Barcoding intermediate disease hosts

Freshwater snails of the genus Radix are of considerable medical and veterinary importance as vectors of digenean parasites. Radix spp. are known to be intermediate hosts for schistosomatid blood flukes including avian parasites from the genus Trichobilharzia and the cattle parasite Schistosoma turkestanicum, which are agents of human cercarial dermatitis in Eastern Europe and Asia . Radix also transmits the cosmopolitan re-emerging zoonotic disease echinostomiasis caused by echinostomatid flukes in South East Asia, significantly contributing to the global burden of intestinal trematodiasis. However, perhaps the most important role for Radix in Europe and the UK is as intermediate hosts of Fasciola hepatica and Fasciola gigantica, agents of fascioliasis, causing reduced meat and milk production in cows, as well as morbidity in humans with more than 20 million human cases worldwide.

These first lines of the introduction to a new publication by a group of UK researchers might already be enough to spoil breakfast for some of you but I am sure everyone would agree that it is paramount that we are able to accurately identify the snail hosts to help understanding disease epidemiology and to control spread of these diseases. Radix identification is usually done using shell morphology, colouration, and the genital anatomy. However, the utility of these morphological characters is limited e.g. due to the plasticity of shell morphology and colour. The new study shows once more how powerful DNA Barcoding can be in such cases. Not only does it help to reliably identify the UK species tested but it also proved useful for gaining insights into the evolutionary relationships of Radix species populations which might be very helpful to monitor epidemiology of these diseases. 

This is certainly not the first study proposing DNA Barcoding as tool to identify members of the genus Radix but it puts this application in the context  of emerging diseases and food security.