A Descriptive Study of Salmonella in Passerines in Urban Atlanta 公开

Abstract

Salmonella spp. is a genus of gram-negative, zoonotic bacterium with over 2,300 known serotypes. Though a leading cause of foodborne illness in humans, Salmonella enterica infection is of particular concern in birds. Field studies have found Salmonella background carriage rate to be as high as 8.5% in populations of passerines (songbirds) that are gregarious and live near livestock or urban areas. In these urban settings, it is widely accepted that feeding stations are associated with an increase of avian salmonellosis, specifically wintertime Salmonella Typhimurium outbreaks; however, it is unknown if feeders are increasing the background carriage rate of Salmonella. In this study we seek to quantify this background carriage rate by capturing and collecting feces from songbirds captured by mist net across four sites in urban Atlanta (Fulton and Dekalb counties). Specifically, we describe the cohort of passerines captured and outline the association between Salmonella carriage and other gram-negative enterobacteria and selected environmental and ornithological risk factors. We found no association between infection and sex, age, or feeding guild of bird samples. We did not find correlation between infection and the canopy cover within 500 meters of bird capture or the average number of feeders per house within each sample area. Furthermore, we found no bacterial contamination of the birds feeders located in the yards where birds were sampled. Further studies aimed at describing avian bacterial transmission in the urban environment can build on this study of 135 birds at 4 locations by selecting an alternative bacterial pathogen of focus.

Table of Contents

Table of Contents
INTRODUCTION ...............................................................................................................................................1
Avian Enterobacteria ........................................................................................................................................1
Salmonella ......................................................................................................................................................2

Avian Salmonella .............................................................................................................................................3

Bird Feeders and Bird Health ..............................................................................................................................4

Objectives and Hypotheses ...............................................................................................................................6

MATERIALS AND METHODS ................................................................................................................................8

Study Sites ....................................................................................................................................................8

Mist Netting ...................................................................................................................................................8

Salmonella Cultivation ......................................................................................................................................9

Feeder Testing ..............................................................................................................................................10

Standardization .............................................................................................................................................10

Area Specific Measures ...................................................................................................................................11

Individual Specific Measures ............................................................................................................................11

Statistical Methods .......................................................................................................................................12

RESULTS .....................................................................................................................................................13

Landscape ...................................................................................................................................................13

Bird Samples ................................................................................................................................................13

Feeder Sampling ...........................................................................................................................................15

Plate Culture ................................................................................................................................................15

Infection and Landscape ................................................................................................................................16

Infection and Individuals ................................................................................................................................17

DISCUSSION ................................................................................................................................................18

Salmonella Infection ......................................................................................................................................18

Gram-Negative Infection and Individual Specific Measures ....................................................................................19

Gram-Negative Infection and Area Specific Measures ..........................................................................................20

Surface Contamination of Bird Feeders .............................................................................................................22

Limitations ..................................................................................................................................................22

Conclusion ..................................................................................................................................................24

Future Directions ..........................................................................................................................................24

FIGURES .....................................................................................................................................................27

REFERENCES ...............................................................................................................................................41

Figures
Figure 1: Sources (A) and consequences (B) of salmonellosis in wild birds ..............................................................27
Figure 2: Geographic distribution of Salmonella Enteritidis isolates in broiler rinses (2000-2002 vs. 2003-2005)...............28

Figure 3: Location of sampling areas in Atlanta, GA, USA.....................................................................................31
Figure 4: Location of sites within each area .....................................................................................................32
Figure 5 Photos from field collection ...............................................................................................................33
Figure 6: Percent Canopy Cover and Average Feeders/House for each area ...........................................................34
Figure 7: Cumulative Trapping Effort and Catch per Unit Effort (CPUE) over entire sampling period..............................35
Figure 8: Gram-negative bacterial colonies growing on XLT4 agar .........................................................................38
Figure 9: Infection by Landscape variables........................................................................................................40

Tables
Table 1: Incidence (per 100,000 persons) of human salmonellosis in 2011 and 2012 ................................................29
Table 2: Prevalence of Salmonella in wild caught, live passerine species for selected articles published since 1994.........30
Table 3: Description of samples collected by site ..............................................................................................36
Table 4: Species composition at each site .......................................................................................................37
Table 5: Infection data ................................................................................................................................39

About this Honors Thesis

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School	Emory College
Department	Environmental Studies
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Biology, Ecology Health Sciences, General Environmental Sciences
关键词	Urban environment Passerines Salmonella Bacterial transmission
Committee Chair / Thesis Advisor	Vazquez Prokopec, Gonzalo, Emory University
Committee Members	Beck, Christopher, Emory University Kitron, Uriel, Emory University

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