Incidence, distribution, seasonality, and demographic risk factors of Salmonella Enteritidis human infections in Ontario, Canada, 2007–2009

Abstract

BackgroundIn Canada, surveillance systems have highlighted the increasing trend of Salmonella enterica serovar Enteritidis (S. Enteritidis) human infections. Our study objectives were to evaluate the epidemiology of S. Enteritidis infections in Ontario using surveillance data from January 1, 2007 through December 31, 2009.MethodsAnnual age-and-sex-adjusted incidence rates (IRs), annual and mean age-adjusted sex-specific IRs, and mean age-and-sex-adjusted IRs by public health unit (PHU), were calculated for laboratory-confirmed S. Enteritidis cases across Ontario using direct standardization. Multivariable Poisson regression with PHU as a random effect was used to estimate incidence rate ratios (IRRs) of S. Enteritidis infections among years, seasons, age groups, and sexes.ResultsThe annual age-and-sex-adjusted IR per 100,000 person-years was 4.4 [95% CI 4.0-4.7] in 2007, and 5.2 [95% CI 4.8-5.6] in both 2008 and 2009. The annual age-adjusted sex-specific IRs per 100,000 person-years ranged from 4.5 to 5.5 for females and 4.2 to 5.2 for males. The mean age-adjusted sex-specific IR was 5.1 [95% CI 4.8-5.4] for females and 4.8 [95% CI 4.5-5.1] for males. High mean age-and-sex-adjusted IRs (6.001-8.10) were identified in three western PHUs, one northern PHU, and in the City of Toronto. Regression results showed a higher IRR of S. Enteritidis infections in 2009 [IRR = 1.18, 95% CI 1.06-1.32; P = 0.003] and 2008 [IRR = 1.17, 95% CI 1.05-1.31; P = 0.005] compared to 2007. Compared to the fall season, a higher IRR of S. Enteritidis infections was observed in the spring [IRR = 1.14, 95% CI 1.01-1.29; P = 0.040]. Children 0–4 years of age (reference category), followed by children 5–9 years of age [IRR = 0.64, 95% CI 0.52-0.78; P < 0.001] had the highest IRRs. Adults ≥ 60 years of age and 40–49 years of age [IRR = 0.31, 95% CI 0.26-0.37; P < 0.001] had the lowest IRRs.ConclusionsThe study findings suggest that there was an increase in the incidence of S. Enteritidis infections in Ontario from 2007 to 2008–2009, and indicate seasonal, demographic, and regional differences, which warrant further public health attention.

Evaluating area-level spatial clustering of SalmonellaEnteritidis infections and their socioeconomic determinants in the greater Toronto area, Ontario, Canada (2007 – 2009): a retrospective population-based ecological study

“…This finding could be explained by children’s higher susceptibility to salmonellosis, which has been demonstrated by individual-level studies [29,51,52]. Risk factors associated with S. Enteritidis infections in children include international travel [53,54], riding in shopping carts and exposure to raw meat and poultry products [55], person-to-person transmission in daycare centres and in private homes [56], and contact with reptiles [54,57,58] and cats [57].…”

“…The average number of children at home per census family and the average number of persons per census family were highly correlated (rho = 0.94, P < 0.01); average number of children at home was kept for the multivariable model because of its smaller p-value on univariable analysis and because children were identified as having the highest incidence rate of S. Enteritidis infections in Ontario during the study period [29]. …”

Molecular Epidemiology of Nontyphoidal Salmonella in Poultry and Poultry Products in India: Implications for Human Health

“…This can result in diarrhoeal disease, bacteraemia and extraintestinal focal infection in infants such as meningitis, and may also result in more serious complications among the elderly and immunocompromised patients [2]. S. enterica serovar Enteritidis (S. Enteritidis) is a major public health problem globally and is the most common serotype among the NTS in the US [3]. Poultry and their products are the most frequently implicated reservoirs of NTS in the human food chain.…”

Area-level global and local clustering of human Salmonella Enteritidis infection rates in the city of Toronto, Canada, 2007–2009

“…Salmonella Enteritidis infections in humans have typically been associated with consumption of contaminated chicken products [ 6 , 7 ] and eggs [ 8 , 9 ]. However, salmonellosis has recently been linked to other factors, including international travel [ 10 , 11 ], demographic [ 12 , 13 ] and socioeconomic [ 14 , 15 ] characteristics, and animal contact [ 7 , 16 ].…”

“…In 2009, an estimated 2.7 million people lived in the city, accounting for 21 % of Ontario’s total population [ 35 ]. Toronto’s forward sortation areas ( FSAs ; areas signified by the first three characters of the postal code; see Study design and data sources section) have diverse age- and sex-based populations that can affect area-level infection rates, due to sex differences of salmonellosis rates [ 36 , 37 ], and younger and older residents’ higher salmonellosis rates [ 13 , 16 , 38 ]. Standardization of area-level infection rates based on the age and sex distribution of the population has been recommended to overcome this problem [ 39 ].…”