Schistosoma haematobium infections acquired in Corsica, France, August 2013.

A 12 year-old boy in Germany developed urinary schistosomiasis in January 2014. He had bathed in rivers in south-eastern Corsica five months earlier. Before this case, human schistomiasis had not been reported on the island, although its vector, the snail Bulinus truncatus, locally transmitted the zoonotic Schistosoma bovis. The boy's father excreted S. haematobium ova that were not viable; the boy's three siblings had a positive serology against schistosomes.

Life-history traits indicate local adaptation of the schistosome parasite, Schistosoma mansoni, to its snail host, Biomphalaria pfeifferi.

The digenean trematode Schistosoma mansoni causes schistosomiasis (Bilharziasis), a significant human disease especially in sub-Saharan Africa. We tested local adaptation of this parasite to its intermediate host, the freshwater snail Biomphalaria pfeifferi, by exposure of S. mansoni to B. pfeifferi from one sympatric and four allopatric populations and measurement of life-history traits of both species over time. The pre-patent period, infection rate, and cercarial production of the parasite were determined, and the shell diameter, fecundity, and survival of the snail host were determined. The results provide evidence for local adaptation of S. mansoni to its sympatric snail host: the pre-patent period was the shortest, the cercarial production was moderate and accompanied by a higher survival rate, the growth was greater during the pre-patent period, and the fecundity was greater during the pre-patent period. The greater growth and fecundity of sympatric B. pfeifferi suggests the presence of growth and fecundity compensation. These fitness traits are relevant to energy allocation of the snail host and to the transmission strategy of the schistosome parasite.

Morphometric and molecular characterizations of schistosome populations in Estuaire province Gabon.

The aim of this study was to test the hypothesis of the presence of hybrids between Schistosoma guineensis and S. haematobium in the Estuaire province (Western Gabon). Egg morphometry and single-stranded conformational polymorphism (SSCP) analysis on adult worms were used in order to characterize the schistosome populations of two sites. The morphology of the eggs showed three morphotypes: S. haematobium, S. guineensis and intermediate morphotypes, but the eggs of the morphotype S. guineensis were smaller compared to the values found in the literature. Furthermore, the SSCP analysis of the adult schistosomes showed that all the patterns corresponded to that of S. haematobium and gave evidence that hybrids were absent from our samples.

Biased sex ratio in the European eel (Anguilla anguilla) swim-bladder parasite Anguillicola crassus, experimentally induced by 11-ketotestosterone.

Parasites are intimately connected to the host in which they live, and some may be affected by the polluted environment of their host. The present study describes the effect of a steroid hormone (11-ketotestosterone) on the sex ratio of the invasive hematophagous nematode Anguillicola crassus Kuwahara, Niimi & Itagaki, 1974, when experimentally injected to European eels, Anguilla anguilla. Our results showed that this steroid induced a significant male-biased ratio in the nematode A. crassus infrapopulations, suggesting that the presence of endocrine disruptors in the environment may lead to skewed sex ratios among parasites.

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.

[Epidemiology of urinary schistosomiasis among school children in Péhunco area, Northern Benin. Malacological survey]. / Épidémiologie de la schistosomose urinaire chez les enfants scolarisés de la commune de Péhunco dans le Nord Bénin: prospection malacologique.

Schistosomiasis is a public health problem in Benin but prevalence estimates vary widely. Parasitological (from May to September 2010) and malacological surveys (from September 2010 to June 2012) were conducted to determine the current status of urinary schistosomiasis among 1 585 schoolchildren from 18 primary schools of Péhunco area, North-West Benin, using two parasitological tests. Pupils were enrolled with a mean age of 11 years (from 7 to 16 years-old age) and 51.48% of them were girls. Urines samples were examined using both urine reagent strips and filtration method. Structured questionnaires were used to identify environmental and socio-economic factors. Malacological surveys were conducted to ascertain general freshwater snail diversity and specific diversity of the schistosome host snails. The results showed a general prevalence of 29.40% with boys (36.67%) significantly more affected than girls (22.55%). Among the 844 collected snails, 5 species freshwater snails were identified: two species known as potential schistosome intermediate host snails, Bulinus forskalii and B. globosus, and three species known as non-schistosome transmitting snails Lymnaea natalensis, Physa marmorata and Melanoides tuberculata. B. forskalii was a most largely distributed snail and none of snails were found naturally infected by schistosome. No freshwater snails were found naturally infected by schistosome.

Freshwater snail diversity in Benin (West Africa) with a focus on human schistosomiasis.

The aim of this study was to conduct a large-scale freshwater snail survey in Benin to assess the malacological diversity and the larval trematode infections with a focus on Schistosoma genus. We conducted 82 freshwater snail surveys in 35 sites ranked in 4 types and belonging to 9 out of 12 departments. Among 19,200 collected snails, 11 species of freshwater snails were identified. Four species of human schistosome transmitting snails, Bulinus forskalii, B. globosus, B. truncatus and Biomphalaria pfeifferi and seven species of non-human schistosome transmitting snails. Although B. forskalii and B. globosus were the most largely distributed snails, none of the Bulinus snails were found naturally infected by schistosomes. B. pfeifferi was found naturally infected by S. mansoni only in one site with a 0.56% prevalence. The most risky areas were Borgou and the four coastal departments. Preliminary contempory information on human schistosomiasis was provided from three different sites. Schistosoma haematobium was found with 57.1%, 96% and 100% prevalences (two of which were new records for this species in Benin) while S. mansoni was restricted to one site (Toho-Todougba) with 74.3% prevalence. Our data showed that both schistosomiasis haematobium and mansoni prevalences increased during the last nineteen years in Toho-Todougba site.

Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni.

This paper analyzed, experimentally, the influences of pattern of exposure, parasite genetic diversity, and parasite sex on the degree of protection against reinfection with Schistosoma mansoni in the mouse. The results show that, (1) in infections with one male parasite genotype, successive infections induced a significant decrease in the infectivity of the parasite and significant increases in the spleen and liver weights compared to mass infections, (2) successive infections with one male genotype induced a significant decrease in the infectivity of the parasite compared to successive infections with five male genotypes, and (3) genotype infectivities were determined by the order at which they were used in the successive infections. These results are discussed in terms of protective effect and concomitant immunity and provide an ecological explanation of the natural sex-biased dispersal toward the male schistosomes.

Schistosoma mansoni: cercarial shedding patterns from a mixed infection of Biomphalaria glabrata with two (early and late) chronobiological variants.

The cercarial emergence rhythms of Schistosoma mansoni were analyzed for mixed infection of the snail Biomphalaria glabrata with two chronobiological strains, one with an early shedding pattern and the other with a late shedding pattern. Under these conditions, each parasite strain kept its own circadian cercarial emergence pattern. When the chronobiological variants were of the same species, no interference between the trematode larvae occurred during the cercarial emergence process. These results confirm that within the host-parasite system the parasite component is directly responsible for the cercarial emergence pattern.

Phylogeography of Biomphalaria glabrata and B. pfeifferi, important intermediate hosts of Schistosoma mansoni in the New and Old World tropics.

The historical phylogeography of the two most important intermediate host species of the human blood fluke Schistosoma mansoni, B. glabrata in the New World, and B. pfeifferi in the Old World, was investigated using partial 16S and ND1 sequences from the mitochondrial genome. Nuclear sequences of an actin intron and internal transcribed spacer (ITS)-1 were also obtained, but they were uninformative for the relationships among populations. Phylogenetic analyses based on mtDNA revealed six well-differentiated clades within B. glabrata: the Greater Antilles, Venezuela and the Lesser Antilles, and four geographically overlapping Brazilian clades. Application of a Biomphalaria-specific mutation rate gives an estimate of the early Pleistocene for their divergence. The Brazilian clades were inferred to be the result of fragmentation, due possibly to climate oscillations, with subsequent range expansion producing the overlapping ranges. Within the Venezuela and Lesser Antilles clade, lineages from each of these areas were estimated to have separated approximately 740 000 years ago. Compared to B. glabrata, mitochondrial sequences of B. pfeifferi are about 4x lower in diversity, reflecting a much younger age for the species, with the most recent common ancestor of all haplotypes estimated to have existed 880 000 years ago. The oldest B. pfeifferi haplotypes occurred in southern Africa, suggesting it may have been a refugium during dry periods. A recent range expansion was inferred for eastern Africa less than 100 000 years ago. Several putative species and subspecies, B. arabica, B. gaudi, B. rhodesiensis and B. stanleyi, are shown to be undifferentiated from other B. pfeifferi populations.