Disease Prevention In Tortoise and Turtle Collections
reprinted with permission by Andy C. Highfield

This article explains a series of sensible precautions you can take which if followed will greatly reduce the possibility of any disease entering your collection.  If a disease should occur within your collection then these precautions will greatly reduce the chances of cross-infection.

It is very important to realize that an animal may be infectious without appearing to be sick itself. It is no use therefore simply avoiding evidently ill animals- even an outwardly healthy specimen may be carrying a disease which could be lethal to others which it contacts. Recent evidence suggests that some viruses may exist within a tortoise for up to 10 years without causing obvious symptoms; during this time the animal will present a serious hazard to all others it comes into close contact with.

Parasitic Organisms
These include nematodes ('worms'), flagellate and ciliate protozoan organisms and ectoparasites such as ticks (these are usually only seen on freshly imported tortoises or on tortoises which have been kept in close proximity to sheep or goats).  All of these parasites can cause serious difficulties by themselves, but more worrying still is their ability to act as potential vectors for other, much more serious bacterial and viral pathogens.  Ticks in particular are major vectors of haemolytic (blood-borne) pathogens.

Bacterial organisms
These include a wide range of Gram-negative organisms which can prove highly resistant to antibiotics and which are frequently implicated in the disease of tortoises and turtles (e.g. pseudomonas, citrobacter, klebsiella, serratia and aeromonas etc.)-
these are commonly isolated from such diseases as stomatitis ('mouth rot') or necrotic dermatitis ('shell rot') and from abscesses.  These organisms are frequently highly tenacious and are very easily transmitted.  Tit is not unusual for entire groups of tortoises in a collection to succumb to diseases caused by these pathogens - especially if hygiene measures are not up to standard.

Viral organisms
Viral organisms represent an extremely serious threat.  They must never be underestimated.  Unfortunately, a  lot remains unknown about the viruses affecting tortoises and turtles- but what has been discovered leaves no doubt that  a0 they exist and b) are frequently highly contagious and extremely lethal.  They are not easy to detect, are difficult if not impossible to treat effectively, and can be spread very easily from animal to animal.  Specific viruses causing severe forms of stomatitis, shell disease, and hepatitis in tortoises and turtles have recently been described in the technical literatrue.  Classes of viruses so far positively identified in tortoises and turtles include; Herpesvirus, Papillomaravirus, tridovirus, Poxvirus, Retrovirus, Reovirus and Paramyxo-like virus.  In addition, tortoises and turtles may act as passive carriers, or reservoirs, of Flavivirus, Togovirus and Bunyaviruses.  At time of writing, no easily accessible or reliable test is available to determine carriers or infected animals.

Mycoplasma organisms
Recently, it has become clear that these are implicated in many outbreaks of contagious respiratory disease.  The best known example is the epidemic affecting California Desert Tortoises (gopherus/Xerobates) in the United States.

Other infectious/contagious pathogens include Chlamydia spp. and mycotic (fungal) organisms.  Generally speaking, the same preventative stips suggested for bacterial and viral diseases will also suffice to reduce risk of infection by these organisms.

Basic Precautions
   It is wise to follow the following basic guidelines as a routine management procedure in all collections, small and large.  In fact, the larger your collection and the more incoming and outgoing animals you have the greater the danger of contracting or transmitting disease.  The safest collections are those which are small in number and are stable, with no new arrivals.  Large collections with many mixed species tend to have the much worse overall health records than small, stable and specialized groups

*  Quarantine all new arrivals for at least 6 months, preferably a year to 18 months
*   Keep quarantine animals entirely separate from all other stock and feed separately      using different utensils for each.
*  Do not randomly mix species in collections

Mixed collections tend to have very poor overall survival rates.  Keeping species (and geographical sub species) separately not only improves captive breeding success, mixing 'spur-thighed' tortoises from Turkey with those from north Africa is definitely not a good idea; there is no doubt whatsoever that where this is done on a large scale the more delicate north African species suffer a much enhanced rate of disease and mortality.  When kept separately there is no such problem.  It is the view of the Tortoise Trust that a combination of adopting good general hygiene measures and maintaining only naturally sympatric species in close contact makes a major contribution to the safety of any collection.  If tortoises from widely differing backgrounds are allowed to mix at random, there is no doubt that some will have no natural immunity to organisms carried normally by others.

Further Precautions

Always use a high quality antiseptic routinely for cleaning food preparation surfaces, feeding utensils, vivarium accommodation and medical equipment.  We recommend ' Betadine' (providone-Iodine) which has good antibacterial and anti-viral properties.

* Wash hands regularly after handling all animals.
* Use different footwear (or overshoes) in quarantine areas.

Flies are a real hazard and can easily spread disease.  Some foods are especially attractive to flies, particularly sugar-rich fruits.  These are best avoided, especially in warm weather.  Not only does a high proportion of fruit in the diet attract flies but it can also cause diarrhea and loose motions- these in turn form a secondary hazard.  The natural diet of most land tortoises comprises green leaf material and flowers. These are high in fiber, rich in essential trace elements and does not attract flies.

Remove all sick animals from the rest of the collection immediately and obtain expert veterinary treatment as quickly as possible.  Where an infectious disease is suspected always commission laboratory tests to determine the nature of any pathogen.  Such data could prove invaluable should the disease later spread.

Some specific practices should definitely be avoided as they contribute enormously to the danger of acquiring or transmitting disease:

Never employ invasive treatment or study techniques (e.g. tube feeding, injections or identification tagging, marking etc.) without first ensuring that all implements are satisfactorily sterilized each and every time.

DO NOT mix large groups of tortoises from different origins together.

DO NOT overcrowd animals

DO NOT allow large groups of animals to feed together.  This is guaranteed to spread disease if any is present. Feed individually or at worst in small groups.  One animal with stomatitis is enough to spread the disease though an entire collection if the animals are allowed to feed together.

BE CAREFUL when 'holiday homing' or when taking animals on breeding loan.

MATING is also a high risk activity insofar as spreading disease is concerned. It is best to restrict mating to established small groups or pairs.  Random mating should not be permitted, especially if new introductions are present.

DO NOT attend meetings with your tortoises or turtles; such gatherings are an ideal place to acquire or spread diseases.  It is very difficult to ensure adequate disease precautions prevail at public meetings where large numbers of animals congregate and it takes only one careless person to infect a large number of animals.

IN THE CASE OF AQUATIC TURTLES install a sufficiently powerful UV-C sterilizer unit in circuit with the filtration system.  While not entirely reducing all risks of cross-infection, such a system, if properly maintained, will substantially reduce the risk factor.

Special considerations apply if you are involved with studies on wild tortoise populations.  In recent years a number of epidemics have occurred which threaten some species with extinction.  It is the responsibility of all researchers to ensure that their actions in no way contribute to the spread of disease:

Ensure that all invasive marking procedures are carried out under conditions of strict hygiene. Use one-shot sterile implements or adopt working practices which guarantee that blood or tissue is never transferred between specimens.

Under no circumstances transfer specimens between populations.

Do not release ex-captive animals back into the wild, or keep animals destined for release in the proximity of other captive animals.  Treat all such animals as quarantine stock.

Be especially careful when taking cloacal temperatures or blood samples; ensure that your hygiene procedures are adequate to guarantee that no pathogens are transferred between specimens.

copyright A.C. Highfield and The Tortoise Trust 1992-1999 (revised)