| Anaplasma phagocytophilum, the agent of granulocytic anaplasmosis (GA), and Borrelia burgdorferi, the agent of Lyme Disease (LD), are tick-borne bacterial pathogens with complex, inter-related ecologies. Previous studies have documented that many bird species are often parasitized by vector ticks, such as Ixodes pacificus in California; that certain species can be naturally infected with A. phagocytophilum; and that others can be naturally and/or experimentally infected with B. burgdorferi, both sensu stricto (s.s.) and sensu lato (s.l.). Both pathogens are well established in California; however, the extent to which birds are involved in their ecologies is not completely understood. Consequently, we investigated the role birds play in the transmission of these pathogens within California, particularly whether birds can be transport hosts for the ticks and pathogens per se. We grouped bird species into four ecological guilds following published accounts, and classed bird species as migratory or non-migratory to identify which types of avian species collect and potentially move significant numbers of ticks. We screened blood and ticks collected from birds caught in central California in 2011 and 2012 at two interior coast range field sites, and serum from birds caught in southern California in 2005-2007. Migratory species were infested with I. pacificus on more capture events and had a greater number of ticks than non-migratory. Blood from a golden-crowned sparrow, Zonotrichia atricapilla, and a European Starling, Sturnus vulgaris, were positive for A. phagocytophilum DNA, but at very low levels. Two pools of I. pacificus nymphs, one from an Oregon junco, Junco hyemalis, the other from a hermit thrush, Catharus guttatus, were positive for B. burgdorferi. Furthermore, eight species caught in central California were seropositive for B. burgdorferi, and a single Oregon junco was seropositive for A. phagocytophilum. No samples from southern California were seropositive for A. phagocytophilum, but migratory golden-crowned sparrows and non-migratory Western scrub-jays, Aphelocoma californica, were seropositive for B. burgdorferi. It has been previously noted that avian migration may alter contact of vectors, reservoir hosts, and humans, and may therefore potentially increase the dissemination of vector-borne pathogens. Our findings show that birds, especially migratory species, commonly serve as bloodmeal sources for immature I. pacificus ticks. We conclude that birds contribute to the ecologies of LD and GA in California through the transport of fed immature ticks. However, low infection prevalence indicates that most species are unlikely reservoirs. |
