Researchers have suggested that chicken meat is an important source of infections from a type of Salmonella in Israel.
Salmonella surveillance in humans in Israel relies on reporting of cases to the national reference laboratory of the Ministry of Health. In the poultry sector, the Egg and Poultry Board and Israeli Veterinary Services conduct a surveillance program in breeding flocks and layer hen farms.
According to a study published in the journal Emerging Infectious Diseases, since 2018, Salmonella Muenchen has emerged as a dominant serotype in Israel. It accounted for 2 percent (101 of 5,072) of Salmonella cases in 2017 and 35.4 percent (1,124 of 3,171) in 2022.
A similar trend was found in Salmonella isolates from poultry: from 3.8 percent (63 of 1,672) of the animal and poultry sources in 2017 to 23.6 percent (202 of 857) in 2021, and from 4.9 percent (12 of 245) of the food industry and ready-to-eat products (mostly from poultry slaughterhouses) in 2017, to 20 percent (43 of 215) in 2021.
Whole genome sequencing compared 109 Salmonella Muenchen isolates from poultry, food, and humans in Israel from 2020 to 2023 to 125 global isolates.
Salmonella Muenchen analysis
Scientists used a collection of Salmonella Muenchen isolates from broiler flocks in Israel to determine the genetic relatedness among isolates from broilers, humans, and other poultry sources and the presence of antimicrobial resistance (AMR) genes.
They also looked at the prevalence in commercial broiler flocks and the potential transmission routes between different growth stages to observe whether vertical or horizontal transmission plays a major role in bacterial spread.
The team found genetic similarity in isolates from poultry and chicken meat and from humans. The emerging multidrug-resistant Salmonella Muenchen strain in Israel also closely resembles isolates from other countries.
“Our findings strongly suggest that poultry broilers are an important source of human infections caused by Salmonella Muenchen in Israel. The high genetic similarity between strains collected from broiler flocks and layer flocks may indicate that eggs serve as an additional source for human infections, however their role as a route of transmission to humans needs to be further explored,” said researchers.
Route of transmission
Salmonella Muenchen prevalence in commercial broiler flocks was 61.5 percent. Strains could not be traced to breeder flocks, but on-farm persistence existed.
Vaccinating breeder flocks can be effective if transmission is mainly vertical from the parent to production flocks. However, Salmonella Muenchen may be transmitted horizontally to broiler flocks after hatching.
Researchers said mandatory vaccination of breeder flocks against Salmonella Muenchen from March 2024 may result in a limited reduction of the pathogen, because Salmonella persists in the farm soil or barn litter. Other measures include increasing biosecurity, the use of probiotics and more surveillance and control along the production chain.
Salmonella Muenchen strains were genetically similar to strains collected in the UK, South Africa, and the United States. This suggests travel-associated transmission or a common origin and global dissemination of contaminated poultry breeding stock, said scientists.
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