Morphological description and molecular characterization of Leucocytozoon australis sp. nov. (Apicomplexa: Haemosporida: Leucocytozoidae) infecting the Austral parakeet (Enicognathus ferrugineus), an endemic parrot from the southern Andes.

Birds of the order Psittaciformes are rarely infected by haemosporidian blood parasites in the wild, and the few records of Leucocytozoon in parrots correspond to host-generalist lineages detected in captive birds. Here we describe a new species, Leucocytozoon australis sp. nov., infecting the Austral parakeet (Enicognathus ferrugineus) in the southern Andes. We examined 18 individuals - 15 sampled for blood (preserved on FTA cards and as stained blood films) and 3 sampled for liver - collected between 2004 and 2021 at two regions separated by ∼1500 km (Navarino Island, Chile, and the Bariloche area, Argentina). Infection was assessed by microscopy of stained blood films and by PCR and sequencing of a cytochrome b fragment that fully encompasses the standard HaemFL-HaemR2L barcode region. Leucocytozoon was detected in 8 of 18 birds by PCR and in 5 of 8 blood films examined. The morphological description is based on films from Navarino Island infected exclusively with a single lineage. Gametocytes are roundish but usually irregular and develop in roundish host cells with a markedly irregular nucleus; infected cells are typically distorted. Two closely related cytochrome b lineages were recovered, ENIFER01 and ENIFER02 (GenBank PZ371351 and PZ371352), differing by seven substitutions (0.93%); neither matched any lineage in the MalAvi database, confirming both as previously unreported. Both fall within a well-supported subclade of Leucocytozoon from South American passerines, with which they share 97.8-98.3% (ENIFER01) and 98.8-99% (ENIFER02) identity. To our knowledge, L. australis sp. nov. is the first Leucocytozoon species to be formally described, morphologically and molecularly, from a Psittaciformes host. The omnivorous diet of Austral parakeets, a trait previously associated with haemosporidian infection in Psittaciformes, may facilitate exposure.