Analysis of Feces Samples Collected from a Wild-Bird Garden Feeding Station in Scotland for the Presence of Verocytotoxin-Producing Escherichia coli O157

Abstract

Composite wild bird feces collected at regular intervals from a garden feeding station in southwest Scotland over a 3-year period were examined for verocytotoxin-producing Escherichia coli O157. One sample was positive for Escherichia coli O157. The isolate belonged to phage type 21/28 and possessed vtx 2 , eaeA, and enterohemorrhagic E. coli hlyA genes.Verocytotoxin-producing Escherichia coli (VTEC) O157 is particularly prevalent in Scotland, where the majority of infections are sporadic (13). VTEC strains are characterized by the production of one or both of two toxins, Shiga toxin 1 or Shiga toxin 2, which are encoded by the genes vtx 1 and vtx 2 . A subset of VTEC, designated enterohemorrhagic E. coli (EHEC), carries the additional virulence genes eae, associated with attachment and effacement of enterocytes in vitro, and hly, which encodes enterohemolysin (3).Direct or indirect contact with animals and their products has been demonstrated to be important in transmission of VTEC O157 in human infections (5,7,10,14). Cattle are regarded as the main animal reservoir for VTEC O157 (9,15,24), but the organism has also been recovered from a range of other domesticated animals, including sheep, goats, pigs, horses, and dogs (23); free-ranging deer (19,20); zoo animals (4); rodents (2); and flies (2, 9). Among avian species, VTEC O157 has been reported to be present in broiler chickens (8), turkeys (11), and wild birds, including seagulls (25) and geese (22). Garden birds represent a group with which the Scottish public has increasing contact, but little is known about the potential impacts on human health that such interactions may cause. This paper is the first longitudinal study of the presence of VTEC O157 in the feces of wild birds visiting a garden feeding station in Scotland.Two hundred thirty-one composite samples of wild-bird feces were collected over a 36-month period from a garden feeding station in a rural setting in Dumfries and Galloway, Scotland, as previously described (18). Specimens were collected twice weekly and the numbers and species of birds visiting the site recorded (18). The table (60 by 40 cm and 135 cm above the ground) was scraped clean daily to remove uneaten food, husks, and feces and was disinfected only if it was heavily soiled (18). Samples were transported to the laboratory and portions removed for Salmonella and E. coli O86 testing (18). The remainder was immediately frozen at Ϫ20°C and subsequently transferred to Ϫ80°C. Samples for testing were rapidly thawed in a water bath at 50°C before being tested for E. coli O157. Previous trials using spiked feces had demonstrated that E. coli O157 numbers were maintained when subjected to this rapid thaw process following freezing at Ϫ80°C (unpublished findings).One-gram fecal samples were tested using a standard immunomagnetic separation methodology (6) followed by plating on sorbitol MacConkey agar (Oxoid, Basingstoke, United Kingdom) containing cefixime and tellurite (Mast Diagnostics, Bootle, United Kingdom) (CT-SMAC). Non-sorbitol-f...

Animal Reservoirs of Shiga Toxin-ProducingEscherichia coli

“…Similar results were also obtained in England where 1.5% of wild bird samples had the stx1 gene, 7.9% the stx2 gene, and 4.9% the eae gene (109). Similarly, low prevalence rates of STEC O157:H7 in the starling (Sturnus vulgaris) population in Ohio and other wild bird species in Scotland and Japan have also been reported (110)(111)(112). Though the STEC prevalence levels are reportedly low, the potential of these birds to transmit STEC to other birds and contaminate the environment is of serious risk.…”

“…Pigeons and finches have been identified as two species that can potentially serve as a source of human infection since these birds inhabit buildings, parks, and other recreational areas and are in close association with the human population (111,116). Fecal depositions by these birds in areas frequented by humans increase the exposure potential to STEC.…”

Assessment of Shiga Toxin-ProducingEscherichia coliIsolates from Wildlife Meat as Potential Pathogens for Humans

“…STEC strains were shown to be spread to different animal species on farms (4,12,37,48), and transmission of STEC strains from wildlife to farm animals and vice versa may occur through fecal pollution of farmland (43). Migrating birds serve as vectors of transmission of STEC strains over long distances (17,37,47). Taken together, these data indicate that there is a flow of STEC strains between the wildlife reservoir and the domestic animal reservoir.…”

“…Deer have been suggested to play a role as transmitters of EHEC O157 strains to cattle by fecal contamination of farmland (43). Wild migrating birds have been identified as STEC excretors and participate in the spread of EHEC O157 and other STEC strains over long distances (17,37,47). To date, only a few reports have been published on the contamination of raw game meat and other game products with STEC strains.…”

Prevalence and Characteristics of eae - and stx -Positive Strains of Escherichia coli from Wild Birds in the Immediate Environment of Tokyo Bay

“…In one study of wild birds in southwest Scotland, only one out of 231 composite fecal samples from wild birds was stx positive (6). Similarly, a study of cloacal samples from wild birds at cattle or pig farms reported that four out of 244 samples were found to be stx positive by PCR analysis and that the frequency of STEC-positive wild birds was low, at only 1.6% (18).…”