Chapter 8 Snakes

Table 8.1 Commonly kept species of snake: Key facts

Species	Notes	Common disorders
The royal python (Python regius)	This is a small python, growing to 90–120 cm. It has a not undeserved reputation for prolonged fasting, probably as a result of poor husbandry and endogenous cycles, although this is less pronounced with the modern captive-bred individuals and colour morphs	Dermatitis, dysecdysis and pneumonia. Anorexia, especially in wild caught or captive farmed individuals
The Burmese python (Python morulus bivittatus)	This python is a potentially very large snake; adults can reach up to 5–7 m long with a large muscular cross-section. Adults are usually reasonably behaved but hatchlings and youngsters can be aggressive	Dysecdysis, burns, pneumonia, inclusion body disease (IBD)
Boa constrictor (Constrictor constrictor)	A large snake up to 1.8–3.0 m long. Usually handleable but some individuals can be aggressive. Several colour morphs available and there is some selective breeding to reduce size using naturally occurring dwarf island subspecies	Snake mites, dysecdysis, inclusion body disease (IBD)
Corn snake (Elaphe guttata guttata)	Moderate-sized rodent-eating snakes that make excellent introductions to snake-keeping. This is probably the nearest there is to a domestic snake; it is available in a very wide range of colour morphs, grows to a manageable size (around 1.0 m) and readily takes frozen-defrosted prey	Dysecdysis, cryptosporidium
King snakes (Lampropeltis spp)	King snakes are natural predators of snakes and other reptiles and so are usually kept individually	Dysecdysis, obesity
Garter snakes (Thamnophis spp)	Small to medium-sized snakes. Can be nervous on handling. Many of these are earthworm, fish and amphibian predators, although they can be readily converted on to mammalian prey	Septicaemia, thiamine deficiency

The internal anatomy of a snake is shown in Figure 8.1 (see also ‘Radiography’, in Musculoskeletal Disorders).

Fig. 8.1 Internal anatomy of a snake (lateral).

Consultation and handling

A healthy snake should be reasonably alert and responsive to touch. If it is flaccid or exhibiting CNS signs, such as ‘star-gazing’ it is likely to be suffering a septicaemia, poisoning or possibly a protozoal infection such as acanthamoeba.

Start the examination at the head and work backwards. Larger snakes such as the pythons and boas may require one or more people to hold them while you perform your examination. A gag is usually required to open the mouth – wooden spatulas work reasonably well and are less traumatic than metal equivalents. Do not encourage staff or clients to drape large constricting snakes across the shoulders and around the neck because if the snake feels insecure, it may well tighten its grip unexpectedly.

Venomous snakes require specialist handling equipment and should only be handled by a competent herpetologist or while under an anaesthetic.

Nursing care

Provide an appropriate environment, including provision of:

1 Optimal temperature (basking lights, heat mats, etc., to allow thermoregulation). Use of max–min thermometers will assist in monitoring temperature ranges incumbent reptiles are exposed to

2 Full-spectrum lighting appears to be relatively unimportant for snakes with some exceptions, e.g. rough green snake (Opheodrys aestivus)

3 Humidity

4 Ventilation

5 Easily cleaned accommodation; use paper substrate and disposable/sterilizable hides and other vivarium furniture (Fig. 8.3)

6 Keep individually to minimize intra-specific stress and competition for resources.

Fig. 8.3 Clinical vivarium setup for snakes (lighting is optional – see text).

Nutritional support

Liquidized normal diet or proprietary support diets can be used, given either by stomach tube or by oesophagostomy tube. Force-feeding of prey species may prove traumatic in inexperienced hands.

Skin disorders

Normal ecdysis in snakes

Shedding in snakes is a cyclical event with synchronous replacement of the whole epidermis at the same time. Snakes should shed their skin in one continuous sheet, starting rostrally, and any deviation from this should be considered abnormal. Ecdysis is under both environmental and endocrinologic control. Ecdysis in snakes follows the following sequence:

1 Resting phase. There is only one stratum corneum and stratum germinativum.

2 The stratum germinativum undergoes intense proliferation to form a new stratum corneum, but there is no outward visible change in the snake.

3 The new stratum corneum begins to differentiate and keratinize. At this point there is a slight dulling of the skin of the snake, and the spectacle may appear slightly cloudy.

4 A new layer – the stratum intermedium – is now apparent. This lies between the inner and outer layers of strata cornea. The epidermis is thickest now and so the snake’s colours are at their dullest; the spectacle is cloudy.

5 The stratum intermedium is dissolved away by lymph carrying enzymes – this leaves a cleavage plane between the two strata cornea. The snake’s colours will be seen to brighten and the spectacle will clear.

6 Approximately 4–7 days after the spectacles clear, the outer stratum corneum is shed.

Differential diagnoses of skin disorders

Spontaneous rupture of skin (hypovitaminosis C)

Neoplasia

• Squamous cell carcinoma

• Fibrosarcoma

• Chromatophoroma (malignant)

• Liposarcoma

• Lipoma (esp. cornsnakes, Elaphe guttata).

Findings on clinical examination

• Dysecdysis: One or more patches of retained skin. In some areas the skin will appear dull and thickened where several layers of skin have built up over successive dysecdysis episodes. In some cases rings of unshed skin may form bands around the tip the tail. As these dry they constrict, acting as tourniquets and compromising blood flow to the extremity. The spectacles may be retained (see Ophthalmic Disorders)

• Small mites found on snakes; tend to accumulate under the scales, the postorbital area, labial pits and any skinfolds around the mouth or cloaca. Snake may spend much of time submerged in water bowl (snake mites)

• Large arthropod parasites (ticks)

• Red patches resembling bruising (haemorrhages – septicaemia, trauma)

• Anaemia (heavy ectoparasitic infestations)

• Swellings (neoplasia, subcutaneous parasites, e.g. filarial nematodes, but also consider coelomic disorders).

Treatment/specific therapy

• Hyperthyroidism

• Antithyroid drugs, e.g. methimazole at 2 mg/kg s.i.d.

• Possible try other antithyroid drugs such as carbimazole

• Partial or complete thyroidectomy may also be appropriate dependant upon the case

• Ventral dermal necrosis

• Usually associated with too damp an environment – in semi-aquatic species, it can be initiated by the dermal penetration of hookworm larvae. If left untreated it may progress to a septicaemia

• Treatment is with topical povidone-iodine plus appropriate systemic antibiosis – successful antibiotics include enrofloxacin, amikacin or even gentamicin

• Parenteral vitamin A at 1000–5000 IU will induce ecdysis helping to remove much of the infected skin and necrotic material

• Abscess/granuloma

• Any abnormal swelling should be investigated as a potential abscess or granuloma and may require surgery plus systemic antibiosis

• Dermatophytosis and fungal mycoses

• Topical chlorhexidine (0.26 mL/L)

• Topical antifungals, e.g. miconazole, terbinafine

• Ketoconazole at 15 mg/kg every 72 h p.o.

• Griseofulvin at 15 mg/kg every 72 h p.o.

• Kalicephalus

• Fenbendazole at 25 mg/kg weekly for at least 2–3 weeks)

• Filarial nematodes and pentastomids

• Ivermectin at 200 μg/kg s.c. (toxic to indigo snakes)

• Surgical resection of associated skin granulomas

• Adult pentastomids usually present in lung following extensive tissue migration

• Cestodes

• Surgical removal where feasible

• Praziquantel at 5 mg/kg p.o., s.c. or i.m. Repeat after 2 weeks

• Adhesive tape entanglement

• The outer epithelial layers may be removed and owners may tear the skin in their efforts to remove the tape

• Use a solvent (such as halothane or isoflurane) to gradually remove the adhesive; an anaesthetic may be required especially if tape is adhered to the spectacle (see Ophthalmic Disorders)

• Repair any skin lesions; small lesions can be sealed with tissue glue, larger may require suturing

• Covering antibiosis if necessary

• Spontaneous rupture of skin

• Clean, debride and suture edges of lesion

• Supplement with ascorbic acid. May be linked to feeding starved and, therefore, vitamin C deficient rodent prey

• Ticks

• Individual removal of ticks

• Ivermectin at 200 μg/kg s.c. (toxic to indigo snakes)

Note that ticks are vectors for Babesia/Hepatozoon and Ehrlichia-like organisms

• Snake mites

• Parthenogenetic so numbers can rapidly build up in vivaria; treatment must include the thorough cleansing of all affected vivaria. What cannot be sterilized with a mild bleach solution (5 mL per gallon) must be disposed

• Replace usual substrate with paper (changed daily)

• Repeated washing with warm water will physically remove any mites

• Application of topical fipronil spray once weekly for at least 4 weeks. This is best first applied to a cloth and rubbed over the entire surface of the snake. Fipronil can also be used to treat the environment

• Injection of ivermectin at 200 μg/kg s.c. (Note: toxic to indigo snakes and chelonia) every 2 weeks will kill those that feed on the snake.

• Commercial imidacloprid (100 g/L) plus moxidectin (25 g/L) (Advocate Dog, Bayer) applied at double (32 mg/kg imidacloprid + 8.0 mg/kg moxidectin) to 10-fold dosages (160 mg/kg imidacloprid + 40 mg/kg moxidectin) according to thickness of skin (care with garter snakes Thamnophis spp.) (Mehlhorn et al 2005b)

• Cultures of predatory mites (Hypoaspis miles) are commercially available for use in vivaria

• Linked to septicaemia and IBD outbreaks (see Systemic Disorders) as possible vector

• Neoplasia

• Surgical resection

• Chromatophoromas carry a poor prognosis with early metastasis

• Chemotherapy in reptiles is in its infancy and most tumours are managed surgically. Accessible cutaneous tumours can be treated by injecting cisplatin directly into the tissue mass on a weekly basis as a debulking exercise.

Respiratory tract disorders

Investigations

1 Microscopy

a Sputum examination (either from mouth, pulmonary lavage or endoscopic collection)

b Staining for cytology

c Gram stain

d Lungworm eggs and larvae

2 Radiography

3 Routine haematology and biochemistry

4 Serology for Cryptococcus (also consider isolation from lung lavage)

5 PCR and HI serology for paramyxovirus

6 Culture and sensitivity

a Pees et al (2007) offer the measurements in Table 8.2 for CT examinations of the lungs of healthy Indian pythons (Python morulus) and pythons with respiratory tract disease

b Also the mean (±SD) measurements of attenuation in defined lung areas for CT examinations of healthy pythons and pythons with respiratory tract disease (Table 8.3).