Visceral Lepidopterism in Captive Otariids Due to Migration of Caterpillar Setae Associated with Systemic Vasculopathy and Death
Lepidopterism refers to pathology caused by invertebrates of the order Lepidoptera, moths and butterflies. Pathology is produced by irritant chitinous hairs or setae found on the larval exoskeleton. Caterpillar setae have been associated with irritant dermatitis, ophthalmitis, and oropharyngitis in humans and dogs following contact and/or migration of these barbed chitinous structures.1-7 In recent years, migrating caterpillar setae were linked to reproductive losses and mortality in horses in the United States and Australia, the first demonstration of visceral lepidopterism in any species.8-11 Visceral lepidopterism has not been reported in any other species. In December 2015, an 8-yr-old captive-born California sea lion (Zalophus californianus) at Taronga Zoo died following 3 wk of nonspecific illness. Postmortem examination revealed a marked vasculocentric mural granulomatous gastro-colitis associated with foreign bodies consistent in morphology with migrating chitinous invertebrate setae. Some setae were observed penetrating submucosal blood vessels. Death was attributed to major vascular and circulatory events: pancreatic apoplexy, centrilobular hepatic necrosis, and renal thromboembolic fibrinoid vasculitis. These findings prompted a review of prior deaths in otariids at Taronga Zoo. Between 1998 and 2017, 10/19 non-neonatal deaths had microscopic evidence of visceral caterpillar setae migration and associated pathology including 2/2 California sea lions, 5/6 Australian sea lions (Neophoca cinerea), and 3/8 long-nosed fur-seals (Arctocephalus forsteri). Microscopically, the setae are morphologically consistent with those shed by bag-shelter moth (Ochrogaster lunifer) larvae which are known to cause visceral lepidopterism in Australian horses.11 O. lunifer caterpillars have subsequently been found in and around otariid enclosures at Taronga Zoo.
The authors would like to thank the Marine Mammal and Horticultural departments at Taronga Zoo for their assistance in investigating this disease.
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