Abstract
Avian infecting piroplasms are largely under-studied compared to other hemoparasites, and this paucity of information has blurred our phylogenetic and biological comprehension of this important group as a whole. In the present study, we detected and characterized Babesia from yellow-legged gull (Larus michahellis) chicks from a colony in southern France. Based on morphological and molecular characterizations, a new Babesia species belonging to the Peircei group, a clade of avian-specific piroplasms, was identified. Due to the complexity of species delineations and the low number of parasites characterized in this clade to date, a species name was not yet attributed; we refer to it for now as Babesia sp. YLG (Yellow-Legged Gull). High prevalence (85% and 58% in 2019 and 2020, respectively) and high parasitemia (up to 20% of parasitized erythrocytes) were recorded in chicks, without any obvious clinical signs of infection. Although the 16 isolates had identical 18S rRNA gene sequences, 6 genetic variants were described based on partial cox1 sequencing, with evidence of chicks co-infected by two variants. Transmission of Babesia sp. YLG via the soft tick Ornithodoros maritimus is discussed.