Abstract:
Paramphistomoids are ubiquitous and widespread digeneans that infect a diverse range of
definitive hosts, being particularly speciose in ruminants. We collected adult worms from
cattle, goats and sheep from slaughterhouses, and cercariae from freshwater snails from
ten localities in Central and West Kenya. We sequenced cox1 (690 bp) and internal
transcribed region 2 (ITS2) (385 bp) genes from a small piece of 79 different adult
worms and stained and mounted the remaining worm bodies for comparisons with
available descriptions. We also sequenced cox1 and ITS2 from 41 cercariae/rediae
samples collected from four different genera of planorbid snails. Combining
morphological observations, host use information, genetic distance values and
phylogenetic methods, we delineated 16 distinct clades of paramphistomoids. For four of
the 16 clades, sequences from adult worms and cercariae/rediae matched, providing an
independent assessment for their life cycles. Much work is yet to be done to resolve fully
the relationships among paramphistomoids, but some correspondence between sequenceand anatomically based classifications were noted. Paramphistomoids of domestic
ruminants provide one of the most abundant sources of parasitic flatworm biomass, and
because of the predilection of several species use Bulinus and Biomphalaria snail hosts,
have interesting linkages with the biology of animal and human schistosomes to in
Africa.