Devastating: What a tortoise viral disease really looks like if it enters a group or collection.
- tortoisetrust
- 3 hours ago
- 14 min read
Andy Highfield
Following on from our recent articles on the critical importance of having effective disinfection and quarantine protocols, we felt it equally important that keepers fully understand what happens if these should fail. Here are two real-life reports that detail exactly how traumatic this can be. Both appeared in editions of our printed Newsletter some years ago but they are still 100% relevant today. Indeed, even more so as many 'new' and equally dangerous pathogens have emerged in recent years.
These include, but are certainly not not limited to: Helicobacter: Newly identified spiral-shaped bacteria linked to fatal respiratory disease and severe nasal discharge in American gopher tortoises but that have the potential to also infect other species. Tortoise Picornavirus (Virus "X"): Associated with emerging shell dystrophy, metabolic bone abnormalities, and severe renal disease. Emydomyces testavorans: An emerging fungal pathogen causing destructive shell and skin infections (dermatological mycoses) across aquatic and terrestrial species, plus Iridovirus and Ranavirus etc.
In the autumn of 1990 we published a stark warning to all tortoise keepers in a paper entitled “Is there a Tortoise AIDS in our midst?” (this title was based upon the symptoms observed by ourselves in multiple cases, and from identical symptoms reported to us by numerous members and contacts: Tortoises 'crashing' with multiple, varied bacterial, fungal and protozoan infections accompanied by weight loss and emaciation suggesting their immune system was being severely comptomised, followed, inevitably by death). At that time human HIV/AIDS was very much in the news and the parallels were striking. From our own tortoise collection and rescue we noted that “the first case subject to study was of north African origin and had a recent history of repeated flagellate attacks, RNS and generalised debilitation; in other words it fitted the clinical profile we now recognise as suggestive of some form of chelonian immune suppression syndrome. This tortoise failed to respond to treatment and finally died from pneumonia and liver failure. Immediately after death the liver was removed and subjected to histopathology using electron microscopes. The report confirmed our worst fears; “a large number of the nuclei within the liver cells have a very dense appearance, much different to the other nuclei and this is abnormal”. We concluded that in all probability “these are viral inclusion bodies”. That same year, we met the late Professor Dr. Walter Sacchse (1932-2020) at a conference in France, and discussed these cases with him. Walter was not only a highly respected researcher of freshwater turtles, but his professional background was in genetics, cellular biology and human medicine. Later I (Andy Highfield) visited with him in Germany and we continued to exchange ideas on the subject. Walter was certain that something strange was going on as he was independently investigating a number of remarkably similar cases.
This proved highly controversial at the time. We were accused of "scaremongering". However, this was subsequently later proven to be prophetic, as a terrestrial strain of Chelonian Herpesvirus was then identified, and preserved tissue samples from those early cases confirmed this as the cause.
Even now, new strains of CHV are being discovered and they pose increasing dangers to anyone and everyone who has or who rescues tortoises and turtles. See for example "A novel herpesvirus detected in 3 species of chelonians" (J. Vet. Diagnostic Investigation, 34:4, 2022).
It is critical to stress that one single new introduction can rapidly spread diseases like these throughout an entire creep, or collection. If that occurs, mortality rates of 100% are not unusual. The dangers are compounded by the fact that some of these diseases have extremely long "incubation times", where affected tortoises can appear perfectly healthy but at the same time are shedding virus that can and will infect others. There is, therefore, no truly safe and guaranteed quarantine period. We are aware of tortoises that remained asymptomatic for several years before eventually succumbing to CHV.
It is vital that everyone who works with rescued tortoises and turtles, and all those who have private collections, fully understand the risks and implications of this.
Achieving and maintaing truly effective quarantine is extremely challenging. It is also incredibly time-consuming and costly, involving the use of disposable clothing and frequent intensive disinfection. See our separate article "Tortoise Epidemic: Quarantine and Barrier Nursing Techniques" for more on this.
Testing
It is important to remark on testing, especially in respect of CHV. Since the early outbreaks, when no tests other than electron microscope exams of tissue, usually post-mortem, were possible today we do have the capacity for sensitive PCR tests based on oral swabs as well as tissue. This is a considerable and genuinely useful advance. There are some caveats, however. The first is cost. A typical test will cost between $70 and $100 (40 to 70 EUR) per sample, plus additional charges if it is necessary to differentiate the strain involved. This is clearly not a massive issue if only a single or small number of animals need to be checked, however, in a rescue or sanctuary environment when large numbers of tortoises or turtles may be involved, the cost might prove prohibitive. We ourselves have received 100 to 200 tortoises at a single time, for example, following illegal wildlife seizures. Any single individual could be a carrier. It does not take much to work out that funding laboratory costs like that is going to be a huge problem for just about any size of organisation, and remember, one is all it takes.
There is also the problem that tests only exist for certain diseases and strains, not all. In addition infected tortoises and turtles often shed virus intermittently rather than continually, meaning that a negative PCR test is not any kind of guarantee the animal really is free of virus and can be regarded as "safe".
Combine this with the challenges of establishing and maintaining an effective quarantine and disinfection protocol, and possessing the necessary facilities, staff (this is all incredibly labour-intensive) and sufficient funds to achieve this, then it should be transparently obvious to any reasonable and intelligent person why accumulating large groups of tortoises at any one site with frequent entries of new animals is incredibly reckless and ill-advised.
This is precisely why for years we have advised people who have tortoises that need to be rehomed to avoid allowing them to pass through large sanctuaries and centres that house high concentrations of other tortoises, especially any location that houses multiple different species. The risks in that are very real and cannot be ovestated. Even with good general hygeine and handling practices, some of these diseases are so contagious or infectious that nothing short of high level quarantine and rigorous testing procedures will come close to being adequate, and there are no guarantees even then.
An outbreak
In the words of the Tortoise Trust member who experienced this first-hand:
"It was March, and I had been having problems with my three semi-adult Leopards, who were now under veterinary supervision. I had obtained them from a reptile dealer largely because they appeared to be in poor health, and was hoping that love and proper husbandry, alongside my vet's knowledge and enthusiasm, would lead to a full recuperation. They were to die, however, over the following months, and I now believe that their condition was responsible for the problems which were to ensue within my main collection.
I was beginning the awakening of my tortoises (Mediterranean sp.) when I found to my dismay that a relatively new male had emerged and died since my last check. The babies, meanwhile, had been out a month and were eating voraciously, soon to be followed by the rest of the males. My lone T. ibera, however, was very slow to get going, and a visit to the vet revealed an unhealthy blood cell count and low thyroid level. A course of antibiotics and thyroid tablets afforded no improvement, and after a month he was dead.
My females were woken and busy feeding within a couple of days; the regular layers rapidly increasing in weight, a sign for me to ensure that the greenhouse was warm, damp, and ready for nest-building. By the end of April, several clutches of eggs had been laid, and I began to re-home some of my hatchlings before the arrival of the new ones. Then, one evening in mid-June I discovered one of my male Horsfield's dead. A post-mortem indicated that he had fed recently, and revealed the sole symptom of an inexplicable reddening in the top field of his lungs.
My usual careful attention became an obsession; if an animal didn't eat immediately, I was weighing and inspecting daily. When in early July, a female rejected her favourite food, a veterinary examination diagnosed possible viral infection. A course of antibiotics, intravenous fluids and tender loving care lasted all of 4 days after which she too died, and another post-mortem provided samples for laboratory analysis.
Soon two 3 year olds had ceased to eat, and my usual vet being unavailable, an appointment was made with (Ed: renowned tortoise specialist) Stuart McArthur to which I was told to bring as much information as possible. We discussed food, disinfectants, water supplies, numbers and types of animals kept, plus the case studies of the past deaths in detail, and although the prognosis for the two babies was not optimistic, the decision was made to attempt treatment. My collection was immediately divided into small groups, food and water sources changed, with individual members of my family responsible for the different groups of tortoises. All the animals received prophylactic treatment with Baytril, and with Trigene, the disinfectant selected by my vet.
It wasn't long before some positive test results had been obtained; they revealed the presence of the "Chlamidya" organism, for which exposed animals can be treated but remain carriers. Within another week the two youngsters returned home, much improved and eating well. The treatment of the other animals was reduced in frequency and concentration but strict quarantine still observed, and for a short period, the medication alone was stopped. After a few weeks, however, symptoms began to re-emerge in further animals, and my vet and I were in constant communication.
The lab results on the first female death were fairly inconclusive, but did yield remarks about infiltrations of white blood cells in other bodily tissues and multiple divisions of these cells. Leukaemia was a possibility, but, hitherto unknown in UK tortoises, was considered an unlikely diagnosis. More and more animals began to degenerate over the next few weeks, however, and more and more samples were taken, each demonstrating similar results. It was beginning to look as though something had indeed caused an epidemic of leukaemia in my collection, and how such a development might have occurred needed research. This was a task of vast proportions, and the possibilities of: radiation; toxins, and virus were investigated thoroughly.
The viral option was considered the most probable as despite the considerable size of the collection, the problem remained limited to two groups only. The major task was then to find a laboratory to attempt to locate the virus. An eminent avian virologist was persuaded to conduct the research with the co-operation and resources of several professional bodies necessary in such new work. Samples from the dead animals were used to develop cell cultures and investigation began. Meanwhile other pathology labs were given the opportunities examine samples and formulate their opinions. One such lab was quick to comment that the tissue alteration looked not dissimilar to that caused by a strain of herpes virus in poultry causing a condition called "Mareks Disease". This observation was widely discussed, and the results of further tests helped to decide that the similarity was not coincidental.
All the remaining animals from the original collection were exhibiting symptoms by this time. The condition, if viral, was either the same as the avian herpes that had crossed species, or a chelonia variation of it. The chance of survival being nil, the awful decision was taken to euthanase the tortoises. Although for some time a number of animals had been demonstrating signs of improvement, deterioration had soon followed, and so, I lost my main collection.
Next I had to rid my home of this dreadful virus. The entire house was thoroughly cleaned; a task taking several weeks and many gallons of disinfectant, and it was many weeks more before I allowed myself contact with my remaining tortoises. I am now convinced that my Leopards were the cause of the problem. They experienced a demise identical to that of the others, and I maintain that they must have contracted the virus before being bought by me, hence their initial poor health. Needless to say, it is my hope that this experience is not repeated, but should it be, communication within the tortoise world is essential if a solution is to be found for the condition. I would like to offer heartfelt thanks to all the many people who provided help and support throughout my ordeal and a wish that something valid may be learnt from it".
The Contemporary Veterinary Report
By Stuart McArthur, MRCVS. Author of 'Medicine and Surgery of Tortoises and Turtles'.
During 1996 an outbreak of disease associated with lymphoproliferative disease (viral lymphoma), immunosuppression, respiratory disease and paralysis was investigated at Holly House Veterinary Surgery, Leeds, England. The outbreak occurred in a large breeding colony of about 45 mainly Testudo hermanni tortoises. The colony was composed of several separate groups, one of which had temporarily contacted sick leopard tortoises (Geochelone pardalis) and an African hingeback (Kinixys erosa). The affected unit was made up of 25 Testudo hermanni tortoises. The other unaffected tortoises were one Testudo graeca ibera, five leopard tortoises (Geochelone pardalis), four Testudo horsfieldii, one Kinixys erosa, two Geochelone sulcata and a further 16 juvenile Testudo hermanni. These were kept in individual species groups, isolated from each other and the main affected group.
During the disease outbreak the entire colony was divided into two groups. Those known to have contacted sick tortoises were nursed on the original site, and those animals assumed to be clear of exposure were quarantined in small groups of two or three animals in new sites where no other chelonians were present.
The disease achieved 100 per cent mortality and morbidity rates in the exposed groups, but the isolated animals currently remain unaffected after eight months' quarantine.
One juvenile Testudo hermanni that left the affected group eight months previously was returned to the affected group with early signs of the disease. The course of disease in this individual was similar to those that remained in the group and a histopathological diagnosis of lymphoma was also made from this individual. This suggested the possibility of a long symptomless incubation period.
The leopard tortoises were the first to show the disease; the main group of Testudo hermanni demonstrated significant symptoms after a time lag of several months. The presenting signs in the leopard tortoises included hypersecretion of ocular and nasal fluids, anorexia, muscle wastage, and fore and hind limb paralysis. Later a spastic neck muscle paralysis retained the necks of two leopard tortoises in flexion. Post mortem findings included lymphoma, jaundice, tracheitis, pneumonia, hepatitis, bile duct rupture and renal failure. The disease in the leopard tortoises tended to be chronic.
The Testudo hermanni tortoises generally showed a more acute onset of signs that included non-specific symptoms of collapse. These animals had pale greyish mucous membranes, dyspnoea and a whitening of the eyes that cleared over a period of a week or so in most animals. Some of the Testudo hermanni tortoises died within 12 hours of displaying these signs. Other animals were nursed through the initial crisis. Those that remained stable for some weeks were then either overwhelmed by non-specific infections or went into acute hepatic and renal failure. This was demonstrated from blood biochemistry and haematology. Many of these animals required humane euthanasia; the remainder died despite treatment.
Treated animals were given Enroflaxin (Baytril:Bayer) at a dose rate of either 5mg/kg daily or 10mg/kg daily by intramuscular injection along with cyclical courses of Ketoconazole (Nizoral Suspension:Jaansen) at 15mg/kg orally for five days at a time. Intensive fluid therapy was undertaken and environmental and nutritional support was actively given. Liquidised vegetable diets were regularly tubed into some animals and more active animals were force-fed a vegetarian diet by hand. While this treatment did not cure the affected animals it did stabilise them and certainly appeared to decrease overwhelming secondary infections.
Six post mortem examinations of recently dead or euthanased tortoises yielded histopathology consistent with lymphoproliferative disease (lymphoma) affecting spleen and/or liver. Samples were sent to two independent external laboratories, both of whom reached a similar diagnosis: lymphoma relating to a lymphoid infiltration of affected organs with occasional mitotic cells. Lymphoma was present in both leopard and Testudo hermanni tortoises, indicating that the causative agent had crossed a species barrier.
Further samples from these post mortem, lymphoma-positive animals were despatched to the Ministry of Agriculture, Fisheries and Food, Central Veterinary Unit, Avian Virology Unit, where electron microscopy easily demonstrated significant numbers of herpes virus particles in both spleen and liver tissue. It has also been possible to grow the virus on CAM at a variety of temperatures, and further typing of the virus is being carried out.
Affected tortoises also demonstrated degenerative changes affecting the trachea and lung tissue. Microbiology findings were consistent with overwhelming bacterial and fungal infections. Animals which had been nursed for some time showed further changes relating to muscle wasting and fatty degeneration of the liver. Some had large numbers of intestinal parasites.
Samples from sick tortoises under intensive treatment revealed occasional positive pharyngeal swabs for Chlamydia spp and a variety of presumably secondary bacterial and fungal agents. A PCR faecal test for chlamydial agents was also positive in several animals.
Blood from 14 affected animals under treatment was tested serologically for Mareks disease (an avian onchogenic herpes virus causing lymphoma with paresis) but this did not reveal any positive results. There appear to be significant similarities between the progress of Mareks disease in birds and the symptoms of this onchogenic herpes virus infection in tortoises. Virus cultures under way may yet demonstrate related antigens between these two viruses and hence it may become possible to use a Mareks disease vaccine in the face of similar outbreaks in breeding colonies of endangered chelonia. However, safety and efficacy may be hard to assess.
There are many reports of herpes virus infections in chelonia. It is also possible that currently unexplained disease epidemics globally in many species of both tortoises and turtles are due to a similar if not related herpes virus infection. The use of endoscopic organ biopsy in live animals and subsequent histopathology, viral culture and investigation may allow viral screening of colonies to identify potential carriers of virus infections. Such investigations would require considerable financial input from an interested sponsor but could identify the cause of fatal disease epidemics that occur after a tortoise colony is exposed to a different species tortoise assumed to carry a latent, symptomless infection. Serology may become a useful way in which affected individuals could be identified. However, the response to Mareks disease serology was disappointing and leaves this area open to further research.
It may be worthwhile to treat similar chelonian infections with antiviral agents such as Acyclovir, currently used to treat children with chicken pox caused by a herpes virus infection. However, if this proved to be of therapeutic value we would not know for how long recovered animals may still excrete virus and remain infectious to animals with which they come in contact.
Recently in the UK there have been a large number of cases of unexplained hind- and forelimb paralysis of Mediterranean tortoises. These could be consistent with a neurotropic onchogenic herpes virus. This would indeed be a chelonian parallel to avian Mareks disease. It is possible that the virulence and pathogenicity of a herpes virus may vary significantly with the species affected, some species being symptomless, some showing neuropathies or upper respiratory signs such as runny nose syndrome (RNS), and the remainder suffering fatal disease.
References
CALNECK, B.W. and WITTNER, R.L. (1984) Mareks Disease. Diseases of Poultry (8th ed) p 325-354. Editor: Hofstad, M.S. Iowa State University Press.
COOPER, J.E., GSCHMEISSNER and BONE (1988) Herpes-like Virus in Necrotic Stomatitis of Tortoises. Veterinary Record 123 (21), p 544.
COOPER, J., LAWTON, M.P.C., JACOBSEN and ZWART, P. (1991) Deaths in Tortoises. Veterinary Record 128 (15), p 364.
FRYE, F.L. et al (1977) Herpes Virus-like Infection in Two Pacific Pond Turtles. JAVMA vol 171 (9), p 882-883.
HAINES, H. and KLEESE, W. (1977) The Effect of Water Temperature on a Herpes Virus Infection of Sea Turtles. Infection and Immunity, Vol 15 (3), p 756-759.
HELDSTAB, A. and BESETTI, G. (1982) Spontaneous Viral Hepatitis in a Spur-tailed Mediterranean Land Tortoise. Journal of Zoo and Wildlife Medicine. 13, p 113-120.
JACOBSEN, E.R. (1994) Causes of Mortality and Disease in Tortoises: A Review. Journal of Zoo and Wildlife Medicine vol 25 (1) p2-17.
LANGE, H., HERBST, W., WIECHERT, J.M. and SCHLIESSER, T.H. (1989) Electron Microscopical Evidence of Herpes Virus and High Mortality in Hermann's Tortoises and Four-toed Tortoises. Tierarztl. Praz 17, p 319-321.
OETTLE, E.E., STETYTLER, Y.G.M. and WILLIAMS, M.C. (1990) High Mortality in a Tortoise Colony. South African Journal of Wildlife Research 20 (1), p 21-25.
RANDAL, C.J. (1991) Mareks Disease (Including Transient Paralysis). A Colour Atlas of Diseases and Disorders of the Domestic Fowl and Turkey. p 70-75. Wolf Publishing Limited.
REBELL, G., RYWLIN, A. and HAINES, H. (1975) A Herpes Virus-type Agent Associated with Skin Lesions of Green Sea Turtles in Aquaculture. American Journal of Veterinary Research vol 36 (8), p1221-1224.
VANROMPAY, D., DE MEURICHY, W., DUCATELLE, R. and HAESEBROUCK, F. (1994) Pneumonia in Moorish Tortoises Associated with Avian Serovar A Chlamydia psittaci. Veterinary Record vol 135 (12), p 284-285.
