Disinfection Protocols for Tortoise
& Turtle Keepers
Andy C. Highfield
Health, Safety and Infection Control
It is of paramount importance when handling, maintaining and treating tortoises and turtles that adequate steps are taken to prevent personal injury and the further spread of diseases to other animals or humans.
There are three key stages in maintaining hygiene and preventing the transmission of pathogens:
The best known human risk factor in connection with chelonia is, of course, Salmonella, but there are a number of other pathogens that these animals may carry that are equally dangerous. The presence of children, the elderly or immune compromised persons in the vicinity of turtles is not generally advised and should in any event be monitored carefully with all necessary precautions rigourously enforced. Examples of bacterial organisms capable of affecting humans include (but are not limited to) Campylobacter, Pseudomonas, Aeromonas, Clostridium, Yersinia, Edwardsiella, and Burkholderia pseudomallei (most frequently associated with turtles of Asian origin). Other potential risks include exposure to Mycobacterium (the organism responsible for tuberculosis) and the fungus Zygomycetes. Another potentially zoonotic organism of concern is cryptosporidium. In this case, both treatment and diagnosis is far from easy and strict isolation procedures should be employed for any animal which is suspected as a carrier. All keepers and institutions should therefore have an effective infection control protocol in place.
For most keepers, good general hygiene practices will provide adequate protection. Standard procedures include not eating or putting anything in the mouth when working with turtles, regular and thorough hand washing using hot water, soap or a disinfectant scrub after handling animals, and the regular use of disinfectants such as dilute (1:10) household bleach or a 10% povidone-iodine solution to clean feeding utensils, instruments and work surfaces. In the context of a rescue or rehabilitation facility, however, additional measures will be necessary, as the constant intake of animals that may be carrying a very wide range of bacterial, viral and fungal pathogens presents a serious hazard not only to existing stock but also to those involved in handling and treating them.
Routine cleaning to a high standard is of critical importance in any animal establishment, and especially so in a rescue or rehabilitation centre where there will be a constant influx of infectious and contagious cases. The object when cleaning is to remove all traces of visible dirt in the environment by means of wiping, flushing and scrubbing using hot water and a detergent agent. Detergents reduce surface tension, thereby dramatically increasing the penetrating ability of water and releasing dirt more easily. Most commercial detergents comprise a combination of anionic and non-ionic sulficants. Physical cleaning must always precede disinfection as the presence of organic matter such as blood, fat or similar organic materials will severely degrade the performance of most disinfectants. Cleaning is a vital first step to full disinfection and it has been estimated that thorough cleaning alone can reduce bacterial levels in an environment by as much as 90%. It is important when cleaning to remove potentially infected matter, and not merely to disperse and distribute it. Loose, dusty material (e.g., vivarium substrate) should be dampened to minimise aerosol spread. Wear an approved mask to prevent inhalation and goggles to prevent contamination of the eyes. Wear protective gloves at all times. Boots or overshoes should also be worn and thoroughly cleaned and disinfected before moving from one area to another. A properly maintained disinfectant boot bath is recommended. Use high pressure sprayers and vacuum cleaners with extreme caution. They may simply result in the widespread particle aerosol distribution of pathogens. Generally, low pressure cleaning is preferable.
Disinfection follows cleaning, and the object is the removal of all micro-organisms except bacterial spores (which are extremely resistant to most disinfectants). There are three widely recognised categories of disinfection: Low-level disinfection destroys most bacteria and some viruses. Intermediate-level disinfection destroys most bacteria, mycobacterium, most viruses and most fungi but will not neutralise bacterial spores. High-level disinfection kills all micro-organisms except bacterial spores. It should be noted that the term ‘disinfectant’ refers to a product that is applied to an inanimate object. Where a product is applied to living tissue (such as a wound) to achieve the same aim, it should be referred to as an ‘antiseptic’. Some products used as disinfectants can also be used in the role of antiseptics. Others are based upon caustic or volatile substances that render them unsafe for contact with skin under any circumstances. Disinfectants are classified according to their type of activity:
Bacteriostatic disinfectants inhibit the growth and proliferation of bacteria but do not necessarily kill them.
Bactericidal disinfectants kill bacteria. This class of disinfectant is therefore to be preferred.
Useful disinfectants include:
Household bleach (5.25% Sodium hypochlorite) has the advantage of being readily available almost everywhere and it is highly effective against an extremely wide range of pathogens, including enveloped viruses. Used at a 1:10 dilution (1 part bleach in 10 parts water), household bleach may be sprayed or wiped onto surfaces to produce a high level of disinfection. A thirty second exposure is generally recommended. It is effective against a broad spectrum of bacteria, lipid and non lipid virus particles, fungi, nematodes, protozoa and algae. It is important to recognise, however, that some pathogens are resistant to bleach, such as Cryptosporidium which is killed only by exposure to ammonia or hydrogen peroxide. Used at a 1:100 dilution, bleach may be used on pre-cleaned non-porous surfaces and left to air dry. The disadvantages of bleach are that it may damage or discolour some surfaces and fabrics, and at the concentrations required for the effective disinfecting of non-porous surfaces causes corrosion to many metals. It must never be used in combination with any other cleaner containing ammonia, as toxic chloramines are produced that can cause severe respiratory damage if inhaled. Bleach solutions are also rapidly deactivated by the presence of organic matter such as blood, dirt or faeces, and degrade when exposed to UV light (bleach should always be stored in opaque plastic containers out of direct sunlight and away from artificial UV light sources). Bleach is not suitable for use as a skin disinfectant and any item cleaned with bleach must be very thoroughly rinsed before it is allowed to come into contact with living tissue.
It is extremely important that visibly dirty surfaces to be disinfected with bleach are pre-cleaned with moist disposable paper towels (which must then be disposed of safely). Fresh bleach solutions should be made up every few days as solutions stored at room temperature lose 40-50% of their effectiveness over a period of a month. Some domestic bleach products fall far short of the >5% level required for effectiveness. Many domestic ‘budget’ products (often sold as ‘thin bleach’ or ‘value bleach’) contain as little as 1.8% sodium hypochlorite.
Povidone iodine is a well-established topical disinfectant which is popular as a pre-surgical scrub. Tincture of iodine was developed 200 years ago, although it was some time before its full potential was understood. It was first used surgically in France in 1839, and gained rapid acceptance thereafter in reducing infections following wounds, including battle injuries sustained during the American Civil War. Although highly effective against a broad spectrum of bacterial, viral and fungal pathogens, and protozoa, tincture of iodine is irritant and can be unpleasant to use. A less aggressive formulation known as povidone-iodine is therefore generally preferred. It is typically offered in two variants, a 10% or 5% antiseptic solution and as a foaming surgical scrub. Although less irritating to tissues than tincture of iodine, it does share some disadvantages, including staining, and prolonged use may cause skin sensitisation. It is also harmful if inhaled and there is some risk of excessive absorption of iodine resulting in hyperthyroidism, renal problems and electrolyte disturbances. These risks are low if used with caution. The best known brand is Betadine. To achieve maximum disinfection of the hands continuous washing with surgical scrub for a full five minutes is recommended. Clean thoroughly under the fingernails. Use a brush if necessary. Rinse well. Surfaces may be disinfected by wiping or spraying antiseptic solution and allowing to air dry. Povidone-iodine has a limited effect on enveloped viruses, however, e.g. coronaviruses, herpesviruses, orthomyxoviruses, paramyxoviruses and retroviruses. These are all potentially carried by reptiles, including tortoises and turtles, so this limitation is serious.
Chlorhexidine (Nolvasan, Hibiscrub) is effective against a wide spectrum of bacteria (though some resistant strains of gram-negative bacteria commonly encountered in chelonia such as pseudomonas and proteus have been reported), fungus and viruses (with limited effectiveness) and is available as a liquid disinfectant, a topical wound cleaner and as a foaming hand scrub. Advantages are that it is non-corrosive to metals, retains some effectiveness even in the presence of organic matter and has good persistence. It is generally considered to be relatively gentle and non-irritating to skin. It it, however, highly toxic to fish and aquatic invertebrates and this may restrict its application in aquatic installations or with turtles where environmental contamination may occur.
Virkon-S (potassium peroxymonosulfate and sodium chloride) is a proprietory peroxygen molecule, organic acid and surfactant combination, with a very broad spectrum of activity against bacteria, enveloped and non-enveloped viruses, yeasts and fungi. It retains some efficacy in the presence of organic material, but pre-cleaning is still advised. It is usually supplied as a powder or in tablet form to be disolved in water. A fresh solution should be made up every five days. It may be used to soak items or applied as a spray. A 10-minute exposure followed by thorough rinsing will normally result in adequate disinfection.
Disinfectants based on quaternary ammonium compounds have poor activity against Gram negative bacteria and therefore should not be used in tortoise and turtle management situations where such organisms are commonplace.
Alcohol should only be used as a disinfectant in exceptional circumstances, and then only in small quantities to minimise the risk of fire.
Phenol-based disinfectants, such as Lysol, are highly toxic to many animals and may cause skin and respiratory irritation to humans. Domestic versions are of limited effectiveness against many pathogens encountered in reptiles.
Pine-oil based disinfectants (such as many common domestic products) are toxic to animals, and are of very limited effectiveness against common reptile pathogens.
Alcohol-based hand sanitisers are widely available in the form of liquids and gels, and are very convenient in use, but they are of limited effectiveness.
While these products initially reduce surface-borne bacterial loads substantially, they have very limited residual activity, and they have low effectiveness against certain viruses and bacteria, including clostridium. In addition, they have no mechanical cleaning capacity. It is therefore recommended that hands be washed first with soap and water if physical particle contamination is present. Hand sanitisers should never be relied upon as a first line of defence against cross infection, but only as an adjunct to a thorough hand washing regime. In that role, studies have shown that they can provide additional useful protection. If hand washing is impractical, then use of a hand sanitiser between handling animals is certainly better than nothing. A minimum 30-second second exposure of sanitiser solution containing at least 60% alcohol is typically required for significant effectiveness. A typical 5-15 second usage (as is often encountered) merely conveys a false sense of security and is therefore counter-productive to infection control efforts. It is extremely important that alcohol based liquids and gels are never used in the presence of a naked flame, in an oxygen rich environment, or in the presence of sparks or electrical equipment that may produce sparks ,as they are highly flammable and may have a flash point of less than 100 degrees Fahrenheit.
Benzalkonium chloride based hand sanitisers offer some major advantages over alcohol based types. They have better persistence, resulting in germicidal activity for several hours, and they have none of the incendiary properties that render alcohol based preparations so hazardous. As with alcohol based sanitisers, however, it is vital that physical debris and dirt are removed first using soap and water.
The goal of sterilisation is the complete destruction of all forms of microbial life, including bacterial spores. This is usually achieved using wet heat under pressure, as in an autoclave, as this is more reliable than immersing in boiling water for a minimum of fifteen minutes (which used to be widely practised). Although boiling will kill most pathogens if sustained for long enough, it is not 100% effective against all known spores. Dry heat may also be used, but sustained temperatures in excess of 160 C (320 F) for at least four hours are required. Other options to achieve sterilisation include total immersion in liquid chemicals such as formaldehyde, glutaraldehyde or 6% hydrogen peroxide. These are volatile and dangerous substances, however, and their use is strictly regulated. They should only be used under controlled conditions, with appropriate equipment, and by adequately trained staff. Gamma ray radiation and gas sterilisation (often based upon ethylene oxide or hydrogen peroxide gas plasma) are other methods, but again, they are impractical outside of an industrial or hospital setting where extreme precautions are taken to prevent personal injury or environmental contamination. This type of high level sterilisation is, fortunately, normally only required for surgical instruments. The practical solution in most circumstances likely to arise in a tortoise or turtle rehabilitation setting is to purchase certified sterile disposable instruments for once only use, and to employ an autoclave, carefully following the manufacturer’s directions, in all other cases.
Faeces and dirty water should be disposed of carefully and safely; tortoise and turtle waste is not suitable for composting as Salmonella organisms can survive this process. All wastes should be assessed for content and risk factor and local regulations consulted for further guidance on the proper (and lawful) method of disposal. A separate bin should be used for all animal waste, and this should be thoroughly disinfected at least weekly. A bin that opens by foot pedal is preferable to one requiring the use of the hands. Sharps (used needles, disposable blades, etc.) should only be disposed of in approved containers using approved methods (typically incineration).
Help and advice from other experienced keepers can be obtained via our user forum at www.tortoisetrustforum.org