Prevalence and Pathogenic Potential of Campylobacter Isolates from Free-Living, Human-Commensal American Crows

Abstract

Recent studies have suggested a potential role for wild birds in zoonotic transmission of Campylobacter jejuni, the leading cause of gastroenteritis in humans worldwide. In this study, we detected Campylobacter spp. in 66.9% (85/127) of free-ranging American crows (Corvus brachyrhyncos) sampled in the Sacramento Valley of California in 2012 and 2013. Biochemical testing and sequence analysis of 16S rRNA revealed that 93% of isolates (n ‫؍‬ 70) were C. jejuni, with cytolethal distending toxin (CDT) and flagellin A genes detected by PCR in 20% and 46% of the C. jejuni isolates (n ‫؍‬ 59), respectively. The high prevalence of C. jejuni, coupled with the occurrence of known virulence markers CDT and flagellin A, demonstrates that crows shed Campylobacter spp. in their feces that are potentially pathogenic to humans. Crows are abundant in urban, suburban, and agricultural settings, and thus further study to determine their role in zoonotic transmission of Campylobacter will inform public health.

Genomic Comparison of Campylobacter spp. and Their Potential for Zoonotic Transmission between Birds, Primates, and Livestock

“…C. jejuni isolates from these birds have been implicated in human disease (11,16,17). Other studies indicate that some Campylobacter isolates found in wild birds may not be pathogenic to humans (14,(18)(19)(20)(21)(22)(23). These conflicting reports indicate that studies using higher resolution molecular methods …”

“…As such, American crows have the potential to transfer pathogens from human waste or infected animal manure to human food, waterways, and livestock, potentially acting as both a reservoir and a transport host (22). Previous studies indicate that Campylobacter prevalence is high in crow species around the world.…”

Campylobacter in the environment: A major threat to public health

“…The intestinal carriage of campylobacters in wild birds (e.g. crows, ducks, geese, pigeons, magpies, house sparrows, and various other species), have been frequently isolated from the feces of apparently healthy birds without obvious clinical manifestations associated with Campylobacter infections [5,[7][8][9][10][11]. This observation suggests that Campylobacter species inhabiting the guts of wild birds are regarded as commensals; an observation that might be related to the body temperature of the birds (42 °C ) being the optimal growth temperature for thermotolerant campylobacters [5,7].…”

“…Preston agar; Modified charcoal, cefoperazone and deoxycholate agar [mCCDA]) plates [64,65], as high number of target organism are present. Similarly, direct plating onto selective media has been frequently used for the detection of campylobacters in avian/animal fecal samples and/or cecal contents [9,11,66]. Although direct plating of fecal materials on Campylobacter selective agar plates has been successfully employed in detecting the organism in human and birds/animal fecal samples, it might guarantee a high recovery rates of campylobacters particularly from avian and animal origin or might result in failure to detect the organism in feces [67,68], therefore, incubating fecal samples in selective enrichment broth prior to selective plating potentially increase the detection of campylobacters [5].…”

Determining the pathogenicity of bacteria present in wetland waters and crow feces in Bothell

“…Determining the pathogenicity of bacteria present in wetland waters and crow feces in Bothell studies on Campylobacter 14 . Amplification was done in a 25 µL reaction mixture that included: 12.5 µL of Jumpstart™ REDTaq ® ReadyMix™ (SIG-MA); 2 µL of flaA primers containing 0.2 µM of each primer; 3 µL of DNA extract; and all were dilut-ed with nuclease-free water to a final volume of 25 µL.…”