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Introduction to reptile medicine (Proceedings)
There are about 3100 species of snakes throughout the world. Only the Arctic regions, Antarctica, Iceland and Ireland, along with a few other very small oceanic islands lack the presence of snakes.
There are about 3100 species of snakes throughout the world. Only the Arctic regions, Antarctica, Iceland and Ireland, along with a few other very small oceanic islands lack the presence of snakes. The suborder Serpentes belongs in the order Squamata that contains both the lizards and snakes. There are about 18 recognized families of snakes containing over 400 genera (http://www.reptile-database.org/db-info/SpeciesStat.html; accessed 7/09). Snakes come in a variety of shapes and sizes but all have scales, are cylindrical in shape and lack legs and external ear openings. They range in size from about 10 cm to over 10 meters.
Anatomy and physiology
1. Most snakes have six rows of teeth, four are in the upper jaw attached to the palatine and maxillary bones and two in the lower jaw, one attached to each of the mandibles. All teeth can be periodically shed and replaced (including venom fangs).
2. Snakes lack "true" eyelids, which fuse during development to form a transparent structure that covers the eye called the spectacle. This spectacle or "lens cap" is shed when the snake under goes ecdysis.
3. Snakes lack an external ear opening, tympanum, and middle ear, but do have an inner ear that aids in balance. Snakes can detect substrate vibrations and at least some species can hear airborne sounds.
4. Some snakes, including the boids and vipers, possess heat-sensing pits located on the external surface of the face and jaws.
5. Snakes do not see particularly well but are good at detecting movement.
6. Snakes can extend their glottis anteriorly when swallowing prey. This adaptation for breathing is possible because of an elastic ligament at the mandibular symphysis.
7. Snakes frequently flip their tongues as a means of chemosensory detection. Most snakes possess "taste buds" in the roof of their mouth in a structure commonly referred to as "Jacobson's organ." The tip of the tongue flips scent particles up to this organ.
8. Most species have one functional lung (the right) and there is no diaphragm. The vestigial left lung forms an air sac in some species.
9. The stomach is fusiform (other reptiles have an "S" shaped stomach).
10. The liver is fusiform (other reptiles have bi-lobed livers) and like all reptiles a gall bladder is present. The pancreas is adjacent to the duodenum and the spleen may be attached to the pancreas.
11. Snakes have more than 200 vertebra (some more than 400). Each vertebra has a pair of ribs that protect the internal organs.
12. Snakes have two kidneys with the left kidney lying behind the right.
13. Locomotion is accomplished by moving the large ventral scales in groups, by lateral undulatory musculoskeletal contractions, or in some cases, both methods are employed.
a. More details can be found by reading: Funk RS. 2006. Snakes. In: Mader D.R. Reptile Medicine and Surgery, Second Edition. Elsevier/Saunders Co., Phila, 42-58.
1. Simple diagnostics like blood sampling, radiography and physical examination do not require anesthesia. Larger snakes may require an extra handler or two for proper restraint.
2. As with lizards, many injectable and inhalant anesthetic agents have been used. The use of injectable barbiturates should be discouraged since there are several reports of anesthetic death. Snakes may be masked down with 3-5% isoflurane or placed into an induction chamber (an aquarium works well) that contains isoflurane. Snakes are easy to intubate due to the prominent glottis that opens into the trachea. At the NCSU-CVM we frequently intubate snakes with manual restraint. Depth of anesthesia can be monitored by heart rate (the heart is located about one quarter of the length of the snake from the head and can be observed beating on the snake's ventral surface) and respiratory rate. A portable Doppler® apparatus works well for heart monitoring. Special care should be taken to observe respiration since all of a snake's breathing is facilitated by the abdominal muscles (they lack a diaphragm). Snakes that are not breathing may be "bagged" and care should be taken to avoid a large dead space (their lung...and they only have one that is functional...is much smaller than those of dogs and cats). Ketamine has been used as an anesthetic agent for snakes at approximately 30-75 mg/kg but recovery times may be prolonged (hours to days). Propofol is preferable if venous access can be obtained. Anesthetized snakes should be kept between 70 and 85 degrees F and recovered at the same temperature. The highly lipid soluble isoflurane may cause a problem if a reptile is warmed up after anesthesia since the animal could fall back into an anesthetic state. A number of agents have been used for analgesia in snakes. A recent study (Sladky et al., 2008) found that butorphanol may be superior to morphine in snakes. A study (Olesen et al., 2008) involving ball pythons (Python regius) determined that neither butorphanol (5.0 mg/kg) nor meloxicam (0.3 mg/kg) were likely effective analgesics. Anesthetic/analgesic agent doses are listed in the reptile formulary provided with the course notes.
3. Hydration is an important consideration when dealing with surgery and anesthesia. Lactated ringers and physiological saline solutions work well on snakes, as a 1:2 dilution of the two respectively (sometimes called "reptile ringers"). Some clinicians feel that LRS alone is sufficient for fluid therapy in reptiles. Guideline maintenance values are 15-25 ml/kg/day. A subcutaneous route is the easiest way to administer parenteral fluids in snakes although oral and intracoelomic routes can be advantageous.
Blood collection and hematology
1. The easiest and safest way to obtain a blood sample from a snake is via the caudal vein. Pick an area slightly caudal to the cloacal opening and carefully place the needle at about a 60-80 degree angle between the scales until resistance from the vertebral bone is felt. Applying gentle negative pressure and slightly withdrawing the needle should reveal blood in the hub of the needle. A heparinized syringe is recommended. Another frequently employed method is cardiac puncture. The heart is visualized and a needle is directed into the apical area of the beating organ. Sterile preparation of the blood collection site is recommended as is sedation or anesthesia of the animal. Cardiac puncture is recommended for euthanasia in snakes. In larger snakes, the highly visible palatine-pterygoid veins in the mouth may be used to obtain a small sample.
2. Snakes, like all reptiles, have nucleated red blood cells and a full complement of leukocytes as well as thrombocytes to facilitate clotting. Hematopoiesis occurs in the spleen liver and bone marrow. Although relatively little has been published on reptile clinical pathology reference ranges, this body of literature is expanding. Please refer to Diethelm (2005), Campbell (2006), and Campbell & Ellis (2007) for clinical pathology reference ranges and other information.
1. Thermal burns. Reptiles are attracted to heat but may not realize that they are being burned by a hot rock or other device. Severe wounds may require systemic antibiotics, fluids, and analgesics. Superficial wounds may be managed topically with Silvadene® Cream (silver sulfadiazine).
2. Rodent Bites. Owners may leave a live rodent in a cage and if the snake does not subdue it on its first attempt the snake may retreat. Rodents (especially rats) may actually bite or even eat portions of the snake. The client needs to be educated on the dangers of feeding live food. The snake's wounds should be treated openly with antibiotic ointments. Severe wounds (down to the musculature or into the coelomic cavity) should be treated with systemic antibiotics, fluids, and analgesics.
3. Impaction. Not particularly common among snakes but does occur. Usually due to improper cage substrate (corn cob, wood chips) becoming lodged in the gastrointestinal tract. May require surgery. Diagnosis made from history and radiographs.
4. Egg/embryo Retention. Occasionally seen in the egg laying pythons and live bearing boas. Hysterotomy (salpingotomy) and subsequent removal of the eggs/embryos is the treatment of choice. It may be possible to lubricate the oviducts with a lubricating jelly and manually assist the removal of the eggs or injecting oxytocin at a dose of 3-10 IU/kg before attempting surgery. Radiographs will help with the location and number of eggs/embryos present.
5. Blister disease. This problem usually is secondary to high humidity and poor cage hygiene. Snakes will present with necrotic and inflamed ventral scales. The problem is frequently multifocal. Treatment includes correcting the environmental problems and treating the lesions topically with Betadine® or Nolvasan® ointments/solutions. Severe cases may warrant the use of systemic antibiotics to prevent sepsis. The old damaged scales may disappear with subsequent molts.
6. Dysecdysis. Refers to an incomplete or retained shed. A common problem that may be secondary to low humidity, poor nutritional status, or an underlying disease process. Snakes should be soaked in warm water for up to an hour and the retained skin carefully removed piece by piece. This can be accomplished by placing the snake in a covered plastic container with 1-3 inches of warm water. Special care should be taken in the ocular regions where the retained spectacles exist. Multiple retained spectacles can lead to infection and even blindness. Do not let the client try and remove retained spectacles. The best approach is to moisten the eyes with warm water and use a pair of fine jewelers forceps to elevate some scales peripheral to the eyes and then gradually remove the attached lens cap(s). Snakes with retained spectacles frequently will not feed creating a vicious cycle and perpetuating the demise of the animal.
7. Prolapsed hemipenes.- This condition may have a variety of causes. Prolapse may be unilateral or bilateral. If attended to quickly, a lidocaine gel may be applied and the organ reduced manually. A loosely attached absorbable purse string suture may be used to partially close the cloaca to prevent prolapse. This suture must allow for urinary and fecal wastes to pass and may be left in place for between 2 and 3 weeks. A second prolapse may require amputation (if the problem is unilateral the snake can still be a breeding animal since they have two separate reproductive tracts). Rectal prolapses occur but are less common. They can be treated in a similar manner but ultimately may require surgery and a pexy procedure.
8. Gout- The deposition of urates in the kidneys, other organs and joints is usually secondary to dehydration but can be caused by primary renal or metabolic disease. Tophi may be visible on radiographs. Proper hydration and a balanced diet is the best way to prevent this disease.
1. Stomatitis. Also called ulcerative stomatitis or "mouth rot," it is one of the most common disease problems of snakes. The disease begins with the appearance of excessive saliva or mild petechiae in the mouth. Snakes will usually go off feed and the oral mucus membranes will become more inflamed and ulcerative. As the disease progresses osteomyelitis may develop and teeth will loosen and fall out. The head may become quite swollen and the infection can become systemic. At this stage the prognosis must be guarded. Stress from poor husbandry usually precipitates the problem. Bacteria frequently cultured from these lesions include Aeromonas, Pseudomonas, Proteus, and Citrobacter. Treatment should be both topical and systemic. The oral cavity should be flushed at least once daily with a Nolvasan® (0.5%) or povidone iodine (1%) solution. A topical antimicrobial ointment can be applied (Silvadene® cream) and in advanced cases injectable enrofloxacin (5-10 mg/kg SID for 10 days) or amikacin (2.5 mg/kg every other day for five treatments) should be used. An antibiotic effective against anaerobic bacteria such as clindamycin (5.0 mg/kg q. 24 hours) should also be included in the treatment regimen. Increasing the environmental temperature along with medical treatment will greatly increase the chances of recovery from this disease. It is not unreasonable to bring the cage temperature to 90-95 degrees F when a snake is ill. Some workers recommend injectable vitamin C (10-20 mg/kg SID, IM) as an aid to facilitate healing in cases of mouth rot.
2. Osteoarthritis/osteoarthrosis. A relatively recent study described a proliferative osteoarthritis and osteoarthrosis in several species of snakes caused primarily by Salmonella (Isaza et al.,, 2000). It is likely that the bacteria enter the blood stream from the gut and then are spread hematogenously to bone. Salmonella also has serious zoonotic potential and proper hygiene should be emphasized to owners with pet reptiles. Numerous studies have reported on this important topic.
3. Respiratory disease. It is very common to see snakes with upper, lower or combined respiratory disease. Snakes present clinically with open mouth breathing, nasal discharge, audible wheezing and increased lung sounds on auscultation. The history will usually include inadequate environmental temperatures or the recent addition of a new animal to the cage or collection. Bacteria are commonly involved and the best treatment is to combine antibiotic, fluid and heat (see above) therapy. Fungi can also be involved and may be seen via culture or histopathology on necropsy. Snakes that are not eating and appear thin should also be tube fed.
4. Paramyxoviral disease. Caused by an rna virus named Ophidian Paramyxovirus (OPMV). Has been described from several species of snakes. Clinical signs include anorexia, regurgitation, head tremors, "star gazing," and respiratory difficulty. Clinical signs may last up to 10 weeks before the animal succumbs. Animals may ultimately die of secondary bacterial diseases. Antibiotics and supportive care are warranted. Diagnosis is made from the history (recent exposure to non-quarantined animals), hemagglutination-inhibition antibody titer (available through the University of Florida), and histopathology and electron microscopy. The virus has never been isolated from a live animal so definitive antemortem diagnosis is not possible. When this disease is suspected, strict isolation and quarantine protocols must be adhered to. New animals should be quarantined for at least 90 days before being exposed to other animals in the collection.
5. Inclusion body disease. Also known as IBD, this disease occurs primarily but not exclusively in the Boidae (boas and pythons). The causative agent appears to be an RNA virus, perhaps belonging to the Retrovirus group. Clinical signs include regurgitation, head tremors, ataxia, and incoordination. As a rule, boas tend to regurgitate and the pythons display tremors, disorientation, and appear flaccid. There is no treatment and diagnosis is made upon histological and transmission electron microscopical examination of the brain, spinal cord, liver, pancreas, and kidney. Affected snakes have eosinophilic intracytoplasmic inclusion bodies in the cells of the above-mentioned tissues. This is a serious disease and quarantine, disinfection, and isolation should be used judiciously to prevent its spread.
6. Protozoal parasites. Snakes harbor a number of internal protozoans but not all are pathogens. The two most important protozoal diseases of snakes are amoebiasis (Entamoeba invadens) and cryptosporidiosis (Cryptosporidium serpentis.). Clinical signs of amoebiasis include anorexia, bloody diarrhea, rectal prolapse and acute death. Diagnosis is made by identifying amoebic cysts in eosin stained feces (the cysts do not pick up stain and stand out as white spheres). Treatment is frequently with metronidazole (see formulary, which can be provided with an e-mail request). The life cycle is direct and certain species of snakes and other reptiles will act as carriers but never show clinical signs.
a. Cryptosporidiosis is frequently reported in snakes. Some specimens will shed oocysts in feces for years without any clinical signs. Sick animals will have a thickened gastric mucosa. A swelling of the animal may appear near the mid-point of its body. Clinically affected animals regurgitate food within a few days of feeding. Antemortem diagnosis may be made by locating oocysts in the feces either by examining unstained smears or with the aid of a DMSO acid-fast stain. At the NCSU-CVM our lab uses an Auromine-O stain that fluoresces under the light of a fluorescent microscope. There is also a fecal antigen ELISA test available through the Cornell University Diagnostic Laboratory. Post mortem changes include a much-thickened gastric mucosa and organisms will be seen on histopathology. There is no proven treatment for this disease. Any suspect snake should be quarantined and any object or potential fomite should be disinfected before transfer form cage to cage.
b. See the Further Reading section for access to more details on protozoal parasites of reptiles.
7. Helminth parasites. Many species of acanthocephalans, cestodes, nematodes, and trematodes infect snakes. There are literally hundreds of serpent helminth parasites. Nearly all of the helminth parasites respond well to standard veterinary parasiticides.
a. See the Further Reading section for access to more details on helminth parasites of reptiles.
8. Arthropod parasites. A number of ticks and mites are ectoparasitic on snakes. There are over 250 species of snake mite parasites alone! This is also one of the more common problems the clinician in private practice will be presented with. Most mites and ticks are found in areas where there is moisture and a place to hide. The eyes, mouth, throat, and cloaca are commonly parasitized. These parasites are easily transferred from one animal to another and the history will often include a new animal in the collection. Puppy or kitten flea and tick spray can be gently applied with a moist cloth once a week. The cage, bowl and hide box must be disinfected and new animals need to be quarantined. Soaking the snake daily in warm water is an excellent way to remove mites, but must be accompanied by cleaning the environment. Some clinicians use injectable ivermectin to kill arthropod parasites of snakes (see formulary). Exotic animal clinicians have had empirical success using the canine product Frontline (Fipronil) to kill mites and ticks in snakes. There is an excellent review of snake mite biology and control published in the Journal of Herpetological Medicine and Surgery (Wozniak et al., 2000).
a. Pentastomids are actually arthropods even though they appear helminth-like. The adult worm lives in the lungs of snakes and other reptiles. Eggs are laid by the adults and coughed up, swallowed, and excreted with feces. Each egg contains a four-legged larva that develops in an intermediate host (frequently a mammal). Once the prey item is consumed, the intermediate stages penetrate the snake's GI tract and migrate to the lungs. Infections in serpents are often sub-clinical but there may be focal tissue damage.
Lizards (please refer to the snake section for overlapping material)
There are over 5000 species of lizards worldwide. The suborder Sauria belongs in the order Squamata that contains both the snakes and the lizards. There are 26 recognized families of lizards containing approximately 400 different genera (http://www.reptile-database.org/db-info/SpeciesStat.html; accessed 7/09). Lizards occur on every continent except Antarctica (surprise) and occupy both island and mainland habitats. The majority of species are centered in the tropical and sub-tropical regions of the world. Lizards may be as small as 1.5 cm in length or as long as 3 meters. Most are in the 20-30 cm range.
Anatomy and physiology
1. Most lizards have well developed tongues.
2. Most lizards have external ear openings and eyelids that can be closed.
3. Nearly all species have teeth that can be replaced.
4. Some species possess a parietal eye also known as the "third eye." This structure is located at the top of the head and is usually covered by a thin opaque scale. The "eye" connects directly via nervous tissue to the pineal body in the brain. Researchers believe this structure functions in regulating the biological clock via changing photoperiods. Do not mistake this structure for a lesion!
5. Lizards have two well-developed lungs and lack a true diaphragm.
6. The heart, like in most reptiles, has three chambers (two atria and one ventricle). There is a partial ventricular septum but very little mixing of oxygenated and unoxygenated blood.
7. Fertilization is internal in the oviduct, which is usually paired. Male lizards have two separate reproductive tracts (the paired testes have their own copulatory organs called hemipenes). A male lizard may exhaust its supply of sperm from one teste and then switch hemipene to utilize the other teste. In a few species the females can store sperm and some species of lizards are actually parthenogenetic (all of the animals are females and young develop from unfertilized eggs). This occurs in some species of whiptails, geckos and rock lizards (who says males are necessary?)
8. Lizards have paired kidneys. A common cloacal opening is utilized by the urogenital and gastrointestinal tracts.
9. The gastrointestinal tract is a fairly standard vertebrate model. A large oral cavity (the glottis is located directly behind the tongue) leads to an esophagus that opens into an S-shaped stomach. A gall bladder is always present and the liver, spleen and pancreas are well developed.
10. Certain species of lizards can voluntarily shed their tail or a portion of it as a defense mechanism (some skinks iguanids, and geckos). A new tail can be grown but is rarely as nice as the original.
a. More details can be found by reading: Barten SL. 2006. Lizards. In: Mader D.R. Reptile Medicine and Surgery, Second Edition. Elsevier/Saunders Co., Phila, 42-58.
1. Simple procedures such as blood sampling, radiography and general physical examination can be performed without anesthesia in most lizards. A pair of thick gloves may help protect the handler from superficial bites and scratches.
2. Invasive procedures like abdominal surgery, orthopaedic surgery and surgical biopsy will require general anesthesia. A number of anesthetics are reported in the literature for use in lizards. Both injectable and inhalant anesthetic agents have been used. Intravenous propofol (see formulary) works well for fast induction and recovery. Another and "older" approach is to induce lizards (specifically iguanas) with 15 mg/kg IM ketamine (given in a front limb) and then place them on inhalant isoflurane. If the lizard is not too fractious it may simply be masked down with isoflurane and then intubated without the use of ketamine. Small lizards can be placed in a plastic bag containing isoflurane and oxygen from the anesthesia machine. Some clinicians choose to use ketamine alone and a dose of 30-60 mg/kg may be required. Dexmedetomidine in combination with a lower ketamine dose and then reversal with atipamezole shows some promise, although medetomidine alone appears ineffective in iguanas. Lizards are easy to intubate since the highly visible glottis is located at the base of the tongue. Most lizards will be too small for standard mammalian endotracheal tubes so the clinician will have to improvise with a red rubber catheter or tomcat catheter. The tube can be tied in with gauze. Detecting a pulse during anesthesia can be difficult. The heart is located far cranially and can be auscultated almost directly between the base of the forelimbs. During surgery, when the animal is in dorsal recumbency, the pulse can be monitored quite effectively with a contact Doppler® device. A well-placed esophageal stethoscope can also detect the cardiac pulse. A number of agents have been used for analgesia in lizards. Sladky et al. (2008) found morphine superior to butorphanol in bearded dragons (Pogona viticeps). Please refer to the formulary for details of drugs and dosages.
3. Hydration; please see snake section.
Blood collection and hematology
1. The most practical site for blood collection in lizards is in the tail. Most workers like to use the ventral caudal vein which is located just ventral to the vertebral bodies of the tail. A needle is placed between the scales and perpendicular to the tail until it meets resistance from bone. Negative pressure is applied and the needle is slowly withdrawn until blood is seen in the hub (think of bleeding a cow from the tail vein). Others prefer bleeding from the dorsal spinal vessels that are located above the vertebral bodies on the dorsal aspect of the animal. This site has the advantage of not needing to turn the animal on its back. Again, the needle is inserted at a near 90-degree angle until resistance is felt and then negative pressure is applied with the syringe.
2. Please refer to Diethelm (2005), Campbell (2006), and Campbell & Ellis (2007) for detailed clinical pathology reference ranges and other information. LeBlanc et al. (2000) provides a good review of bearded dragon hematology including some helpful photomicrographs.
Non-infectious diseases (please refer to snake section for overlapping material)
1. Thermal burns.
2. Impaction. Certain species of lizards including iguanas have a narrow passage between the colon and the rectum. Cage substrate materials like sand, gravel, corncob or even hay may become lodged in the gastrointestinal tract if these items are consumed. Radiographs may be needed for an accurate diagnosis and surgery may be warranted in severe cases. If abdominal (coelomic) surgery is to be performed, a ventral paramedian incision is recommended since some lizards (iguanas) have a large mid-ventral vein (some surgeons use the mid-ventral incision site without complication). Enterotomy and closures can be performed as in mammals. The peritoneum is extremely thin and is usually not closed separately. Skin sutures should stay in for a minimum of 4-6 weeks.
3. Egg retention. Female iguanas and perhaps other species of lizards will frequently produce infertile eggs in captivity but not lay them. The owner will usually notice abdominal distension coinciding with a decrease in appetite. This usually occurs between February and April in green iguanas. Radiographs will confirm the presence of eggs. A green iguana may lay between 10 and 70 eggs although the norm is closer to 25. Animals with retained eggs will start to appear emaciated and lethargic. Egg retention probably has several causes, nearly all of which relate to shortcomings in captivity. Iguanas in the wild lay eggs in elaborate burrows that are difficult to simulate in captivity. Nutritional problems or other diseases may predispose a lizard to egg retention (also called egg-binding). Once the animal has stopped eating completely and has lost a significant amount of muscle mass (these animals may not lose much weight since the developing eggs weigh a lot) surgery is in order. Some clinicians like to perform an ovario-hysterectomy in these instances while others may find it easier to perform a hysterotomy/salpingotomy and remove the eggs one at a time. There are two branches or horns of the uterus (also termed the oviduct) and both usually contain eggs. If the ovaries and uterus are to be removed, care must be taken to avoid the adrenals and to be aware of the vena cava that is in close proximity to the ovaries. As with any coelomic cavity surgery in lizards, care must be taken to avoid the large mid ventral vein. However, this vein is not usually adhered to the body wall so a careful mid-ventral incision should be satisfactory. The bladder can also be quite large and is located in the caudal ventral abdomen. If you see a large ventral fat pad once the abdomen has been opened you may be too far caudal with your incision.
a. Some clinicians have reported success using oxytocin to aid in resolving egg retention. I have seen this work one time, but still, all of the eggs were not voided and the animal went to surgery. An empirical dose would be 3.0 IU/kg oxytocin IM. One risk with this treatment would be the chance that the oviduct could rupture expelling eggs into the coelom.
4. Metabolic bone disease. This is probably the number one disease of captive green iguanas although it is not common in other species of (carnivorous) lizards. Metabolic Bone Disease (sometimes referred to as MBD) actually has a complex of causes, all of which result in demineralization of bone. The causes include insufficient calcium in the diet, too much phosphorus in the diet, a lack of vitamin D, and more rarely a primary endocrine imbalance involving the thyroid or parathyroid glands. What actually happens is termed nutritional secondary hyperparathyroidism, in which the body mobilizes calcium from bone for other bodily functions.
a. Animals will present with a history of lameness, anorexia or depression. Some animals will have an enlarged rubber-like mandible while others will have limbs that appear large and swollen. These signs represent the condition of severe osteodystrophy. Radiographs will reveal thin bone cortices and commonly pathological fractures or evidence of recently or partially healed fractures.
b. Treatment involves educating the client and supplementing the iguana's diet with calcium, vitamin D, ultraviolet light (preferably natural sunlight). I have seen animals that have been on very well balanced vegetarian diets with vitamin supplementation present with MBD. In order to remain healthy, green iguanas seem to some require some exposure to natural sunlight. Ideally, owners should allow their animals to remain outside for several hours each week in a protected and secure area that also provides some shade. Iguanas should not be left outside if temperatures drop below 70 degrees F. There are several ways to supplement calcium (see formulary and Further Reading section).
c. Foods that have a desirable calcium to phosphorus ratio (greater than 1.5:1) include watercress, kale, broccoli tops, carrots, oranges, cantaloupe and raisins. Foods with poor ratios (phosphorus greater than calcium) include lettuce, tomato, cucumber, grapes, apples, pears and bananas. A small amount of low protein dog food (eg. Hill's KD Diet) can be included in the diet each week (not to exceed 10% in juveniles and 5% in adults) although current empirical literature states that iguanas should receive no animal protein.
d. Vitamin D3 (cholecalciferol) is the active form of vitamin D in that it facilitates calcium uptake in the gut. In nature, sunlight converts D to D3 but indoors the aquarium may require artificial UV light. There has been much debate on this topic in the reptile keeping world. Ultraviolet light in the 290 -320 nanometer wavelength converts D to D3 in nature. Vitalite (Durotest Corp., Lyndhurst, NJ) and Colortone 50 (Westinghouse, Somerset, NJ) are two brands that appear to provide proper UV wavelengths. Some herpetoculturists combine one of these bulbs with a black light bulb to achieve more ultraviolet rays.
5. Hypervitaminosis D. Most common in green iguanas over supplemented with vitamin D. Blood vessels, renal tubules and other structures may become calcified. Radiographs used to monitor a supplemented iguanas progress may help prevent this condition.
6. Fractures. Commonly associated with MBD. In these cases the calcium imbalance must be corrected in order for normal bone healing to occur. Do not attempt to apply internal or external fixators on bones with thin cortices. Each fracture must be evaluated independently but in the paired long bones (radius/ulna; tibia/fibula) if only one of the two is fractured (which is common) the other bone may act as a natural splint for the fractured bone. Mid-shaft humeral fractures may be aligned and immobilized by bandaging the limb against the side of the body for 2-3 weeks or until an adequate callous has formed. Fractures of the digits will usually heal nicely when the diet has been corrected. Attempting to repair a fracture without correcting nutritional imbalances will prove to be unproductive.
7. Prolapsed Hemipenes.
8. Neoplasia. Not commonly reported in lizards. This is partly due to the fact that only in the past couple decades has a serious interest in the diseases of lizards been developed. Reported neoplasias include melanoma, lymphoma, hepatoma, myxoma, adenocarcinoma and osteochondroma.
1. Bacterial problems. Systemic bacterial diseases occur in lizards but are usually secondary to trauma or poor husbandry. The majority of lizard bacterial pathogens are gram negative and include the following genera: Aeromonas, Pseudomonas, Bacteroides, Klebsiella, Proteus and Salmonella. Numerous other bacterial pathogens have been reported but these are the most common. Clinical signs of bacterial disease might include stomatitis, pneumonia, cellulitis, dermatitis and the presence of abscesses. In order for a definitive diagnosis to be made culture and sensitivity tests must be performed. Effective antibiotics and routes of administration are included in the reptile formulary that you have been provided with. Remember that a large percentage of bacterial infections in reptiles are mixed aerobic/anaerobic and should be treated accordingly.
2. Viral problems. It is uncommon to diagnose a viral disease in lizards. A herpesvirus has been isolated from green iguanas and green lizards (Lacerta viridis) but the presence of a virus does not necessarily mean that it is pathogenic. Adenoviruses have been reported in a Jackson's chameleon, bearded dragons, and other species. As lizards and other reptiles are more thoroughly examined it is likely that more viral diseases will be described.
3. Fungal problems. These diseases are uncommon in lizards. Proper nutrition and cage hygiene will greatly reduce the threat of fungal disease. Most fungal diseases are either superficial or deep. Candida and Aspergillus are the most common fungal organisms cultured. When present there is usually an underlying problem which has lead to an immunocompromised animal. Fungal problems will sometimes respond to medical treatment.
4. Protozoal parasites. A number of protozoa appear to be normal inhabitants of the lizard gastrointestinal tract. These include Balantidium, Paramecium, and Nyctotherus (all of which are ciliates). Very young lizards have even been observed to ingest conspecific feces in order to establish an appropriate gut flora. Such "commensal" organisms will only present a problem when the host's immune system has been compromised. Amoebiasis, caused by Entamoeba invadens, is the most serious protozoal parasitic disease of lizards. Clinical signs include depression, anorexia, rectal prolapse, diarrhea and even acute death. Diagnosis is made by identifying amoebic cysts in the feces. Amoebic trophozoites destroy the mucosal lining of the intestine and may even become systemic. The disease can be treated with metronidazole at a dose of 125 mg/kg repeated in two weeks (see formulary). The second most serious protozoal parasite of lizards is the coccidian parasite Cryptosporidium. This parasite is a serious problem in snakes where it is normally found in the stomach. Snakes with this condition are chronic regurgitators while lizards usually do not regurgitate but continue to lose weight. No effective treatment has been identified but workers have observed some positive results with trimethoprim sulfa at an exaggerated dose of 60 mg/kg SID for 60 days. The best way to challenge this disease is through prevention. Any new lizard being added to a collection should be quarantined and any materials (including hands and water bowls) should be disinfected before being placed in different cages.
5. Helminth Parasites. Primarily internal parasites of lizards, this group includes dozens of ascarids, strongyloids, threadworms, hookworms, lung worms, acanthocephalans, flukes and tapeworms.
Turtles are found throughout the world on all continents and in all oceans except Antarctica. There are over 300 species of turtles (far fewer than snakes or lizards) that belong to about 90 genera in 13 families (http://www.reptile-database.org/db-info/SpeciesStat.html; accessed 7/09). 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 turtle and one of the largest living reptiles!
Anatomy and physiology
Witherington & Wyneken (2003) have published a nice color anatomy guide for the turtle (see Further Reading).
1. Turtles can live a long time and tortoises generally live longer than aquatic species. Reports of Aldabra and Galapagos tortoises living up to 260 years exist. Some species can be aged by growth rings on the scutes, but as the animal ages accuracy suffers. This does not hold true for many aquatic species that periodically shed their scutes.
2. Both the pelvic and pectoral girdles are contained entirely within the rib cage that is fused to the protective shell. The shell is a vascular bony structure that should be included when calculating drug dosages from the animal's weight.
3. 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.
4. Turtles lack teeth but most possess a sharp beak called a rhamphotheca or tomium. They also have tongues that aid in prehending food but cannot be extended beyond the mouth (as is the case with many snakes and lizards).
5. The gastrointestinal tract is standard in that it includes a simple S-shaped stomach, liver, gall bladder, pancreas, spleen, small and large intestine. A cecum may be present but fermentation, when applicable, occurs primarily in the large intestine. Nearly all aquatic turtles must eat in the water.
6. Like most other reptiles, the heart has three chambers (one ventricle and two atria).
7. 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.
8. Turtles have paired kidneys and a cloacal opening for the urogenital and gastrointestinal tracts. The ureters open into the cloaca and urine then passes from the cloaca to the more cranial urinary bladder.
9. The chelonian cloaca is divided into three zones: the cranial coprodaeum where the rectum attaches; the medial urodaeum where the ureters and reproductive tracts attach; the proctodaeum where urinary and fecal waste are stored.
10. All turtles have internal fertilization. Courtship is usually a part of most chelonian copulation. Some freshwater species (sliders, cooters) have an elaborate ritual in which the male waves its long forelimb nails in front of the female's face. The single phallus is employed during copulation. Unlike snakes and lizards, the chelonian penis has erectile tissue. The semen is conducted through a seminal groove that terminates between distinct folds (known as plicae) of the glans. Some female turtles have a clitoris located in the ventral cloaca that anatomically resembles the penis.
11. 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.
12. Sea turtles possess special salt glands in their head behind each eye that allow them to drink seawater.
a. More details can be found by reading: Boyer TH and Boyer DM. 2006. Turtles, Tortoises, and Terrapins. In: Mader D.R. Reptile Medicine and Surgery, Second Edition. Elsevier/Saunders Co., Phila, 78-99.
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. We have had favorable results with many chelonian species using 3-10 mg/kg propofol IV for induction or relatively quick procedures like fish hook removal. Ketamine hydrochloride at a dose of 5-10 mg/kg combined with medetomidine at 50 mcg/kg IM or IV works very well. The medetomidine is then reversed with atipamezole. This regimen may also be used in order to sedate a turtle for intubation and placement on inhalant isoflurane or sevoflurane. Telazol® is used by some clinicians to anesthetize chelonians (see formulary). Barbiturates should be avoided if possible because of deleterious effects. Butorphanol, ketoprofen, buprenorphine, morphine, and other agents have been used for analgesia in chelonians. A recent study (Sladky et al., 2007) found that morphine may be superior to butorphanol in turtles. Buprenorphine can also be used and has been studied in red eared sliders (Trachemys scripta) by Kummrow et al., 2008. Please refer to the formulary for details.
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, sub-carapacial sinus, brachial vein, and cardiac puncture. As a rule, the caudal vein is not always productive in turtles. The tail tends to be short compared to other reptiles and the shell frequently is in the way. In some cases the dorsal tail vein can be quite productive (especially in male turtles where the tail is larger). 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.
2. Please refer to Diethelm (2005), Campbell (2006), and Campbell & Ellis (2007) for detailed clinical pathology reference ranges and other information.
1. Abnormal beak/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 that 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 that 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. The Piedmont Wildlife Center (PWC) has had success using an adhesive bandage called Mefix®, introduced this protocol to the NCSU-CVM Turtle Rescue Team, and we have had favorable results in some cases.
a. 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.
b. 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.
1. Hypovitaminosis A. Usually a 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 that may be receiving an inadequate diet. The lack of vitamin A results in metaplasia of squamous cells that causes a decrease in mucus production and an increase in the production of keratin. Animals should initially receive a parenteral dose of vitamin A (see formulary) and then should be placed on a well balanced diet that 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). There is some evidence that environmental organochlorine toxicity inhibits vitamin A metabolism in wild box turtles and contributes to aural abscesses and upper respiratory disease (Holladay et al., 2001).
2. 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 that can be dabbed onto the food or tomium.
3. 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 that 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.
4. 6. Egg retention (dystocia). Dystocia appears to be a fairly common problem among captive turtles. A number of factors have been linked to this condition including lack of appropriate nesting substrate, dehydration, hypocalcemia, poor nutrition, and trauma. Radiography is very helpful in diagnosing this problem, however, eggs can frequently be palpated digitally within the coelomic cavity. Affected animals should be given a physical examination along with a thorough history. Once the animal is properly hydrated and nourished, a suitable nesting substrate can be provided. If this conservative approach is unsuccessful, then a regimen of oxytocin (see formulary) preceded by calcium gluconate and fluids may be in order. Before using oxytocin the clinician needs to be sure there is not an obstruction. It can be difficult to determine if a turtle with eggs is truly "egg-bound." History, time of year, and egg morphology can help make this determination. Eggs can even end up in the urinary bladder, most likely from being "retropulsed" from the cloaca. Surgery and endoscopy have been used to remove such eggs.
5. Ruptured oviduct. While apparently not a common problem, turtles with obstructive dystocia are especially at risk, especially if given oxytocin or arginine vasotocin. This can be a fatal condition due to peritonitis and endotoxemia.
6. Prolapsed phallus. Owners quickly recognize this condition. If treated early it may be possible to reduce the phallus (a lidocaine gel may help with this procedure) and then loosely purse-string the vent closed (leaving enough of an opening for urates and feces to pass). If the phallus has been out for a period of time it will appear inflamed or even necrotic. In these situations amputation is the best option. While the turtle will no longer be reproductively sound, he will lead a relatively normal life since urine flows directly from the cloaca to the vent.
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). Treatment with NSAID's and allopurinol may be warranted.
8. Shell Rot. Primarily a disease of aquatic species. Usually secondary to the turtle spending all of its time in the water or water that is of poor quality. Treated by correcting water quality problems and providing a place for the turtle to "haul out."
1. Viral Diseases. A number of viral diseases have been reported in sea turtles. Important viral diseases of freshwater and terrestrial chelonians include Herpesvirus Disease of tortoises (multiple clinical signs and high mortality may occur) and Iridoviral (Ranavirus) Disease of Box Turtles (mortality may be high and clinical signs include pharyngeal ulcers, focal skin sloughing, and marked lethargy). See Origgi FC (chapter 57, Mader, 2006) for a review of Herpesvirus Disease of tortoises and Jacobson (2007) for a review of chelonian viral diseases.
2. 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.
a. Septic cutaneous ulcerative disease (SCUD) is a problem most frequently observed in freshwater 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.
b. Mycoplasmosis, also termed Upper Respiratory Tract Disease (URTD), is a well-studied and serious disease affecting some chelonian species, especially tortoises. Affected animals generally experience a chronic infection with varying degrees of clinical signs. Mortality may occur but is rarely acute. Infected animals probably only rarely clear the organism. Treatment regimens are anecdotal but worth pursuing in some cases. Diagnosis can be accomplished by culture, plasma ELISA, or PCR testing. See Wendland et al. (chapter 73, Mader, 2006) and Jacobson (2007) for more details.
1. 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 that have been cultured from superficial lesions of turtles include Basidobolus ranarum, Dermatophyton sp., Fusarium sp., and Aspergillus sp.
2. 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.
3. 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.
4. 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.
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General reference material
Exotic DVM Magazine
Journal of Zoo and Wildlife Medicine
Journal of Herpetological Medicine and Surgery