Many different kinds of herpesviruses are found in reptiles. Herpesviruses cause disease in all groups of reptiles except alligators and crocodiles. All of the reptile herpesviruses that have been found are in the subfamily Alphaherpesvirinae.
Herpesviruses in reptiles also have some interesting names such as fibropapillomitosis (big warts on the eyes in sea turtles); grey patch disease (sounds like the plague); lung, eye, and trachea disease; loggerhead genital-respiratory herpesvirus (need I say more about these?), and some boring names that reflect which was discovered first, second, etc. and in what reptile, such as: Tortoise herpesvirus 1; Tortoise herpesvirus 2; herpesvirus 4, Varanid herpesvirus 1; Gerrhosaurid herpesvirus 1; Gerrhosaurid herpesvirus 2; Gerrhosaurid herpesvirus 3; Iguanid herpesvirus 1; Iguanid herpesvirus 2; and you don’t have to remember any of these!
Tortoises are the most common group of captive reptiles affected with diseases caused by herpesviruses, and lizards the second most common. We’ll mention herpesvirus disease in all groups, but will focus here on it in tortoises.
Herpesviruses are generally fairly host specific. These means that in their natural host, they only cause a mild disease. However, in non-host species or when a host species is stressed or immune compromised, they can cause a much worse or even a fatal disease.
Herpesviruses are sensitive to environmental factors; they can be killed easily and don’t survive long outside of the reptile. Risk factors that can make getting a herpesvirus disease more likely include: young animals due to their less well developed immune system; stressed animals appear to be more likely to develop clinical disease; mixed-species enclosures can result in spread of a herpesvirus that is relatively benign in one species and may cause fatal disease in another. Immunosuppressed tortoises, particularly ones that have been exposed to different species of tortoises or turtles, are most at risk. Stressors that inhibit immune function include removal from the wild and subsequent shipment, crowding, inappropriate temperatures, lack of appropriate light, unsanitary practices, dehydration, poor diet, and exposure to other pathogens such as internal parasites. Some types of herpesviruses are seem more often in the spring.
Herpesvirus causes lesions in the lining of the mouth, tongue and choana (the opening on the inside roof of the mouth allowing the nose to connect with the windpipe). As the infection continues, a thick, off-white to yellow “membrane” will coat the inside of the mouth. A sick tortoise is often reluctant to eat or drink, typically has a runny or crusty nose and a drooling or crusty mouth. You may hear an audible whistle or gurgling noise when the tortoise breathes, and many tortoises open-mouth breathe or gape because they cannot draw air in through the swollen, inflamed tissues of the nostrils. Many infected tortoises have closed or swollen eyes, hide and sleep a lot, and are reluctant to move much. In rare cases, herpesvirus has been associated with neurological diseases such as circling and uncoordinated movement. Some tortoises die without the owners being aware that they are sick.
Herpesvirus may go into remission, effectively hiding in the tortoise’s body for months or years before causing a subsequent illness. This means that an outwardly healthy tortoise may still be infected and able to spread herpesvirus to others.
In lizards, herpesvirus infections are typically associated with stomatitis or mouth rot (sounds fun) or large warts all over the skin (papillomas). The mouth infection may be severe and cause the reptile to stop eating. Liver disease has also been caused by herpesviruses in lizards, and this is usually seen to be a “sick” lizard due to the destruction of the liver cells.
There is no known risk of infection to humans from reptile herpesviruses, so you don’t have to worry about people.
It is likely that almost all reptile species can be infected with a herpesvirus. The most commonly seen species in captivity are some species of tortoises and lizards such as Testudo species, particularly Russian tortoises (Agrionemys (Testudo) horsfieldii), pancake tortoises (Malacochersus tornieri), and spur-thighed (Greek) tortoises (Testudo graeca). Desert tortoises (Gopherus agassizii) have their own unique herpesvirus.
It is likely that each species of tortoise has a herpesvirus that may cause illness when it goes to a different species. This is one reason why it is unwise to mix different species of turtles and tortoises together.
In lizards, monitor species (Varanus spp.) and plated lizards (Gerrhosaurus spp) have been the two groups most commonly diagnosed with herpesvirus infections. Other lizard species with herpesvirus infections are European green lizards (Lacerta viridis), red-headed agamas (Agama agama), San Esteban chuckwalla (Sauromalus varius) and the green iguana (Iguana iguana).
A Greek Tortoise with Herpesvirus Infection
There are whitish, raised bumps on the tongue. Photo by Dr. Craig Staehle
Your veterinarian will begin by taking a thorough history and physical examination. The physical signs of herpesvirus in tortoises and lizards are often enough to be suspicious of this disease. However, your veterinarian may suggest obtaining some cells from a mouth swab to be examined under a light microscope to detect herpesvirus inclusions in the cells. This is a rapid test that can be done in most veterinary clinics but it only picks up moderate to high levels of infections and may miss early infections.
Bloodwork is important to check liver health since herpesvirus can quickly cause serious liver disease. Radiographs may help to detect other problems associated with an infection with herpesvirus.
Confirmatory testing and to identify the species of herpesvirus infecting your reptile requires a swab of the mouth lesions to be submitted to a diagnostic laboratory for a PCR test. At the same time your veterinarian may want to obtain a biopsy of one of the lesions to be sent to an outside laboratory to be looked at under the microscope to confirm the diagnosis.
The goal of treatment is to alleviate or reduce clinical disease. It is not possible to completely get rid of a herpesvirus once an animal or human has had an infection. However with treatment and good husbandry, some animals never show signs of the disease again but they are lifelong carriers.
The mouth may need cleaning to remove pus and debris. The choana may need to be flushed every 48 to 72 hr to unclog the nostrils and reduce inflammation. Tube-feeding and hydration using injectable fluids may be needed. Some tortoises need to have a feeding tube surgically implanted so that they can more easily receive oral medication and liquid diets. Pain relievers may be prescribed. Extremely ill tortoises may need hospitalization for several days until they are stable enough for home care.
Antiviral medications may be prescribed by your veterinarian. These are given by mouth, and often by a stomach tube or a surgically-placed feeding tube, and is important to combat the herpesvirus infection of internal organs such as the liver. A cream form of this medication may be applied to lesions in the mouth to help speed healing. Antibiotics may be prescribed also to manage bacterial infections that spread from sores in the mouth. Periodic bloodwork may be needed depending on which medications are used; some, like acyclovir, may cause kidney problems if not used properly
The goal is not to allow the disease to enter the collection. Quarantine monitoring is critical: all tortoises coming into a collection should have a PCR test performed for herpesvirus before they join the collection. Given the length of time herpesvirus may lay dormant in a tortoise, a 180-day to one-year quarantine is not unreasonable.
Because infected reptiles are life-long carriers of herpesvirus, there are some general practices that your veterinarian can discuss with you to prevent or minimize spread of the disease to other reptiles in house.
To prevent the spread of the disease, isolate the sick reptile and all reptiles that have had close contact with it. Do not allow infected animals to hibernate or brumate.
Providing a stress-free environment and the best husbandry practices are also important aspects of preventing herpesvirus disease. Infected animals should be considered lifelong carriers. During dormant (latent) phases, there is no shedding or disease, and during active phases, shedding and disease transmission to healthy cage-mates may occur.
Using separate or clean utensils for each cage and washing hands between cages and handling of animals is essential as the main mode of transmission is transferring the feces of infected animals to uninfected animals on cleaning tools or hands of owners.
Chlorine bleach (one cup household bleach in one gallon water) is an effective disinfectant for tools, water bowls and cages. Outdoor enclosures with dirt and plants are likely to be contaminated for a year or more; they should not be used to house healthy tortoises or lizards. Wear disposable gloves or wash your hands with warm water and soap after handling or working with an infected tortoise. Do not wear the same shoes when servicing an infected enclosure as when you work in the pens of healthy tortoises.
Tortoises and lizards that have minor oral ulcers, stopped eating within the past few days, and are otherwise alert and active generally recover with treatment. Tortoises that have been ill for more than a week, particularly if they are not eating or drinking, have a more guarded outlook.
VIN News Service commentaries are opinion pieces presenting insights, personal experiences and/or perspectives on topical issues by members of the veterinary community. To submit a commentary for consideration, email email@example.com.