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Background: The Kato-Katz technique is recommended for diagnosis of Schistosoma mansoni infection by the World Health Organization. However, egg counts are subject to variability. The aim of this study is to determine the prevalence of S. mansoni infection in school children using two different techniques and to recommend the technique that should be routinely used in the diagnosis of this infection. Methodology: Field investigations on faecal samples from 299 Cameroonian school children were carried out in 2016 to compare the effectiveness of the Kato-Katz and Formalin-ether techniques in diagnosis of S. mansoni infections. Results: Schistosome eggs were detected in 37 (12.3%) samples with the Kato-Katz technique and 61 (20.4%) samples with the Formalin-ether technique. The difference between the prevalence observed for the two techniques was significant in males and age group 10 - 12 years (p < 0.5). Conclusion: The Formalin-ether technique was more sensitive than the Kato-Katz method for detecting S. mansoni eggs in faecal matter. Despite its cost, the Formalin-ether technique can be routinely used in the laboratory for epidemiological studies of intestinal schistosomiasis. Contexte: La méthode Kato-Katz est recommandée par l'Organisation mondiale de la santé pour le diagnostic de l'infection à Schistosoma mansoni. Cependant, le nombre d'oeufs est sujet à une variabilité. Le but de cette étude est de déterminer la prévalence de l'infection à S. mansoni chez les écoliers en utilisant deux techniques différentes et de recommander la technique à utiliser systématiquement pour le diagnostic de cette infection. Méthodologie: Des enquêtes sur le terrain sur des échantillons de selles provenant de 299 écoliers camerounais ont été menées en 2016 pour comparer l'efficacité des techniques de Kato- Katz et au formol-éther dans le diagnostic des infections à S. mansoni. Résultats: Des oeufs de schistosomes ont été détectés dans 37 échantillons (12,3%) avec la technique de Kato-Katz et 61 échantillons (20,4%) avec la technique au formol-éther. La différence entre la prévalence observée pour les deux techniques était significative chez les hommes et chez les 10-12 ans (p <0,5). Conclusion: La technique au formol-éther était plus sensible que la méthode de Kato-Katz pour détecter les oeufs de S. mansoni dans les matières fécales. En dépit de son coût, la technique formol-éther peut être utilisée systématiquement en laboratoire pour des études épidémiologiques sur la schistosomiase intestinale. [ABSTRACT FROM AUTHOR]

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In order to characterize the demographic traits and spatial structure of Cameroonians Bulinus globosus, intermediate host of Schistosoma haematobium, genetic structure of seven different populations, collected from the tropical zone, was studied using six polymorphic microsatellites. Intrapopulation genetic diversity ranged from 0.37 to 0.55. Interpopulation genetic diversity variation clearly illustrated their significant isolation due to distance with gene flow substantially limited to neighbouring populations. The effective population sizes (Ne) were relatively low (from 3.0 to 18.6), which supposes a high rate from which populations would lose their genetic diversity by drift. Analysis of genetic temporal variability indicated fluctuations of allelic frequencies (35 of 42 locus-population combinations, P<0.05) characteristic of stochastic demography, and this is reinforced by events of bottlenecks detected in all populations. These findings demonstrated that Cameroonian B. globosus were mixed-maters with some populations showing clear preference for outcrossing. These data also suggest that genetic drift and gene flow are the main factors shaping the genetic structure of studied populations. [ABSTRACT FROM AUTHOR]

The article examines the potential of Egyptian Radix natalensis to act as an intermediate host in the lifecycle of Fasciola Hepatica. The researchers experimentally exposed R. natalensis to miracidia using lymnaeids and observed live larval forms of F. hepatica both in the single- and double-exposed snails. Findings also revealed a significant increase in snail survival after 28 days of exposure as well as a decrease in the prevalence of infection when the shell height of snails at exposure increases. The snails shed cercariae of F. hepatica during a mean patent period of 24.3 days and released all these cercariae during two-13 waves of shedding.

Experimental infections of Galba sp. (origin, Colombia) with allopatric isolates of Fasciola hepatica from France or Fascioloides magna from the Czech Republic were carried out during five successive snail generations to determine if this lymnaeid might sustain complete larval development of either parasite. In snails exposed to F. hepatica, 7 of 400 snails harboured several rediae and only two snails contained a small number of free cercariae on day 50 post-exposure. In contrast, the intensity of F. magna infection in Galba sp. progressively increased from the F1 to F5 generations. Spontaneous cercarial shedding of F. magna occurred in 7 of 100 Galba sp. belonging to the F5 generation and the number of shed cercariae did not differ significantly from that noted in control Galba truncatula of French origin. Galba sp. from Colombia can be added to the list of potential intermediate hosts for F. magna.

Experimental infections of two South American lymnaeid populations with Fascioloides magna were carried out to determine whether these snails may sustain larval development of this digenean and, if so, to quantify their potential for cercarial production. The reference group was a French population of Galba truncatula infected and raised according to the same protocol. According to the internal transcribed sequence (ITS)-1 segment of their genomic rDNA, these South American populations were identified as Lymnaea neotropica (origin, Argentina) and Lymnaea viatrix var. ventricosa (origin, Uruguay). In the snail groups followed for cercarial shedding, longer prepatent periods and lower numbers of shed cercariae were noted in South American lymnaeids. In other snails dissected at day 65 post-exposure, the redial and cercarial burdens of F. magna found in the bodies of L. neotropica and L. v. ventricosa were significantly lower than those noted in G. truncatula. Compared to the total cercarial production noted in the dissected snails, the percentage of cercariae that exited from snails was 51.3% for G. truncatula, 32.2% for L. neotropica and 46.8% for L. v. ventricosa. The two South American species of snails can thus be considered as potential intermediate hosts of F. magna.

In order to evaluate the snail host contribution on the variability of mollusk/schistosome compatibility, the genetic structure of seven Cameroonian populations of the schistosome vector, Bulinus truncatus, was studied using four variable microsatellite loci. A substantial polymorphism mainly distributed among populations was observed. No heterozygous genotype was scored, confirming the high level of selfing rate occurring in B. truncatus populations. Contemporaneous samples were highly and significantly differentiated with a marginally significant correlation with geographical distances (P-value=0.069). The different sites sampled seemed to rarely exchange migrants with very small Nm (∼0.22 or below). The data also suggest that B. truncatus subpopulations might be composed of very small and isolated units at much smaller surfaces than what was investigated. Even if more data (in particular more loci) will be needed to confirm these issues, they suggest that restricted gene flow plays an important role in maintaining differentiation among snail populations in the transmission foci, potentially leading to specific adaptation between each B. truncatus population and its local Schistosoma haematobium population., (Copyright © 2010 Elsevier B.V. All rights reserved.)