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      Pseudosuccinea columella: age resistance to Calicophoron daubneyi infection in two snail populations Translated title: Pseudosuccinea columella: résistance à l’infestation par Calicophoron daubneyi chez deux populations de limnées en fonction de l’âge

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          Individual infections of Egyptian and French Pseudosuccinea columella with five miracidia of Calicophoron daubneyi were carried out to determine whether this lymnaeid was capable of sustaining larval development of this parasite. On day 42 post-exposure (at 23 °C), infected snails were only noted in groups of individuals measuring 1 or 2 mm in height at miracidial exposure. Snail survival in the 2-mm groups was significantly higher than that noted in the 1-mm snails, whatever the geographic origin of snail population. In contrast, prevalence of C. daubneyi infection was significantly greater in the 1-mm groups (15–20% versus 3.4–4.0% in the 2-mm snails). Low values were noted for the mean shell growth of infected snails at their death (3.1–4.0 mm) and the mean number of cercariae (<9 in the 1-mm groups, <19 in the 2-mm snails). No significant differences between snail populations and snails groups were noted for these last two parameters. Most infected snails died after a single cercarial shedding wave. Both populations of P. columella showed an age resistance to C. daubneyi infection and only juveniles measuring 2 mm or less in shell height at exposure can ensure larval development of this digenean up to cercarial shedding.

          Translated abstract

          Des infestations individuelles de Pseudosuccinea columella provenant d’Egypte et de France, avec cinq miracidiums de Calicophoron daubneyi, ont été réalisées afin de déterminer si cette limnée était capable de soutenir le développement larvaire de ce parasite. Au 42 ème jour post-exposition (à 23 °C), seuls les groupes constitués par des individus mesurant 1 ou 2 mm lors de l’exposition miracidienne ont montré la présence de mollusques infestés. La survie des limnées dans le groupe 2 mm est significativement meilleure que celle trouvée chez les individus de 1 mm, quelle que soit l’origine géographique de la population. Par contre, la prévalence de l’infestation avec C. daubneyi est significativement plus importante dans les groupes 1 mm (15–20 % au lieu de 3,4–4,0 % chez les individus de 2 mm). De faibles valeurs ont été notées pour la croissance moyenne des individus infestés à leur mort (3.1-4.0 mm) et le nombre moyen de cercaires émises (< 9 dans les groupes 1 mm, < 19 chez les individus de 2 mm). Aucune différence significative entre les deux populations et également entre les groupes n’a été trouvée pour ces deux derniers paramètres. La plupart des individus infestés sont morts après une seule vague d’émission cercarienne. Les deux populations de P. columella montrent une résistance à l’infestation par C. daubneyi en fonction de l’âge des individus et seuls les juvéniles mesurant 2 mm de hauteur ou moins lors de l’exposition peuvent assurer le développement larvaire de ce Digène jusqu’aux émissions cercariennes.

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          Most cited references 20

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          Hosts and parasites as aliens.

          Over the past decades, various free-living animals (hosts) and their parasites have invaded recipient areas in which they had not previously occurred, thus gaining the status of aliens or exotics. In general this happened to a low extent for hundreds of years. With variable frequency, invasions have been followed by the dispersal and establishment of non-indigenous species, whether host or parasite. In the literature thus far, colonizations by both hosts and parasites have not been treated and reviewed together, although both are usually interwoven in various ways. As to those factors permitting invasive success and colonization strength, various hypotheses have been put forward depending on the scientific background of respective authors and on the conspicuousness of certain invasions. Researchers who have tried to analyse characteristic developmental patterns, the speed of dispersal or the degree of genetic divergence in populations of alien species have come to different conclusions. Among parasitologists, the applied aspects of parasite invasions, such as the negative effects on economically important hosts, have long been at the centre of interest. In this contribution, invasions by hosts as well as parasites are considered comparatively, revealing many similarities and a few differences. Two helminths, the liver fluke, Fasciola hepatica, of cattle and sheep and the swimbladder nematode, Anguillicola crassus, of eels are shown to be useful as model parasites for the study of animal invasions and environmental global change. Introductions of F. hepatica have been associated with imports of cattle or other grazing animals. In various target areas, susceptible lymnaeid snails serving as intermediate hosts were either naturally present and/or were introduced from the donor continent of the parasite (Europe) and/or from other regions which were not within the original range of the parasite, partly reflecting progressive stages of a global biota change. In several introduced areas, F. hepatica co-occurs with native or exotic populations of the congeneric F. gigantica, with thus far unknown implications. Over the fluke's extended range, in addition to domestic stock animals, wild native or naturalized mammals can also serve as final hosts. Indigenous and displaced populations of F. hepatica, however, have not yet been studied comparatively from an evolutionary perspective. A. crassus, from the Far East, has invaded three continents, without the previous naturalization of its natural host Anguilla japonica, by switching to the respective indigenous eel species. Local entomostrac crustaceans serve as susceptible intermediate hosts. The novel final hosts turned out to be naive in respect to the introduced nematode with far reaching consequences for the parasite's morphology (size), abundance and pathogenicity. Comparative infection experiments with Japanese and European eels yielded many differences in the hosts' immune defence, mirroring coevolution versus an abrupt host switch associated with the introduction of the helminth. In other associations of native hosts and invasive parasites, the elevated pathogenicity of the parasite seems to result from other deficiencies such as a lack of anti-parasitic behaviour of the naïve host compared to the donor host which displays distinct behavioural patterns, keeping the abundance of the parasite low. From the small amount of available literature, it can be concluded that the adaptation of certain populations of the novel host to the alien parasite takes several decades to a century or more. Summarizing all we know about hosts and parasites as aliens, tentative patterns and principles can be figured out, but individual case studies teach us that generalizations should be avoided.
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            Fasciola hepatica and Paramphistomum daubneyi: changes in prevalences of natural infections in cattle and in Lymnaea truncatula from central France over the past 12 years.

            A retrospective study was carried out over a 10- to 12-year period to analyse the changes in prevalences of natural fasciolosis and paramphistomosis among cattle and snails in central France, and to determine the causes which had induced these changes. The prevalences of natural fasciolosis in cattle increased from 1990 to 1993 (13.6% to 25.2%) and diminished afterwards up to 1999 (at 12.6%). Those of natural paramphistomosis showed a progressive increase between 1990 and 1999 (from 5.2 to 44.7%). The prevalences of natural infections and the numbers of free rediae counted in the snails (Lymnaea truncatula) infected with F. hepatica did not show any significant variations over time. By contrast, the prevalences of natural paramphistomosis in snails significantly increased from 1989 to 1996 and remained afterwards in the same range of values (3.7-5.3%), while the number of free rediae significantly increased up to 2000 (from a mean of 6.5 to 13.8 rediae per infected snail, respectively). Three hypotheses may explain the increase of paramphistomosis in cattle and snails: a better quality of diagnosis for the detection of P. daubneyi eggs in veterinary analysis laboratories, the use of specific molecules in the treatment of cattle fasciolosis since 1993, and the lack of an effective treatment up to now against cattle paramphistomosis. Since the objective of most farmers in central France is to obtain the highest antiparasitic efficiency with a single treatment of cattle per year, it is reasonable to assume that the prevalence of bovine paramphistomosis will continue to increase in the future.
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              Some observations on the epidemiology of fascioliasis in relation to the timing of molluscicide applications in the control of the disease.

               C Ollerenshaw (1971)

                Author and article information

                EDP Sciences
                10 February 2015
                : 22
                : ( publisher-idID: parasite/2015/01 )
                [1 ] Department of Zoology, Faculty of Science, University of Tanta Tanta Egypt
                [2 ] INSERM 1094, Faculties of Medicine and Pharmacy 87025 Limoges France
                Author notes
                [* ]Corresponding author: gilles.dreyfuss@ 123456unilim.fr
                parasite140130 10.1051/parasite/2015003
                © Y. Dar et al., published by EDP Sciences, 2015

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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                Figures: 0, Tables: 2, Equations: 0, References: 44, Pages: 6
                Research Article


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