A mouse's tail: how to settle an insurance dispute

Over the last years insurance companies have shown an increased interest in identifications of pest species, either as a form of risk assessment or to address liability issues. This paper describes a case report of such a forensic insurance investigation. The names of the corporations involved have been withheld in compliance with a pre-existing confidentiality agreement. A sea container containing sterile goods was shipped from China to the Netherlands. Upon inspection at its final destination, the contents were declared lost due to the presence of a dead mouse. Determination of which company should be held liable for this loss depended on where the mouse entered the container. The specimen was identified as belonging to the genus Apodemus (Muridae) based on morphology. Two species, A. sylvaticus and A. flavicollis occur in the Netherlands, two different species, A. agrarius and A. draco, occur in the relevant area in Eastern China. The distribution areas of these Dutch and Chinese Apodemus species do not overlap. Because the specimen was adolescent and partly mummified, key morphological characters for species-level identification were missing or not discernable. Published literature and sequence data available on GenBank showed that the four candidate species could be distinguished based on Cytochrome B barcode sequences. Given the decayed condition of the specimen, we expected possible DNA degradation. Therefore, both internal Cyt B primers (designed to amplify a short nucleotide sequence) and universal primers (which amplify a fourfold larger fragment) were employed. Remarkably, the primerset that was designed to amplify a short Cyt B sequence of A. draco amplified a well-studied pseudogene of A. sylvaticus. Both the Cyt B and the pseudogene sequence confirmed that the specimen in question is A. sylvaticus. Contamination of the sterile goods must therefore had taken place in the Netherlands.