The role of litter beetles as potential reservoir for Salmonella enterica and thermophilic Campylobacter spp. between broiler flocks

We evaluated the role of beetles infesting broiler chicken rearing facilities as potential reservoirs for Salmonella enterica infections between successive broiler flocks. In addition, their role as potential reservoirs for thermophilic Campylobacter spp. was also investigated. Fourteen broiler houses located at 11 different farms were included in the study. The houses were nonrandomly selected on the basis of their salmonella status; nine were persistently contaminated with salmonella whereas five were salmonella negative. For each broiler house, two consecutive broiler flocks (i.e., 28 broiler flocks in all) as well as beetles collected during both rotations of production and in the empty period (after cleaning and disinfection) between these flocks were monitored for the presence of salmonella. Examinations for the presence of campylobacter in the same sample materials were also performed. Beetles sampled during production were positive for salmonella or campylobacter or both. Furthermore, in one house, the occurrence of Salmonella indiana in two consecutive broiler flocks coincided with the presence of S. indiana-contaminated beetles in the empty period between the flocks. The genotype of the identified S. indiana was in all cases identical when analyzed by pulsed-field gel electrophoresis. However, our results also suggest that salmonella from beetles may not always be transmitted to the chickens and that beetles living in contaminated houses can remain free of infection. All cases of campylobacter-positive beetle samples were detected in connection with a positive chicken flock; in no case was campylobacter isolated from beetles taken from the empty period between rotations. Four beetle species were identified during this study. Alphitobius diaperinus was found in all houses and was relatively abundant in most. Typhaea stercorea and Ahasverus advena were found in eight and nine houses, respectively, and were abundant in most of these. Carcinops pumilio was found in small numbers in eight houses. No other insect species was identified. These investigations have shown that beetles in broiler houses infrequently are positive for salmonella. However, transmission of S. indiana between two consecutive broiler flocks can coincide with the presence of salmonella-contaminated beetles in the empty period, indicating that the beetles were the reservoir of S. indiana between the two flocks. Concerning campylobacter, the results suggest that beetles do not play a significant role as a reservoir of campylobacter from one rotation to the next.