Strange brew: Genetic and isotopic analyses to identify the provenance for wildlife forensics and food safety

Abstract

Forensic point of origin testing is a key tool in identifying the provenance of a sample, whether it be for human remains, the food industry, or illegal wildlife trade. A variety of techniques – morphological, genetic and isotopic – have been developed to provide resolution on the origin of an individual or sample. Herein, we employed all three approaches to identify a reported case of food contamination. A consumer in New Jersey, USA reported finding a rodent in a beer can, which was bottled in Dallas-Fort Worth (DFW), Texas, USA. Photographs of the organism as well as biological material (muscle and hair) were evaluated to determine the species, location and ultimate source of the contamination. The rodent removed from the can was surprisingly intact and was identified belonging to the family Cricetidae and subfamily Neotominae, and likely of the genus Peromyscus spp. Sequencing of the COIII mitochondrial gene confirmed a species identification of P. leucopus. The analysis of δ²H and δ¹⁸O and subsequent probability assignment showed little support that the sample did not originate from the bottling facility (P_DFW = 0.02 ± 0.02) but very high support that the mouse originated from New Jersey (P_{New Jersey} = 0.98 ± 0.02). Together, these results provide clear and consistent results that the mouse did not enter the food system at the bottling facility. This complimentary approach of morphological and molecular identification as well as point-of-origin assignment using stable isotope analysis yielded a highly cost-effective and probabilistic approach to assign origin of species that can be used by future forensic scientists.