title: Borrelia burgdorferi sensu lato spirochetes in wild birds in northwestern California: associations with ecological factors, bird behavior and tick infestation.
abstract: Although Borrelia burgdorferi sensu lato (s.l.) are found in a great diversity of vertebrates, most studies in North America have focused on the role of mammals as spirochete reservoir hosts. We investigated the roles of birds as hosts for subadult Ixodes pacificus ticks and potential reservoirs of the Lyme disease spirochete B. burgdorferi sensu stricto (s.s.) in northwestern California. Overall, 623 birds representing 53 species yielded 284 I. pacificus larvae and nymphs. We used generalized linear models and zero-inflated negative binomial models to determine associations of bird behaviors, taxonomic relationships and infestation by I. pacificus with borrelial infection in the birds. Infection status in birds was best explained by taxonomic order, number of infesting nymphs, sampling year, and log-transformed average body weight. Presence and counts of larvae and nymphs could be predicted by ground- or bark-foraging behavior and contact with dense oak woodland. Molecular analysis yielded the first reported detection of Borrelia bissettii in birds. Moreover, our data suggest that the Golden-crowned Sparrow (Zonotrichia atricapilla), a non-resident species, could be an important reservoir for B. burgdorferi s.s. Of 12 individual birds (9 species) that carried B. burgdorferi s.l.-infected larvae, no birds carried the same genospecies of B. burgdorferi s.l. in their blood as were present in the infected larvae removed from them. Possible reasons for this discrepancy are discussed. Our study is the first to explicitly incorporate both taxonomic relationships and behaviors as predictor variables to identify putative avian reservoirs of B. burgdorferi s.l. Our findings underscore the importance of bird behavior to explain local tick infestation and Borrelia infection in these animals, and suggest the potential for bird-mediated geographic spread of vector ticks and spirochetes in the far-western United States.
authors.affiliation: Energy and Resources Group, University of California, 310 Barrows Hall, Berkeley, CA 94720, United States of America; Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, CA 94720, United States of America.
authors.forename: Erica A
authors.initials: EA
authors.lastname: Newman
authors.affiliation: Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523, United States of America; Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 80522, United States of America.
authors.forename: Lars
authors.initials: L
authors.lastname: Eisen
authors.affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 80522, United States of America.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Eisen
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, CA 94720, United States of America.
authors.forename: Natalia
authors.initials: N
authors.lastname: Fedorova
authors.affiliation: Hawaii Department of Health, Sanitation Branch, Vector Control, Honolulu, Hawaii 96813, United States of America.
authors.forename: Jeomhee M
authors.initials: JM
authors.lastname: Hasty
authors.affiliation: University of California Hopland Research & Extension Center, Hopland, CA 95449, United States of America.
authors.forename: Charles
authors.initials: C
authors.lastname: Vaughn
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, CA 94720, United States of America.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Lane
mesh_terms: D000465:Algorithms; D000818:Animals; D000835:Animals, Wild / Q000382:microbiology*; D001522:Behavior, Animal; D001715:Bird Diseases / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission; D001717:Birds / Q000145:classification / Q000382:microbiology*; D025065:Borrelia burgdorferi / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D002140:California; D055669:Ecological and Environmental Phenomena; D008962:Models, Theoretical; D015995:Prevalence; D013984:Tick Infestations