Medical History

A detailed and thorough history is invaluable in determining any potential disease in chameleons. Each client should complete a detailed history form containing questions about the animal's caging, diet, prior medical history, etc. A client should be able to recall with some specificity the temperature ranges, cage dimensions, brand of lighting, and cage decorations.²

The chameleon's diet plays a major role in its health. The veterinarian should not only elicit the types of food items (i.e., crickets, superworms, waxworms, etc.), but also the percentages of each item eaten by the chameleon. The veterinarian should determine if the prey items have been "gut loaded" (i.e., fed calcium and vitamin-rich food sources) or if the prey items have been dusted with any supplements. If so, the veterinarian should ask which products or brands have been used.²

Examination

As with any animal species, a thorough, systematic approach to the examination will provide clues to an appropriate diagnosis. Precaution should be taken when handling these animals because chameleons have sharp claws, and the larger species have a noticeable bite. The patient should be examined for general demeanor as it climbs on a perch, and it should be restrained for the rest of the exam by grasping the head by the thumb and forefinger behind the eyes. This approach will enable control of the head. The palm of the hand should rest along the back allowing the fingers to catch the chameleon's feet.

Diseases and Therapeutics

Eyes

Enophthalmia is a very common indicator of disease in chameleons. It is usually combined with other signs such as anorexia, dehydration, and emaciation. The "sunken eyes" are generally a poor prognostic indicator. Exophthalmia is another common sign of disease in chameleons. The swelling can come from the globe itself, the surrounding conjunctiva, or the retrobulbar space. The globe can increase in size because of uveitis or panophthalmitis and is best treated with systemic antibiotics to provide better antibiotic levels in the intraocular tissues.

Corneal damage can come from trauma secondary to shipping or aggression. Superficial lesions are responsive to topical treatments with common ophthalmic antibiotic preparations. Deep corneal lesions or lacerations may require enucleation if medical or surgical options fail. Because of the visual impairment caused by even a mild disease, the chameleon is often anorexic, and supportive care including syringe-feeding or hand-feeding may need to be initiated.

If the globe of the eye looks normal, then the surrounding structures need to be addressed. Parasites that have larval stages will sometimes migrate within the conjunctival tissues, retrobulbar tissues, intraocular space, or the conjunctival sac. Surgical removal of the parasites may provide relief and the return to normal visual function. Typical parasiticides may not completely remove these parasites and may cause toxic reactions from the decaying parasites. Conjunctival or retrobulbar abscesses may cause intense swelling around the eye. The infection may come from the conjunctiva itself or as an ascending stomatitis infection from the nasolacrimal duct. The abscess should be drained and cleaned with dilute chlorhexidine. The chameleon should be placed on broad-spectrum antibiotics, preferably based on culture and sensitivity reports.³

Oral Cavity

Chameleons naturally have pigmented gingiva. Many species of wild-caught chameleons have very xanthic (yellow) oral gingiva. Most captive-bred chameleons do not have the same degree of pigmentation and may be gray to pink in color. The variability in their normal coloration may be misinterpreted as a disease condition such as icterus, shock, etc. The lateral commissures of the mouth have glands that produce a very musky, waxy residue that aids in fly/prey attraction. These areas need to be checked and periodically cleaned due to propensity to become infected.

Chameleons have a primitive acrodont dentition, which is also found in frilled lizards (Chlamydosaurus kingii), bearded dragons (Pogona spp.), and water dragons (Physignathus lesueurii). The teeth are not within sockets and are attached to the dorsal surface of the mandible and maxilla. This type of dentition seems to be predisposed to periodontal disease. Once the teeth are damaged, they are not replaced, unless the damage occurs while the chameleon is a very young juvenile. Care must be exercised with oral speculums to avoid damage to the dental arcade.

Mild cases of periodontal disease may present as erythema to the gingiva or as a recession of the gum line. More severe cases can develop into stomatitis or even osteomyelitis. Stomatitis may also develop from infections by opportunistic pathogens from other causes such as stress, inappropriately decreased environmental temperatures, poor nutrition, or trauma. These underlying conditions need to be corrected before appropriate treatment can begin to work. Severe abscesses and deep lesions need to be cleaned and/or surgically debrided. In some cases, the area of the mandible will need to be debrided or even the rostral aspect removed. The cytology of the lesions should be examined to aid in determining an etiology. Organisms, such as some anaerobes, fungi, and Mycobacterium, are more difficult to isolate in the laboratory, and cytology may be the only certain means for diagnosis. Organisms, such as Aeromonas, Pseudomonas, Klebsiella, etc. are commonly cultured from stomatitis lesions. The most important part of the culture is determining the sensitivities. The sensitivity helps determine antibiotic treatment. The appropriate antibiotic will need to be used for an extended period from 12 to 16 weeks. Follow-up cultures and sensitivities may need to be performed if the lesions do not heal in an appropriate amount of time.³

The chameleon has a modified hyoid bone (entoglossal process) that acts as a firing pin for the projectile tongue. The tongue is accordion folded along the conical shaped bone. When firing, the accelerator muscle will contract down along the bone, projecting the tongue towards its prey at over five meters per second. The tongue can extend roughly the length of the chameleon's body. The tip of the tongue contains a muscular tongue pad that contains microscopic ridges similar to the toe pads of arboreal geckos. The tongue pad contains glands that secrete mucin to aid in sticking to the prey. The lingual surfaces of the mandibular mucosa also contain glands that produce saliva that coats the outer surface of the tongue pad. The tongue pad also contains longitudinal adductor muscles that contract to "grip" the prey. Once the tongue attaches to the prey item, the lateral surfaces of the tongue contain retractor muscles (hyoglossal muscles) that retract the tongue back over the entoglossal process.

This complex lingual system is prone to injury and can cause considerable morbidity. Most injuries come from infection or trauma. Injuries may come from trauma from the rough prey surface or prey bites. These injuries under normal conditions should heal on their own. Under abnormal conditions, such as suboptimal temperatures or systemic disease, opportunistic bacteria may form lingual abscesses. These abscesses need to be opened, and the chameleon should be placed on appropriate broad-spectrum antibiotics determined through culture and sensitivity results.

Trauma to the tongue can be due to muscle strain from hyperextension. A chameleon may miss the prey and attach to a fixed object, i.e., cage wire, branch, etc. The chameleon will attempt to contract the tongue while attached to the fixed object. This causes microtears in the delicate muscles. Most chameleons will then make subsequent attempts to snare prey and will either not be able to extend the tongue or weakly shoot part of the way. These chameleons need to rest from all attempts at remote capture of prey and require two to six weeks of direct hand-feeding. Direct hand-feeding is accomplished by presenting the prey item within two to five centimeters of the head. Sometimes presenting the prey inside the cage through the wire mesh is beneficial and may not stress the chameleon. Once the chameleon seems able to obtain prey easily in this manner, then the distance can be slowly increased until normal distances are reached.

Musculoskeletal

Noninfectious diseases of the musculoskeletal system are common in chameleons. Metabolic bone disease (MBD) is one of the most common forms seen in practice. Clinical signs include lethargy, deformed/curled limbs, "rubber-jaw," stunted growth, or even death. MBD, most commonly, is the result of a nutritional secondary hyperparathyroidism (NSHP) resulting from a multifactorial disease affecting calcium metabolism. The major contributing factors of MBD include insufficient dietary calcium supplementation, lack of available UV light source, insufficient vitamin D₃, excess of dietary phosphorus, etc. Treatment of this form of MBD follows the same guidelines established for other lizard species. The goal of treatment is to establish a positive calcium balance by proper supplementation of calcium/Vitamin D₃ and exposure to UV light.³

Other causes of noninfectious musculoskeletal disease include neuropathies and fractures. Neurologic diseases in chameleons are rare. Chameleons may allow one limb to dangle while resting on a branch. Some chameleons do this with no signs of physical disease. Others do this as early signs of gout or joint disease. Some wild-caught chameleons may have fractures or related soft tissue injuries. In the wild, the native collectors usually grasp the chameleon and force it from its branch. When the chameleon is out of reach, the collectors will use long bamboo shafts to beat and knock them off branches. Many of these injuries are associated with the carpal and tarsal joints. These injuries may be healed through restrictive activity and possible splinting. Long bone fractures (non-pathologic) in chameleons are not very common due to their structural design, lightweight, and agility. Most fractures arise from traumatic falls or intraspecies aggression. These fractures may be healed by lightweight external fixation.³

Osteomyelitis is a very devastating disease in chameleons. One of the most common locations is the mandible (described above). Untreated fractures, bite wounds, thermal burns, or joint injuries may lead to localized infections that spread into the bone or joints. Diagnosis can be derived from cytology or biopsy of the lesions. Use of different stains such as Wright's stain, Gram stain, or acid-fast may rule in or out different causes such as bacterial, fungal, neoplastic, parasitic, or mycobacterial. Aggressive therapy is needed for these cases. Initial treatment lies with aggressive surgical debridement and deep antiseptic wound cleansing. In bacterial infections, a culture and sensitivity is extremely valuable in antibiotic selection. Treatment with appropriate antibiotics generally lasts for a minimum of 8 to 12 weeks and may last for six months. Even with appropriate treatment, amputation of the bone/limb may be required.³

Genitourinary

The current market today in chameleons mainly revolves around breeding. This widespread breeding effort has led to an increased number of reproductive problems. One of the more common reproductive problems is dystocia or egg binding. Several improper husbandry factors have been identified as contributing factors. Some of the most common factors are an improper nesting site, lack of a nesting site, or inadequate nutrition (i.e., calcium deficiency, decreased vitamin A, etc.). Other physical factors attributable to dystocia include uterine diseases such as infection, stricture, rupture, torsion, or doubled egg.¹

The diagnosis of dystocia may be made through physical examination and radiographs. Differentiation of pre- or post-ovulatory stasis must be determined prior to medical treatment. Pre-ovulatory stasis may be treated with supportive care or surgical intervention; and if initiated early in the disease process, medical therapy may avert surgical intervention. Samples should be collected for evaluation, including complete blood cell count (CBC) and plasma biochemistries. Radiographs may be used to determine the cause of dystocia, as well as assist in determining if the female is in pre- or post-ovulatory stasis. Any problems found in the diagnostics, such as dehydration, hypocalcemia, etc. should be corrected prior to medical or surgical intervention.³

References

1.  Barrie MT. Chameleon medicine. In: Fowler ME, Miller RE, eds. Zoo & Wild Animal Medicine. 4th ed. Philadelphia, PA: WB. Saunders Co; 1999:200–205.

2.  Coke RL. Old World chameleons: captive care and breeding. Bull Assoc Rept Amphib Vet. 1998;8(2):4–10.

3.  Mader DR. Reptile Medicine and Surgery. 2nd ed. St. Louis, MO: Elsevier Saunders; 2006:1242.