD) are known, including regurgitation of prey, infections of the digestive tract, leukemia, abscesses on the skin, rapid loss of weight and muscle mass, chronic diphteroid-purulent enteritis (small and large intestine, appendix), often combined with septicemic salmonella, as well as infection and deformation of the vertebra.

3. General Infection through Salmonella

Dr. Udo Hetzel from the Institute of Veterinary Pathology at the University of Giessen told the authors about an interesting thesis, which however, has yet to be proven.

In approximately 40% of the the inclusion body disease (IBD) cases at this institute, cases of enteritis (infection of the intestines), usually caused by salmonella sp. Poly B, had also been confirmed.

Salmonella are normally part of the natural bacterium spectrum of the animals (although occasionally also pathogenic).

In the inclusion body disease (IBD) – according to the hypothesis by Dr. Hetzel – the viral infection leads to abnormalities in the intestine enterocytes, which enables salmonella to break through the mucous barrier and to spread throughout the body. The use of antibiotics leads to a temporary improvement of the general condition. However, as soon as the use of the antibiotics is discontinued, the cycle repeats itself all over again.

4. How is the inclusion body disease (IBD) diagnosed or excluded?

According to the most recent knowledge there is no such thing like a waterproof IBD diagnosis!

Please read the statement of Dr. med. vet. Wolfgang Heuberger. He and his wife Dr. med. vet. Katharina Heuberger are running a reptile surgery in Bavaria:

Based on ten years of practical experience, it is our opinion that there are a multitude of factors that may appear to be antigens affecting the immune system, yet they may not have anything to do with IBD. A clear distinction does not seem to be possible, because – according to both the Department of Veterinary Medicine in Detmold (Germany) and the “IBD experts” in Liverpool (UK) – it is not currently possible to diagnose IBD in a live animal, despite earlier indications suggesting otherwise.  Since reliable diagnoses are not possible in live specimens, we generally discourage our customers from having their animals tested for IBD. Of course, in cases of animals with obvious neurological symptoms that test positive in blood tests, the relevance of those results is certainly debatable.

However, even the relevance of those post-mortem examinations, in which inclusion bodies are detected, is heavily debated because several groups of viruses can produce inclusion bodies, and we are barely able to classify a tiny portion of reptilian viruses at large, and even fewer of those that are specific to snakes. If you think about how many viruses are known in humans, and how much fewer are known even from traditional pets, then the assumption that we are barely scratching the surface in reptilian virology seems logical.

Even if inclusion bodies are diagnosable, it does not provide any information regarding the pathogenic characteristics of the viruses that are causing the inclusion bodies, since it is often not possible to determine which virus produced them, and whether or not they are merely cellular waste that was left over from a previous viral infection. In the history of IBD, many animals have been euthanized based on diagnoses that would have been interpreted differently by other institutions.

Yet, whenever symptoms occur that match those of the inclusion bodies (suspected neurological symptoms, respiratory infections, etc.), it is frequently alleged (or claimed?) to be a case of clearly diagnosed IBD.  

5. Is there a cure of the inclusion body disease (IBD)?

At this point, there is no cure. All boids that contract the inclusion body disease (IBD)  will die sooner or later when they begin to show signs of the disease. It is generally recommended to euthanize the sick animal. Nevertheless, it must be assumed that there are specimens of Boa constrictor that live with the virus for many years without displaying any type of symptoms. Animals that have been diagnosed with the inclusion body disease (IBD) but have not yet progressed to active symptomatic may therefore be kept as individual animals, all the more since a positive proof of IBD isn't possible (see paragraph 4)!

6. How is the inclusion body disease (IBD) transmitted?

It is thought that the snake mite is the main cause for the contagion of the inclusion body disease (IBD). It can be transmitted if one of the parasites had a meal from an infected snake and changed hosts afterwards. A transmission via body fluids is also thought possible, in particular via excrements (feces, urine), oral secretions (saliva, slime), and exchange of body fluids during mating. The risk of contagion is very high among animals that are kept in the same enclosure, yet it is not entirely imperative. If careful hygiene is applied, a transmission of the virus from one enclosure to the next is not very likely.

If the hygiene is lacking, a transmission may occur via tools (hemostats, shovel, hook) over the course of months or even years.

A vertical contagion is also likely, meaning that the young contract the virus from the mother animal during gravidity. However, there was a case that has been documented in the literature, in which the young of the infected animal did not contract the virus. It is therefore believed that a transmission of the virus does not necessarily occur in such a case.

Meanwhile experience shows that an IBD epidemic within a stock generally correlates with a major mite issue. The current knowledge is that IBD is not transmitted by air. It seems that the routes of infection are similar to HIV.

Cases are reported that healthy boas have been kept for a long time in the same terrarium with "IBD boas" without contracting this disease (Heuberger, pers. information).

The fact stated in paragraph 4 may also be the reason for this.

7. How resistant is the IBD virus outside of its host?

According to what is known about this virus today, common disinfectants with an alcohol basis (e.g. Sagrotan, Desderman, Microzid) eliminate the virus. Being a retrovirus, it does not survive outside of its host for long anyway (always considering the limitation that it is believed to be a retrovirus, which has yet to be fully confirmed).

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8. How common is the inclusion body disease (IBD)?

There are no verified datas, furthermore one can't trust any test results (see paragraph 4). But it is a certainty that bacterial infections and infestation with unicellular organism are much more frequently the cause of diseases in boa and pythons.

Following is a figure of speech that is drilled into medical students at universities:

If you hear hoofs in the parking lot, don’t go looking for zebras

What does this mean? Very simple: Common diseases are common, whereas less common diseases are, well, less common. There is therefore no need to panic if your boa is congested or regurgitates a couple of times. In most cases, this is no more than a bacterial infection. Even the uncontrolled tilting of the head, the so-called “stargazing“, is usually caused by a bacterial infection, poisoning (mite control substances, medications, etc.) or a prior overheating of the animal.  

Do you expect a zebra, if you hear hoofs while hiking in the local woods? Exactly.

9. What do I need to do if the inclusion body disease (IBD) is suspected in one of my boas?

  • Every snake is to be left in its current enclosure, and no animal should now be placed with another
  • Use different tools for each enclosure (scoop, hemostats, hook, etc.)
  • Fight mites aggressively (very important!)
  • Do not offer rejected prey items to other snakes
  • Extreme hygiene should be applied, and all tools should be disinfected on a regular basis
  • Wash your hands after and between handling every individual animal before touching the next
  • Enclosures in which IBD - positive snakes have been housed can be used again after being meticulously disinfectioned.

    A disinfectant with HIV virus effectiveness is mandatory!

At this point it should be noted that most of these measures should be standard procedure anyway.

10. A case study from the U.S.

In order to provide a better understanding of the inclusion body disease (IBD) (as it applies in real life), we have quoted a case study from the book “The Boa Constrictor Manual“ by Philippe de Vosjoli. The events occurred exactly as reported.

Case Study:

A boid keeper acquired from a good friend of his a 2-year old male Boa constrictor for his two females, which he had had for three years. After a quarantine period of three months and an examination by a veterinarian, who certified the male boa a clean bill of health, the three animals were placed together.

The keeper had previously initiated this breeding attempt by subjecting the animals to a short cooling period. The male promptly developed a light respiratory infection, which however, was cured through the administration of antibiotics and an increase in temperature. The animal was then subjected to another short cooling period, which did not pose a problem, and was subsequently placed with the two females.

The mating was successful and without complications, resulting in 21 neonate boas, which were sold to friends and local pet stores.

However, after giving birth to the young, the mother did not feed as usual and showed signs of mouth rot (infectious stomatitis), which were successfully treated with antibiotics and accompanying measures. Afterwards, the female began to feed again and began gaining weight again.

All would have been well, hadn’t it been for one of the babies becoming sick and being diagnosed with the inclusion body disease (IBD). After this, the parent animals were examined, and both tested positive for the inclusion body disease (IBD) as well.

These events lead to the following possibilities:

  • The male was infected with the inclusion body disease (IBD) and transmitted the virus to the (previously) healthy female.
  • At the point of purchase, the male was healthy and did not carry the the inclusion body disease (IBD) virus. The female, on the other hand, was infected with the virus. However, due to a healthy immune system, she remained “healthy” for a long period of time, while infecting the male. Although this possibility is less likely than the former, it cannot be ruled out.
  • Both animals already carried the inclusion body disease (IBD), but did not actually develop the disease until stressed by a change of location or by being co-housed (also less likely, but not impossible by any means).

A few thoughts about the inclusion body disease (IBD)

Until recently, it was considered common practice among envious reptile dealers and breeders in the U.S. to accuse one another of having the inclusion body disease (IBD) in their collections, in order to harm their business.

The the inclusion body disease (IBD) hysteria in the U.S. has since notably diminished, which luckily put an end to these type of “games“.

Since we in Europe always tend to be a few years behind in most new developments in the U.S., it does not take a rocket scientist to figure out that similar occurrences will soon take place over here as well.

Therefore our advice: Beware of people who tend to point the finger at others regarding the issue of the inclusion body disease (IBD), as the motives for such accusations are usually rooted in the monetary aspect of it.

To make this clear and simple: No keeper of boas and pythons can claim that his/her collection does not have the inclusion body disease (IBD), because even a negative test result does not rule out the inclusion body disease (IBD) with certainty.

No quarantine period is long enough to be able to claim that the inclusion body disease (IBD) is not in a given collection, because Boa constrictor may carry the virus for many years (possibly for their entire lifetime?) without actually being affected by it.

Ads, as we have seen them in the classifieds journal of the DGHT (“… Boa constrictor from the inclusion body disease (IBD)-free collection for sale”) are thus pure nonsense, with whom the seller advertises little more than his/her own ignorance on the topic.

It is also impossible to locate the source if the inclusion body disease (IBD) does occur in a given collection. Was the virus obtained with a recently acquired animal or were the own animals already infected, yet did not show symptoms until the new animal produced stress in the established group? As you can see, it is quite difficult to determine this with certainty!

Therefore our advice: Don’t drive yourself crazy about the inclusion body disease (IBD). The inclusion body disease has been known since the mid seventies and it is really anyone’s guess how many animals have already reached a lifespan of 20 years while carrying the virus. It may be possible that there are carriers of the virus that are never really affected by it. This is only a speculation, though.

Be aware of the fact that the inclusion body disease does exist, and always apply the highest degree of hygiene with your animals, in order to prevent a contamination within your collection if the worst case scenario ever does occur.  The inclusion body disease (IBD) should otherwise be considered for what it is: A factor that has long been present among private keepers of boas and pythons, yet has only recently received attention and publicity. 

It can't even be excluded, that IBD isn't responsible for the disease of the boa. It might be that the inclusion bodies are only found by coincidence in sick boas and that there is in fact no connection between the illness and the inclusion bodies. 

That is, that IBD maybe doesn't exist at all but the animals die from infections caused by bacterium's and unicellular organisms, frequently induced by stress (insufficient housing, frequent being sold and the connected change of residence, breeding season et cetera)


Roundtable Inclusion Body Disease; Bulletin of the Association of Reptilian and Amphibian Veterinarians; Volume 9, No. 2, 1999;

Elliot R. Jacobson, MS, DVM, PhD, DACZM; Roger J. Klingenberg, DVM; Bruce L. Homer, DVM, PhD, DACVP; Douglas R. Mader, MS, DVM, DABVP (CA); Moderator: Robert Nathan, DVM

Inclusion Body Disease in boid snakes; Journal of Zoo and Wildlife Medicine 25(4);

Juergen Schumacher, Dr. med. vet.; Elliot R. Jacobson, MS, DVM, PhD; Bruce L. Homer, DVM, PhD, DACVP; Jack M. Gaskin, DVM., PhD;

The Boa constrictor Manual; von Philippe de Vosjoli, Roger Klingenberg DVM, Jeff Ronne, erschienen in der Reihe “The Herpetocultural Libraryâ”, Ó 1998 by Advanced Vivarium Systems, INC.