The distribution of Schistosoma bovis Sonsino, 1876 in relation to intermediate host mollusc-parasite relationships.

Schistosoma bovis is a digenean platyhelminth that is responsible for a parasitic disease called schistosomiasis or bilharziasis in bovines. It has a natural wide mollusc intermediate host spectrum and is compatible, experimentally, with a wide range of species. Our working hypothesis is that the Mediterranean Sea and the Sahara were two physical barriers that could have separated the populations of S. bovis in three parts and may have played a role in gene flow. Experimental data were collected from earlier published studies, and the different intermediate host spectra and the mollusc-parasite geographical compatibilities were compared between the North Mediterranean zone, the South Mediterranean zone and the South Saharan zone. From our results, the three major groups of S. bovis populations that could be determined were the Iberian, the Mediterranean and the South Saharan populations. Our tested hypothesis was thus not confirmed concerning the Mediterranean sea barrier but was confirmed with the Saharan one. A paleogeographical scenario of S. bovis is proposed following three major steps from a South Saharan origin to a possible local adaptation of the parasite in the Iberian Peninsula.