Morphological and genomic characterisation of the Schistosoma hybrid infecting humans in Europe reveals admixture between Schistosoma haematobium and Schistosoma bovis.

Schistosomes cause schistosomiasis, the world's second most important parasitic disease after malaria in terms of public health and social-economic impacts. A peculiar feature of these dioecious parasites is their ability to produce viable and fertile hybrid offspring. Originally only present in the tropics, schistosomiasis is now also endemic in southern Europe. Based on the analysis of two genetic markers the European schistosomes had previously been identified as hybrids between the livestock- and the human-infective species Schistosoma bovis and Schistosoma haematobium, respectively. Here, using PacBio long-read sequencing technology we performed genome assembly improvement and annotation of S. bovis, one of the parental species for which no satisfactory genome assembly was available. We then describe the whole genome introgression levels of the hybrid schistosomes, their morphometric parameters (eggs and adult worms) and their compatibility with two European snail strains used as vectors (Bulinus truncatus and Planorbarius metidjensis). Schistosome-snail compatibility is a key parameter for the parasites life cycle progression, and thus the capability of the parasite to establish in a given area. Our results show that this Schistosoma hybrid is strongly introgressed genetically, composed of 77% S. haematobium and 23% S. bovis origin. This genomic admixture suggests an ancient hybridization event and subsequent backcrosses with the human-specific species, S. haematobium, before its introduction in Corsica. We also show that egg morphology (commonly used as a species diagnostic) does not allow for accurate hybrid identification while genetic tests do.

First morphogenetic analysis of parasite eggs from Schistosomiasis haematobium infected sub-Saharan migrants in Spain and proposal for a new standardised study methodology.

Schistosomiasis is a Neglected Tropical Disease caused by trematode species of the genus Schistosoma. Both, autochthonous and imported cases of urogenital schistosomiasis have been described in Europe. The present study focuses on eggs, considered pure S. haematobium by genetic characterisation (intergenic ITS region of the rDNA and cox1 mtDNA). A phenotypic characterisation of S. haematobium eggs was made by morphometric comparison with experimental populations of S. bovis and S. mansoni, to help in the diagnosis of S. haematobium populations infecting sub-Saharan migrants in Spain. Analyses were made by Computer Image Analysis System (CIAS) applied on the basis of new standardised measurements and geometric morphometric tools. The principal component analysis (PCA), including seventeen non-redundant measurements, showed three phenotypic patterns in eggs of S. haematobium, S. bovis and S. mansoni. PCA showed that the S. bovis population presented a large egg size range with a pronouncedly larger maximum size. Similarly, S. bovis shows bigger spine values than S. haematobium. Mahalanobis distances between each pair of groups were calculated for each discriminant analysis performed. In general, S. mansoni and S. bovis present larger distances between them than with S. haematobium, i.e. they present the greatest differences. Regarding the spine, S. haematobium and S. mansoni are the most distant species. Results show the usefulness of this methodology for the phenotypic differentiation between eggs from these Schistosoma species, capable of discerning morphologically close eggs, as is the case of the haematobium group. Schistosoma egg phenotyping approaches may be applied to assess not only hybrid forms but also potential influences of a variety of other factors.

Assessment of tegumental damage to Schistosoma mansoni and S. haematobium after in vitro exposure to ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine using scanning electron microscopy.

BACKGROUND: Schistosomiasis is one of the most harmful parasitic diseases worldwide, praziquantel being the only drug in widespread use to treat it. We recently demonstrated that ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine (Fc-OXA, Rc-OXA and Bn-OXA) are promising antischistosomal drug candidates. METHODS: In this study we assessed the tegumental damage of these three derivatives of oxamniquine using scanning electron microscopy. Adult Schistosoma mansoni and S. haematobium were exposed to a concentration of 100 µM of each drug and incubated for 4-120 h, according to their onset of action and activity. RESULTS: While on S. mansoni the fastest acting compound was Fc-OXA, which revealed high activity after 4 h of incubation, on S. haematobium, Rc-OXA revealed the quickest onset, being lethal on all males within 24 h. In both species studied, the three derivatives showed the same patterns of tegumental damage consisting of blebs, sloughing and tegument rupturing all over the body. Additionally, on S. mansoni distinct patterns of tegumental damage were observed for each of the compounds: tissue ruptures in the gynaecophoric canal for Fc-OXA, loss of spines for Rc-OXA and oral sucker rupture for Bn-OXA. CONCLUSIONS: Our study confirmed that Fc-OXA, Rc-OXA and Bn-OXA are promising broad spectrum antischistosomal drug candidates. All derivatives show fast in vitro activity against S. mansoni and S. haematobium while validating the previous finding that the parent drug oxamniquine is less active in vitro under the conditions described. This work sets the base for further studies on the identification of a lead oxamniquine derivative, with the aim of identifying a molecule with the potential to become a new drug for human use.

Cholinergic components of nervous system of Schistosoma mansoni and S. haematobium (Digenea: Schistosomatidae).

A comparison has been made for the first time between the cholinergic components of the nervous system of important human digeneans namely Schistosoma mansoni and Schistosoma haematobium from infected hamster (Cricentus auratus) in Egypt. In each parasite, the central nervous system consists of two cerebral ganglia and three pairs of nerve cords (ventral, lateral, and dorsal) linked together by some transverse connectives and numerous ring commissures. Peripheral cholinergic innervation was detected in oral and ventral suckers and in some parts of female reproductive system in both species, but there were some differences. The possible functions of some of these nervous components are discussed.

Biological and morphological changes in worms in mixed infection of Schistosoma mansoni and S. haematobium in hamsters.

Hamsters infected with Schistosoma mansoni and S. haematobium either simultaneously or after maturation of an initial infection with either schistosome species were examined to estimate the biological and morphological changes under mixed infection conditions. The results indicate a high level of acquired resistance. The degree of immunity was evidenced by the significant reduction in the worm load as well as in the size of mature worms. Some disturbance was observed in the worm distribution. The results are important for epidemiological and immunological uses, as well as in development of a vaccine from one species that might be effective against both species.

Biological and biochemical comparative studies on Schistosoma mansoni from two localities in Egypt where S. haematobium is endemic.

The changing pattern of Schistosoma mansoni and S. haematobium distribution in Egypt is generally attributed to ecological changes caused by the construction of the Aswan High Dam. Although S. mansoni was previously restricted to Lower Egypt, it is now found at certain foci in Upper Egypt. In areas of Lower Egypt where S. mansoni and S. haematobium are sympatric, S. mansoni eggs are shed almost exclusively in the stools of patients, whereas in Upper Egypt they are more frequently shed in the urine. In spite of this difference, the eggs and adult worms obtained from hamsters infected with S. mansoni strains from each of these areas proved to be morphologically identical. Protein patterns and isoenzyme profiles of male or female adult worms of each of the two isolates, obtained from infected hamsters, also proved virtually identical. In hamsters with mixed infections of S. mansoni and S. haematobium, some S. mansoni females cross-mated with S. haematobium males and they then developed ovaries and laid eggs which were typical of S. mansoni and which were excreted from the urinary bladder. In Upper Egypt, which is predominantly a S. haematobium area, patients with established infections may have a preponderance of S. haematobium males associated with S. mansoni females. These females may then migrate to the vesicular plexus and deposit S. mansoni eggs in the urinary bladder, to be shed subsequently in the urine. The observations appear to be better explained by the phenomenon of parthenogenesis than by the production of true genetic hybrids.

Human bilharzial ureters: I. Fine structure of eggs deposited in the submucosa and muscularis.

The internal fine structure of the partially calcified Schistosoma haematobium eggs in the lower ureteral segments of Saudi patients with chronic urinary schistosomiasis is described. The egg shell is penetrated by cribriform pores and consists of the three previously described layers: outer microspinous, middle intermediately dense, and inner dense layers. The space between the egg shell and the developing embryo is partitioned by three layers. An outer acellular Reynolds' layer of unknown origin and function consists of a fribrillar material mixed with a finely granular matrix extending to the egg-shell pores via racemose channels. The middle von Lichtenberg's envelope consists of a single layer of flattened epithelial cells containing several mitochondria as in other previously described Schistosoma eggs suggesting an active, and perhaps selective, transport in or out of the egg shell. The inner fluid filled cavity, or Lehman's lacuna, between the von Lichtenberg's envelope and the embryo contains numerous lipoid bodies suggesting a relation to vitelline cells. Four systems (out of eight previously described for the free, mature Schistosoma miracidium) have been recognized for the first time in the developing miracidium within S. haematobium eggs and include: (1) ciliated epidermal plates representing the epithelial system, (2) an outer circular and an inner longitudinal muscle layer forming the musculatures, (3) lateral penetration glands, and (4) ciliated flame cells representing the excretory system.

Identification of Schistosoma mansoni, S. rodhaini, S. bovis, S. haematobium, and S. intercalatum cercariae using segmentation analysis.

Cercariae of five species of schistosomes identified with certainty were fixed in boiled alcohol and mounted in glycerol-alcohol mixture. The cercarian body (Cbl) and tail-furcae lengths (Ctl) were measured, the values of which were treated using a computer. Even mean values allowed partly identification of the present species, the segmentation analysis gave better informations for separating any cercaria taken at random, with a given probability (p). Thus, five classes (A, B, C, D, E) have been established: class A: Cbl > 139 microns and Ctl, > 236 microns, p = 0.59 to be considered as S. bovis; class B: Cbl > 139 and Ctl < 236, p = 0.86 to be considered as S. haematobium; class C; Cbl < 114 microns, p = 0.75 to be considered as S. intercalatum; class D: 114 < Cbl < 125 microns, p = 0.57 to be considered as S. mansoni; class E: 125 < Cbl < 139 microns, p = 0.57 to be considered as S. rodhaini. Two groups of schistosome have been established on basis of cercarian morphometry with S. intercalatum, S. mansoni and S. rodhaini from one side, S. haematobium and S. bovis to the other side.

Schistosomiasis of the appendix.

The clinicopathological features of schistosomiasis of the appendix are discussed, based on the clinical presentation, operative findings and morphological changes in the specimens of patients seen in Ibadan between 1980 and 1989. Schistosoma haematobium was implicated as the causal agent of a granulomatous inflammatory reaction with eosinophilia and fibrosis. Intramuscular oviposition was associated with frank acute appendicitis, and serosal involvement resulted in peritoneal adhesions, with ileoileal intussusception in one patient. The actual role of schistosomal infestation as a contributory factor in appendicitis is still open to debate, but the diagnosis must be entertained in patients in the tropics with features of acute appendicitis or recurrent abdominal pain.

A new focus of Schistosoma haematobium/S. intercalatum hybrid in Cameroon.

Terminal-spined schistosome eggs were found in both stool and urine specimens of a high proportion of infected individuals in Kinding Njabi, a village located in a savannah/forest ecotone of Center Province, Cameroon. Infections with terminal-spined schistosomes are not common in that region and first appeared in Kinding Njabi in the mid-1980s. The village population, determined by house-to-house census in 1986, was 345. Of 302 stool samples examined by a thick smear technique, 58 (19%) were positive, and of 320 urine samples examined by sedimentation, 40 (12%) were positive. Twenty-six (37%) of a total of 71 infected persons passed eggs in both stool and urine. Egg size distribution and morphology were similar to previous reports for Schistosoma haematobium/S. intercalatum hybrids. Bulinus forskalii was the only snail found during extensive surveys in and around Kinding Njabi; infected snails were recovered from several temporary habitats. This focus is of particular interest because it represents the first report of transmission of hybrid schistosomes outside of the hybrid zone. Interviews with villagers and local health officials suggest that schistosomiasis was introduced by immigrants from Loum, a town approximately 100 km southwest of Kinding Njabi, where S. haematobium, S. intercalatum, and their hybrid are known to exist. Results from snail host specificity studies using the Kinding Njabi parasite showed that stool-derived miracidia were compatible only with B. forskalii, the exclusive host for S. intercalatum in Cameroon. Urine-derived miracidia were compatible only with B. truncatus, a S. haematobium host in Cameroon.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotypic differences in Schistosoma mattheei ova from populations sympatric and allopatric to S. haematobium.

Schistosoma mattheei ova were collected from cattle in different localities in South Africa and after hatching, miracidia were used to infest Bulinus (Physopsis) globosus. Cercariae harvested from these snails were used to infest the definitive host Praomys (Mastomys) coucha and eggs from the resulting female S. mattheei were collected. These ova were compared with a Schistosoma haematobium X S. mattheei hybrid similarly collected from an infested P. (M.) coucha. The results indicate that S. mattheei populations which are sympatric to S. haematobium possess S. haematobium characteristics. It is suggested that the gene pools of populations of the parasite in these areas are infiltrated with S. haematobium genes via the S. mattheei X S. haematobium hybrid originating from human hosts.

[Use of bladder biopsy in the study of urinary schistosomiasis]. / Apport de la biopsie vésicale dans l'étude des bilharzioses urinaires.

It is common to find Schistosoma eggs in urine, faeces, and biopsies from rectal mucus membranes presently in use. It is less common to observe adults in routine bladder biopsies. The authors report such a case and discuss the importance of the bladder biopsy to estimate tissular inflammatory response which could reflect the host-parasite balance.

Appendiceal schistosomiasis. Method of classifying oviposition and inflammation.

Twenty surgical specimens of appendiceal schistosomiasis were reviewed retrospectively. They constituted 1 percent of 1984 appendices seen among approximately 15,000 surgical specimens examined at free central laboratories serving the Igbos of Nigeria, West Africa. Oviposition by Schistosoma haematobium was classified according to its association with suppurative appendicitis and normal appendices. Seven of ten infested appendices obtained at curative operations showed suppurative appendicitis, whereas eight of nine infested appendices removed at incidental appendectomies were negative. One interval appendectomy was also negative. It is postulated that utilization of this novel classification on a worldwide basis will help to end the controversy concerning the etiologic role of schistosome ova in acute appendicitis.

Studies on experimental mixed infections of Schistosoma mansoni and S. haematobium in hamsters.

Golden hamsters were superinfected simultaneously with 100 Schistosoma haematobium cercariae, 1 and 3 weeks after initial infection with 100 S. mansoni cercariae. Results indicate that there was a higher degree of resistance to superinfection with S. haematobium at 1 week following initial infection with S. mansoni than that produced in the other two superinfections. This resistance was evidenced by a reduction in the number and size of worms of both species, decrease in S. haematobium egg extrusion per female and by a striking deviation in the egg distribution pattern of both species. Such an early host resistance was not recorded in previous works. Cross-mating was observed but no hybridization took place and the eggs produced were hatchable and typical of their species.

[A comparison of the superficial argentophilic structures of miracidia from 12 species of the genus Schistosoma]. / Comparaison des structures argyrophiles superficielles des miracidiums d'une douzaine d'espèces du genre Schistosoma.

Observation of miracidia of twelve species of Schistosoma shows the fundamental epidermal cell pattern is: 6, 9, 4, 3. Comparison of superficial argentophilic organites permits us: --to divide these species into three inequal groups: mansoni group: Schistosoma mansoni, S. rodhaini. haematobium group: S. haematobium, S. bovis, S. indicum , S. intercalatum, S. margrebowiei , S. mattheei, S. nasale and S. spindale . japonicum group: S. japonicum, S. incognitum . --to emphasize the relatively narrow specificity between members of each group and the snail-hosts. --to position the above species of Schistosoma within the Schistosomatoidea . Furthermore this character gives us some idea of the degree of evolution of species of Schistosoma.

Stereo-scan observations on the cercaria of Schistosoma haematobium.

The scanning electron microscope was employed to observe the hinge region and excretory canal of the cercaria of Schistosoma haematobium.