COLUBRIDS: COMMON CONDITIONS OF COMMON SNAKES

Transcription

1 COLUBRIDS: COMMON CONDITIONS OF COMMON SNAKES Dr Stephen J. Hernandez-Divers, BVetMed, DZooMed, MRCVS, Diplomate ACZM College of Veterinary Medicine, University of Georgia, Athens, GA Colubrid snakes belong to the family Colubridae, a truly huge and eclectic group composed of over 1700 species in 325 genera. Consequently, there are few characteristics shared by all members; some are oviparous, others viviparous; some are venomous, while others are constrictors. There is great variation in morphology, behavior, natural history, and therefore captive care requirements. The most commonly kept pet species include the rat (or corn) snakes, kingsnakes, milksnakes, racers, watersnakes, gartersnakes, bullsnakes, pinesnakes, and gophersnakes. Color mutants are common and have been developed through intensive (in)breeding, and may command high prices (eg, albino Arizona mountain x queretaro kingsnakes currently offered at $1000), while others may be sold for less than $10 (water snakes). MEDICAL HISTORY In addition to any immediate problem, a detailed anamnesis should include information on source and origin, captive husbandry, nutrition, quarantine and preventative medicine (Table 1). Space does not permit a detailed review of the diverse topic of captive colubrid management, and therefore readers are advised to consult the references. Table 1. History Form Reptile name or ID: Species, subspecies: Date of birth, age: Sex: Duration in owner s care/captivity: Origin (captive bred, wild import): Source (breeder, store): Enclosure/vivarium specifications: Environment: Diet: Water: Water and food supplements: Breeding details: Other specimens in same vivarium: Other specimens in same room or air space: Disease history of presented animal: Details of any diseased in-contact animals: Quarantine protocol: Other details of relevance: Type (arboreal, terrestrial, aquatic) Size Construction (materials, fittings) Décor and furnishings Ventilation (mesh, grills) Cleaning routine (agents used) Heating equip Heating control Day-time temperature gradient Night-time temperature gradient Water temperature Lighting equip (type, position, age) Photoperiod Humidity Type and quantities Frequency of feeding When food offered Changes of appetite Method of provision (spray, bowl) Frequency of water changes, water quality Changes in drinking behaviour Type and frequency of use 1762

2 Exotics Reptiles Figure 1. Hypovitaminosis B in a garter snake that was fed fish high in thiaminase, without additional thiamin supplementation. PHYSICAL EXAMINATION The head of an aggressive snake or a snake of unknown disposition should be identified and restrained before opening the transportation bag and removing the animal. In general, the head of the snake is held behind the occiput using the thumb and middle finger to support the lateral aspects of the cranium. The index finger is placed on top of the head. The other hand is used to support the serpentine body. An assessment of demeanor will quickly become obvious. Nervous or aggressive (nonvenomous) snakes can be restrained using plexiglass tubes or sedated prior to examination. A tame snake should be permitted to roam over the hands and arms thereby enabling the clinician to gauge muscle tone, propioception, and mobility. Propioception can be assessed by placing the snake in dorsal recumbency and monitoring the effort and ability of the snake to right itself. Systemically ill serpents will often be limp, lack strength, and be less mobile. Head carriage, body posture, cloacal tone, propioception, skin pinch, withdrawal, ocular and righting reflexes can be used to assess neurologic function. The entire integument, particularly the head and ventral scales, should be thoroughly examined for evidence of dysecdysis (poor shedding), trauma, parasitism (especially the common snake mite, Ophionyssus natricis) and microbiological infection. If available, the recently shed skin should also be examined for evidence of retained spectacles. Skin tenting and ridges may indicate cachexia ( poverty lines ) or dehydration while mites may congregate in skin folds, nostrils and ocular rims. The eyes should be clear, unless ecdysis is imminent. The spectacles covering the eyes should be smooth as any wrinkles usually indicate the presence of a retained spectacle. The subspectacular fluid drains through a duct to the cranial roof of the maxilla. When blocked, the build up of fluid cause a subspectacular swelling that often becomes infected resulting in a subspectacular abscess. Damage to the underlying cornea can result in panophthalmitis and ocular swelling, while retrobulbar abscessation will result in protrusion of a normal sized globe. Other ocular pathologies can include uveitis, corneal lipidosis, and spectacular foreign bodies including splinters of wood chip or other vivarium materials. Examination of the oral cavity is often left until the end of the examination as many snakes object to such manipulation. However, even before the mouth is opened the tongue should be seen flicking in and out of the philtrum with regularity. The mouth can be gently opened using a tongue depressor or blunt sexing probe to assess the mucous membranes, teeth, and glottis. The pharynx and glottis should be examined for hemorrhage, foreign bodies, parasites and discharges. It is important to observe the glottis during respiration in an attempt to differentiate between discharges originating from the respiratory and gastrointestinal tracts. Unfortunately due to the stresses of examination, respiratory rates are often elevated in normal reptiles and therefore tachypnea may not be considered a definitive indicator of respiratory disease unless observed in the undisturbed snake. However, open mouth breathing is a reliable indicator of severe respiratory compromise. During the oral examination the patency of the internal nares and the state of the polyphyodontic teeth should be noted. Working from cranial to caudal, the head and body are palpated for abnormal swellings, wounds and other abnormalities. The position of any internal anomalies, noted as a distance from the snout and interpreted as a percentage of snout-vent length (SVL), will enable an assessment of possible organ involvement. Depending 1763

3 Figure 2. Digenic trematodes (Renifers) in the oral cavity of a wild-caught black racer. upon the musculature, feeding habits and fat reserves of the snake, it may be possible to palpate the normal heart, stomach, liver, active ovaries, eggs, kidneys and fecal material. Recently fed snakes will have a mid-body swelling associated with the prey within the stomach, but handling such individuals may well lead to regurgitation. Eggs and pre-ovulatory follicles may also be palpated. The clinical examination should differentiate between coelomic (internal) and extracoelomic (subcutaneous) masses. The majority of subcutaneous masses are usually abscesses but parasitic cysts, blisters and neoplasia are occasionally seen. Internal masses may represent abscesses, neoplasia, granulomas, obstipation, organ hypertrophy, retained eggs or ova. The cloaca should have muscle tone and not be gaping open, be free from fecal staining with no discharges. Nervous snakes, especially colubrids will often expel the contents of their cloacal glands and cloacae in a defensive reaction to a perceived threat. This foul smelling material does not represent infection, but merely an annoyance as the smell is difficult to eradicate from clothing. Examination of the cloaca can be carried out using a dedicated otoscope or rigid endoscope. Digital palpation is often overlooked but is a useful technique. In small to medium snakes a latex-gloved, lubricated finger can be passed into the cloaca and may allow palpation of eggs, cloacoliths, fecoliths, or abscesses. Examination of the tail length or probing of the hemipenes (in males) should confirm the gender. The tail length (and the number of subcaudal scales) is always smaller in females than males but this method requires access to published information on tail length and scale counts unless both sexes are available for simultaneous examination. The hemipenes are entered by placing a blunt probe, lubricated with a water-soluble material, either side of midline, just inside the caudal cloacal rim. In males the probe passes to a depth of 6 to 14 subcaudal scales whereas in females the probe enters a cloacal gland to a depth of only 2 to 6 subcaudal scales. COMMON PROBLEMS Detailed descriptions of disease processes can be found in the references. Table 2. Approximate Body Organ Position in Colubrids Approximate % Organ position from snout to vent Heart Right lung (excluding air sac) Liver Stomach Left ovary Right ovary Left testis Right testis Left kidney Right kidney

4 Exotics Reptiles Figure 3. Intracoelomic mass (90% snout-vent) causing constipation in an albino Californian kingsnake. The mass proved to be a granulosa cell tumor and was successfully removed. REFERENCES 1. Applegate R. General care & maintenance of milk snakes, Advanced Vivarium Systems Inc, BowTie Press, Irvine, CA, Love K, Love B. Corn snakes: The comprehensive owners guide. Advanced Vivarium Systems Inc, BowTie Press, Irvine, CA, Perlowin D. Garter snakes and water snakes, Advanced Vivarium Systems Inc, BowTie Press, Irvine, CA, Perlowin D. Common kingsnakes, Advanced Vivarium Systems Inc, BowTie Press, Irvine, CA, Gibbons JW, Dorcas ME. North American Watersnakes: A Natural History. University of Oklahoma Press, Norman, OK, Richardson A. North American racer snakes, Capstone High-Interest Books, Mankato, MN, McCracken HE. Organ location in snakes for diagnostic and surgical evaluation. In Fowler ME and Miller RE (eds): Zoo & Wildlife Medicine Current Therapy 4. Philadelphia: WB Saunders, 1999, pp Mader DR. Reptile Medicine and Surgery. Philadelphia: WB Saunders, Raiti P, Girling S. Manual of Reptiles, British Small Animal Veterinary Association, Cheltenham, England, Table 3. Differential Diagnoses by Clinical Signs (most common problems in bold type) Clinical sign Anorexia Head and mouth Differential Diagnoses Parasites: protozoa (Cryptosporidia, Coccidia, Entamoeba), helminths Gastrointestinal foreign body or impaction Ecdysis and dysecdysis Stomatitis, esophagitis, gastritis, enteritis Pneumonia, hepatitis, nephritis (gout and neoplasia) Systemic disease (eg, septicemia, toxemia, metabolic disease) Normal gravidity and dystocia Seasonal (winter) anorexia Intraspecific and interspecific aggression/suppression Poor management, especially temperature, photoperiod, inappropriate food offered Maladaption (especially recent wild imports, change of ownership) Tongue trauma or infection Stomatitis (digenic trematodes) Respiratory disease Pharyngitis Petechiae (septicaemia, poisoning) Pale deposits (urate tophi, abscessation) Submandibular cellulites 1765

5 Table 3. Continued. Regurgitation Coelomic mass or swelling Diarrhoea Integumental Ataxia, paresis, convulsions Ocular Reproductive Circulatory Respiratory Skeletal Stomatitis, esophagitis, gastroenteritis Protozoal and helminth parasites especially Cryptosporidia Septicemia, intoxication, gastrointestinal foreign body, abscess, neoplasia Poor management (inappropriate temperature, handling after feeding, rotten food item, insecurity) Granuloma, abscess, neoplasia Gastric hypertrophy (Cryptosporidium serpentes) Obstruction/constipation (parasites, too large a prey item, too frequent feeding, feeding dehydrated defrosted prey items, concurrent dystocia, foreign body) Parasites (especially Entamoeba) Iatrogenic (medication, force-feeding, excessive oral fluid therapy) Gastroenteritis Inappropriate temperature, rotten food item, inappropriate food item or change of diet Dysecdysis (mites and rarely ticks, low humidity and inappropriate temperature, starvation) Blister disease (too high humidity, unhygienic conditions) Rodent trauma Thermal burns, chemical irritation Petechiae (septicemia, bacterial or viral dermatitis, transcutaneous hookworm (Kalicephalus) infection Bacterial and mycotic infections, including abscesses Myiasis Rostral abrasions due to repeated escape attempts Starvation, debilitation Hypoglycemia, hypovitaminosis B1 (excess thiaminase in fish eating species), hypocalcaemia Trauma Meningitis (parasitic, bacterial, viral especially Paramyxovirus and boid inclusion body disease) Hepatic encephalopathy Renal disease, hyperphosphataemia Intoxication including medicines, eg, organophosphorus, ivermectin Septicemia, toxemia Intraocular panophthalmitis, subspectacular abscess Extraocular retrobulbar abscess (bacterial, fungal), ascending infection secondary to stomatitis or respiratory infection. Diffuse opacity normal ecdysis Focal opacity corneal scarring, corneal lipidosis, corneal foreign body Wrinkled eye surface retained spectacle (low humidity) Infertile mating, laying unfertilised ova infertile male and/or female, unsuccessful copulation, inappropriate pre-breeding conditioning or poor seasonal stimulation, diseased reproductive tract Stillbirths poor management of gravid female especially lack of suitable basking site or poor egg incubation, reproductive tract infection, trauma especially rough handling, lack of appropriate nest site Dystocia obesity, incorrect temperature, lack of nest site, disturbance and other stresses, infertility, reproductive tract disease, egg/foetal abnormality, systemic or metabolic disease True anaemia - hemorrhage, neoplasia, chronic disease, excessive blood collection Iatrogenic (false) anemia lymphatic contamination during venipuncture, excessive rate of intravenous fluid therapy Petechiae septicemia, toxemia Blood parasites usually nonpathogenic Circulatory RBC Mitosis normal Cardiomegaly true cardiomyopathy, illusion due to starvation and emaciation, non-cardiac mass Nasal discharge rhinitis, pneumonia, stomatitis Dyspnea pneumonia, airway obstruction, eg, stomatitis, normal wheeze upon disturbance or during ecdysis Glottal discharge pneumonia (aspiration, bacterial, viral, parasitic) Spinal deformities trauma, osteomyelitis, kyphosis, scoliosis, metabolic bone diseases, hypertrophic osteopathy, congenital anomalies 1766