ID Consult

Salmonella infections: The source may be as close as your patient’s backyard

Publish date: September 26, 2017

I recently received a group text from a friend voicing her frustration that her neighbor had acquired chickens, and she shared a photo of some roaming freely in the front yard. Naturally, my response was related to the potential infectious disease exposure and infections. Another friend chimed in “fresh eggs, and these are free range chickens. They don’t get sick. ... Many people in my area have chickens.” Unbeknownst to my friends, they had helped me select the ID Consult topic for this month.

Nontyphoidal Salmonella bacteria are associated with a wide spectrum of infections which range from asymptomatic gastrointestinal carriage to bacteremia, meningitis, osteomyelitis, and focal infections. Invasive disease is seen most often in children younger than 5 years of age, persons aged 65 years or older, and individuals with hemoglobinopathies including sickle cell disease and those with immunodeficiencies. Annually, the Centers for Disease Control and Prevention estimates that nontyphoidal salmonellosis is responsible for 1.2 million illnesses, 23,000 hospitalizations, and 450 deaths in the United States. Gastroenteritis is the most common manifestation of the disease and is characterized by abdominal cramps, diarrhea, and fever that develops 12-72 hours after exposure. It is usually self-limited. As previously reported in this column (June, 2017), Salmonella is one of the top two foodborne pathogens in the United States, and most outbreaks have been associated with consumption of contaminated food. But wait, contaminated food is not the only cause of some of our most recent outbreaks.

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Salmonella is a zoonotic bacteria commonly found in the intestinal tract of several animals including poultry (chickens, ducks, geese, and turkeys), reptiles, and amphibians. Humans can acquire infection after both direct and indirect contact with infected animals. Most infected animals are asymptomatic and shed bacteria intermittently. Current U.S. outbreaks involve both pet turtles and poultry. Let’s stay focused on poultry.

Live poultry-associated salmonellosis (LPAS)

LPAS was first reported in the 1950s. More recent epidemiologic data was published by C. Basler et al. (Emerging Infect Dis. 2016;22[10]:1705-11). LPAS was defined as two or more culture confirmed human Salmonella infections with a combination of epidemiologic, laboratory, or traceback evidence linking illnesses to contact with live poultry. From 1990 to 2014, a total of 53 LPAS outbreaks in the United States were documented and associated with 2,630 illnesses, 387 hospitalizations, and 5 deaths. The median outbreak size involved 26 cases (range, 4-363) and 77% (41 of 53) were multistate. The median age of the patients was 9 years (range, less than 1 to 92 years), and 31% were aged 5 years or younger. Exposure to chicks and ducklings was reported in 85% and 38%, respectively. High-risk practices included keeping poultry inside of the home (46%), snuggling baby birds (49%), and kissing baby birds (13%). The median time from purchase of poultry to onset of illness was 17 days (range, 1-672), and 66% reported onset of illness less than 30 days after purchase. Almost 52% reported owning poultry for less than 1 year.

The number of outbreaks continued to increase. From 1990 to 2005, there were a total of 17 outbreaks, compared with 36 between 2006 and 2014. Historically, outbreaks occurred in children around Easter when brightly colored dyed chicks were purchased. In the above review, 80% of outbreaks began in February, March, or April with an average duration of 4.9 months (range, 1-12).

Salmonella isolates

Dr. Bonnie M. Word

Serotypes traditionally associated with foodborne outbreaks are not usually isolated in LPAS outbreaks. Most chicks are acquired from small mail order hatcheries that house multiple species, and the potential for comingling exists not only of birds but their pathogens. In contrast, commercial hatcheries typically are closed facilities with one breed. It is thought that this is one reason for multiple serotypes associated with backyard flock associated salmonellosis. In the 1990-2014 review, while S. montivideo was the most common serotype isolated (36%), 5 other serotypes also were reported.

Backyard flocks and LPAS

More recently outbreaks have been associated with backyard flocks occurring year round and affecting both adults and children in contrast to seasonal peaks. The first multistate backyard flock outbreak was documented in 2007. Currently, the CDC is investigating 10 separate multistate outbreaks that began on Jan. 4, 2017. It involves 48 states, 961 infected individuals, 215 hospitalizations, and 1 death. At least 5 salmonella serotypes have been isolated.

What about the hatcheries?

It’s estimated that 50 million live poultry are sold annually. Birds are shipped within 24 hours after hatching via the U.S. Postal Service in boxes containing up to 100 chicks. Delivery occurs within 72 hours of hatching. Approximately 20 mail order hatcheries provide the majority of poultry sold to the general public. The National Poultry Improvement Plan (NPIP) is a voluntary state and federal testing and certification program whose goal is to eliminate poultry disease from breeder flocks to prevent egg-transmitted and hatchery-disseminated diseases. All hatcheries may participate. They also may participate in the voluntary Salmonella monitoring program. Note participation is not mandatory.

Preventing future outbreaks: patient/parental education is mandatory

1. Make sure your parents know about the association of Salmonella and live poultry. Reinforce these are farm animals, not pets. Purchase birds from hatcheries that participate in NPIP and the Salmonella monitoring programs.

2. Chicks, ducklings, or other live poultry should not be taken to schools, day care facilities, or nursing homes. Poultry should not be allowed in the home or in areas where food or drink is being prepared or consumed.

3. Poultry should not be snuggled, kissed, or allowed to touch one’s mouth. Hand washing with soap and water should occur after touching live poultry or any object touched in areas where they live or roam.

4. Contact with live poultry should be avoided in those at risk for developing serious infections including persons aged 5 years or younger, 65 years or older, immunocompromised individuals, and those with hemoglobinopathies.

5. All equipment used to care for live birds should be washed outdoors. Owners should have designated shoes when caring for poultry which should never be worn inside the home.

Hopefully, the next time you see a patient with fever and diarrhea you will recall this topic and ask about their contact with live poultry.

Additional resources to facilitate discussions can be found at www.cdc.gov/salmonella.

Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She said she had no relevant financial disclosures. Email her at pdnews@frontlinemedcom.com.