title: A PELAGIC OUTBREAK OF AVIAN CHOLERA IN NORTH AMERICAN GULLS: SCAVENGING AS A PRIMARY MECHANISM FOR TRANSMISSION?
abstract: Avian cholera, caused by the bacterium Pasteurella multocida , is an endemic disease globally, often causing annual epizootics in North American wild bird populations with thousands of mortalities. From December 2006 to March 2007, an avian cholera outbreak caused mortality in marine birds off the coast of Atlantic Canada, largely centered 300-400 km off the coast of the island of Newfoundland. Scavenging gulls ( Larus spp.) were the primary species detected; however, mortality was also identified in Black-legged Kittiwakes ( Rissa tridactyla ) and one Common Raven ( Corvus corax ), a nonmarine species. The most common gross necropsy findings in the birds with confirmed avian cholera were acute fibrinous and necrotizing lesions affecting the spleen, air sacs, and pericardium, and nonspecific hepatomegaly and splenomegaly. The etiologic agent, P. multocida serotype 1, was recovered from 77 of 136 carcasses examined, and confirmed or probable avian cholera was diagnosed in 85 cases. Mortality observed in scavenging gull species was disproportionately high relative to their abundance, particularly when compared to nonscavenging species. The presence of feather shafts in the ventricular lumen of the majority of larid carcasses diagnosed with avian cholera suggests scavenging of birds that died from avian cholera as a major mode of transmission. This documentation of an outbreak of avian cholera in a North American pelagic environment affecting primarily scavenging gulls indicates that offshore marine environments may be a component of avian cholera dynamics.
authors.affiliation: 1   Memorial University of Newfoundland, 230 Elizabeth Avenue, St. John's, Newfoundland and Labrador A1B 3X9, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Wille
authors.affiliation: 2   Canadian Wildlife Health Cooperative, Atlantic Region, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada.
authors.forename: Scott
authors.initials: S
authors.lastname: McBurney
authors.affiliation: 3   Wildlife Research Division, Science and Technology Branch, Environment and Climate Change Canada, 6 Bruce Street, Mount Pearl, Newfoundland and Labrador A1N 4T3, Canada.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Robertson
authors.affiliation: 4   Canadian Wildlife Service, Environment and Climate Change Canada, 6 Bruce Street, Mount Pearl, Newfoundland and Labrador A1N 4T3, Canada.
authors.forename: Sabina I
authors.initials: SI
authors.lastname: Wilhelm
authors.affiliation: 5   US Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Blehert
authors.affiliation: 6   Ecotoxicology and Wildlife Health Division, Science & Technology Branch, Environment and Climate Change Canada, 115 Perimeter Road, Saskatoon, Saskatchewan S7N 0X4, Canada.
authors.forename: Catherine
authors.initials: C
authors.lastname: Soos
authors.affiliation: 7   Private Veterinary Practice, St. John's, Newfoundland and Labrador A1K1G8, Canada.
authors.forename: Ron
authors.initials: R
authors.lastname: Dunphy
authors.affiliation: 8   Animal Health Division, Forestry and Agrifoods Agency, PO Box 7400, St. John's, Newfoundland and Labrador A1E 3Y5, Canada.
authors.forename: Hugh
authors.initials: H
authors.lastname: Whitney
mesh_terms: D000818:Animals; D001715:Bird Diseases / Q000453:epidemiology*; D001717:Birds; D002170:Canada; D046091:Charadriiformes / Q000382:microbiology*; D002771:Cholera / Q000453:epidemiology / Q000635:transmission*; D004196:Disease Outbreaks; D005247:Feeding Behavior; D009523:Newfoundland and Labrador / Q000453:epidemiology
keywords: Atlantic Canada; Laridae; Newfoundland; Pasteurella multocida; avian cholera; gulls; pelagic; scavenging