No abstract

Annecy Lake is a well-known focus of human cercarial dermatitis in France. Identification of the parasites, however, was not performed in the past. Previous studies suspected two species, Trichobilharzia franki and Trichobilharzia regenti, based on the presence of parasites in mallards and/or morphological identification of snails emitting ocellate furcocercariae. Following a standardized molecular approach, we studied snails and furcocercariae and compared their haplotypes with those deposited in GenBank. The selected markers were the second internal transcribed spacer ITS-2 for the snails and ITS-2 and D2 domain of the ribosomal DNA for the parasites. Our results confirm the presence of T. franki and T. regenti and two probable new species that could be potential agents of cercarial dermatitis. All the snails emitting the ocellate furcocercariae belong to the same species identified as Radix peregra (=Radix ovata = Radix balthica). Parasite-host relationships between species of the genus Trichobilharzia and snails of the genus Radix do not seem to be as specific as supposed previously.

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The prevalence of human cercarial dermatitis (HCD) caused by bird schistosomes appears to be increasing in France, in light of the impact of tourism combined with high densities of wild aquatic hosts in freshwater areas. The present work expands our knowledge of schistosome systematics by including samples of bird schistosomes collected from their natural hosts in France. Heads (318) and viscera (81) of aquatic birds belonging to 16 species from five orders, collecting during the hunting seasons or found dead, were autopsied for nasal and visceral schistosomes. Eggs and/or adults were analysed by molecular methods using the D2 domain and the second internal transcribed spacer (ITS-2) region of rDNA to determine species. Even if nasal eggs were polymorphic according to the host, all haplotypes were similar to that of Trichobilharzia regenti. Marked diversity of visceral species was observed. Final hosts under natural conditions were reported. For the first time, Trichobilharzia franki is reported in its natural bird hosts, Anas platyrhynchos, Anas crecca, Aythya fuligula and Cygnus olor. We also identified T. szidati in A. crecca and Anas clypeata. Bilharziella polonica was found in six species of aquatic birds, including Grus grus. This finding is the first record of bird schistosomes in this aquatic bird. Three new taxa of visceral schistosomes in Anser anser are strongly suspected according to their haplotypes. Futhermore, a new haplotype of visceral schistosomes isolated in Cygnus olor and similar to Allobilharzia visceralis was identified.

The genus Culicoides includes vectors of important animal diseases such as bluetongue and Schmallenberg virus (BTV and SBV). This genus includes 1300 species classified in 32 subgenera and 38 unclassified species. However, the phylogenetic relationships between different subgenera of Culicoides have never been studied. Phylogenetic analyses of 42 species belonging to 12 subgenera and 8 ungrouped species of genus Culicoides from Ecuador, France, Gabon, Madagascar and Tunisia were carried out using two molecular markers (28S rDNA D1 and D2 domains and COI mtDNA). Sequences were subjected to non-probabilistic (maximum parsimony) and probabilistic (Bayesian inference (BI)) approaches. The subgenera Monoculicoides, Culicoides, Haematomyidium, Hoffmania, Remmia and Avaritia (including the main vectors of bluetongue disease) were monophyletic, whereas the subgenus Oecacta was paraphyletic. Our study validates the subgenus Remmia (= Schultzei group) as a valid subgenus, outside of the subgenus Oecacta. In Europe, Culicoides obsoletus, Culicoides scoticus and Culicoides chiopterus should be part of the Obsoletus complex whereas Culicoides dewulfi should be excluded from this complex. Our study suggests that the current Culicoides classification needs to be revisited with modern tools.