Clinical Signs, Management, and Outcome of Presumptive Ivermectin Overdose in a Group of Dendrobatid Frogs

Abstract

Ivermectin is routinely used as an anthelmintic in amphibians at the National Aquarium, Baltimore (MD). Presumptive inadvertent overdose occurred in dendrobatid frogs administered oral ivermectin via micropipette at volumes below the 0.5 μl lower limit of the unit. Forty-eight frogs, 19 Dendrobates auratus (green and black poison dart frog) and 29 Dendrobates tinctorius (dyeing and blue poison dart frog), were administered ivermectin as part of a parasite management program. Within 48 h of administration, clinical signs consistent with ivermectin toxicity developed, including ataxia, flaccid paralysis, pulmonary respiratory depression, and total unresponsiveness to stimuli. Multiple frogs also demonstrated generalized fluid accumulation consistent with hydrocoelom. Clinical signs developed in 31 frogs; 19/19 Dendrobates auratus and 12/29 Dendrobates tinctorius. Management included fluid and nutritional support and calcium, antibiotic, and furosemide administration. The overall survival rate for frogs that developed clinical signs was 32% (10/31). Of the 21 mortalities, seven frogs were euthanized and 14 were found dead. In surviving frogs, clinical signs lasted up to 3 wk, but were mild after 2 wk. Even frogs with severe central nervous system depression survived and supportive care is warranted in toxicity events.