SARCOCYSTOSIS IN A CAPTIVE FLOCK OF THICK-BILLED PARROTS (RHYNCHOPSITTA PACHYRHYNCHA) FROM 2005 TO 2016: MORBIDITY, MORTALITY, DIAGNOSTICS, AND MANAGEMENT STRATEGIES

Abstract

Sarcocystosis was diagnosed in a captive flock of thick-billed parrots (Rhynchopsitta pachyrhyncha) at the Wildlife Conservation Society's Queens Zoo. Since the index case in 2005, 45% of mortalities in birds over 30 days of age were due to sarcocystosis. Sarcocystis falcatula was repeatedly identified as the causative agent. The disease predominantly affected younger adult parrots. Administration of antiparasitic medications prior to development of respiratory signs prolonged life in infected birds, but disease was fatal until utilization of a three-drug combination (pyrimethamine, trimethoprim-sulfamethoxazole, and ponazuril). This protocol may require in excess of 6 mo of therapy to achieve clinical resolution of active disease. Plasma creatine kinase activity was found to be the most useful test in diagnosing infection and monitoring response to therapy. Polymerase chain reaction (PCR) for apicomplexan organisms on antemortem whole blood, blood smears, or dried blood spots helped confirm suspected cases, but due to the poor sensitivity was sometimes misleading when assessing response to therapy or resolution of clinical disease. Preventive measures, focusing on exclusion and removal of Virginia opossums (Didelphis virginiana) from zoo grounds failed to curtail the occurrence of sarcocystosis in the flock. Other preventative steps, such as modification of feeding stations to exclude potential arthropod paratenic hosts and prophylaxis trials with diclazuril, appeared to successfully mitigate new infections. Given the diagnostic and therapeutic challenges, prevention of exposure to S. falcatula is essential to ex-situ conservation efforts for thick-billed parrots.