Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2011
Publication Date: April 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/57313
Citation: Zheng, L., Crippen, T.L., Sheffield, C.L., Poole, T.L., Ziniu, Y., Tomberlin, J. 2012. Evaluation of Salmonella movement through the gut of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae). Vector-Borne and Zoonotic Diseases. 12:287-292. Interpretive Summary: Salmonellosis in humans is largely contracted by eating food contaminated with Salmonella. These bacteria can pass through the food chain from production facilities to households or food-service operations. The resulting food-borne disease is a public health burden and represents a significant cost to society, estimated by the World Health Organization to be at least $3 billion annually. Poultry producers are very concerned about maintaining healthy birds and limiting the presence of disease causing bacteria on retail chicken products. The movement of Salmonella within a poultry facility is not yet fully understood and many elements are likely at play. Unwanted insects are a common occurrence in facilities where poultry are raised and one of the most plentiful insects is the lesser mealworm (Darkling Beetle). These insects can harbor disease-causing bacteria internally, as well as externally, making them participants in the spreading of pathogens into the environment. Little is known about the uptake and subsequent dispersal potential of bacteria by this beetle. This study determined the minimal gut transit time of Salmonella. These data will be useful in determining if Salmonella can colonize the alimentary canal of these insects and in determining the mechanism of pathogen dispersal by this insect. There are many things to consider to minimize pathogen load within a poultry facility. All reservoirs which harbor pathogenic agents and their manner of passing on pathogens must be identified and characterized so that control measures can be instituted.
Technical Abstract: The lesser mealworm, Alphitobius diaperinus, is an important poultry pest prevalent during production, capable of vectoring pathogens. This study was undertaken to determine the gut transit time of Salmonella for biosecurity risk analysis of pathogen dispersal into the environment. Adult and larval A. diaperinus were exposed to two concentrations of a fluorescently labeled Salmonella enterica for 15, 30, and 60 min time periods, then externally disinfected to evaluate internal transfer of Salmonella. The insects were monitored every 30 min over 4 h and evacuated frass (feces) processed for the marker Salmonella. The minimum time monitored was 45 min (15 exposure + 30 min time point) and the maximum was 5 h (60 exposure + 4 h time point). Adults treated with 106 or 108 cfu/ml, which produced Salmonella positive frass within the 5 h experimental time, displayed a mean gut transit time of 144.4 min (range 90 to 270 min) and 186.3 min (range 120 to 300 min), respectively. Larvae treated with 106 or 108 cfu/ml displayed a mean gut transit time of 172.5 min (range 120 to 300 min) and 131.7 min (range 60 to 300 min), respectively. Understanding the sources and contribution of reservoir populations of pathogens in poultry production operations is important for development of biosecurity to mitigate their transfer. A. diaperinus are prevalent in production operations and difficult to suppress. Management standards accept the reutilization of litter in which insects survive between flock rotations. Removing litter and spreading it onto nearby fields often results in the inadvertent dispersal of beetles. Few studies demonstrating the specific bacterial dispersal capacities of these insects have been performed. This study determined that Salmonella acquired internally transits the gut, allowing the insect to disperse viable pathogenic bacteria usually within 2 to 3 h.