Serpentovirus (Nidovirus) in Snakes
Respiratory disease is one of the more common conditions we see in ball pythons. While there can be several causes for respiratory signs, one of the more recent concerns has been Serpentovirus — previously and perhaps more commonly known as Nidovirus. The virus can cause inflammation of the pharynx, sinuses, mouth, and trachea, and can also result in pneumonia. Signs in affected snakes include reddening of the mucosa (tissue inside the mouth), excessive mucus production, and audible clicking sounds when breathing.
What Causes It?
Serpentovirus belongs to the order Nidovirales — a group of RNA viruses that cause a wide range of diseases in different animals, including coronaviruses. Like coronavirus in people, one suspected route of transmission is respiratory droplets. The virus has also been found in the gastrointestinal tract, likely from swallowing infected discharge, so fecal exposure is also a possible route. Once the virus damages respiratory tissue, secondary bacterial infections can develop and lead to additional complications such as pneumonia.
Which Snakes Are Affected?
Among snakes, Serpentovirus most commonly causes problems in pythons. It has also been found in other boid snakes such as boas and, more rarely, in colubrid snakes.
What Does It Look Like?
In addition to general signs of illness such as reduced appetite and lethargy, more specific signs of respiratory disease in snakes include open-mouth breathing and abnormal posturing. Large amounts of mucous discharge from the mouth is a sign particularly associated with Serpentovirus.
How Is It Diagnosed?
To determine whether Serpentovirus is causing your snake’s respiratory signs, a swab is typically taken and tested using PCR to detect the genetic material of the virus.
Other pathogens can also cause respiratory disease in snakes, so your veterinarian will likely discuss additional diagnostics to rule out other causes and assess the extent of the illness. This may include testing for other viruses such as paramyxovirus (respiratory disease) or arenavirus (Inclusion Body Disease, which causes immunosuppression), culturing the airway for bacterial or fungal secondary infections, bloodwork to assess overall health, and radiographs to evaluate whether the lower airway is affected.
How Is It Treated?
Unfortunately, there is no known cure for Serpentovirus. In collections of snakes, it can be fatal and spread quickly. Since no medication exists to eliminate the virus itself, treatment focuses on supporting the snake’s immune system with supportive care — including fluids for hydration and nebulizations to help clear the airway. If a secondary bacterial infection is suspected, antibiotics may be prescribed. Antibiotics will not kill the virus itself. Because these snakes can develop recurrent infections, culturing the mucoid discharge to identify the best antibiotic and monitor for antibiotic resistance may also be recommended.
How Can You Prevent It?
As with any infectious disease, the best defense is a healthy immune system. For exotic species, good health starts with proper husbandry.
For larger collections, minimizing exposure to the virus through strong quarantine and biosecurity practices is equally important. This includes:
- Washing hands and changing gloves between individuals
- Using separate equipment for suspected sick animals
- Disinfecting all surfaces and instruments between animals from different sources
- Screening new animals before introduction to a collection
- Maintaining a quarantine period before introducing new animals to an existing collection — a minimum of 90 days is often discussed, though the exact duration is debated
