Why is Salmonella making more people sick? (Poultry Welfare)

(Editor’s note: Dr. Shawna L. Weimer is an Extension Assistant Professor at the University of Maryland.)

Salmonella is a significant cause of foodborne illness in people around the world.
Salmonella is a zoonotic bacteria, which is a bacteria that can be transmitted and cause disease in both people and animal hosts.
Salmonella can survive in many types of hosts and environmental conditions.
This makes controlling the spread of Salmonella challenging, especially the types that are resistant to antibiotics.
According to the CDC, Salmonella infects about 1.35 million people in the United States every year.
Salmonella can contaminate many types of food, including eggs and meat form poultry.
In 2011, the USDA recalled 36 million pounds of ground turkey linked to Salmonella and remains one of the largest meat recalls in U.S. history.
There are more than 2,300 types of Salmonella and at least 100 of them can live in people and animals.
Salmonella enteritidis and typhimurium are the most common in the United States and are responsible for about half of all pathogenic foodborne illnesses.
Infection typically results in fever, cramping, and diarrhea, but can cause severe complications in people with weak immune systems.
Contact with live animals can also transmit Salmonella and backyard poultry are an increasing source of Salmonella outbreaks.
The figure to the right shows the reported cases and hospitalizations from Salmonella infection in people who were in contact with live poultry from 2011-19 in the U.S. and that these outbreaks have generally been increasing.
Why are people who handle live poultry becoming sick from Salmonella more now more than ever?
Two words: Backyard poultry.
In fact, the CDC is still currently investigating the largest ever-recorded number of people to become sick from Salmonella after contact with live poultry. Since the outbreak began this past January, over 1,600 people have reported illness after handling live poultry from multiple sources in all 50 states. The CDC has directly linked this outbreak to the backyard poultry community.
Raising small backyard flocks is a trend that continues to grow in popularity. The coronavirus pandemic has led to an explosion of public interest because people are stuck home and looking for new pets and hobbies. So much so that many mail-order hatcheries are sold out of chicks and hatching eggs for the next several months.
So, how are more people getting sick from backyard poultry?
One word: Biosecurity.
Basically, some people are not properly washing their hands after caring for or handling backyard poultry. Contaminated hands are not the only way people can infect themselves with Salmonella after handling live poultry and certain “practices” have led CDC to post reminders for people not to “snuggle, kiss, or hold live poultry close to your face” for the more affectionate backyard poultry enthusiasts.
Salmonella lives in the intestinal tract of the host and spreads to new hosts via the oral-fecal route. An infected animal will spread it in its droppings, which contaminates the animal, its surrounding environment, and anything else it touches.
Most types of Salmonella are commensal or non-harmful resident bacteria in the gastrointestinal tract of poultry; so Salmonella is usually undetected because it rarely causes signs of clinical illness in most poultry species.
Poultry can transmit Salmonella throughout their lifecycle. If Salmonella is present in the mother hen’s reproductive tract, it can deposit into the egg yolk released from the ovary during egg lay. Salmonella can also be deposited on the eggshell during lay from contact with fecal matter either from the vent of the hen or by contact with fecal material in the environment. While washing eggs is a common and effective sanitation practice, the chemicals used in the detergents can damage the cuticle (protective outer layer of the eggshell). This can increase opportunities for contamination because eggshells are actually porous, so bacteria on the surface of the eggshell can enter into the egg albumen.
Salmonella spreads via interactions between the bird, the bacteria, management practices, and the environment.
The table below provides a summary of the bird (host), bacteria (agent), and management practices (environment) that can spread Salmonella in poultry.
(Note: Publications associated with this article are: Snyder, A. and S. Weimer. Salmonella in Backyard Poultry. Poultry Extension Collaborative (PEC). 6: September 2020 Newsletter; and Snyder, A. and S. Weimer. 2020. Understanding Salmonella; Its presence and control in live poultry. University of Maryland Extension Bulletin. FS-1137.)