YVCipedia REPTILES: SNAKES
INCLUSION BODY DISEASE IN SNAKES
- IBD is the most commonly diagnosed viral disease of captive boid (boas and pythons) snakes. Snakes other than boids have been diagnosed with IBD. It is likely that all snakes are susceptible. It has not been diagnosed in wild snakes.
- It is not completely certain, but IBD appears to be caused by a viral infection, reptarenavirus. There are several strains of reptarenavirus and there is some evidence that snakes can be infected by multiple strains of reptarenaviruses simultaneously.
- We believe that snakes become ill because they develop a weakened immune system following infection. There may be other as yet unidentified ways that IBD occurs.
- A weakened immune system leads to secondary infections that may be bacterial, fungal, or protozoal. These infections have been identified in the nervous system, respiratory system, liver, and digestive tract.
- Reptarenavirus infections have also been associated with neoplasia, including lymphoma and round cell tumors.
- Pythons with IBD tend to have a rapid course of disease. They will develop neurologic symptoms and die within a few weeks.
- Boas with IBD have a variable assortment of symptoms and usually die within weeks or months. Some boas will recover from their symptoms and become healthy-looking carriers.
- IBD is transmissible but we do not understand how it is spread. It spreads more readily and rapidly in environments with snake mite infestations, in homes or collections where new snakes are added regularly, and also in sub-standard environments (poor hygiene, wrong temperature and humidity, etc.)
- There is recent evidence that reptarenavirus can be spread from parent snakes to offspring.
- It is unknown, but very unlikely, that people cannot contract IBD from their snakes.
- There is a small amount of evidence that some snakes can clear the reptarenavirus infection, but this possibility is very small and otherwise unpredictable. Also, when a snake that tested positive subsequently tests negative, we do not yet know if the snake will continue to test negative forever or relapse at some time, and we do not know if the snake can still transmit the illness despite a negative test.
- Some snakes appear healthy but test positive for reptarenavirus. Our knowledge of this healthy-looking carrier state is far from perfect. We cannot predict the likelihood that a snake with IBD will recover from its symptoms, beyond saying that it is unlikely. When one does recover, we cannot predict how long it will remain healthy, and we do not know how contagious a healthy-looking carrier snake is.
SIGNS OF IBD
- Pythons most often have neurologic signs and poor body condition at the time of diagnosis.
- Boas at the time of diagnosis most often have not been eating well and losing weight for months, have regurgitation or other digestive tract signs, and sometimes have respiratory signs.
- Most affected snakes have multiple signs
- Head tremors
- Arching of the head backwards (stargazing)
- Pupils of uneven size
- Decreased appetite
- Impaired righting reflex (inability to turn over when turned upside down)
- Poor body condition
- Mental dullness
- Skin disease
- Respiratory disease
- Oral disease
- There are many diseases with the same signs as IBD. We may have a strong suspicion that IBD is the problem based on the patient’s exam and history, but we cannot say this with complete certainty.
- Snakes can simultaneously have IBD and other diseases (co-morbidities).
- We can use tests to look for inclusions (in cells of the blood, nervous system, liver, pancreas, digestive tract and respiratory tract) and reptarenavirus (esophageal swab cell and blood cells).
- The most sensitive, reliable test for reptarenavirus is a laboratory test, qPCR. The best sample for this test from a live snake is a swab from the esophagus. This can usually be easily collected without anesthesia. PCR can also be run on blood and some other samples. False negatives are possible: a snake that tests negative for reptarenavirus may actually have the disease.
- IBD can also be diagnosed in live snakes with surgically-obtained biopsies of liver, pancreas, esophageal tonsil and/or kidney.
- When a snake dies or is euthanized because of IBD / reptarenavirus infection we recommend necropsy (animal autopsy) with biopsies. This test is most valuable when the snake was part of a multiple snake environment.
- There is no effective treatment for IBD / reptarenavirus.
- Treatment for secondary problems, for example, general supportive care, antibiotics for respiratory or oral infections, can be attempted but is often ultimately unrewarding.
- Euthanasia is unfortunately the most reasonable and humane option in most cases.
- There is no vaccination for reptarenavirus.
- The best way to manage reptarenavirus / IBD in multiple-snake situations is to test new snakes, quarantine them, and test them again prior to release.
- Quarantine should be strict and long: 3 months for pythons and 6 to 9 months for boas and other snakes.
- Because of the uncertainty about healthy-looking snakes that test positive for reptarenvirus we recommend that these snakes not be added to multiple-snake situations.
- Because of the uncertainty about healthy-looking snakes that tested positive at one time and subsequently test negative we recommend being very cautious about adding them to a multiple-snake situation, and doing so only after an appropriate quarantine.
- Snakes of different species should not be housed together.
- Snakes should be kept in a clean environment appropriate for the species. Particular care should be taken to prevent or treat snake mite infestations.