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Disease prevention in tortoise collections

 

A C Highfield

This caresheet 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. Please also see 'Further Reading' list for other relevant articles.

It is very important to realise 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.

Few reptile keepers (and field researchers) take infectious diseases seriously enough. It is infinitely safer to be over-cautious than careless. There are several broad categories of pathogens to consider:

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 hemolytic (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 diseases 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. It 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.  They are not easy to detect, are extremely difficult to treat, 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 been described in the technical literature.

Mycoplasma organisms

Recently, it has become clear that these are implicated in many outbreaks of contagious respiratory disease.

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 specialised groups.

  • Quarantine all new arrivals for at least 6 months, preferably a year or 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, but 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  for cleaning food preparation surfaces, feeding utensils, accommodation and medical equipment. We recommend 'Betadine' (povidone-iodine) which has good antibacterial and even some anti-viral properties. Virkon-S is another useful product for disinfection.

Wash your 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 diarrhoea and loose motions - these in turn form a secondary hazard. The natural diet of most land tortoises comprises green leaf material and flowers. This is high in fibre, rich in essential trace elements ans 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 sterilised 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 through 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.

Studies on wild tortoises

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.

Further Reading:

Disinfection protocols for Tortoise & Turtle Keepers

Quarantine & Barrier Nursing Techniques

Experience of a viral disease outbreak



Updated November 2014 (c) Tortoise Trust