Metabolic bone disease also called nutritional osteodystrophy, nutritional secondary hyperparathyroidism, or rubber jaw is probably the most common disease of iguanas. The condition typically results from a lack of calcium and/or vitamin D3 in the diet. Increased dietary phosphorus, primary renal or hepatic disease, or thyroid or parathyroid disease can also cause metabolic bone disease. Even though the blood calcium level usually remains normal, the animal can show signs of illness. Early signs include swelling of the mandibles, later swelling of the limbs, usually the rear legs, is seen. Many owners often mistake this swelling for increased muscularity, despite the fact that the iguana may be losing weight and actually appears thin. Later in the course of the disease, weakness, lethargy, and anorexia become evident. Pathologic fractures can occur due to cortical bone thinning, and paralysis may result if the spine is fractured and the spinal cord is severed. Hypocalcemic tetany may be manifested by muscle twitching. A plantigrade or palmigrade stance (walking on the hocks or wrist) may also appear as a sign of weakness. With metabolic bone disease, any combination of these symptoms is possible.If the iguana is still eating and active, the prognosis for recovery is good to excellent. The first step in treatment is a complete physical examination. Often, sick animals also have infectious stornatitis, septicemia, and infection with internal parasites. A good examination can provide a wealth of prognostic information.
Obstructions of the gastrointestinal tract can occur in iguanas. Obstructions can be caused by heavy parasite burdens (typically pinworms), foreign bodies (usually in young iguanas), cage bedding (especially if sand, shells, or corncob is used), or neoplasia. Symptoms are nonspecific but may include abdominal distention with tympany.
Gout. In reptiles, uric acid is the end-product of protein metabolism and is excreted by the renal tubules.Uricemia occurs when the kidneys are unable to filter uric acid from the blood; as a result, urates deposit in various body sites. Hyperuricemia can develop secondary to dehydration, high-protein diets, renal failure, and antibiotic usage. In one study in snakes, post-prandial uric acid levels peak by the fourth day after feeding; levels returned to normal within 2 weeks after feeding. The same phenomenon may occur in other reptiles; uric acid levels should be evaluated in light of diet and time of recent feeding. Visceral and articular gout may he seen in iguanas. Signs of this condition depend upon the site affected. Appendicular gout, which causes lameness and swelling, is less common than visceral gout (to which the liver, kidney, spleen, and pericardium are predisposed). Subcutaneous and sublingual uric acid deposits may also be seen in gout; obstipation can be seen if the intestines are involved.
Burns are commonly seen as a result of the popular "Hot Rocks" and "Sizzle Stones." Most owners are surprised to learn that a reptile seeking warmth will lie on a hot surface and burn itself. Burns can also occur if the reptile is not protected from direct contact with a heat source such as a light bulb. Treatment of burns is supportive and may include topical medication, parenteral antibiotics, and surgical debridement. Thermal burns tend to generate a large amount of scar tissue; healed skin may be depigmented (vitiligo).
Infectious stomatitis is more commonly known as "mouth rot." The disease is almost always caused by bacteria. Certainly a filthy environment contributes to this problem, internal parasites, poor diet, improper environment and improper environmental temperature (low body temperature in any animal decreases the ability of the body's immune system to fight off infection; for the ectothermic reptiles, proper environmental temperature is critical to survival), shipping (e.g., when a pet is brought into an owner's home after purchase), too little or too much handling, a too humid or too dry cage, and almost any other stress. Early symptoms that often go unnoticed by owners are petechial hemorrhages inside the oral cavity. These signs are often observed during a routine physical examination of an asymptomatic iguana.
Respiratory diseases may occur secondary to other conditions, such as improper diet, environment, or infectious stomatitis. Respiratory disease can be as mild as rhinitis or as severe as pneumonia; caustive organisms include bacteria (most commonly), fungi, viruses, and parasites. Lack of a diaphragm prevents active coughing from the air-sac-like lungs of reptiles, and the mainstem bronchi and trachea enter the lungs more cranially than in mammals. These factors favor the retention of respiratory secretions in the lower airways; simple respiratory infections are more prone to developing into pneumonia than in mammals. Many "simple" respiratory infections in reptiles are actually signs of serious lower respiratory disease and may require aggressive treatment. While the prognosis for such infections is always guarded, many reptiles will survive if appropriate aggressive treatment is instituted. To be safe, any reptile that is anorectic and lethargic and has respiratory symptoms (e.g., sneezing, wheezing, mucopurulent nasal discharge, dyspnea, open-mouth breathing) should be taken to a veterinarian. . Many of these pets are gravely ill and hospitalization is essential.
Anorexia/constipation/regurgitation syndrome is an ill-defined condition that is usually seen in iguanas that fail to adapt to captivity. Often the iguana has had a recent change in owner, diet or environent. Pets with this condition are often chronically, seriously debilitated, and many have concurrent disorders (e.g., parasites, infectious stomatitis). These animals are critically ill and require immediate and intensive hospitalization and treatment. The prognosis is guarded, as many of these pets have not eaten for several weeks.
Fractures. Most fractures of the extremities, especially those caused by metabolic bone disease, are stable and heal rapidly as the disease resolves through treatment and improved diet (especially in the smaller iguanas. Fractures of the vertebrae may or may not heal; often neurological impairment is permanent, hut euthanasia should always be considered only as a last resort. Unstable limb fractures, as well as vertebral and mandibular fractures, can be immobilized.
Hypervitaminosis D. There exists some controversy on whether or not true hypervitaminosis D" actually occurs in iguanas. Some research seems to indicate that reptiles are unable to absorb vitamin D from the intestinal tract. If this is true, then it is unlikely that iguanas would develop hypervitaminosis D from excess dietary vitamin D. Nevertheless, most current literature still discusses "hypervitaminosis D" when referring to the syndrome of severe hypercalcemia that seems to be related to an incorrect diet containing excess vitamin D. While hypovitaminosis D3 often contributes to metabolic bone disease, hypervitaminosis D is also harmful. This condition usually occurs when owners oversupplement with vitamins (only a light sprinkling is needed a few times a week) or give dog or cat food to their pets (both contain excessive amounts of vitamin D, as well as excess fat and protein). Periovulatory females can show marked hypercalcemia that has no significance. Clinical signs arc nonspecific and resemble many diseases; often, only anorexia and lethargy are seen. Treatment includes slowly correcting the diet, and hospitalization to correct the high calcium level. Treatment is often unsuccessful. Prevention is once again the best course.
Avascular Necrosis. Iguanas may be examined for avascular necrosis of the digits or tail. These necrotic areas appear darker than the surrounding tissue. Left untreated, the necrosis can spread cranially up the tail or digit. The exact cause isn't always determined, but can include septicemia, mycotoxicosis, mycobacteriosis, a fungal infection, or retained skin after molting. Treatment is simple when the condition is caught at an early stage, and involves amputation of the affected area. The tail usually grows back if left unsutured.
. (Reptile diseases by Shawn P. Messonnier)
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