Soil borne helminths and microbial contamination of longhorn grasshoppers (ruspolia differens) from selected districts of central Uganda

Abstract

In central Uganda, the consumption of the longhorn grasshopper (Ruspolia differens) is a traditional practice deeply rooted in the local culinary culture. However, concerns regarding the biological safety of these edible grasshoppers persist, prompting the need for comprehensive scientific evaluation. This study aimed to assess the contamination of edible grasshoppers (Ruspolia differens) collected from central Uganda with soil-borne nematodes and bacteria. Six districts in central Uganda were purposively(due to their involvement in longhorn grasshopper trade) for sample collection, resulting in a total of 116 samples obtained between November-December 2020 and April-May 2021. The study encompassed fresh unprocessed (unplucked) grasshoppers, those with plucked appendages (plucked), and fried samples directly purchased from harvesters, markets, and roadside vendors. The collected samples underwent meticulous laboratory analysis at the Microbiology and Parasitology units in COVAB at Makerere University. Microbial analyses included determining total aerobic plate count, total coliform count, Escherichia coli count, and total yeast and mold counts. Parasitological assessment involved the detection of soil-borne helminths through nematode egg detection. The highest count of non-viable nematode eggs was observed in unplucked samples though no significant difference was noted compared to plucked and fried samples. Unplucked grasshoppers showed the highest Total Plate Counts and total coliform counts and no significant differences were observed among fried, plucked, and unplucked samples for TPC (p=0.406) and total coliforms (p=0.172). The overall mean E. coli count in grasshopper samples was 1.4x10^7 cfu/g in unplucked samples, signifying potential fecal contamination. Additionally, aflatoxin-producing fungi were detected, with the highest occurrence in unplucked samples (9.97 ± 4.09). In conclusion, this study highlights significant microbial and parasitological concerns in edible longhorn grasshoppers, emphasizing the necessity of addressing safety issues for the safe consumption of this traditional delicacy in central Uganda.