Forensic hair analysis to identify animal species on a case of pet animal abuse

Abstract

As part of an investigation of a case of pet animal abuse, we attempted to identify small mammalian species by morphological analysis and single-nucleotide polymorphism (SNP) typing of the cytochrome b gene using guard hairs as an analytical material. Guard hair samples from several species were measured for length, width, medulla formation, and cuticle scale pattern under a light microscope or scanning electron microscope. These samples were also analyzed for SNPs in the cytochrome b gene using a multiplex single-base primer extension reaction. Morphological analysis of cuticle scale pattern and medulla formation was able to discriminate ferret hairs from other hair samples that included rabbit, gerbil, degu, and Djungarian hamster. However, this also revealed a similarity of the guard hairs of the ferret (Mustela putorius furo) and Japanese weasel (Mustela itatsi). Although at three sites, the nucleotide color signals of SNPs in the cytochrome b gene could be used to discriminate completely among human, dog, and gerbil, the signals for cat, ferret, and Japanese weasel occurred at the same nucleotide sites. Unfortunately, no signals were obtained from degu, Djungarian hamster, and rabbit hairs. Although the discriminated hair samples were 100% identical to those of the ferret, there was only a 5% difference from Japanese weasel in the partial sequence of the cytochrome b gene. Construction of a database of mammalian hairs would be useful not only in forensic science, but also for investigating smuggling of endangered species in contravention of the Washington Convention.