Redescription of Isospora vanriperorum Levine, 1982 (Apicomplexa: Eimeriidae) from the Northern Cardinal, Cardinalis cardinalis (L.) (Passeriformes: Cardinalidae), in North Texas, USA.

Little is known about the coccidian parasites of North American birds of the family Cardinalidae. A single isosporan, Isospora vanriperorum was previously described over 40 years ago from the northern cardinal, Cardinalis cardinalis from Hawaii. Since then, it was also reported in the green-winged saltator, Saltator similis from Brazil but the identification was invalidated recently. Feces were collected in July 2022 from two C. cardinalis found dead in Lamar County, Texas, USA. One sample contained oöcysts representing I. vanriperorum. Oöcysts are spheroidal to subspheroidal with a smooth uni-layered wall, measure (L × W) 23.8 × 22.4 µm and have a length/width (L/W) ratio of 1.04; a micropyle and oöcyst residuum are absent but polar granule(s) are present. Sporocysts are ovoidal and measure 15.5 × 10.5 µm, L/W 1.5; a knob-like Stieda body and a rounded sub-Stieda body are present. The sporocyst residuum is more often composed of various-sized granules dispersed between and across the sporozoites; it is less often in a compact rounded mass. This isosporan has now been reported from the northern cardinal for the second time but most importantly, from the mainland USA for the first time.