Multistate outbreaks of salmonellosis linked to contact with backyard poultry-United States, 2015-2022

Abstract

Aims: Contact with backyard poultry (i.e., privately-owned, non-commercial poultry) was first associated with a multistate outbreak of salmonellosis in 1955. In recent years, backyard poultry-associated salmonellosis outbreaks have caused more illnesses in the United States than salmonellosis outbreaks linked to any other type of animal. Here, we describe the epidemiology of outbreaks from 2015-2022 to inform prevention efforts.

Methods and results: During 2015-2022, there were 88 multistate backyard poultry-associated salmonellosis outbreaks and 7866 outbreak-associated illnesses caused by 21 different Salmonella serotypes. Salmonella Enteritidis accounted for the most outbreaks (n = 21) and illnesses (n = 2400) of any serotype. Twenty-four percent (1840/7727) of patients with available information were <5 years of age. In total, 30% (1710/5644) of patients were hospitalized, and nine deaths were attributed to Salmonella infection. Throughout this period, patients reported behaviours that have a higher risk of Salmonella transmission, including kissing or snuggling poultry or allowing poultry inside their home.

Conclusions: Despite ongoing efforts to reduce the burden of salmonellosis associated with backyard poultry, outbreak-associated illnesses have nearly tripled and hospitalizations more than quadrupled compared with those in 1990-2014. Because this public health problem is largely preventable, government officials, human and veterinary healthcare providers, hatcheries, and retailers might improve the prevention of illnesses by widely disseminating health and safety recommendations to the public and by continuing to develop and implement prevention measures to reduce zoonotic transmission of Salmonella by backyard poultry.

Keywords: salmonella; backyard poultry; one health; outbreak; zoonotic.

FIGURE 1

Number of backyard poultry (BYP)-associated salmonellosis outbreaks and outbreak-associated illnesses by year of the first illness onset–United States, 2015–2022. PFGE, Pulsed-field gel electrophoresis; WGS, whole genome sequencing; *Kubota et al. (2019); ^#WHO (2020); ^§Nichols et al. (2021).

FIGURE 2

Cumulative number of backyard poultry-associated Salmonella illnesses by month of illness onset—United States, 2015–2022. The number of cases identified each month in a given year is indicated by the area shaded by each different colour, with the overall curve demonstrating the cumulative number of cases during 2015–2022 for each month. When patient illness onset date was not reported, an estimated onset date was determined as 3 days before the reported isolation date.

FIGURE 3

Number of backyard poultry-associated salmonellosis outbreak patients by state or territory of residence–United States, 2015–2022. Thresholds for categorizing jurisdictions were determined based on equivalent quantiles for illness count.

FIGURE 4

Number of backyard poultry-associated Salmonella outbreak patients, proportion of hospitalization, and proportion with bloodstream infection by age group—United States, 2015–2022.

FIGURE 5

(a) Proportion of patients with available information reporting contact* with backyard poultry (BYP)—United States, 2015–2022. Overall, 3452 of 4979 (69%) people with available information reported contact with BYP. *Contact was defined as directly interacting with BYP or the environment where they live and roam, consumption of eggs or meat obtained from BYP, or residing with a household member that has direct interaction with BYP. (b) Proportion of patients reporting they practiced specific biosecurity or husbandry behaviours —United States, 2015–2022. Of patients reporting contact with BYP, some provided information on the specific behaviours performed when interacting with poultry. Patients could designate that they performed more than one behaviour in the questionnaire.

FIGURE 5

(a) Proportion of patients with available information reporting contact* with backyard poultry (BYP)—United States, 2015–2022. Overall, 3452 of 4979 (69%) people with available information reported contact with BYP. *Contact was defined as directly interacting with BYP or the environment where they live and roam, consumption of eggs or meat obtained from BYP, or residing with a household member that has direct interaction with BYP. (b) Proportion of patients reporting they practiced specific biosecurity or husbandry behaviours —United States, 2015–2022. Of patients reporting contact with BYP, some provided information on the specific behaviours performed when interacting with poultry. Patients could designate that they performed more than one behaviour in the questionnaire.