Collyriclum faba (Bremser, 1831) (Digenea: Collyriclidae) in the Azure jay, Cyanocorax caeruleus (Vieillot, 1818): the first report of the parasite in Brazil.

This study aims to document the first record of the trematode Collyriclum faba in Brazil. This species parasitizes various bird groups, including Passeriformes, Galliformes, and domestic birds, across Europe, Northeast Asia, and the Americas. An Azure Jay (Cyanocorax caeruleus) found in Praia Grande, Santa Catarina State, southern Brazil, exhibited an unusual enlargement and obliteration of the pericloacal region by an approximately 4 cm diameter, multilobular mass was firm in consistency. A sample of the excised tissue was extracted and sent for histopathological analysis, revealing eight adult C. faba specimens within the cyst. Each cyst cavity contained two parasites, surrounded by fibrous connective tissue, forming multiple cavitations. Longitudinal and transverse sections of the trematodes showed a tegument-covered body with parenchymal lining inside the cavity. The uterus contained numerous thick-walled, yellowish-brown eggs. The parasites were encircled by a predominant infiltrate of macrophages, multinucleated giant cells, and diffuse heterophils, accompanied by bacterial colonies, resulting in the formation of a parasitic heterophilic granuloma.