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Common conditions of the Bearded Dragon

PostPosted: Thu Apr 23, 2009 8:29 am
by Tigg

I saw someone post asking for a list of diseases, and then came across this article in one of my wife's online textbooks, thought some might find it interesting...

Common Conditions of the Bearded Dragon
British Small Animal Veterinary Congress 2007
M.A. Mitchell, DVM, MS, PhD
University of Illinois, College of Veterinary Medicine
Urbana, IL, USA

Inland bearded dragons (Pogona vitticeps) are omnivorous lizards that are native to Australia. These agamids have become quite popular as pets in both the United Kingdom and United States. As the popularity of these lizards continues to grow, veterinarians can expect these animals to be presented to their hospital. The purpose of this presentation is to provide the delegates with an overview of the common disease conditions encountered with captive bearded dragons.

Diseases of Dragons

Infectious Disease

Bearded dragons are susceptible to a range of infectious diseases. Bacterial diseases are generally attributed to opportunistic gram-negative microbes (e.g., Pseudomonas spp., Klebsiella spp., Salmonella spp., Citrobacter spp., and Serratia spp.), although opportunistic gram-positive microbes can also be associated with clinical disease. A culture and antimicrobial sensitivity test is recommended to speciate the isolate and determine the 'best' antimicrobial for the case. When antimicrobial selection cannot be based on culture than the veterinarian should select a broad-spectrum antibiotic with appropriate gram-negative coverage.

Bearded dragon adenovirus was first reported in Australia in the early 1980s. The virus was not characterised in the United States until more than a decade later. Since that time, the virus has spread through the bearded dragon population in the USA and is considered endemic. Transmission of the virus is primarily by the direct route (faecal-oral), although vertical transmission may also be possible. Affected animals may present with anorexia, weight loss, limb paresis, diarrhoea and opisthotonous. Concurrent dependovirus and coccidial infections have also been observed in neonatal bearded dragons. Biopsies of the liver, stomach, oesophagus, and kidney may be collected to confirm diagnosis (ante-mortem). On histopathology, basophilic intranuclear inclusion bodies are strongly suggestive of adenoviral infection. Currently, there is no non-invasive antemortem diagnostic test to confirm adenovirus in the reptile; however, the author is currently working on a polymerase chain reaction (PCR) assay to detect adenovirus in the faeces of affected animals. There is no effective treatment for adenoviral infections, although supportive care (e.g., fluids, enterals, antibiotics) may be useful in stemming the secondary effects of the disease. Again, very little is known regarding the epidemiology of this virus; therefore, special precautions should be taken when working with affected animals. Because there is no effective treatment, affected bearded dragons should be culled from breeding populations.

Coccidiosis is a major cause of morbidity and mortality in bearded dragons. The causative species that has been identified in bearded dragons is Isospora amphiboluri. These endoparasites are especially problematic in neonatal dragons, often resulting in stunting, diarrhoea and death. Whereas most coccidial infections in higher vertebrates are self-limiting, these infections often persist in bearded dragon colonies. Eliminating coccidia from bearded dragons is difficult. Most of the therapeutics used to eliminate coccidia are coccidiostatic and produce inconsistent results in reptile patients. The author has found that treatment regimens recommended in the veterinary literature (3-5 days) are far too short. A combination of extended treatment (14-30 days) with a coccidiostat, quarantine and environmental disinfection/sanitation are required to eliminate coccidia from dragon colonies.

Microsporidians are obligate intracellular parasites. The life cycle of these parasites includes both merogenic and sporogenic phases. These parasites are common in lower vertebrates (e.g., fish), but have also been implicated as a concern in humans with acquired immunodeficiency virus. Bearded dragons infected with these parasites can present with a similar clinical picture as adenovirus or coccidiosis. Affected dragons are anorectic, unthrifty, cachectic and may die suddenly. Diagnosis is generally made at postmortem. Hepatic and renal necrosis is common, although other organ systems (e.g., intestine and gonads) may also be affected. There is no effective treatment. To limit the likelihood of introducing this parasite into a collection, herpetoculturists should only acquire animals from reputable breeders and quarantine any new arrivals for a minimum of 60-90 days.

Oxyurids, or pinworms, are a common finding in captive bearded dragons. These parasites are generally found in the large intestine, although occasionally they are found more cranial in the small intestine. These parasites are considered as commensals by some veterinarians. In the author's experience, dragons with oxyurid infestations are generally asymptomatic. In these cases, the author does not recommend treatment. If an animal is found to have clinical disease (e.g., diarrhoea) associated with the presence of the parasites, than the author recommends treating the dragon with an appropriate antiparasitic (e.g., fenbendazole).

Nutritional Disease

Dragons not provided a balanced diet might develop secondary nutritional hyperparathyroidism (metabolic bone disease). Secondary nutritional hyperparathyroidism is most commonly diagnosed in animals offered a calcium deficient diet, phosphorus rich diet, and/or vitamin D deficient diet. Affected dragons are often depressed, anorectic, develop muscle tremors, have soft pliable bones and seizures. In severe cases, affected animals can die from secondary nutritional hyperparathyroidism. Fast-growing juveniles and reproductively active females are most commonly affected. Diagnosing this nutritional disorder can generally be done by taking a thorough history and physical examination. Inadequate nutrition is a common finding, and the physical examination findings are consistent with those described previously. Radiographs can be used to confirm the presence of pathological fractures and a general loss of cortical bone density. Plasma biochemistries are not generally rewarding, and affected animals are normocalcaemic. In the terminal stages of the disease it may be possible to observe a hypocalcaemia. Treatment should focus on stabilising the patient. These animals should be considered an emergency, as a hypocalcaemic episode could prove fatal. Calcium can be provided parenterally or orally. Oral calcium is considered more bioavailable. Vitamin D should also be given parenterally to ensure that the calcium is absorbed through the intestine. The provision of full-spectrum lighting should also be considered for these animals. Fluid therapy should be provided to correct any deficits. Caloric support should be provided to animals that are not eating on their own. The prognosis for these animals is generally poor to fair if the animals are diagnosed early and treated aggressively.

Commercially available larval insects have a very high fat content. Because these prey items routinely comprise a large portion of a captive dragon's diet, these lizards are susceptible to an over-accumulation of fat. Dragons, like other lizards, primarily store their fat in two large coelomic fat bodies. The fat bodies are anchored in the caudal coelomic cavity, and the cranial aspects of the fat bodies are unattached. In obese dragons, it is often possible to palpate the fat bodies. Obesity can lead to a number of health issues in captive dragons, including dystocia and hepatic disease. To limit the likelihood of complications associated with obesity, it is important that clients provide an appropriate diet for their dragons. The number of larval invertebrates should be limited in an adult dragon's diet, and ad lib greens provided. Dragons should also be removed from their enclosures regularly and provided exercise too. When exercising dragons it is important to consider the public health risks (e.g., Salmonella spp.) associated with these animals, and appropriate precautions taken to limit the spread of potential pathogens.