Redescription of Babesia ardeae Toumanoff, 1940, a parasite of Ardeidae, including molecular characterization

Among the actual 16 identified and thought to be valid avian piroplasm species, certain parasites are only known from their original description with no subsequent report. Babesia ardeae Toumanoff, 1940 is one of them. It was described from a single sacrificed gray heron (Ardea cinerea) from Vietnam and had never been reported since this date despite inhabiting a very common avian host. The present study reports the accidental rediscovery of B. ardeae from an injured wild gray heron rescued in Singapore. This report confirms the existence of this parasite species in the gray heron from Southeast Asia, highlights the similarities with the original description, provides additional morphologic and morphometric data, and designates neotype material for B. ardeae. Additionally, the report also furnishes the first molecular data about B. ardeae with the amplification and sequencing of the near-full-length 18S rRNA gene sequence and its comparison with the other available sequences of avian piroplasms. Phylogenetic analysis based on this gene was performed to study the relationship of B. ardeae with the other piroplasms from mammals and birds and indicated that B. ardeae appears as a brother group of a clade formed by several avian piroplasm species isolated from seabirds, altogether clustering in a well-supported clade related to the "Babesia duncani group" and protothelerids. Scarcity of this parasite is discussed as well as its taxonomy in relation to the conundrum about the systematics of piroplasms.