The Efficacy of the Natural Plant Extracts, Thymol and Carvacrol Against Campylobacter Colonization in Broiler Chickens

Campylobacter is one of the major causes of foodborne bacterial gastroenteritis in the United States. Case control studies have demonstrated that the majority of human illnesses due to Campylobacter spp. were associated with either consumption or handling of raw or under-cooked chicken. Campylobacter is highly prevalent in poultry flocks worldwide and it has been reported that more than 70% of poultry flocks in the U.S. are positive for Campylobacter contamination. Thus, a reduction of this pathogen in chicken would greatly reduce the risk of human campylobacteriosis. Unfortunately, most treatments fail to produce consistent reductions in Campylobacter colonization in chickens. The efficacy of natural plant extracts, such as thymol and carvacrol, have been tested against pathogens like Salmonella, E. coli, Shigella and Listeria. However, their ability to reduce Campylobacter in chickens has not been reported. The objective of this study was to determine the efficacy of different concentrations and combinations of thymol and carvacrol in feed to reduce cecal Campylobacter counts in broilers. In Trial 1, birds (n=10 chicks/dose) were fed 0%, 0.25%, 0.5%, 1% or 2% thymol or carvacrol. In Trial 2, the doses were repeated with the addition of lower doses of both compounds (0.0625% or 0.125%). In Trials 3 and 4, the doses of 0.125%, 0.25% or 0.5% of thymol or carvacrol and combinations of these doses were tested. Birds were dosed during the entire 10 day study. At day 3, all birds were orally challenged with a five strain mixture of wild type of C. jejuni strains and cecal samples were collected for Campylobacter enumeration at day 10. Campylobacter counts were reduced for the 0.25% thymol (Trial 1), 1% carvacrol or 2% thymol (Trial 2) or a combination of both thymol and carvacrol at 0.5% (Trial 4) in this study. These results indicate that supplementation of these compounds in chicken feed may potentially reduce Campylobacter colonization in chickens but additional research is required to develop treatment regimes providing consistent efficacy.