Inclusion body disease and serpentovirus: the viruses that end snake collections

Quick answer

Most snake problems are husbandry or parasites, and both are fixable. The two viral diseases in this article are not, which is why they change how a collection is run.

A snake that regurgitates repeatedly, wastes despite eating, or holds its head up and back gazing at nothing is not showing a feeding problem. A python that gets a chest infection, clears it on antibiotics, and gets it again a month later does not have a stubborn bacterial infection.

Both patterns point at viruses. Inclusion body disease, associated with reptarenaviruses, and serpentovirus, sometimes called nidovirus, are the two diseases that end multi-snake collections, and neither has a cure.

• Boas can carry inclusion body disease for a long time with few signs. Pythons tend to get sick and die. A mixed collection is the dangerous arrangement.
• Stargazing and loss of the righting reflex are late signs, not early ones.
• A recurring respiratory infection in a python is a reason to ask for a serpentovirus swab, not a fourth course of antibiotics.
• Quarantine for these viruses is measured in months, in a separate room, with separate equipment.
• A single negative test does not clear a snake. Shedding is intermittent.

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Never sell, rehome, breed from, or trade a snake with suspected or confirmed inclusion body disease.

There is no treatment and no reliable way to declare an animal free of it. Passing it on is how single cases become regional outbreaks, and it is how somebody else's collection of twenty snakes is destroyed by one animal that looked well on the day of collection.

If neurological signs are established and the snake can no longer right itself or feed, discuss euthanasia rather than prolonged supportive care.
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Why these two are different

Almost everything else that goes wrong with a pet snake is fixable. Mites are eradicated, stomatitis is treated, respiratory infections resolve, husbandry is corrected, parasites are cleared with the right drug and a clean enclosure.

That experience sets an expectation, and these two diseases break it. There is no antiviral treatment for either, no vaccine, and no way to be certain an exposed animal is clear. What you control is exposure, and exposure is controlled before the animal enters the house.

That is the whole practical argument for treating quarantine seriously in a hobby where a new snake usually goes on a spare shelf for a fortnight.

Inclusion body disease

What it is.

A disease of boas and pythons in which characteristic inclusion bodies form inside cells throughout the body. It is associated with reptarenaviruses, a group identified in the last decade, and experimental infection of boas has reproduced the inclusions. The full picture is still being worked out, including why some animals carry multiple viral segments.

The species split that catches people out.

Boas frequently carry it for months or years, sometimes appearing well, and can shed virus while doing so. Pythons more often develop severe neurological disease and die relatively quickly.

The consequence is uncomfortable. In a mixed collection the reservoir is often the animal that looks best, and the first sign of a problem is a python dying. Any collection holding both should treat that asymmetry as the central risk.

What owners actually see, in order.

Early, it is unremarkable. A regurgitation. A slightly poor shed. A few grams lost. A snake that goes off food for longer than its usual seasonal pause.

Established, the immunosuppression shows. Mouth rot that keeps returning. Pneumonia. Skin infections. Repeated regurgitation, which is the sign most often noticed and most often blamed on prey size or handling.

Late, the neurological signs arrive. Stargazing, where the snake holds its head up and back and appears to look at the ceiling. Corkscrewing of the neck. Tremors. Disorientation. Loss of the righting reflex.

The righting reflex, and how to check it safely.

A healthy snake placed gently on its back rights itself immediately and without apparent effort. Do this on a flat surface, supporting the body, once, and note what happens.

A snake that stays upside down, or that rights itself slowly and clumsily, has a serious neurological problem. This is a genuinely useful home observation because it is objective, it takes seconds, and it does not depend on interpreting a posture.

What it is not.

Stargazing is not exclusive to this disease. It also follows thiamine deficiency in snakes fed fish containing thiaminase, septicaemia, head trauma, damage from a heat source that has failed, toxin exposure and severe dehydration.

Separately, several ball python morphs, spider being the best known, carry an inherited neurological wobble that produces head shaking, corkscrewing and poor coordination from birth. It is genetic, lifelong, non-infectious, and completely unrelated. Knowing which morph you own answers a lot of this before any test is run.

Serpentovirus, and the respiratory infection that keeps coming back

The pattern.

A python develops respiratory signs: mucus in the mouth, bubbling at the nostrils, gaping, open mouth breathing, a clicking or wheezing sound, and often a head held raised. It is treated with antibiotics, improves, and relapses when the course ends. Then it happens again.

Antibiotics treat the secondary bacterial infection sitting on top of the viral damage. They do nothing to the virus, so the cycle repeats until the underlying cause is identified or the snake dies of pneumonia.

Who gets it.

Documented most in ball pythons, carpet pythons and green tree pythons, and found in other species. Some snakes carry it without obvious signs, which is the same problem as with inclusion body disease: the animal that spreads it may not be the animal that looks ill.

The test that changes the plan.

A PCR run on an oral or choanal swab. It is a simple sample to collect and it is the single most useful thing to ask for in a python with recurrent respiratory disease. Ask your exotics vet which laboratory they send to, since availability varies a great deal by country and samples sometimes have to be shipped internationally.

What management looks like.

There is no cure. What helps is correcting the environment so the animal is not fighting husbandry as well as a virus, treating secondary bacterial infection based on culture rather than guesswork, keeping the snake well hydrated, and permanent separation from other snakes.

Some snakes live a long time as carriers. That is not a reason to relax the separation, because they remain a source for everything else in the house.

Quarantine that actually works

Quarantine is a tub, a separate room, a dedicated set of equipment and a written log. The log is what turns four months of observation into evidence.

A separate room, not a separate shelf.

Sharing airspace with the collection defeats the purpose for a respiratory virus. If a separate room is genuinely impossible, get as much distance and as much separation of ventilation as you can, and extend the time.

Time measured in months.

For mites and internal parasites, a few weeks is defensible. For these viruses it is not, because signs can take months to appear and carriers may never show any. Many experienced keepers and exotics vets work to a minimum of six months for a new boa or python entering an existing collection, and longer where the source is unknown.

Quarantine last, always.

Feed, water, clean and handle the established collection first, then the quarantine animals. Never the other way round, and never back and forth on the same day. Change clothes, wash hands and forearms, and treat the quarantine room as a one way trip.

Nothing crosses.

Dedicated hooks, tongs, tubs, water bowls, hides, substrate scoop and thermometer for quarantine. Not shared and washed. Dedicated.

Clean before you disinfect.

Organic matter inactivates most disinfectants. Physical cleaning first, then a disinfectant appropriate for reptile enclosures used at the stated contact time. Read the contact time, because almost nobody leaves it on long enough.

Treat mites as a biosecurity problem.

Mite control belongs in this article because mites are a suspected route of transmission for inclusion body disease and are a proven route for moving pathogens around a rack. A mite infestation in a collection is not only a welfare problem.

Test during quarantine, and understand the limits.

Ask about reptarenavirus PCR and a blood smear for a new boa or python, and a serpentovirus swab for a new python. Then understand what the results mean. A positive is meaningful. A negative reduces the probability and does not clear the animal, because shedding is intermittent and inclusions come and go.

Log everything.

A settled quarantine animal with a hide, correct substrate and clean water. Four uneventful months here is worth more than any single test result.

Weekly weight. Every feed accepted or refused. Every regurgitation with the interval since feeding. Every shed and its quality. A mouth check at each handling. Any change in posture or in the righting reflex.

The routine that catches problems early

What never to do

Do not sell, give away, rehome or breed from a snake with suspected or confirmed inclusion body disease.

Do not run repeated antibiotic courses for a recurring respiratory infection in a python without asking for a serpentovirus test.

Do not quarantine on a different shelf of the same rack.

Do not add boas to a python collection, or the reverse, on the strength of the animal looking healthy.

Do not treat a single negative PCR as a clearance certificate.

Do not freeze a snake that dies unexpectedly if a necropsy is possible. Refrigerate it and call the practice, because freezing destroys the tissue detail that answers the question for every other animal in the house.

Do not assume stargazing means inclusion body disease. Check the heat source, the diet and the morph first, because three of the look-alikes are fixable.

When to get help

The point of the whole exercise: a settled, feeding, steady weight snake, and nothing new arriving that has not been through a proper quarantine.

Book an exotics veterinarian who sees reptiles for any of these:

• Two or more regurgitations that are not explained by prey size, handling after feeding, or temperature
• Any respiratory sign that has returned after treatment
• Stargazing, corkscrewing, tremors, or a delayed righting reflex
• Unexplained weight loss in a snake that is eating
• Mouth rot or skin infection that keeps coming back
• Any unexpected death in a household with more than one snake
• Before adding a new boa or python to an existing collection

Bring the weight log, the feeding record with dates and refusals, the acquisition list for every animal in the house, your measured temperatures and humidity, photographs or video of the posture and of the mouth, and the details of anything already treated.

Expect the consultation to be about the collection rather than only the individual. Expect the vet to want a blood sample, an oral swab, or both, and to explain what a negative result does and does not rule out. Ask which laboratory the samples go to and how long results take, because that determines how long the quarantine arrangements need to hold.

If a snake dies, ask about a necropsy before you do anything with the body. It is the one test that reliably gives an answer, and the answer is about every snake you still own.