Diagnosis and surgical management of idiopathic bile duct cysts in a bearded dragon (Pogona vitticeps)

The case presented shows the clinical signs, diagnosis and surgical management of idiopathic bile duct cysts in a bearded dragon (Pogona vitticeps). A 12-year-old female bearded dragon presented with constipation resulting from the consumption of sand. A soft mass about 4 cm wide could be palpated in the mid-coelom after the substrate passed. The animal started eating, but soon started showing signs of kyphosis. Ultrasound, radiography and computed tomography examinations revealed that the mass was a cyst 4 cm in diameter. Diagnostic laparotomy was performed and the large cyst and affected liver tissue were removed with a partial hepatectomy. Cytology of the cyst was unremarkable, but histopathological examination showed the lesions to be bile duct cysts. No sign of malignancy or inflammation could be seen.

Successful Treatment of Nannizziopsis guarroi Infection using Systemic Terbinafine in a Central Bearded Dragon (Pogona vitticeps)

Nannizziopsis guarroi infection in lizards presents therapeutic challenges as reports of poor clinical outcomes, including antifungal toxicity, incomplete clearance of infection and recrudescence of infection are common. The case presented here describes the successful treatment of a N. guarroi infection using systemic terbinafine and environmental disinfection in a captive-bred central bearded dragon (Pogona vitticeps). The lizard presented with darkly colored cutaneous lesions and mycologic culture samples were identified as N. guarroi using Matrix-Assisted Laser Desorption/Ionization – Time Of Flight (MALDI-TOF). Based upon the lack of clinical resolution of cutaneous lesions, weight loss, and reduced appetite, initial treatment with voriconazole was discontinued. Terbinafine was prescribed and weekly environmental disinfection with sodium hypochlorite was initiated until cutaneous clearance of the fungus was confirmed by negative culture, histopathology, and N. guarroi qPCR from cutaneous swab. Terbinafine treatment was discontinued after 80 days. There were no clinical signs of toxicity associated with the prolonged treatment and the lizard has not developed any cutaneous lesions or illness in more than two years of clinical follow up. While the most ideal treatment of N. guarroi is still being investigated, this case demonstrates a promising and safe treatment option for an increasingly common and devastating disease.

Developmental dynamics of sex reprogramming by high incubation temperatures in a dragon lizard

In some vertebrate species, gene-environment interactions can determine sex, driving bipotential gonads to differentiate into either ovaries or testes. In the central bearded dragon (Pogona vitticeps), the genetic influence of sex chromosomes (ZZ/ZW) can be overridden by high incubation temperatures, causing ZZ male to female sex reversal. Previous research showed ovotestes, a rare gonadal phenotype with traits of both sexes, develop during sex reversal, leading to the hypothesis that sex reversal relies on high temperature feminisation to outcompete the male genetic cue. To test this, we conducted temperature switching experiments at key developmental stages, and analysed the effect on gonadal phenotypes using histology and transcriptomics. We found sexual fate is more strongly influenced by the ZZ genotype than temperature. Any exposure to low temperatures (28oC) caused testes differentiation, whereas sex reversal required longer exposure to high temperatures. We revealed ovotestes exist along a spectrum of female-ness to male-ness at the transcriptional level. We found inter-individual variation in gene expression changes following temperature switches, suggesting both genetic sensitivity to, and the timing and duration of the temperature cue influences sex reversal. These findings bring new insights to the mechanisms underlying sex reversal, improving our understanding of thermosensitive sex systems in vertebrates.