Turtle (Chelonian) Medicine
Greg Lewbart M.S., V.M.D., Dipl. ACZM
Turtles are found throughout the world on all continents and in all oceans except Antarctica. There are 247 species of turtles (far fewer than snakes or lizards) which belong to 75 genera in 13 families. Turtles appeared in the fossil record over 200 million years ago and were on earth long before mammals and other forms of present day reptiles. They occur in terrestrial, freshwater aquatic, semiaquatic, and marine environments. They range in size from 11 cm to 185 cm and one species can weigh close to a ton, making it (the leatherback sea turtle) the world's largest reptile!
II. Anatomy and Physiology
The following facts apply to most species of turtles kept in captivity.
1. Both the pelvic and pectoral girdles are contained entirely within the rib cage which is fused to the protective shell. The shell is a vascular bony structure which should be included when calculating drug dosages from the animal's weight.
2. Sexual dimorphism exists in many species. Male tortoises have a concave plastron and male aquatic turtles usually have very long toenails on their front feet. The tail is relatively larger in males than in females but this does not always hold true.
3. Turtles lack teeth but most possess a sharp beak called a tomium.
4. Turtles can live a long time and tortoises generally live longer than aquatic species. The documented record is 152 years by a Seychelles island tortoise. Some species can be aged by growth rings on the scutes. This does not hold true for many aquatic species which periodically shed their scutes.
5. Turtles lack a diaphragm and since they are housed in a shell most have little or no abdominal breathing component. Most pressure changes allowing for lung expansion are accomplished by muscles in the pockets surrounding the fore and hind limbs. Aquatic species can also respire through their skin and the mucus membranes of the throat and cloaca.
6. Turtles have paired kidneys and a cloacal opening for the urogenital and gastrointestinal tracts.
7. Like most other reptiles, the heart has three chambers.
8. All turtles lay eggs and most bury them in the earth. Some species may lay several clutches per year and females of certain species can store sperm for several years.
9. The gastrointestinal tract is standard in that it includes a simple S-shaped stomach, liver, gall bladder, pancreas, spleen, small and large intestine.
10. Sea turtles possess special salt glands in their head behind each eye which allow them to drink seawater.
1. Simple procedures like radiography and blood sampling usually do not require sedation. Most turtles will remain still for the time it takes to produce a radiograph.
2. Invasive surgical procedure will require anesthesia. A number of agents are used in turtles including injectable and inhalant compounds. For relatively quick procedures like minor shell repairs and abscess lancing, ketamine hydrochloride at a dose of 5-10 mg/kg combined with medetomidine at 50 mcg/kg IM works very well. The medetomidine is then reversed with atipamezole. This regimen amy also be used in order to sedate a turtle for intubation and placement on inhalant isoflurane or sevoflurane. Telazol and propofol are used by some clinicians to anesthetize chelonians (see formulary). Barbiturates should be avoided if possible because of deleterious effects.
3. Hydration is important prior, during, and after anesthesia. It is difficult to accurately assess the hydration status of a turtle because of the fixed shell and nonelastic skin. Animals that have sustained a traumatic injury or are anorectic should be considered to be dehydrated and in need of fluids. Maintenance levels for turtles range considerably but the 15-25 ml/kg/day figure will suffice. Lactated ringers solution, saline, or a 1:2 ratio of the two respectively ("reptile ringers") have all been used with success.
IV. Blood Collection and Hematology
1. There are several sites for blood collection in turtles. These include the caudal vein, jugular vein, supra-occipital (dorsal cervical) sinus, brachial vein, and cardiac puncture. As a rule, the caudal vein is not productive in turtles. The tail tends to be short compared to other reptiles and the shell frequently is in the way. Turtles have a large supra-occipital sinus located on the lateral aspect of the head just ventral to a large ligament. This sinus is bilateral so either side may be used for blood collection. The jugular vein can be difficult to hit, especially if the turtle's head cannot be extracted. A small gauge needle place at a 45 degree angle near the lateral carpus is an excellent place to bleed smaller aquatic turtles. Some clinicians will use cardiocentesis if they cannot obtain blood from another site. This is a last resort procedure in my opinion. Clinical pathology reference ranges can be found in a number of texts and book chapters.
V. Non-Infectious Diseases
1. Abnormal Tomium. Some turtles and especially tortoises in captivity will develop overgrown "beaks." This is usually due to the consumption of unnatural foods. Can be corrected by trimming or grinding down with a Dremel drill which is frequently used in birds with similar problems.
2. Cracked Shell. This is unfortunately a very common problem in turtles and tortoises. Chelonians have two things working against them. They like to cross roads, and they are slow! Lawn mowers and other heavy machinery take their toll too. The wound should be flushed very well with a dilute antiseptic like Nolvasan (1:40) with clean water, or if the coelomic cavity is exposed, a physiological saline. The older literature describes techniques to repair shells using epoxy, fiberglass, and hoof or dental acrylic. While these techniques do have value, they should be limited to fractures of peripheral shell areas not involving an exposed coelomic cavity. Here at the NCSU-CVM, we utilize open surgical techniques which will be taught to you in the turtle shell repair laboratory. Properly placed sterile bone screws and surgical wire work very well to reduce and stabilize shell fractures. The human artificial skin product, Tegaderm, may be used to temporarily close large defects in the shell. External "heat-pliable" orthopedic materials (Orthoplast, Hexalite) are also effective in reducing and stabilizing shell fractures.
Injured turtles should also receive fluids, analgesics, and aggressive antibiotic therapy. Post-operative nursing is extremely important in the survival of "cracked" turtles. Force feeding, appropriate temperature, rest, and access to fresh water are a must.
While the shell is protective, it also makes diagnosis of internal injuries very difficult. Simply repairing the shell and restoring it to its original appearance does not produce a "cured" turtle or tortoise. I have seen turtles live for weeks with severe internal injuries before succumbing to peritonitis. We generally do not feel a turtle is releasable until it is eating on its own and has been allowed to recuperate for at least 3 months.
3. Hypovitaminosis A. This is probably the most common disease of freshwater aquatic turtles. Turtles frequently present with swollen eyes, a nasal discharge, tympanic (aural) abscesses, and in advanced cases, respiratory distress. The condition is especially common in captive box turtles and small freshwater aquatic turtles which may be receiving an inadequate diet. The lack of vitamin A results in metaplasia of squamous cells which causes a decrease in mucus production and an increase in the production of keratin. Animals should initially receive a parenteral dose of vitamin A (2000-5000 IU/kg) and then should be placed on a well balanced diet which contains appropriate levels of vitamin A. Dog and cat foods as well as some of the commercially available reptile "sticks" and pellets provide adequate levels of vitamin A. Care should be taken not to over supplement with vitamin A (see below).
4. Hypervitaminosis A. This problem occurs secondary to administration of supplemental vitamin A. Clinical signs include sloughing of the skin and secondary bacterial infections of the exposed tissues. To prevent this condition, turtles should receive just a single dose of injectable A followed by a change in the diet or perhaps oral vitamin A supplementation in the form of cod liver oil which can be dabbed onto the food or tomium.
5. Metabolic Bone Disease. Certainly not the problem it is in iguanas but it does occur in turtles and tortoises. Turtles fed primarily organ meats (liver, heart) or pure muscle (beef, pork, chicken) will develop metabolic bone disease and other nutritional problems. If these foods must be fed they need to be supplemented with calcium and multivitamins. Crickets and mealworms are two insect foods which have a poor calcium to phosphorus ratio (more phosphorus than calcium). Some people "shake and bake" these insects with powdered vitamin and calcium supplements before feeding and others simply feed the insects powdered milk to increase their nutritional value.
6. Prolapsed Organs. Turtles have been known to prolapse the penis (turtles only have one and it is extruded by means of a hemodynamic erection while lizards and snakes evert their sac-like hemipenes), rectum, and even the kidney. These prolapses are treated in a similar manner to those of snakes and lizards.
7. Gout. Gout has been reported in several species of turtles. Accumulation of uric acid crystals or tophi is most commonly secondary to water deprivation or a protein imbalance in the diet (see snake notes).
8. Shell Rot. Primarily a disease of aquatic species. Usually secondary to the turtle spending all of its time in the water or water which is of poor quality. Treated by correcting water quality problems and providing a place for the turtle to "haul out."
VIII. Infectious Diseases
1. Bacterial Problems. Like snakes and lizards, turtles are prone to a number of bacterial pathogens, most of them being gram negative. In addition to infection of traumatic wounds, debilitated chelonians are vulnerable to respiratory diseases caused by bacteria. Aquatic turtles with lung disease will frequently float in the water asymmetrically or have difficulty surfacing or submerging. Radiographs can help confirm the presence of a pneumonia (the lung fields are quite large and located in the dorsal portion of the coelomic cavity beneath the carapace). A lateral or anterior-posterior view is the best way to visualize the lungs of turtles. Culture and sensitivity tests will help in the diagnosis and treatment of bacterial diseases.
Septic cutaneous ulcerative disease (SCUD) is a problem most frequently observed in feshwater aquatic turtles like sliders and cooters. The causative agent is Citrobacter fruendii, a Gram-negative rod. Affected animals may present with deep skin ulcers in a variety of locations.
2. Fungal Diseases. Turtles are prone to both superficial and deep mycoses. There are several reports in the literature of fungal granulomas in the lungs of turtles and fungi cultured from skin and shell tissues are even more common. Systemic infections are very difficult to treat and are usually secondary to a poorly functioning immune system. Superficial fungal infections can be readily treated with topical antifungal agents and proper hygiene. Decreasing the pH of the water below 6.5 may also help alleviate fungal problems. Fungi which have been cultured from superficial lesions of turtles include Basidobolus ranarum, Dermatophyton sp., Fusarium sp., and Aspergillus sp.
3. Protozoal Diseases. Fortunately for turtles, they are rarely infected with Entamoeba invadens or Cryptosporidium sp. Turtles can be sub-clinical carriers of amoebiasis. There are reports of protozoans causing disease in chelonians, but by the same token, the appearance of protozoans in a stool sample does not mean there is a problem. The Hexamita /Spironucleus flagellates do cause disease in turtles, and if present in large numbers, may be treated with metronidazole. A wide variety of protozoans have been reported in turtle blood. Since these parasites are not usually a clinical problem they will not be elaborated upon but the student should be aware that they exist.
4. Helminth Parasites. Turtles have their share of nematode, cestode, trematode and acanthocephalan parasites. Diagnosis is made by fecal examination and history (turtles captured in the wild will tend to have broader and heavier parasitic loads than captive raised animals). See the notes on snakes and lizards and consult the reptile formulary for drugs and doses.
5. Leeches. These parasites are strictly external and are found on many wild freshwater and marine turtles. In severe cases they may cause anemia and they can act as vectors for blood borne parasites. Treatment is by plucking them off of the turtle.
IX. For More Information
1. Adler, K and T. Halliday. All the World's Animals; Reptiles and Amphibians. Torstar Books, New York, 160 pp., 1986.
2. Barker, D. Preliminary observations on nutrient composition differences between adult and pinhead crickets, Acheta domestica. Bulletin of the Association of Reptilian and Amphibian Veterinarians, 7(1):10-13, 1997.
3. Frye, F.L. Biomedical and Surgical Aspects of Captive Reptile Husbandry (Vols. ! & II). Krieger Publishing Co., Malabar, Fl, 637 pp., 1991.
4. Frye, F.L. & Williams. Self-Assessment Color Guide to Reptiles and Amphibians. Iowa State University Press, 1996.
5. Jacobson, E.R. and G.V. Kollias. Exotic Animals; Contemporary Issues in Small Animal Practice, vol. 9. Churchill Livingstone, New York, 328 pp., 1988.
6. Lutz, P.L. and J.A. Musick. The Biology of Sea Turtles. CRC Press, Boca Raton, FL, 432 pp., 1997.
7. Mader, D.R. Reptile Medicine and Surgery. Saunders Co., Phila., 512 pp., 1996.
8. Marcus, L.C. Veterinary Biology and Medicine of Captive Amphibians and Reptiles. Lea and Febiger, 239 pp., 1981.
9. Mautino, M. and C.D. Page. Biology and medicine of turtles and tortoises, In: Quesenberry and Hillyer (eds): The Veterinary Clinics of North America, Philadelphia,W.B. Saunders, Co., 23:6, 1251-1270, 1993.
10. Harwell, G. Repair of injuries to the chelonian plastron and carapace. In Kirk, RW (ed): Current Veterinary Therapy X: Small Animal Practice. Philadelphia, WB Saunders Co, p. 789, 1989.
11. Murphy, J.B. and J.T. Collins. A Review of the Diseases and Treatments of Captive Turtles. AMS Publishing, Lawrence, KS, 56 pp., 1983.
12. Pritchard, P.C.H. Encyclopedia of Turtles. T.F.H. Publishers, Neptune, NJ, 895 pp., 1979.
13. Ross, R.A. The Bacterial Diseases of Reptiles. Institute for Herpetological Research, Stanford, CA, 114 pp., 1984.
14. The Journal of Herpetological Medicine and Surgery (many issues).
15. The Veterinary Clinics of North America; Exotic Animal Practice, WB Saunders (many issues).
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