Case report: Disseminated larval trematodiasis caused by Clinostomum marginatum in a green tree frog (Hyla cinerea)

• Published in: Veterinary parasitology (Amsterdam) 2024-07, Vol.52, p.101051-101051, Article 101051
• Main Authors: Jones, Håkon, Fenton, Heather M.A., Elsmo, Elizabeth J., Nemeth, Nicole M., Garrett, Kayla B., Cleveland, Christopher A., Yabsley, Michael J.
• Format: Article
• Language: English
• Subjects: Animals; Anura - parasitology; Clinostomum marginatum; Fatal Outcome; Female; Georgia; Green tree frog; Hyla cinerea; Larva; Trematoda - classification; Trematoda - isolation & purification; Trematode Infections - parasitology; Trematode Infections - veterinary; Trematodiasis; Yellow grub
• ISSN: 2405-9390; 2405-9390
• DOI: 10.1016/j.vprsr.2024.101051

Clinostomum spp. are common parasites of piscivorous birds. Metacercaria are typically observed in the muscles or just under the skin of fish and rarely amphibians. We describe an unusually severe case of Clinostomum marginatum infection in an adult female green tree frog (Hyla cinerea) from Georgia (USA). The frog was found in November 2015 with a high number (>250) of widely disseminated, raised, subcutaneous nodules. The frog died in December. At necropsy, it was emaciated, and the skin was covered in raised uniform, tan-green, subcutaneous, ∼2–3 mm diameter nodules. Each nodule contained 1–3 C. marginatum metacercariae. Microscopically, high numbers of trematodes were within subcutaneous tissues and in coelomic and oral cavities, lung, liver, kidney, ovary, orbit and calvarium. Small to large numbers of lymphocytes and melanomacrophages were in connective tissues and epidermis. A 732 bp region of COI was 98.8–99.8% similar to numerous sequences of C. marginatum and, phylogenetically it grouped with these C. marginatum sequences. The ITS-1 region was 100% similar to a C. marginatum sample from a great egret (Ardea alba) from Mississippi. This report represents a novel finding of severe trematodiasis in a free-ranging amphibian with C. marginatum infection. [Display omitted] •Multiple hundred encysted metacercaria were found in an emaciated green tree frog.•Clinostomum marginatum infects frogs in North America.•Parasites were evident in skin and less often in the parenchyma of several organs.•Parasite prevalence and intensity are generally low and morbidity/mortality is rare.•Altered habitat could be associated with high intensity in this individual.