Tracing a Salmonella Outbreak to a Mail-Order Poultry Hatchery, Michigan, 2018

Since 2000, contact with live poultry has been linked to 70 Salmonella outbreaks and 4,794 illnesses in the United States. Yet investigators rarely sample the hatcheries that supply backyard flocks, so the source is seldom confirmed. In 2018, in Michigan, they did.

The outbreak

On June 12, 2018, the Michigan Department of Health and Human Services asked CDC for help. Tracing had linked 24 cases of Salmonella Enteritidis to live poultry from a mail-order hatchery — "hatchery A" — that sells young birds to backyard flock owners directly and through feed stores. Whole-genome sequencing showed the patients' bacteria were closely related to samples taken from hatchery A's shipping containers at stores in several states.

Sampling the hatchery

On June 19, a team of two sample collectors and two recorders, briefed that morning and following best practices for biosecurity, sampled hatchery A. They focused on four areas:

1. Hatching: liners inside egg hatchers and incubators, and their inside and outside surfaces;
2. Pre-shipping: work surfaces;
3. Breeding flock: laying boxes, bedding, and food and water containers;
4. Trucks carrying live birds and eggs on and off site.

They used three kinds of swabs and collected chick-box liners and bedding; even the shoe covers they wore inside were tested. Samples reached the state laboratory within six hours and were cultured and characterized by PCR, pulsed-field gel electrophoresis and whole-genome sequencing.

What they found

Salmonella turned up in 4 of the 45 samples (9 percent), and the investigation confirmed that the outbreak strain was present at hatchery A.

The authors recommend that environmental sampling at poultry hatcheries be part of outbreak responses, and that the priority areas used here guide systematic sampling for Salmonella in hatcheries.

Sources

Based on "Notes from the Field: Environmental Investigation of a Multistate Salmonellosis Outbreak Linked to Live Backyard Poultry from a Mail-Order Hatchery — Michigan, 2018," by Margaret C. Hardy, Scott A. Robertson and colleagues (CDC; Michigan Department of Health and Human Services; Ottawa County Department of Public Health; Colorado State University), Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention; a work of the United States government in the public domain.