Molecular phylogenetics of the elephant schistosome Bivitellobilharzia loxodontae (Trematoda: Schistosomatidae) from the Central African Republic.

One of the most poorly known of all schistosomes infecting mammals is Bivitellobilharzia loxodontae. Nearly all of our available information about this species comes from the original description of worms that were obtained from an animal park-maintained elephant in Germany, probably a forest elephant Loxodonta cyclotis, originating from the present-day Democratic Republic of Congo. We obtained schistosome eggs from faecal samples from wild forest elephants from the Central African Republic. The eggs, which were similar in size and shape to those of described B. loxodontae, were sequenced for the 28S nuclear ribosomal gene and the mitochondrial cytochrome oxidase I (cox1) gene. In a phylogenetic analysis of 28S sequences, our specimens grouped closely with B. nairi, the schistosome from the Indian elephant Elephas maximus, to the exclusion of schistosomes from other genera. However, the eggs were genetically distinct (12% distance cox1) from those of B. nairi. We conclude the specimens we recovered were of B. loxodontae and confirm this is a distinct Bivitellobilharzia species. In addition to providing the first sequence data for B. loxodontae, this report also supports Bivitellobilharzia as a monophyletic group and gives the relative phylogenetic position of the genus within the Schistosomatidae. We also provide a review of the biology of this poorly known schistosome genus.