Ecological Epidemiology of Campylobacter Jejuni Transmission: Linking Wild Birds, Poultry, and Food Safety.

<p>NON-TECHNICAL SUMMARY:<br/> Campylobacter jejuni is the leading cause of gastroenteritis in industrial countries. Most infection of humans results from consumption of contaminated and improperly cooked poultry. In the past two decades, intensive research has been devoted to developing resistant lines of poultry, creating effective quarantine methods, and forming elaborate post-processing methods to reduce the transfer of C. jejuni to humans. However, infection rates in poultry and livestock remain high and past reductions in human incidence appear to have stalled well short of the established national target rates. Despite the cost of C. jejuni research, containment, and treatment, relatively little effort has been devoted to understanding the ecology and epidemiology of C. jejuni. Researchers generally focus on poultry, but C. jejuni is a multi-species pathogen that also
infects wildlife, particularly wild birds.Understanding the dynamics of transmission between and among domestic animals, wildlife, and humans is a critical step in implementing an effective and comprehensive management plan. Wild birds may act as both reservoirs that harbor C. jejuni at critical times of the year and as vectors for long distance dispersal of non-local C. jejuni strains. Although C. jejuni has been isolated from many wild bird species, crows are among the most likely to play a primary role in cross species transmission because of their high rates of infection and because they are abundant in agricultural and urban settings, leading to high contact rates with poultry, livestock, and humans. Here, I propose to study C. jejuni infection dynamics and cross species transmission between domestic poultry, livestock, and wild American crows in Davis, California. Specifically, I
will test two hypotheses that impact food safety and animal production: Wild crows facilitate the transmission of pathogenic C. jejuni between poultry, livestock, and humans. Non-local strains of C. jejuni originate from migratory wild crows. Using the data that I collect in testing each of these hypotheses, I will also build a biologically informed and spatially explicit model of cross-species C. jejuni infection dynamics. This model will be the main deliverable component of my project and will allow me to make predictions about infection dynamics and management recommendations for mitigation efforts.<p>
APPROACH:<br/> I will study both resident and migrant crows in Davis, California. This location is particularly amenable to the questions raised in my proposal because humans, farm animals, and wild crows are all in close proximity with high levels of interaction. For example, crows often encounter farm animals at feedlots on the UC Davis campus during the day and roost in urban environments near downtown community parks and restaurants at night. Resident crows will be intensively monitored during the breeding season by daily observations of approximately 40 active nests on and around campus. During the breeding season, I will collect fecal samples from 30 adults each year by following them until defecation and then swabbing the feces. Each nest will be visited after nestlings have hatched and I will collect fecal samples from 30 nestlings each year along with feather
and toenail samples from nestlings for dietary analysis. I will also sample 5-10 banded and infected birds more intensively, collecting a series of fecal samples once per week to determine the typical length of C. jejuni infection in crows, which will be essential in predicting transmission rates. Migrant crows will be studied from the time that they arrive at winter roosts--generally October--until the time that they depart Davis for the breeding season--generally March. Throughout that period I will conduct weekly surveys of the nocturnal roost. At each survey I will count the number of individuals at the roost and collect feathers below the roost to screen for isotopic analysis. I will also collect 90 fecal samples each year from the winter roost to quantify seasonal changes in the prevalence of C. jejuni. Additionally, I will collect 15 fecal samples each year from poultry and
livestock housed in facilities on campus close to both the winter crow roost and resident crow nests. Each fecal sample that I collect from crows, poultry, and livestock will be submitted to the UC Davis Vet School Clinical Laboratory Services to screen for C. jejuni following standard procedures in the lab. As part of this screening procedure, samples will also be tested for the presence of Salmonella spp. and E. coli 0157. A subsample of C. jejuni isolates cultured from these samples will be submitted to the 100k Pathogen Genome Project for complete genomic sequencing. Feather and toenail samples will be prepared and submitted to the UC Davis Stable Isotope Facility to quantify both migratory distances and dietary composition. Migratory distance will be determined by comparing the isotopic hydrogen ratio of feathers to published hydrogen/deuterium maps and to reference samples of crow
feathers collected at different latitudes [as in 35]. Dietary composition will be determined by comparing isotopic ratios of carbon, nitrogen, and sulfur in toenail and feather samples [as in 13]. Each year, I will capture 10-20 migrant and resident crows to fit with wireless transmitters, which will be used to quantify local movement distances and landscape use. Specifically, I will use Encounternet tags developed by John Burt at the University of Washington. These tags are ideal for my purposes because once deployed, birds do not need to be recaptured to download location data. Each transmitter will record location at a programmable fixed interval and when the bird comes back into range of a base station (at the roost or nest) all of the stored locations will be downloaded wirelessly. Using these data I will be able to quantify the distance traveled for local foraging trips and the
time spent foraging in different locations such as feed lots, agricultural fields, or dumps.</p>