Abstract
Anorexia is a symptom, not a disease. Chronic anorexia may lead to debilitation and eventually death. The most common cause of anorexia is improper husbandry, of which improper temperature management is the major inciting cause. The clinician should familiarise himself/herself with the basic husbandry requirement of a few commonly presented reptiles to his/her practice.
Introduction
Anorexia is a symptom, not a disease, defined as a lack of appetite or lack of feeding response.1,2 It may be manifested in virtually any disease or disorder, ranging from environmental to medical causes.1-3 Identifying and eliminating the underlying cause is essential for long-term success of treatment of anorexia.2 Regardless of the cause, however, anorexia should be diagnosed and treated promptly, as chronic anorexia may lead to debilitation and eventually death.1,2
Causes of Anorexia
Normal Physiological Factors
Temperate climate reptiles may ready themselves for the approach of winter and brumation (winter dormancy of reptiles) by undergoing an "autumn anorexia," irrespective of environmental temperatures.1,4 Many snakes are anorexic before or during ecdysis and will often only resume feeding after shedding.1,4
Husbandry Factors
The most common cause of anorexia is improper husbandry.1,2 The author recommends that the clinician familiarise him-/herself with the basic husbandry requirements of a few commonly presented reptiles to his/her practice.
Improper enclosure temperature is the most frequent cause of husbandry-related anorexia in captive reptiles.1,2 If the reptile cannot reach its ideal body temperature in the environment, it will not feed.5 Too low or too high temperatures may lead to anorexia.1 Ideal enclosures offer a thermal gradient allowing for physiological thermoregulation in reptiles.1,2,4 The reptile's natural habitat and geographic origin will provide clues to what its temperature requirements are.1,2 An incorrect diurnal cycle with inadequate lighting will result in anorexia in captive reptiles.1,2 Lights should never remain on for 24 hours a day.1,2 Feeding cycles also play a role together with diurnal cycles as nocturnal reptiles offered food during the day may appear anorexic to the owner, but when offered food at night, will eat normally.1,2 The location of feeding is important pertaining to strictly terrestrial or aquatic species, as they may not be able to locate the food placed on a branch or on shore, respectively.1,2
If the species is misidentified or unknown, the wrong type of food may be offered to the reptile.1,2,4 If the reptile is sated or the food item is too large, it may also appear anorexic.1,2,4 Too frequent handling of shy specimens or stress from overcrowding can also cause anorexia.1
Nutritional Factors
Metabolic disturbances and anorexia may be caused by improper use of nutritional supplements (hypo-/hypervitaminosis.1,2 Feeding overweight rats to snakes may cause anorexia and high-fat diets may cause pansteatitis and anorexia in crocodilians.6,7 Hypocalcaemia will result in metabolic bone disease manifesting with typical osteodystrophy signs of a flexible mandible, loosening of teeth, ileus of gastrointestinal tract, and lingual muscle weakness in chameleons.8 Some reptiles with perceived anorexia will feed again if a novel or different prey species is offered.1,2,4 Providing a variety of prey species simultaneously will alleviate boredom and stimulate the feed response.1 Some reptiles may also not feed on dead prey and require some movement to induce the predator response.1,2
Reproductive and Social Factors
A subordinate may not eat in the presence of a dominant individual, or the dominant individual may have eaten all the available food.1,2 Reproductively active males may become anorexic during the breeding season due to behavioural changes regarding territoriality and fighting with rivals or they could be searching for a suitable mate.1,2 Gravid snakes and lizards may not feed during late gestation due to coelomic space occupation of the eggs.1,2 Dystocia is another common cause of anorexia.1,2
Gastrointestinal Factors
Many gastrointestinal diseases may lead to anorexia, including parasitism, stomatitis, oesophagitis, gastroenteritis, dental disease, abscessation, foreign body, impaction, neoplasia.1,2 Any disease or injury that affects prehension of food, will cause anorexia.1,2,4 Parasites like cestodes, nematodes, acanthocephalans, and protozoans, may cause gastroenteritis resulting in anorexia.1,4 Enclosure substrate (pebbles, maize cob, wood, bark chips, plastic decoration, or towels) may be ingested causing a foreign body intestinal obstruction.1,2 Viral infections like herpesvirus in tortoises and paramyxovirus in snakes have been described to accompany anorexia.9
Respiratory Factors
In snakes, the trachea is severely compressed during feeding by the food bolus.2 As a result, an upper or lower respiratory infection will make the feeding process a very stressful encounter, causing dyspnoea or apnoea, which may cause reluctance to feed.1,2,4 An iatrogenic bronchooesophageal fistula from traumatic assisted- or force-feeding may cause anorexia.1,2
Miscellaneous Factors
Maladaptation syndrome has been described in some individuals who simply fail to adapt to the captive environment while others thrive.1
Any chronic debilitating disease, such as neoplasia or renal failure, will result in especially terminal anorexia.1
Diagnostics
The most important step in the diagnosis of anorexia in the reptile is a good history and physical examination.1-4,8 Correct identification of the reptile to species level is of cardinal importance for accurate diagnosis and treatment.1,4,8
History
Detailed questions should be asked about the enclosure and husbandry, including: Temperature including thermal gradient; source of ultraviolet light; lighting programme; relative humidity; enclosure furniture/décor; water dishes/spray on decor and frequency; hiding spots; substrate; traffic around cage; and diet (type, source, location of feeding and frequency).1,2
Physical Examination
A thorough clinical examination is critical, as obvious lesions such as an intracoelomic mass or stomatitis cannot be diagnosed based on clinical signs alone.1,3 The clinician should familiarise him-/herself with a structured clinical examination for a few common reptiles.3
Further Diagnostic Techniques1,2,4
Complete blood count
Blood chemistry analysis
Faecal examination (parasites)
Gastric lavage examination (parasites or infectious agents)
Faecal culture
Diagnostic imaging (radiography, ultrasonography, contrast studies)
Endoscopy
Biopsies or fine needle aspirates for cytological examination
Treatment
Treatment regimens may be divided into home care (administered by owner) or in-hospital veterinary care.
Home Care
Since the most probable cause of anorexia in captive reptiles is husbandry related, correcting the husbandry may often resolve the anorexia.1,2,4 The author recommends that veterinarians assist and advise the client according to species-specific requirements.
Food can be prepared and offered in different ways to stimulate a feeding response:3
The cranium of the prey can be opened allowing the reptile (especially snakes and some lizards) to smell and taste the brain tissue.
Rubbing the shed skin of a reptile on dead prey may encourage eating.
Hiding prey/food inside a sheltered area may encourage a feeding response.
Hand-feeding may be attempted by placing the food in the reptile's mouth with a small blunt-ended forceps.
Crushing fragrant leaves or fruits releases scents that will stimulate feeding, since scent plays an important role in food identification and location in the reptile, especially when sight is impaired.
Syringe-feeding may be utilised by feeding small amounts frequently; however, regular handling may increase stress, which may exacerbate the anorexia.
Force-feeding may also be utilised, but great care must be taken to prevent trauma and as a result, it is recommended that this procedure rather be performed by a veterinarian.
Medication or nutritional support can be placed inside food items to ensure uptake.3
It is recommended that owners avoid handling reptiles for a period of 48 hours post-feeding.4
To prevent the occurrence of anorexia in most reptiles, it is recommended that clients purchase healthy, captive-bred reptiles that are already feeding on their own on an easy-to-obtain prey/food item.4
Veterinary Treatment
Reptiles should be treated for parasites on a regular basis.1 Care should be taken with the selection of appropriate pharmaceuticals for the species. The author recommends the use of a reputable formulary as can be found in the BSAVA Manual of Reptiles.3
A vitamin B complex and vitamin C injection may stimulate the reptile to start eating.2
Metronidazole at a dose of 12.5 mg/kg acts as an appetite stimulant - the mechanism of action is still unclear.2,3 It should be noted that metronidazole is toxic to indigo snakes and kingsnakes; it is recommended that the dosage be halved in these species.3 Metronidazole is contraindicated in gravid, debilitated reptiles as well as reptiles with hepatic dysfunction.3
Debilitated patients should be placed in a quiet, warm environment, such as an incubator or vivarium, with minimised handling after the clinical examination has been performed, to reduce stress.2,3,8
Most anorectic reptiles will be dehydrated and it is recommended to administer fluids before attempting to feed it.3,4 Depending on the level of dehydration, kidney and liver function, fluids can be administered per os via a stomach tube, subcutaneously, intracoelomically, intravenously, or with intraosseous catheterisation.4,8
To prevent refeeding syndrome, small amounts of food should be fed initially to allow the digestive tract to adapt to the presence of food again.4
Tube feeding allows for the quickest and most effective restoration of a positive protein, lipid and vitamin balance.2 A high-calorie, low-bulk formula is recommended.2
Other methods for assisted feeding include:3
Hand feeding: Least invasive but beware of increased stress due to regular handling
Syringe feeding: Beware of increased stress due to regular handling
Stomach tube: Excellent for short-term feeding
Oesophagostomy tube: Method of choice for chelonian patients requiring long-term enteric medication, nutrition and fluids. It causes the least stress due to decreased handling and are generally well tolerated.
Once the patient is rehydrated and fed, the underlying cause should be treated or eliminated. If an aetiological diagnosis is made (preferable), targeted and specific treatment should commence immediately.1
The patient's activity levels and defaecation frequency should be monitored.4
Conclusion
Excellent husbandry will improve the reptile's quality of life and general health, which in turn will prevent the occurrence or recurrence of anorexia.4
The clinician should have a basic understanding of the husbandry requirements of a few commonly kept reptile species; this will aid in the diagnosis and treatment of anorexia.8
Client education and compliance form the pillars of recovery in the anorectic reptile.1,8 Veterinarians should actively encourage correct and appropriate husbandry practices for all their captive reptilian patients.
Acknowledgements
Bird & Exotic Animal Hospital, Onderstepoort
Veterinary Academic Hospital, Pretoria
Johannesburg Zoo, Johannesburg
Monica Burger, BSc, University of Pretoria
References
1. Mader DR. Reptile Medicine and Surgery. 2nd ed. Philadelphia, PA: W.B. Saunders; 1996.
2. Animal Veterinary Hospital of Orlando. Care Cards: Reptile Anorexia [homepage on the internet]. No date [cited 2014 June 1]. Available from: wwwDOTcentralfloridaherpsocietyDOTorg/Reptile_Anorexia_Care_Card.pdf (VIN editor: link was reported invalid 3/13/23).
3. Girling SJ, Raiti P, eds. BSAVA Manual of Reptiles. 2nd ed. Gloucester, UK: BSAVA; 2004.
4. Anderson N. Anorexia in snakes [homepage on the internet]. No date [cited 2014 June 1]. Available from: www.petplace.com/reptiles/anorexia-in-snakes/page1.aspx (VIN editor: as of 10/20/15 link was redirected to www.petplace.com/article/reptiles/general/illnesses-conditions-of-reptiles/anorexia-in-snakes).
5. DeNardo DF. Reptile thermal biology: a veterinary perspective. Proc Assoc Rept Amphib Vet. 2004:157–163.
6. Frye FL. Husbandry, Medicine and Surgery in Captive Reptiles. Kansas: Vet Med Publishing; 1973.
7. Jackson OF, Cooper JE. Nutritional diseases. In: Cooper JE, Jackson OF, eds. Diseases of Reptilia. Volume 2. San Diego, CA, USA: Academic Press; 1981.
8. Kahn CM, ed. The Merck Veterinary Manual. 10th ed. Whitehouse Station, NJ: Merck & Co. Inc.; 2010.
9. Jacobson ER. Viral diseases of reptiles. In: Fowler ME, ed. Zoo and Wild Animal Medicine: Current Therapy 3. Philadelphia, PA, USA: W.B. Saunders; 1993.