Microbial contaminants in wild harvested and traded edible long-horned grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae) in Uganda

Abstract

This study investigated the relative abundance and identity of microbial contaminants of the edible long-horned grasshopper (Ruspolia differens) harvested from the wild and traded in informal markets in Uganda, to reveal high health risk points. Raw samples of whole R. differens were collected from wild vegetation, trapping sites and markets. Additionally, samples of plucked and deep-fried ready-to-eat R. differens were collected from the markets. The samples were cultured on standard media for microbial quantification, and pure cultures were characterised using molecular techniques. Bacterial and fungal counts in deep fried ready-to-eat R. differens were ~3- and 2-fold lower, respectively, than in raw samples. Loads of these microbes in deep fried insects were within recommended food safety limits. The highest bacterial counts were detected in whole R. differens samples from the market followed by trapping points. The fungal counts in the raw R. differens were comparable across the sampling points. The bacterial and fungal counts in R. differens in Kampala were not influenced by district of origin. Seven species of bacteria and seven species of fungi were recorded in R. differens samples. The microbial species were most diverse in samples from trapping points and least diverse in the deep-fried insects. The key pathogenic bacteria detected in marketed R. differens were Staphylococcus sciuri, Acinetobacter baumannii and Serratia marcescens, all of which were absent in wild-caught whole insects. Our results demonstrate that R. differens obtained at the trapping sites and markets are contaminated with potentially harmful microbes, therefore they require processing through deep frying to minimise health risks associated with their consumption. Further studies are warranted to elucidate specific handling practices at distribution and trapping points which may prevent introduction of microbes into R. differens.