The Acquisition and Internalization of Salmonella by the Lesser Mealworm,Alphitobius diaperinus (Coleoptera: Tenebrionidae)

Abstract

In poultry broiler production facilities, it is important to understand the sources and contribution of reservoir populations of pathogens. The lesser mealworm beetle, Alphitobius diaperinus (Panzer), is a common pest in poultry litter that is reported to carry pathogens affecting both human and animal health. This study investigates whether the carriage of a bacterial pathogen occurs by the harboring of bacteria internally by these insects. Beetles were exposed to a marker bacterium, Salmonella enterica serovar Typhimurium-green fluorescent protein (ST-GFP), at concentrations up to 10⁷ colony-forming units (cfu)/mL for 0.5 to 12 h, and then subsequently surface disinfected and dissected. The head, gastrointestinal tract and hemolymph were cultured for the presence of ST-GFP. This study definitively demonstrates the internal carriage of Salmonella by this insect and found that the beetles rapidly acquired bacteria from external sources and harbored the bacteria within their alimentary canal after exposure for 30 min at 10⁴ cfu/mL and within the hemolymph after exposure for 2 h at 10⁶ cfu/mL. Beetles internalized an average of 9.5 × 10¹ and 3.2 × 10³ after a 2-h exposure to 2 × 10⁴ and 2 × 10⁶ cfu/mL, respectively. The lesser mealworm is a serious pest within the poultry brooder and laying industry and because of their mobility, voracious feeding habits, and prey potential may represent an active source facilitating the dissemination of Salmonella.