title: Salmonella infection in a remote, isolated wild pig population.
abstract: Although wild pig populations are known to sometimes be infected by Salmonella, the situation in Australia has received little attention and few population-based, planned studies have been conducted. Understanding the distribution of Salmonella infections within wild pig populations allows the potential hazard posed to co-grazing livestock to be assessed. We sampled a remote and isolated wild pig population in northwestern Australia. Faecal and mesenteric lymph node samples were collected from 651 wild pigs at 93 locations and cultured for Salmonella. The population sampled was typical of wild pig populations in tropical areas of Australia, and sampling occurred approximately halfway through the population's breeding season (38% of the 229 adult females were pregnant and 35% were lactating). Overall, the prevalence of Salmonella infection based on culture of 546 freshly collected faecal samples was 36.3% (95% CI 32.1-40.7%), and based on culture of mesenteric lymph nodes was 11.9% (95% CI, 9.4-15.0%). A total of 39 serovars (139 isolates) were identified--29 in faecal samples and 24 in lymph node samples--however neither Salmonella enterica serovar Typhimurium nor Salmonella Cholerasuis were isolated. There was a significant (p<0.0001) disagreement between faecal and lymph node samples with respect to Salmonella isolation, with isolation more likely from faecal samples. Prevalence differed between age classes, with piglets being less likely to be faecal-positive but more likely to be lymph node positive than adults. The distribution of faecal-positive pigs was spatially structured, with spatial clusters being identified. Study results suggest that this population of wild pigs is highly endemic for Salmonella, and that Salmonella is transmitted from older to younger pigs, perhaps associated with landscape features such as water features. This might have implications for infection of co-grazing livestock within this environment.
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, Australia. Electronic address: michael.ward@sydney.edu.au.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Ward
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, Australia.
authors.forename: Brendan D
authors.initials: BD
authors.lastname: Cowled
authors.affiliation: Industry & Investment NSW, Elizabeth Macarthur Agricultural Institute, Camden, Australia.
authors.forename: Francesca
authors.initials: F
authors.lastname: Galea
authors.affiliation: Office of the Chief Veterinary Officer, Department of Agriculture, Fisheries & Forestry, Canberra, Australia.
authors.forename: M Graeme
authors.initials: MG
authors.lastname: Garner
authors.affiliation: School of Biological, Earth & Environmental Sciences, The University of New South Wales, Sydney, Australia.
authors.forename: Shawn W
authors.initials: SW
authors.lastname: Laffan
authors.affiliation: Industry & Investment NSW, Elizabeth Macarthur Agricultural Institute, Camden, Australia.
authors.forename: Ian
authors.initials: I
authors.lastname: Marsh
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, Australia.
authors.forename: Katherine
authors.initials: K
authors.lastname: Negus
authors.affiliation: Institute for Applied Ecology, University of Canberra, Canberra, Australia.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Sarre
authors.affiliation: Victorian Department of Primary Industries, 1 Spring Street, Melbourne, Victoria, Australia.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Woolnough
mesh_terms: D000818:Animals; D001315:Australia / Q000453:epidemiology; D005243:Feces / Q000382:microbiology; D005260:Female; D007774:Lactation; D008297:Male; D011247:Pregnancy; D015995:Prevalence; D012475:Salmonella / Q000145:classification / Q000302:isolation & purification*; D012481:Salmonella Infections, Animal / Q000453:epidemiology* / Q000382:microbiology*; D034421:Sus scrofa; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000382:microbiology*