White Paper on Human Illness Caused by Salmonella from All Food and Non-Foods Vectors: Update March 2013

This white paper summarizes all epidemiological data on the relationships between food and non-food vehicles and vectors, and human illnesses caused by Salmonella published in the past 5 years; compares data published since 2008 with that presented in the 2009 white paper for AMIF on vehicles associated with human illness caused by Salmonella; describes surveillance strategies, regulations, and industry initiatives to control this pathogen; and identifies gaps in understanding of food attribution data and surveillance strategies for illness caused by Salmonella.

Funded in part by The Beef Checkoff, the Pork Checkoff and the U.S. Poultry and Egg Association

Download final report

Objectives

The goals and objectives of this project are to:

• Summarize all epidemiological data on the relationships between food and non-food vehicles and vectors, and human illnesses caused by Salmonella published in the past 5 years.
• Compare data published since 2008 with that presented in the 2009 white paper for AMIF on vehicles associated with human illness caused by Salmonella
• Describe surveillance strategies, regulations, and industry initiatives to control this pathogen
• Identify gaps in understanding of food attribution data and surveillance strategies for illness caused by Salmonella

Conclusions

Over the past five years since the previous white paper on Salmonella and its vehicles of infection, there has not been much progress overall in reducing salmonellosis in the U.S. Incidence of salmonellosis was estimated at 14.89 cases/100,000 persons in 2007 and, according to the most recent figures, was 16.4/100,000 in 2012. However salmonellosis incidence in Europe continued to decline from 34.2/100,000 in 2007 to 20.7/100,000 in 2011. This was attributed to programs instituted in 2007 to better control Salmonella in breeding flocks, laying hens, broilers and eggs. National programs have also addressed preharvest controls for swine.

There have been some changes in important serotypes and vehicles of infection. S. Typhimurium has declined as a percentage of serotyped Salmonella isolates from FoodNet sites from 15% in 2007 to 13% in 2012. S. Enteritidis isolates increased from 16 to 18% during this time while S. Newport increased from 10% to 13% of identified Salmonella isolates. (http://www.cdc.gov/foodnet/data/reports.html) In Europe, there has been a significant increase in multi-drug resistant I 4,[5], 12:i:- isolates in the past decade, largely from pigs and pork. This serovar caused 3 large outbreaks in France in the past 5 years with pork and beef  determined to be vehicles. This strain has also spread to many other countries. Antibiotic resistance remains a concern as some Salmonella isolates from humans and animals are resistant to third generation cephalosporins and some have reduced sensitivity to fluoroquinolines.

Meat and eggs continue to be important vehicles for salmonellosis, generally responsible for 40-50% of outbreaks and cases. Some of the outbreak vehicles categorized as “combination foods” or “bakery products” may actually have a meat or egg ingredient that was the original source of contamination.

With regard to produce, fruit has become an important as a vector with some large outbreaks attributed to melons. In contrast to the previous white paper, during the past 5 years, tomatoes/peppers caused a relatively small number of outbreaks, with greens, fruit, and sprouts responsible for about 85% of outbreaks. There is a great deal of current research investigating survival of salmonellae on different plants and possible methods for decontamination while still maintaining the integrity of the leaf, sprout or fruit so that it can be eaten fresh.

There were no reported outbreaks specifically associated with petting zoos or farm visits in the past 5 years, yet the number of cases associated with animal contact tripled. During the past five years, there have been a total of 25 reported outbreaks, affecting 2,244 people that were traced to  chicks, hedgehogs, aquatic frogs, pet turtles, bearded dragons, and a bandicoot.  It appears that organized events (fairs, petting zoos, etc.) have made progress in preventing Salmonella transmission. But individuals purchasing baby poultry and reptiles need more education on hygiene measures necessary to prevent infections, particularly for more vulnerable people. Some breeders and sellers of these animals also need to improve sanitation at their premises to prevent Salmonella infection/carriage by their animals.

In analyzing outbreak data for clues to the epidemiology of salmonellosis, it is wise to remember that CDC estimates that about 95% of Salmonella infections are sporadic – not linked to a recognized outbreak. Nevertheless, CDC believes that over 85% of these cases result from foodborne infection. Many sporadic cases may be due to the same foods that cause outbreaks but we may be missing.