Inclusion Body Disease

TL;DR. Inclusion Body Disease (IBD) is a contagious, fatal viral infection in snakes that causes progressive neurological damage, shedding issues, and chronic secondary infections.

Stargazing, or holding the head at an unnatural upward angle, is a classic neurological sign of IBD.

What is it?

Inclusion Body Disease (IBD) is one of the most significant and devastating viral diseases affecting captive snakes worldwide. The disease is caused by a retrovirus-like agent, specifically classified under the reptilian arenaviruses. It targets multiple organ systems, with a particular affinity for the central nervous system and the immune system.

When a snake is infected, the virus causes abnormal proteins to accumulate inside the body's cells. These protein clumps, known as "inclusion bodies," disrupt normal cellular function. Over time, this cellular damage leads to progressive neurological decline and profound immunosuppression. Because the virus weakens the snake's natural defenses, affected reptiles frequently succumb to secondary bacterial infections, such as pneumonia or severe skin infections, rather than the virus itself.

Because reptiles have unique metabolic rates and immune systems, much of our clinical guidance relies on specialized herpetological medicine and extrapolation from known viral pathways in other species. For snake owners and breeders, IBD is a major concern because it is highly contagious, can lay dormant in some species for years, and is uniformly fatal once clinical signs develop.

Causes & risk factors

IBD is caused by a reptilian arenavirus. The virus is highly contagious and spreads primarily through direct contact between snakes, shared environments, or from mother to offspring. A major vector for transmission is the common snake mite (Ophionyssus natricis). These parasites feed on the blood of infected snakes and easily transfer the virus to healthy individuals as they move throughout a collection.

While the virus can infect many snake families, members of the Boidae (boas) and Pythonidae (pythons) families are the most frequently affected. Boas often act as chronic, asymptomatic carriers, harboring the virus for months or even years without showing outward signs of illness. Pythons, on the other hand, are highly susceptible and typically develop rapid, acute, and severe clinical signs shortly after exposure.

Signs to watch for

Symptoms of IBD can vary depending on the species of snake, but they generally fall into neurological, dermatological, and respiratory categories.

• Neurologic signs (Common): These are the hallmark of the disease. You may notice "stargazing" (where the snake stares straight up at the ceiling for long periods), corkscrewing of the head and neck, an inability to right itself when placed on its back, or generalized paralysis.
• Dysecdysis / Abnormal shedding (Common): The snake may struggle to shed its skin normally, resulting in retained eye caps or patchy, incomplete sheds.
• Dermatitis (Occasional): Chronic skin infections, scale rot, or non-healing wounds often develop due to a compromised immune system.
• Respiratory disease (Occasional): Wheezing, nasal discharge, open-mouth breathing, and excess mucus in the mouth are common secondary complications.

A loss of the normal righting reflex is a critical warning sign of progressive neurological damage.

Any neurological abnormality, such as stargazing or a loss of righting reflex, is a critical veterinary emergency.

How vets diagnose it

Your vet will begin with a thorough physical examination and a review of your snake's husbandry and exposure history. Because the symptoms of IBD can mimic other conditions, such as pesticide poisoning, extreme heat stress, or bacterial meningitis, definitive diagnostic testing is required.

The gold standard for diagnosing IBD is the identification of characteristic eosinophilic intracytoplasmic inclusion bodies within the host's cells. Your vet will typically perform a biopsy or fine-needle aspiration of specific tissues. The most reliable sites for finding these inclusion bodies include:

• Esophageal tonsils: A minimally invasive biopsy site that can often be accessed under light sedation.
• Liver or Kidneys: Surgical biopsy or ultrasound-guided fine-needle aspiration of these organs provides highly accurate results.

Additionally, blood tests (such as a complete blood count to look for inclusion bodies inside white blood cells) and molecular testing like Polymerase Chain Reaction (PCR) are increasingly used to detect the viral genetic material, especially in asymptomatic carrier snakes.

Treatment options

Currently, there are no specific antiviral medications or curative drug treatments available for Inclusion Body Disease. Treatment is strictly supportive and palliative, focusing on keeping the patient comfortable and managing secondary complications.

If a secondary bacterial infection occurs, your vet may prescribe broad-spectrum antibiotics. However, because the underlying viral infection severely suppresses the immune system, these treatments are rarely successful long-term. As noted in a leading veterinary dermatology reference:

"Historically, Pseudomonas and Aeromonas are the most common bacterial isolates from reptiles. Occasionally, boa-type snakes can also develop a cellulitis at the site of infection, which causes tremendous swelling."

Because of the highly contagious nature of this virus and the lack of an effective cure, supportive care is generally not recommended for snakes living in multi-reptile households or breeding facilities. In these environments, isolation is paramount, and euthanasia is often the most humane and responsible course of action to prevent widespread transmission.

Prognosis

The long-term prognosis for a snake diagnosed with Inclusion Body Disease is grave. There are no documented cases of a snake recovering from IBD. While some individuals (particularly boas) can survive as asymptomatic carriers for extended periods, once a snake begins to show neurological signs, its quality of life declines rapidly. Death typically occurs within weeks to months due to progressive central nervous system failure or overwhelming secondary infections.

Prevention

Because there is no vaccine or cure for IBD, prevention is the only way to protect your reptiles.

• Strict Quarantine: Quarantine all new reptile acquisitions in a separate room for a minimum of 90 to 180 days. Use separate tools, water bowls, and handling protocols for quarantined animals.
• Mite Control: Implement rigorous mite prevention and treatment protocols. Because snake mites are highly effective vectors for the virus, keeping your collection free of parasites is a critical line of defense.
• Pre-purchase Screening: Ask breeders for proof of negative PCR testing for IBD before bringing a new snake into your home, especially if you own highly sensitive species like pythons.
• Hygiene: Wash your hands thoroughly and change your clothes after handling snakes outside your household or visiting reptile expos.

When to call your vet

Contact your veterinarian immediately if your snake exhibits any of the following red flags:

• Inability to right itself when turned upside down
• Stargazing or holding its head at abnormal angles
• Uncontrolled twisting, corkscrewing, or tremors
• Chronic respiratory distress (wheezing, bubbling from the nose or mouth)
• Severe, non-healing skin lesions or repeated shedding failures

For specific breeds

Ball Python

While boas are notorious for carrying the virus silently, Ball Pythons are highly sensitive to IBD. In this breed, the disease progresses rapidly. Neurological signs are typically acute and severe, often accompanied by a rapid decline in body condition and secondary respiratory infections. If you keep Ball Pythons, extreme caution must be taken when introducing any new boid or python species to your home.

Sources

• Small-Animal Dermatology: A Color Atlas and Therapeutic Guide, pages 513, 520.