High burdens of <i>Ixodes scapularis</i> ticks and surveillance for <i>Babesia</i> spp. in Carolina Wrens (<i>Thryothorus ludovicianus</i>) in Missouri, USA

The incidence of human tick-borne diseases is rising globally. Birds are ecologically significant hosts, capable of local or widespread dispersal for ticks and their associated pathogens, including agents of babesiosis. Despite its emerging importance, surveillance for zoonotic Babesia spp. ((Starcovici, 1893) Piroplasmida: Babesiidae) remains lacking, particularly in avian hosts. This study investigates the prevalence of Babesia spp. in a population of Carolina Wrens ((Latham, 1790) Passeriformes: Troglodytidae Thryothorus ludovicianus) in Missouri, USA. Due to their ground-foraging behavior and documented high tick burdens, we hypothesized that Carolina Wrens would have Babesia spp. infections. Birds were captured using mist nets, examined for ticks, and phlebotomized for blood samples. We prepared blood smears which were analyzed via microscopy for the presence of Babesia spp. parasites. During June and July 2018, we captured 70 birds from 14 species and collected 156 ticks, of which 152 were Ixodes scapularis ((Say, 1821) Acari: Ixodidae). Carolina Wrens accounted for the highest tick burdens (130 ticks total) with juvenile birds having significantly higher nymphal tick burdens than adults. Despite examining the blood smears of 23 Carolina Wrens and 5 Louisiana Waterthrushes (Parkesia motacilla) for Babesia spp., we found no evidence of infection. Our findings emphasize the notably high tick burdens in Carolina Wrens while underscoring the need for broader and more sensitive surveillance for Babesia spp. in bird populations. Understanding the role of avian hosts in the ecology of tick-borne pathogens is key for anticipating and mitigating public health risks associated with tick-borne disease.