Environmental stress (including inadequate husbandry) predisposes an animal to infection, by reducing the efficiency of its immune system. Thus knowledge of basic environmental requirements of the reptile is vital in the prevention of many diseases. It is important to be able to identify the species in your care so that its correct housing and feeding requirements can be met. Most diseases of reptiles in the UK are caused by an incorrect diet and/ or incorrect housing conditions. Cage dimensions vary with species; arboreal species require height, terrestrial species floor area, aquatic species water and basking platform. Items that can be ingested e.g., small stones. A 'hide' area is important. A body of water is required for aquatic and semi-aquatic species. Adequate filtration and heating should be provided. Water should always be available to all reptiles in a form that is acceptable to them e.g., chameleons will only lick droplets, tortoises need to immerse their mouth and nose and so should be placed in shallow water 3x/week.
Reptiles are ectotherms i.e., regulate body temperature by behavioural means. Reptiles require a range of temperatures to be able to thermoregulate (known as the preferred optimum temperature zone/ POTZ). Preferred body temperature (PBT) is the optimum temperature for the functioning of the reptile's systems e.g., movement, feeding, digestion, reproduction, and immunocompetence. Sick reptiles tend to seek out the high end of their PBT ('behavioural fever').
Primary heat Source--for background/ ambient heat (at the low end of the POTZ). Use heat tapes, mats, or radiant heat from incandescent bulbs, ceramic lamps. Always provide a heat source that is not also a light source in order to provide the correct period of darkness whilst maintaining the vivarium temperature.
Secondary heat source--specific areas can be provided with a higher temperature.
Monitoring is important to check the range of temperatures. The ambient temp should not exceed the PBT; the temperature under the hot spot should not exceed the maximum tolerated. Max and min thermometers and thermostats are essential. The reptile should be denied direct physical contact with the heat source, as deep burns are common.
Timers are required for the maintenance of a stable photoperiod. Suitable photoperiods are approx. 12-14 hours of light per day. Too many hours of light can be a significant stressor. It is not suitable to have the ambient heat source as a light source.
Quality of the Light
UVA (320-400nm) this range stimulates agonistic and reproductive behaviour in lizards.
UVB (290-320nm) this range is important for the conversion of provitamin D3 to previtamin D3 in the reptile skin, and so is important for calcium metabolism.
50-70% tolerated by most species. Low for desert species e.g., ground leopard gecko (Eublepharis macularis) at 20-30%. A humid chamber should be provided for ecdysis (an ice-cream carton filled with damp tissue paper). High for rainforest species e.g., emerald tree boa (Corallus caninus) at 70-80%, and spraying with tepid water is required.
Humidity should not be increased at the expense of ventilation.
Nutrition and Feeding
Calcium: phosphorous of 1.5: 1 plus vitamin D3. Ensure insects have been fed fruit and supplement for 24h or will be nutritionally empty (nutrient loading). Reptiles, especially youngsters, should not be over-handled when they have recently eaten as they may regurgitate. Aquatic species (which feed in water) e.g., red-eared terrapin (Trachymys scripta elegans) should be fed in a separate feeding tank to prevent water fouling. Terrestrial chelonians are usually herbivorous. Some snakes e.g., constrictors, prefer to eat in a small, dark box; pythons may require 'teasing' with food. For most species, the provision of a wide shallow dish for drinking water is sufficient. Tortoises should be placed in shallow water to drink at least weekly.
Transport animals in an insulated, warm, dark, secure box or bag.
Chelonians. Hold shell slightly cranial to hindlimbs or around the back of the shell between the hindlimbs (particularly in the more aggressive species which scratch and bite). Take added care with the box terrapins (Terrapene spp), which can close its shell via a hinged plastron.
Lizards. Hold around the neck and pelvic girdle with one hand, and with the other around the pelvis and hindlimbs. A soft cloth may be used to catch the delicate skinned geckos. Never handle a lizard by the tail as some species shed them (autotomy) and the regrown tail is never the same shape and size as the original.
Snakes. Can be very aggressive. Boas tend to be more aggressive early evening, so avoid these appointment times. Hold with thumb and second finger behind the occiput and the forefinger on top of the head. Do not hold on 'neck' as they have a single occiput, which can be easily dislocated. Care must be taken as bruising can lead to debility, even death. The ribs of smaller snakes are delicate and easily broken. If bitten, remember the teeth angle to the back of the mouth so resist pulling back. Drops of isopropyl alcohol into mouth encourage release. Ripping the hand out of the mouth can result in a deeper bite and loss of teeth into the wound (foreign body reaction in human, osteomyelitis of jaw in reptile).
Note: over-handling of reptiles, especially youngsters can lead to food refusal. Reptiles are not social animals like most mammals and so tolerate moderate handling only. They should not be bought as pets to 'cuddle'.
In the male the tail houses the two hemipenes, which may be seen bulging in, mature lizards and snakes (more obvious in lizards). In chelonia, the single hemipene makes the tail larger and longer; also the vent is further away from the plastron (the under part of the shell). Ultrasonography can be used to detect ovarian follicles and hemipenes/ penis in many species. Endoscopy can be used to visualise the gonads. The use of temperature dependant sex determination during incubation can be used to predict the sex of the hatchlings.
Check mucous membranes, petechiation indicates septicaemia (common presentation of sick reptiles).
Necrotic digits/distal tail are most commonly due to septic thromboemboli as a sequel to septicaemia.
1. Consult owner's records. These should include feeding, weight, ecdysis, faecal and urate production.
2. Obtain accurate length (rostrum-cloaca) and weight
3. Inspect rostrum, nostrils and infraorbital pits (discharge, occlusion, trauma)
4. Check eyes clear, inspect spectacles under magnification for abnormalities
5. Ensure tongue flicking normally and snake moving normally, able to support head etc.
6. Examine oral cavity and cloaca
7. Palpate for swellings
8. Check scales for lesions
9. Smaller snakes and hatchlings may be Tran illuminated
10. Average organ position in boas and pythons = > cranial 1/3 oesophagus, trachea, heart; middle 1/3 lungs, liver, stomach, cranial air sac; caudal 1/3 pylorus, duodenum, intestines, kidneys, gonads, fat body, cloaca
As above where relevant plus:
1. Check medial temporal joint (orally) for white deposits (= uric acid deposits)
2. Assess limb strength and locomotion, and bone/soft tissue swelling
3. Check digits and tips of tail (dry gangrene with dysecdysis)
4. Smaller lizards, e.g., geckos can be trans-illuminated
As above where relevant plus:
1. Check locomotion and strength
2. Check shape of shell for evidence of metabolic bone disease, haemorrhage, trauma
3. Tympanic membrane should be flat/concave
4. Beak should be evenly apposed
5. Inspect mouth, note clear Eustachian tubes
Aspects of Reptile Medicine
The renal portal venous circulation in reptiles means that injections into the hindlimb musculature may be eliminated via the kidneys before reaching the rest of the body. Care should be taken especially with potentially nephrotoxic drugs. There is still debate as to whether this system significantly affects drug distribution. In patients weighing <100g, no more than 0.2 ml should be given at any one site.
intercostal muscles of body
fore-and hind-leg muscles, tail muscles
as lizard, plus pectoral muscle mass at angle of forelimb and neck
in loose skin (over ribs in snake/lizard)
see blood sampling veins
Most sick reptiles will present dehydrated, requiring fluid therapy or force-feeding. Consider these if the reptile has continued weight loss, dehydration. Fluids given s/c, i/p or i/v. Care; as reptiles lack a diaphragm, the administration of large volumes of fluid i/p may impair breathing and so should be avoided, especially in those already showing respiratory compromise.
Reptiles often deposit urates/faeces when being examined. If not, a colonic wash may be performed.
Insert lubricated French catheter attached to syringe filled with sterile saline into cloaca and colon (it should slide in easily with the right size).
Flush in saline and aspirate several times.
Care: reptiles may pass prey parasites e.g., mouse nematodes, which are nonpathogenic to the reptile.
It is imperative that the maximum blood volume that may be safely withdrawn is accurately calculated, as it is easy to overestimate in small animals. Reptiles total blood volume varies with species but is approximately 5-8% bwt (70 ml/Kg). Of this, 10% may be withdrawn safely. E.g., 100g snake = 5-8 ml blood, withdraw 0.7 ml. Collect blood into lithium heparin tubes and make fresh blood smear.
Palatine vv, ventral tail v, cardiocentesis.
Ventral vein, only method not requiring sedation,--identify cloaca, insert needle distal to this, into tail at midline at 45°-90° angle. Advance to vertebrae, aspirate as slowly withdraw. Vessel just ventral to vertebrae. Use 2ml syringe on 23-25G needle.
Cardiocentesis requires sedation (generally). Palpate/ visualise beating heart, stabilise with finger and thumb. Use 23/25G needle on 3-6 ml syringe.
Large animals (down to 100g)--ventral tail vein as above. Toenail clips contain lymph and tissue contamination and do not produce diagnostic samples.
Cardiocentesis, jugular vv, brachial vv, ventral coccygeal v, subcarapacial vein.
Attempts to venepuncture limb veins often results in collection of lymph only, as these vessels are large and the veins cannot be visualised. The subcarapacial vein is accessed by inserting the needle in the midline, above the head (missing the neck structures) aiming dorsally towards the carapace. Collection from a jugular vein; extend the neck slowly, the jugular vein will be seen as a bulge between the tympanic membrane and the base of the neck. A low dose of ketamine (5-10mg/kg IM) may facilitate head restraint.
Correct positioning is important. Animals can be taped down, radiographed through box or bag if not sedated.
Radiograph regions of suspected lesion only or, take sequential sections along length of snake using lead markers every 10-20cm. Whole body coiled radiographs are almost useless. DV and horizontal beam lateral views most useful.
Poor skeletal density most common finding, if suspected, reduce the kV. Normal lizards show similar bone/soft tissue contrast to mammals. DV and lateral views (using horizontal beam).
DV--Placing animal on a raised column with the feet off the table to aid restraint. Lateral--tilting chelonians onto their side distorts the diaphragm and lungs, thus horizontal beam required; centre beam on 6-7th marginal shield at right angles to vertebral column. Cranio-caudal useful for contrasting two lung fields. Centre horizontal beam on nuchal shield.
Lizards and Snake 7.5 and 10 MHz transducers with standoff for suitable resolution in small reptiles. 5 and 3.5 MHz transducers for larger reptiles linear array transducers are used to view the internal organs via the ventral body wall using an aqueous contact gel. Generally, the same organs scanned in mammals can be usefully scanned in reptiles. Chelonians transducers are placed in the spaces between the carapace, plastron and limbs. The gonads can be visualised for sexing and to monitor reproductive status.