Two agencies in the Netherlands have looked at the prevalence of seleced pathogens in chickens for meat production.

The study reaffirmed Campylobacter, Salmonella and extended-spectrum beta-lactamase (ESBL)-producing bacteria on broiler farms can be transmitted to humans through meat consumption and direct or indirect contact.

In 2018 and 2019 the National Institute for Public Health and the Environment (RIVM) and Netherlands Food and Consumer Product Safety Authority (NVWA) investigated how often these pathogens occurred in broilers. The study involved broilers at 198 of the more than 600 farms in the country as well as 132 livestock farmers, family members and employees from 81 companies.

Meat can become contaminated in the slaughterhouse if it comes into direct contact with manure. People can prevent infection by eating thoroughly cooked chicken. It is also important to prevent other food coming into contact with raw poultry and meat, advised RIVM and NVWA.

ESBL and Campylobacter mostly found
Manure samples were collected at all farms and analyzed for Campylobacter, ESBL-producing E. coli, Listeria monocytogenes and Shiga toxin-producing E. coli (STEC). Dust samples were examined for Methicillin-resistant Staphylococcus aureus (MRSA). Results for Salmonella came from regular monitoring of sampled flocks. Fecal samples from people were tested for Campylobacter, ESBL-producing E. coli and Salmonella while nasal swabs were examined for MRSA.

ESBL-producing bacteria were found in broilers on 36 percent of the farms. For livestock farmers and family members, these bacteria were found in 7 percent of participants. This is comparable to the percentage in the general Dutch population.

Campylobacter was found on almost a third of broiler farms. This is comparable to numbers from surveillance between 1999 and 2002. It was also found in two human participants.

Despite hygiene measures such as using company overshoes or work clothing, showering before entering broiler houses and cleaning and disinfection, the prevalence of Campylobacter in live poultry appears to be difficult to reduce, according to the report.

The model approach used showed nine variables significantly associated with the occurrence of Campylobacter including season, age of broilers at the time of sampling, number of stables on the farm, and stocking density.

Salmonella, STEC and Listeria results
Salmonella surveillance is carried out on all broiler farms as per European legislation. It was reported in broilers from 11 percent of the farms. Salmonella was also found in one person.

The prevalence of Salmonella appears to be higher than the European average of 2018. The emerging serotype Salmonella Infantis was found in almost half of the cases but Typhimurium and Enteritidis were not detected. Salmonella Paratyphi B variant Java was another common serotype.

Six significant risk factors were found for the presence of Salmonella including washing hands after entering the barn, no contact with other poultry in the past 12 hours and pets present on the farm. This shows the need to follow strict biosecurity measures to control Salmonella, according to the report.

STEC and Listeria were found on very few broiler farms, meaning the sites are likely of less importance in the spread of Listeria and STEC and pose a limited risk. They were detected on 1 percent for Listeria, or less for STEC, of investigated farms.

STEC was isolated from two manure samples in one of the sampled barns. The isolate found in both samples was serotype O24: H18, positive for the virulence gene stx2 but negative for the gene eae.

In the surveillance, Listeria monocytogenes was found at two farms. Prevalence of Listeria in broilers in the Netherlands had not been investigated before.

MRSA was not found in any of the 190 broiler farms investigated but concerns were raised about the method not being sensitive enough. It was detected in the nasal swab of four people.