Finding a mouse in a package you’ve just picked up is hardly ever a good thing. Just ask Liz Wray.

But when the package in question is a container load of supposedly sterile medical goods things get really problematic. And that’s where gene sequencing enters the picture.

In a paper newly published in Forensic Science International, Dick Groenenberg and Rene Dekker detail their forensic investigation of the mysterious mouse in the container and how they determined where it came from.

The mouse’s origin was crucial in this case. The medical products were shipped from eastern China to the Netherlands, where the two scientists work at the Netherlands Centre for Biodiversity Naturalis. Exactly where the rodent entered the container would determine who was financially responsible for the formerly sterile goods being a total loss.

The intruder was easily identifiable as a member of the Apodemus genus, but it was partially mummified and not fully developed so it lacked identifying features (presumably including clogs and the keys to a windmill). Therefore, it was not clear whether it belonged to the two Netherlands-based Apodemus species (A. sylvaticus and A. flavicollis) or was a Chinese infiltrator (of A. agrarius or A. draco).

So the researchers took a snip of the deceased animal’s tail and looked at its genetic makeup, thinking they could distinguish between the four possible species by looking at the well studied region Cytochrome B.

Lo and behold, they found the genetic data conclusively pegged the animal as A. sylvaticus.

“We can rule out the possibility that the specimen found in the container could have originated from Eastern China,” write Groenenberg and Dekker. “Contamination of the sterile goods must therefore have been taken place in the Netherlands, not China.”

The intruder was a Dutch mouse and the Chinese company was off the hook.

Image: A. sylvaticus photo by Rasbak via wikipedia.