Non-typhoidal human salmonellosis in Rio Grande do Sul, Brazil: A combined source attribution study of microbial subtyping and outbreak data

Waldemir Santiago Neto^a, Vanessa Bielefeldt Leotti^b, Sara Monteiro Pires^c, Tine Hald^d, Luís Gustavo Corbellini^a

Laboratory of Veterinary Epidemiology, Department of Preventive Veterinary Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.

Abstract

Salmonella spp. remains the most significant foodborne pathogen in south Brazil, but its epidemiology tends to change over time. Using official and surrogate data, a microbial subtyping model attributed different Salmonella serovars to laying hens, pigs, broilers, and turkeys from 2005 to 2015 in Rio Grande do Sul (RS). Additional to the subtyping model, three sub-analyses of outbreak data attributed Salmonella spp. in humans to animal and non-animal food. Laying hens/eggs was the most important source of human salmonellosis in RS, with almost 40% (159 cases; 95% credibility interval, 43–247) attribution proportion, followed by pigs reared in Santa Catarina, a neighbor state (34.5%). The Salmonella serovars Enteritidis and Typhimurium were the most common serovars involved. Source-related parameters had wide credibility intervals but showed a higher risk of illness from contaminated eggs than from the other three animal-food sources. Analysis of the outbreak data corroborated the findings and indicated signs of decreasing importance for eggs and increasing importance for pork consumption.

Keywords: Foodborne zoonoses, Outbreaks, Risk assessment, Salmonella source attribution, Surveillance.