First detection of a Haemoproteus macrovacuolatus-like parasite in two captive birds of the order Anseriformes: Evidence of atypical morphology.

Haemosporidians are vector-borne parasites that infect vertebrates and are commonly detected in captive birds, causing infections ranging from mild to severe and may be fatal, especially those involving Plasmodium and Haemoproteus species. Blood samples from 17 Anseriformes, including 15 captive Ruddy Shelduck (Tadorna ferruginea) and two black-necked swans (Cygnus melancoryphus), were analyzed in this study. An integrative approach identified Haemoproteus infection in one female of each species, with genetic sequences showing 100% similarity to Haemoproteus macrovacuolatus, based on a 478 bp fragment of the mitochondrial cytochrome b (cytb) gene. However, the morphology observed in these birds differed slightly from the parasite's original description, particularly in the absence of large vacuoles, which are considered characteristic of the species. Combined with the molecular findings, this morphological divergence supports the interpretation of the detected parasite as a H. macrovacuolatus-like lineage and underscores the importance of integrative taxonomy for accurate haemosporidian identification, especially when infections are detected in newly reported avian hosts. Traditional diagnostic and species delimitation criteria may vary due to host-related factors, physiological conditions, and host-parasite interactions, all of which may contribute to morphological variation in these parasites.