Prevalence and risk factors for Listeria monocytogenes contamination in Iranian broiler flocks

Background: Microbiological safety and quality of broiler meat are equally important to producers, retailers and consumers. Listeriosis is one of the important emerging bacterial zoonotic infections worldwide. Among the different species of the genus Listeria, Listeria monocytogenes is known to cause listeriosis in humans and animals, Listeria monocytogenes is a causative agent of listeriosis, a severe foodborne disease associated with a high case fatality rate. Several food products have been linked with epidemics and sporadic cases of listeriosis, including meat, dairy, vegetable and fish products. To prevent product contamination with L. monocytogenes, it is essential to understand listerial contamination routes in the food processing industry. There are few published data concerning risk factors for L. monocytogenes contamination in poultry flocks. Information on the occurrence and distribution of Listeria monocytogenes and its risk factors is very limited both in the veterinary and public health sectors in Iran, The aim of this study was to investigate the prevalence and potential risk factors for Listeria monocytogenes contamination in Iranian broiler flocks. Materials, Methods & Results: In this study, farms were separated in two different zones (foothill area in west with less humidity compared with coastal area in north with high humidity). The prevalence of listeriosis in coastal area was higher (52%) than foothill (48%) but not significantly (P = 0.642). A total of 1470 cloacal swab samples were randomly collected from 490 broiler flocks on the slaughter line of 4 abattoirs (2 abattoirs in north and 2 abattoirs in west) of Iran from March 2009 to December 2010. The PCR method with published primers targeting the hemolysin (lily) gene was used to detection of Listeria in cloacal swab samples. To evaluate potential risk factors, each flock was visited once. A questionnaire was completed for each flock. According to the results, the prevalence of L. monocytogenes in north was relatively higher (52%) than west (48%), however not significantly different. In addition, this work presented the relationships between L. monocytogenes and some risk factors. Discussion: This is the first time that an epidemiological study of risk factors for L. monocytogenes contamination in broiler flocks was carried out in Iran. L. monocytogenes was isolated in 44 of 490 flocks; yielding an estimated prevalence of 8.97%. The prevalence of I,. monocytogenes in coastal area was relatively higher (52%) than foothill area (48%). Higher prevalence of Listeria was observed in flocks that used private water sources in comparison with flock that used official approved water, but it was not significant. When pets were present on the flocks site the risk of L. monocytogenes contamination was increased. Disinfection of water and feed by commercial disinfectants was found to decrease the risk of contamination. No relation between a special strain with L. monocytogenes status could be found. In conclusion, this study has demonstrated the presence and distribution of L. monocytogenes in Iranian broiler flocks. The study also showed some potential risk factors that influence on prevalence of listeria in broiler flocks. It was proved that some relationships occur between L. monocytogenes prevalence and the flock's litter quality.