Occurrence of Taeniidae in a Middle Pleistocene speleothem of the Bàsura cave (Toirano, Liguria, Italy).

OBJECTIVE: This study aims to (i) analyse whether speleothems may contain fossil parasitic worm eggs and, if so, (ii) identify the pathogens involved, and (iii) place them in geological, palaeontological, and chronological contexts to know the zoonoses that could affect human and animal populations during the Middle Pleistocene. MATERIALS: A sample of calcite dated to the beginning of MIS 9 and MIS 8 from the Bàsura cave (Liguria, Italy) was analysed. METHODS: The chemical protocol applied is characterised using hydrochloric acid, the reduction of hydrofluoric acid application time, and by the absence of the use of base, dense liquor or acetolysis. RESULTS: An embryophore of a taeniid was recovered. CONCLUSIONS: Endoparasitic worm eggs can be found in speleothems. A taeniid embryophore was found in a calcite level dated to MIS 9. Zoonoses related to the Taeniidae family existed 300,000 years ago in the northern Mediterranean region and may have affected Middle Pleistocene predators, carnivores, or humans. Speleothems are good tools for paleoparasitological studies. SIGNIFICANCE: This is the oldest taeniid recovered and identified. LIMITATIONS: A more precise determination of the genus of this taeniid is not possible in the absence of more precise palaeontological data. SUGGESTIONS FOR FURTHER RESEARCH: An application of this approach to other Pleistocene speleothems could broaden the spectrum of parasites and their zoonoses over remote Pleistocene periods.

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.

[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.

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.

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.

Regulation of Anguillicola crassus (Nematoda) infrapopulations in their definitive host, the European eel, Anguilla anguilla.

The parasitic nematode Anguillicola crassus was recently introduced into populations of the European eel, Anguilla anguilla. We investigated, under experimental conditions, the regulation of A. crassus infrapopulations. We tested the effects of (1) the resource-limited habitat of the parasite and (2) the coexistence of several developmental stages in its niche (the swim-bladder) on the composition of the infrapopulations. The results revealed that the respective effects of these factors differed substantially during the course of the infection. Third-stage larvae (L3s) establishment would not be constrained by the size of the swim-bladder. Their moult to fourth-stage larvae (L4s) would be accelerated as the number of L3s increased. The moulting time of L4s to adults would be reduced by males and would be constrained by the size of the swim-bladder. However, the moult of L4s to adults and their further development would be synchronized with those of the opposite sex. At the time of mating, the number of males and the body weight of adults would depend on the size of the swim-bladder. Soon after the laying of eggs, the developmental constraint on the late L3s would decrease. When adults die, constraints would cease and late larval stages would moult to become adults.

Differential gene expression analysis in European eels (Anguilla anguilla, L. 1758) naturally infected by macroparasites.

We analyzed the relationships between the macroparasite community of the European eel and the expression of genes involved in the host physiology during its continental life. The genes studied are implicated in (1) host response to environmental stress, i.e., heat shock protein 70 (HSP70) and metallothionein (MT); (2) osmoregulation, i.e., beta thyroid hormone receptor (betaTHR) and Na+/K+ATPase; and (3) silvering, i.e., betaTHR, freshwater rod opsin (FWO), and deep-sea rod opsin (DSO). All were enumerated by quantitative reverse-transcription polymerase chain reaction. The epizootiological results for 93 yellow eels caught in the Salses-Leucate Lagoon (France) included 11 species: 1 nematode, 2 acanthocephalans, 1 monogenean, and 7 digeneans. The molecular results revealed (1) a significant negative relationship between digenean abundance and the expression level of all the tested genes, except FWO; (2) a significant negative relationship between the abundance of the nematode Anguillicola crassus and the expression level of the Na+/K+ATPase gene; and (3) a significant positive relationship between the A. crassus abundance and the expression level of the MT gene. Eels infected with digeneans had, on average, a lower level of expressed genes. We hypothesize that the parasites may disturb the eel's ability to withstand environmental stress and delay their migration to the Sargasso Sea because of degeneration of the gut. We further propose that the effect of the invasive species, A. crassus, on the gene expression was mainly linked to an increased trophic activity of infected eels. Moreover, it is possible that the parasite may have an effect on the fish's migratory behavior, which is tied to reproductive purposes. Additional work, including an experimental approach, is required to confirm our hypotheses.

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.

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.

A model to explain the origin of a parasite sex-specific population structure.

A discrete time model was built to understand the origin of the sex-specific population structure of the human blood fluke, Schistosoma mansoni. We have estimated both male/female individual ratio and male/female genotype ratio of this parasite taking into account all the experimental published values on differential male and female life-history traits all along the life cycle. We considered in our model male and female life-history traits when both separated and together. The model showed that both male/female individual ratio and male/female genotype ratio of S. mansoni adults are biased toward males in each combination. This bias was more important in male/female genotype ratio than in the male/female individual ratio for the same initial values of cercarial development success. This model could explain the sex specific population structure of this parasite. Firstly, we showed that the male-biased individual ratio finds its origin in the vertebrate host. Secondly, we showed that the male-biased genotype ratio originates prior to any interrelationship between adult worms and could generate by itself a sex-specific genetic structure.

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.

Preliminary study on sex-related inflammatory reactions in mice infected with Schistosoma mansoni.

The aim of this study was to investigate the contribution of the sex of both the parasite and the host to the inflammatory response induced in unisexual infections of Schistosoma mansoni in mice. Organ weight, cell count and the delayed type hypersensitivity reaction were used as tools in this comparative study. The inflammatory reactions differed as a function of the sex of both the host and the parasite. Female mice showed a stronger inflammatory reaction to schistosome infection than males, while male schistosomes induced a stronger inflammatory response compared to females. The host-related differences in the inflammatory reaction may reflect differences in the factors affecting the immune defence of male and female mice. The differences in the inflammatory response induced by the parasite are discussed in terms of the quantity and quality of antigens among male and female worms.

Relationship between worm burden and male proportion in Schistosoma mansoni experimentally infected rodents and primates. A meta-analytical approach.

This paper investigates the relationship between the worm burden and the male proportion of adult Schistosoma mansoni. This relationship was tested using data from the literature on S. mansoni experimentally infected rodents and primates. The analyses were performed within each animal model (rat, mouse, hamster and monkey) and showed positive linear relationships between worm burden and male proportion. An analysis between the four animal models showed the same positive linear relationship. The role of the genetic diversity of male and female schistosomes in this relationship is discussed.

Male-female larval interactions in Schistosoma mansoni-infected Biomphalaria glabrata.

This paper investigates Schistosoma mansoni male-female larval interactions in simultaneous bi-miracidial Biomphalaria glabrata infections. Larval interactions were analysed at four levels of infection: (i), miracidial infectivity, estimated by the prevalence of mollusc infection; (ii), mollusc pathology, measured by the mollusc growth and survival; (iii), dynamics of the cercarial sex ratio; and (iv), cercarial infectivity, measured as the success of development into adulthood. Our results showed that larval interactions exist in S. mansoni-infected B. glabrata. These interactions do not occur in miracidial infectivity, but occur in mollusc pathology, cercarial sex ratio dynamics and cercarial infectivity. Regarding mollusc pathology, we showed that the bi-miracidially-infected molluscs were smaller than the mono-miracidially-infected ones. This could be the result of larval competition. Regarding the dynamics of the cercarial sex ratio, we showed larval female superiority as compared with male larvae inducing the shedding of female-biased cercarial sex ratios. These sex ratios were rhythmic and could be the reflection of an external expression of the intramolluscan development. Regarding cercarial infectivity, we showed that the simultaneous presence of both sexes in a mollusc increased the cercarial infectivity. This result could be due to male-female larval synergism.

Experimental observations on the sex ratio of adult Schistosoma mansoni, with comments on the natural male bias.

The sex ratio of adult worms has been observed biased towards males in Schistosoma mansoni under natural conditions. The origin of this bias is unknown. This paper determines whether males are more infective than females under controlled experimental bisexual conditions, and hence if the sex ratio is male-biased as a consequence of this. The male and female cercarial infectivities in uni- and bisexual vertebrate host infections using a range of controlled cercarial sex ratios were studied. The results showed that, in experimental unisexual infections, male cercariae were more infective than females, and that in experimental bisexual infections, male cercarial infectivity was similar to that of female, irrespective of cercarial sex ratio. Furthermore, cumulative male and female cercarial infectivity was maximal when sex ratio was equilibrated. The unbiased sex ratios obtained in our experimental bisexual infections are discussed in terms of behavioural and/or biochemical male female interaction. Alternative explanations of the natural biased sex ratio are proposed.

A review of performance and pathogenicity of male and female Schistosoma mansoni during the life-cycle.

The sexual life-history traits of Schistosoma mansoni have been reviewed to compare male and female performance and pathogenicity against Biomphalaria glabrata during the life-cycle. A meta-analysis was used on pooled results from different experiments. In most cases, there was no difference between males and females but male cercariae were significantly more infectious than female cercariae. Conversely, cercarial production and cercarial life-span were significantly greater for females than for males; furthermore, females have a tendency to occur in molluscs of larger size. Each difference is discussed and interpreted when possible in terms of male and female differences in transmission strategies. The female strategy may consist of producing many long-living larvae. The male strategy may consist of producing few short-living larvae and would invest in the quality of these larvae instead of their quantity or their life-span.

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.

Helminth eggs in animal coprolites from a Middle Pleistocene site in Europe.

This paper reports on the discovery of dicrocoelid eggs in a coprolite collected in an archeological layer dated earlier than 550,000 yr BP (before present) from the Caune de l'Arago cave (Tautavel, Pyrénées-Orientales, France). It is the first trematode egg finding in an isolated coprolite from the Middle Pleistocene context.