Expanding knowledge of rodent parasites
The October paper of the month from Parasitology is Bank voles (Myodes glareolus) and house mice (Mus musculus musculus; M. m. domesticus) in Europe are each parasitized by their own distinct species of Aspiculuris (Nematoda, Oxyurida) from Volume 142, issue 12, by M. Behnke, A. Stewart, A. Bajer, M. Grzybek, P. D. Harris, A. Lowe, A. Ribas, L. Smales and K. J. Vandegrift. In this article Professor Jerzy Behnke from University of Nottingham discusses the research.
“I began my career in research in 1970 when I started my PhD in what was then Bedford College, under the supervision of Derek Wakelin. My very first paper ‘The survival of Trichuris muris in wild populations of its natural hosts’ was published in 1973 in Parasitology. The second, a year later, was on Aspiculuris tetraptera (The distribution of larval Aspiculuris tetraptera Schulz during a primary infection in Mus musculus, Rattus norvegicus and Apodemus sylvaticus), also published in Parasitology. The current publication is my 60th full length paper in the journal, including both primary research papers and the reviews that I have contributed to. It has been a privilege to have had the opportunity to publish in this historic journal with its policy of covering the whole of the subject of parasitology, and to have worked with the journal’s editors and referees over all these years.
It has also been rewarding for me to have closed a circle that began in 1970, 45 years ago, when as part of my PhD I found that whilst I could infect bank voles with the A. tetraptera derived from laboratory mice, the worms consistently failed to mature in the voles. However, those same wild caught animals harboured adult worms which I identified as A. tetraptera. I interpreted the failure of the challenge infection larvae to grow in bank voles as the consequence of acquired immunity generated by the earlier wild-acquired worms, preventing subsequent re-infection with the larvae from eggs derived from infected laboratory mice. Clearly I was wrong! The completion of this paper has given me enormous satisfaction and it is a relief to have published our results after so many years of accumulating the isolates that we worked on. Our conclusions have far wider significance than merely reporting that bank voles carry a previously unrecognized species of pinworm.
It is remarkable that, even with well-studied hosts, it is still possible to add to described parasite biodiversity in Europe. The discovery that the Aspiculuris infecting Myodes is not identical with A. tetraptera from house mice, but represents a cryptic but quite different species raises many questions about the origin and phylogeography of both parasites. The diversity of Aspiculuris in voles is striking, and is evidence of a radiation in microtid rodents which has spread across Eurasia and into North America, while A. tetraptera has a different origin, perhaps swapping from other rodents (gerbils?) in the Fertile Crescent when house mice first became pests of agriculture several thousand years ago. Examples such as this give us a fascinating glimpse of the evolutionary scenarios behind the origin of modern parasite faunas; stories which include the role of glaciations, the rise of agriculture and the dramatic range expansions of species associated with humans. Since rodents today remain one of the most important sources of zoonotic infection, it behooves us to understand the origin and evolution of their pathogens as precisely as possible. In the end, careful research combining molecular and morphological approaches is necessary to overcome some of the limitations of early morphological taxonomy. However, we need fresh material, from new locations, to go much further; obtaining such material becomes ever harder in an uncertain world.”