Local Community Composition Drives Avian Borrelia burgdorferi Infection and Tick Infestation.

Marie Lilly,Lucas Pavan,Ravinder Sehgal,Ceili Peng,Arielle Crews,Nghia Tran,Wilmer Amaya-Mejia,Andrea Swei

doi:10.3390/vetsci9020055

Abstract

Globally, zoonotic vector-borne diseases are on the rise and understanding their complex transmission cycles is pertinent to mitigating disease risk. In North America, Lyme disease is the most commonly reported vector-borne disease and is caused by transmission of Borrelia burgdorferi sensu lato (s.l.) from Ixodes spp. ticks to a diverse group of vertebrate hosts. Small mammal reservoir hosts are primarily responsible for maintenance of B. burgdorferi s.l. across the United States. Nevertheless, birds can also be parasitized by ticks and are capable of infection with B. burgdorferi s.l. but their role in B. burgdorferi s.l. transmission dynamics is understudied. Birds could be important in both the maintenance and spread of B. burgdorferi s.l. and ticks because of their high mobility and shared habitat with important mammalian reservoir hosts. This study aims to better understand the role of avian hosts in tick-borne zoonotic disease transmission cycles in the western United States. We surveyed birds, mammals, and ticks at nine sites in northern California for B. burgdorferi s.l. infection and collected data on other metrics of host community composition such as abundance and diversity of birds, small mammals, lizards, predators, and ticks. We found 22.8% of birds infected with B. burgdorferi s.l. and that the likelihood of avian B. burgdorferi s.l. infection was significantly associated with local host community composition and pathogen prevalence in California. Additionally, we found an average tick burden of 0.22 ticks per bird across all species. Predator and lizard abundances were significant predictors of avian tick infestation. These results indicate that birds are relevant hosts in the local B. burgdorferi s.l. transmission cycle in the western United States and quantifying their role in the spread and maintenance of Lyme disease requires further research.

Highlights

Zoonotic vector-borne diseases have emerged over the past several decades and constitute a major public health challenge [1,2,3,4]
This study aims to resolve unanswered questions regarding ecological drivers of avian B. burgdorferi s.l. infection prevalence and avian tick burden to better understand the role of avian hosts in tick-borne zoonotic disease transmission cycles
Statistical analysis of avian tick burden focused on 118 individual birds from six bird species that included individuals infected with B. burgdorferi s.l. and had a sample size ≥5 individuals across all sites: the oak titmouse (Baeolophus inornatus), spotted towhee (Pipilo maculatus), pacific slope flycatcher (Empidonax difficilis), dark-eyed junco (Junco hyemalis), Bewick’s wren (Thryomanes bewickii), and lesser goldfinch (Spinus psaltria) (Table 1)

Summary

Introduction

Zoonotic vector-borne diseases have emerged over the past several decades and constitute a major public health challenge [1,2,3,4]. In the western United States, the primary vector of Lyme disease is the western black-legged tick, Ixodes pacificus [8], a generalist tick that can feed on over 100 species of mammals, birds, and reptiles [13,14,15]. Some of these so-called reservoir hosts can become infected with B. burgdorferi s.l., amplify the bacteria, and transmit it to uninfected feeding ticks— maintaining B. burgdorferi s.l. in the community [16]. Birds may be important in both maintenance and spread of B. burgdorferi s.l. because of their high mobility and shared habitat with important mammalian reservoir hosts [15,21,22]

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