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This paper focuses on the geographical distribution and habitats of Lymnaea truncatula, the intermediate, snail host of the liver fluke, Fasciola hepatica, as reflected by the 723 samples in the database of the National Freshwater Snail Collection, Potchefstroom, South Africa. The 221 different loci (1/16-degree squares) on record reflect an extensive but discontinuous distribution, except in Lesotho and in parts of the Mpumalanga, Gauteng and North West provinces of South Africa. Although recorded from 12 different types of waterbody, it was mostly (42.0 %) recovered from swamps. Most samples (45.8 %) were collected in habitats with slow-flowing water. A muddy substratum was recorded for 62.5 % of the samples. Most samples (86.3 %) were collected in habitats with a mean annual air temperature of 10-20 o C, and more than 69 % came from localities with a mean annual rainfall of 600-900mm. An integrated decision tree constructed from the data indicated that temperature and types of waterbody play a decisive role in determining the presence of L. truncatula in a given area. A temperature index calculated for all mollusc species ranked L. truncatula second in a total of 53 species according to its association with low temperatures. It remains to be established whether its distribution is indeed discontinuous, and whether its preference for a particular habitat, amphibious habits and ability to aestivate could have resulted in some populations having been overlooked during surveys.

International audience; Experimental infections of Lymnaea truncatula with a digenean species (Fasciola gigantica, F. hepatica, or Paramphistomum daubneyi) were performed under laboratory conditions to study the effect of four sources of food (microalgae, romaine lettuce, wheat germs, or modified Boray diet) on cercarial production. The mean number of F. hepatica, F. gigantica, or P. daubneyi cercariae was significantly greater when snail food was microalgae or Boray diet. The lowest cost prices for 100 metacercariae of F. hepatica (9.7-10.1 euros) were noted when algae of Boray diet were used as food for snails. In contrast, the highest prices (18.0-18.5 euros) were found in lettuce-reared snails. The choice of a source of food for breeding the intermediate hosts of F. hepatica and collecting metacercariae must take into account the importance of the commercial demand for metacercariae and will depend on the strategy the producer wishes to develop.; Influence de différentes sources de nourriture sur la production cercarienne chez des Lymnaea truncatula infestées expérimentalement par des Digènes. Des infestations expérimentales de Lymnaea truncatula avec un Digène (Fasciola gigantica, F. hepatica, or Paramphistomum daubneyi) ont été réalisées dans les conditions du laboratoire afin d'étudier l'impact de quatre types de nourriture (algues, laitue romaine, germes de blé, aliment modifié de Boray) sur la croissance des mollusques et la production cercarienne. La production cercarienne de F. hepatica, de F. gigantica ou de P. daubneyi était significativement plus élevée lorsque le mollusque était nourri avec des algues ou avec l'aliment modifié de Boray. Les prix de revient les plus faibles pour 100 métacercaires de F. hepatica (9,7-10,1 euros) ont été obtenus avec l'emploi d'algues ou de l'aliment modifié de Boray. Les prix les plus élevés (18,0-18,5 euros) ont été notés avec l'emploi de la laitue. Le choix de l'alimentation pour élever les hôtes intermédiaires de F. hepatica et recueillir les métacercaires doit tenir compte de l'importance de la demande commerciale pour ces larves et dépendra de la stratégie que le producteur souhaite développer.

Des investigations malacologiques ont ete realisees en 1994-1995 le long de deux secteurs de riviere pour denombrer les gites du mollusque Lymnaea truncatula et determiner leurs caracteristiques. Les deux secteurs etudies concernent a) la Creuse sur 10 km, a cote d'Argenton-sur-Creuse (Indre) et b) la Vienne sur 25 km, entre Saint-Victurnien (Haute-Vienne) et Etagnac (Charente). Le mollusque est present dans 27 stations sur la Creuse mais on note de grandes variations dans l'abondance de la limnee : 6 gites avec moins de 10 L. truncatula en juillet, 9 avec 11 a 20 limnees, 6 avec 21 a 50 mollusques, et 6 avec plus de 51 individus. La longueur des gites ne depasse pas 5 m dans 15 cas, 10 m dans 6 cas, 15 m dans 4 cas et 35 m dans les 2 autres stations. Neuf gites a L. truncatula ont ete retrouves sur les 25 km de la Vienne. Un habitat est fort de 101 limnees tandis que les autres ont de faibles effectifs avec moins de 50 limnees par gite. Le gite s'etend sur 5 metres de rive dans huit cas et sur 30 m dans l'autre cas. De cette etude, il ressort que ces berges de riviere ne constituent pas un milieu favorable pour le developpement de l'espece.

Des investigations malacologiques ont ete realisees en 1974 et en 1994-1995 dans trois prairies de la Haute-Vienne afin de preciser les caracteristiques des gites a limnees lorsque les parcelles sont abandonnees ou modifiees par l'application de mesures agronomiques. L'abandon d'une prairie et l'invasion de ragondins se sont traduits par des modifications dans la distribution des limnees. Lymnaea cf. fuscus a deserte le fosse principal de drainage pour coloniser les rigoles et les couloirs crees par ces rongeurs, ce qui s'est traduit par un accroissement important de la superficie du nouveau gite. Les effectifs moyens de L. cf. fuscus et de L. truncatula ont augmente aux depens de ceux de L. glabra. Un autre mollusque aquatique, Physa acuta, a envahi le fosse laisse libre. Le curage des rigoles dans les deux autres prairies et leur invasion par une ou deux especes aquatiques (L. ovata, Potamopyrgus antipodarum ou Physa acuta) se sont traduits par une extension dans la superficie du gite aussi bien pour les mollusques colonisateurs que pour L. glabra et L. truncatula. Les effectifs des trois premieres especes sont assez importants dans ces deux rigoles ; par contre, on note une reduction du nombre des deux limnees.

The re-examination of the voucher specimens identified by Kanev et al. (1987) as E. echinatum (Zeder, 1803) showed that two distinct species have been considered as E. echinatum: E. sarcinum Dietz, 1909, possessing 47 collar spines [Lymnaea truncatula strain — set ‘L’ (No. 326 TB)] and Echinostoma sp. (?echinatum) with 37 collar spines [Planorbis planorbis strain — set ‘P’ (No. 327 TB)]. The material of E. sarcinum is described and differentiated from E. revolutum and E. echinatum (sensu Kanev, 1985). The present results suggest that species identity of the material described as E. echinatum in Kanev's (1985) experimental study requires further clarification.

Adult Lymnaea truncatula were subjected to 10 days of experimental desiccation and then remained in water for 1 or 8 days before each was exposed to a single miracidium. The infection rate was lower in these snails than in infected controls that were not exposed to stress (52–54% vs 73%). The redial burden clearly decreased in stressed snails (18–25 rediae per snail) than in controls (43 rediae). This numerical decrease concerned essentially: i) live independent rediae of the first generation and the first cohort of the second generation, and ii) dependent rediae of subsequent generations. Mature rediae were more numerous in the first cohort of the second generation than in the other generations. Desiccation before exposure limited the size of the redial burden but placement in water for 8 days just after the stress attenuated the effects of this factor.

Les limnees presentes dans 17 cressonnieres naturelles ont ete soumises pendant 1 ou 2 annees a un controle associant l'emploi d'un molluscicide (CuCl 2 ) et l'introduction d'un mollusque predateur, Zonitoides nitidus. La limnee tronquee a ete eliminee en une seule annee de traitement dans 14 stations, en deux ans dans les trois autres. L'emimination des autres Pulmones aquatiques s'est faite en deux ans pour L. glabra, 3 ans pour L. palustris et en une seule annee pour Physa acuta. Le predateur a disparu de 12 cressonnieres au cours de la 4 e annee apres le traitement, dans les 5 autres, les effectifs de Z. nitidus se sont accrus pendant 1 ou 2 ans avant de diminuer par la suite et de disparaitre

Single-miracidium infections of Lymnaea truncatula by Fasciola hepatica were carried out to determine the cercarial productivity of each redial generation when the first-appearing mother redia (R1a redia) normally developed (usual development of redial generations) or quickly died (unusual development). In both developmental patterns of infection, the number of morulae was significantly higher in the second-appearing mother rediae (R1b group) than in either the daughter rediae from R1a rediae (R2a group) or the rediae from subsequent groups (R2b/R3a). The live R1a group did not produce cercariae. The percentages of cercariae produced by the R1b, R2a, and R2b/R3a groups were 28.2%, 62.8%, and 8.9% when the development of redial generations was usual. In contrast, in an unusual development, they were 69.3%, 20.3%, and 10.2%, respectively. Cercarial production until day 63 post-exposure was essentially provided by the R2a rediae, when the development of redial generations was usual, and by the R1b rediae when it was unusual.

En Colombia se ha registrado la presencia de Paramphistomidae (Trematoda: Digenea) parasitando el rumen de bovinos de la costa Caribe, los Llanos Orientales y el suroccidente. En estas publicaciones se menciona la presencia y prevalencia de los paramfistómidos, pero todas carecen de la descripción morfológica de los digeneos. El hallazgo de paramfistómidos adultos en el rumen de ejemplares Bos taurus, procedentes del sector Llanogrande, en el municipio de Rionegro, Antioquia, motivó la presente investigación, con el propósito de describir los diferentes estadíos del parásito y establecer el estatus taxonómico específico. Del rumen de una hembra, Bos taurus, sacrificada en la Central Ganadera del municipio de Medellín, se extrajeron vivos 52 digeneos adultos. En el laboratorio se aislaron huevos que se incubaron hasta la obtención de miracidios. Con ellos se infectaron 50 moluscos Lymnaea truncatula. La morfología de los adultos y estadíos larvarios del paramfistómido permitió determinarlo como Cotylophoron cotylophorum. En L. truncatula se obtuvo una infección del 5.1 %. Con este registro se amplia la distribución geográfica y altitudinal del parásito a la región altoandina, noroccidental de Colombia. The presence of Paramphistomidae parasites (Trematoda: Digenea) inside the rumen (first stomach) has been recorded in Colombia in cattle from the Caribbean coast, the Eastern Plains region in the east, and the southwest of the country. However, studies on the presence and prevalence of the parasite do not include any morphological description. This study includes research findings from adult Paramphistomidae parasites in the rumen of Bos taurus specimens from Llanogrande in the municipality of Rionegro, Antioquia. The aim of this research was to describe all the developmental stages of the parasite and to establish its specific taxonomical status. 52 live adult parasites were found in the rumen of a female Bos taurus sacrificed in the slaughter house Central Ganadera of Medellin. Eggs from adults were obtained in the laboratory, and hatching was stimulated to obtain miracidia. 50 Lymnaea truncatula snails were exposed to the miracidia, resulting in an infection rate of 5.1 %. The parasite was identified as Cotylophoron cotylophorum by using adult morphology and larval stages. This finding expands the parasite’s geographical and altitudinal distribution to the andean highlands in northwestern Colombia. Na Colômbia tem-se encontrado a presencia de Paramphistomidae (Trematoda: Digenea) parasitando no rúmen de bovinos da costa Caribe, os Llanos Orientales e no sul oeste. Nestas publicações tem-se mencionado a presencia e prevalência dos paramfistómidos, mas todas carecem da descrição morfológica dos digeneos. Do rúmen de uma fêmea Bos taurus proveniente do município de Rionegro e sacrificada na Central Ganadera do município de Medellín, se extraíram vivos 52 digeneos adultos. No laboratório foram isolados os ovo e forma obtidos os miracidios. Com eles foram infetados 50 moluscos Lymnaea truncatula. A morfologia dos adultos e estádios larvários do paramfistómido permitiu determinar-lho como Cotylophoron cotylophorum. Em L. truncatula foi obtido uma infecção de 5.1 %. Com este fato, se amplia a distribuição geográfica e altitudinal do parasita na região alta dos Andes colombianos.

Algunos Paramphistomidae (Trematoda: Digenea) parasitan el sistema digestivo de rumiantes de importancia económica en el mundo. En Colombia han sido reseñadas dos especies en bovinos de la costa Caribe y de los llanos orientales. Esta investigación tuvo como objetivo determinar la frecuencia de un paramfistómido en bovinos y caracoles de una hacienda localizada en Rionegro, Antioquia. En ésta se hicieron cuatro muestreos trimestrales entre julio de 2004 y julio de 2005. Se colectaron heces de los vacunos en ordeño para hacer diagnóstico mediante la técnica de Dennis. Los caracoles se capturaron en diversos ecosistemas acuáticos del lugar y su infección fue establecida mediante disección. Los huevos y los estadíos intramolusco del parásito fueron descritos y fotografiados. La frecuencia del paramfistómido fue del 100% en los 71 bovinos evaluados; de estos, el 80% (51 vacunos) presentaron además un fasciólido. Los huevos de ambos digeneos se diferenciaron mediante su coloración y la familia se confirmó mediante la eclosión de los miracidios. Se colectaron 1.146 caracoles determinados como Lymnaea truncatula y 335 determinados como Lymnaea columella, cuyas frecuencias de infección por el paramfistomido fueron 25, 47 y 1.79%, respectivamente. La morfología de los estadíos intramolusco obtenidos fue compatible con las familias Paramphistomidae y Fasciolidae. Este constituye el primer registro de un foco de paramfistomosis bovina en una zona alto andina, al occidente de Colombia, donde se destaca la presencia en simpatría con Fasciola hepatica y de dos especies de moluscos hospedadoras de ambos digéneos. Las frecuencias de infección en los caracoles, sugieren a L. truncatula como hospedador intermediario principal del paramfistómido y a L. columella como hospedador intermediario alterno del mismo. La alta frecuencia del paramfistomido puede obedecer al desconocimiento de su presencia en el hato y por ende a la ausencia de medidas para su control. Some Paramphistomidae (Region Trematoda: Digenea) parasitize the digestive system of economically important ruminants worldwide. Two species of these flukes have been recorded in cattle from the Caribbean Coast and eastern plains of Colombia. The objective of this study was to determine the frequency of paramphistomids in both dairy cattle (n = 71) and snails on a dairy farm in Rionegro (Antioquia), located in the western Andes. Four quarterly fecal samples were taken in the farm from July 2004 to July 2005. Faeces were collected from lactating dairy cows for diagnosis by using the Dennis technique. Snails were captured in diverse aquatic ecosystems of the locality and their infection status was confirmed by dissection under stereoscopic exam. The eggs and intra-mollusc stages of the parasite were described and photographed. The frequency of the paramphistomid was 100% in the 71 cows evaluated, of which 51 (80%) also presented fasciolid flukes. Eggs of the two digeneid species were differentiated based on their coloration, and the identity of the family confirmed through eclosion of the miracidia. In all 1146 snails were collected and identified as Lymnaea truncatula and a further 335 as L. columella, whose rates of infection to the paramphistomid were 25, 47 and 1.79% respectively. The morphologies of the intra-mollusc stages obtained were compatible with members of the families Paramphistomidae and Fasciolidae. This constitutes the first record of a focus of bovine paramphistomosis in the high Andean zone of western Colombia. The presence in sympatry of the paramphistomid with Fasciola hepatica is noteworthy, as is the finding of two host snail species for both digeneids. The frequencies of infection in the snails indicate that L. truncatula acts as the principal intermediate host of the paramphistomid and L. columella as its alternate intermediate host. Although the frequency of paramphistomids in the herd was very high, presence of the parasite was unsuspected until the present study. This explains the absence of measures for its control. Alguns Paramphistomidae (Trematoda: Digenea) parasitam o sistema digestivo de ruminantes de importância econômica no mundo. Na Colômbia têm sido identificadas duas espécies em bovinos da Costa Caribe e dos Llanos Orientais Nacionais. Este trabalho de pesquisa teve como objetivo determinar a freqüência de um paramfistómido em bovinos e caracóis de uma fazenda localizada em Rionegro, Antioquia. Nesta fazenda foram feitas quatro amostragens trimestrais entre julho de 2004 e julho de 2005 coletando fezes de bovinos em ordenho, para fazer o diagnóstico mediante a técnica de Dennis. Os caracóis foram capturados em diversos ecossistemas aquáticos do lugar e sua infecção estabelecida mediante dissecção. Os ovos e os estádios intramolusco do parasito foram descritos e fotografados. A freqüência do paramfistómido foi de 100% nos 71 bovinos avaliados, de estes, o 80% (51 bovinos) apresentaram ademais um fasciólido. Os ovos de ambos digêneos diferenciaram-se mediante sua coloração e a família se confirmou mediante a eclosão dos miracidios. Foram coletados 1.146 caracois catalogados como Lymnaea truncatula e 335 catalogados como Lymnaea columella, cujas freqüências de infeção pelo paramfistomido foram 25, 47 e 1.79%, respectivamente. A morfologia dos estádios intramolusco obtidos foi compatível com as familias Paramphistomidae e Fasciolidae. Isto constitui o primeiro registro de um foco de paramfistomosis bovina numa região alto andina, no ocidente da Colômbia, donde destaca-se a presença em simpatría com Fasciola hepatica e duas espécies de moluscos hospedeiros de ambos digêneos. As freqüências de infecção nos caracóis, sugerem L. truncatula como hospedeiro intermediário principal do paramfistómido e L. columella como hospedeiro intermediário alternativo do mesmo. A alta freqüência do paramfistomido pode obedecer ao desconhecimento de sua presença no rebanho e por tanto à ausência de medidas para seu controle.

RESUMEN: Algunos Paramphistomidae (Trematoda: Digenea) parasitan el sistema digestivo de rumiantes de importancia económica en el mundo. En Colombia han sido reseñadas dos especies en bovinos de la costa Caribe y de los llanos orientales. Esta investigación tuvo como objetivo determinar la frecuencia de un paramfistómido en bovinos y caracoles de una hacienda localizada en Rionegro, Antioquia. En ésta se hicieron cuatro muestreos trimestrales entre julio de 2004 y julio de 2005. Se colectaron heces de los vacunos en ordeño para hacer diagnóstico mediante la técnica de Dennis. Los caracoles se capturaron en diversos ecosistemas acuáticos del lugar y su infección fue establecida mediante disección. Los huevos y los estadíos intramolusco del parásito fueron descritos y fotografiados. La frecuencia del paramfistómido fue del 100% en los 71 bovinos evaluados; de estos, el 80% (51 vacunos) presentaron además un fasciólido. Los huevos de ambos digeneos se diferenciaron mediante su coloración y la familia se confirmó mediante la eclosión de los miracidios. Se colectaron 1.146 caracoles determinados como Lymnaea truncatula y 335 determinados como Lymnaea columella, cuyas frecuencias de infección por el paramfistomido fueron 25, 47 y 1.79%, respectivamente. La morfología de los estadíos intramolusco obtenidos fue compatible con las familias Paramphistomidae y Fasciolidae. Este constituye el primer registro de un foco de paramfistomosis bovina en una zona alto andina, al occidente de Colombia, donde se destaca la presencia en simpatría con Fasciola hepatica y de dos especies de moluscos hospedadoras de ambos digéneos. Las frecuencias de infección en los caracoles, sugieren a L. truncatula como hospedador intermediario principal del paramfistómido y a L. columella como hospedador intermediario alterno del mismo. La alta frecuencia del paramfistomido puede obedecer al desconocimiento de su presencia en el hato y por ende a la ausencia de medidas para su control. SUMMARY: Some Paramphistomidae (Region Trematoda: Digenea) parasitize the digestive system of economically important ruminants worldwide. Two species of these flukes have been recorded in cattle from the Caribbean Coast and eastern plains of Colombia. The objective of this study was to determine the frequency of paramphistomids in both dairy cattle (n = 71) and snails on a dairy farm in Rionegro (Antioquia), located in the western Andes. Four quarterly fecal samples were taken in the farm from July 2004 to July 2005. Faeces were collected from lactating dairy cows for diagnosis by using the Dennis technique. Snails were captured in diverse aquatic ecosystems of the locality and their infection status was confirmed by dissection under stereoscopic exam. The eggs and intra-mollusc stages of the parasite were described and photographed. The frequency of the paramphistomid was 100% in the 71 cows evaluated, of which 51 (80%) also presented fasciolid flukes. Eggs of the two digeneid species were differentiated based on their coloration, and the identity of the family confirmed through eclosion of the miracidia. In all 1146 snails were collected and identified as Lymnaea truncatula and a further 335 as L. columella, whose rates of infection to the paramphistomid were 25, 47 and 1.79% respectively. The morphologies of the intra-mollusc stages obtained were compatible with members of the families Paramphistomidae and Fasciolidae. This constitutes the first record of a focus of bovine paramphistomosis in the high Andean zone of western Colombia. The presence in sympatry of the paramphistomid with Fasciola hepatica is noteworthy, as is the finding of two host snail species for both digeneids. The frequencies of infection in the snails indicate that L. truncatula acts as the principal intermediate host of the paramphistomid and L. columella as its alternate intermediate host. Although the frequency of paramphistomids in the herd was very high, presence of the parasite was unsuspected until the present study. This explains the absence of measures for its control. RESUMO: Alguns Paramphistomidae (Trematoda: Digenea) parasitam o sistema digestivo de ruminantes de importância econômica no mundo. Na Colômbia têm sido identificadas duas espécies em bovinos da Costa Caribe e dos Llanos Orientais Nacionais. Este trabalho de pesquisa teve como objetivo determinar a freqüência de um paramfistómido em bovinos e caracóis de uma fazenda localizada em Rionegro, Antioquia. Nesta fazenda foram feitas quatro amostragens trimestrais entre julho de 2004 e julho de 2005 coletando fezes de bovinos em ordenho, para fazer o diagnóstico mediante a técnica de Dennis. Os caracóis foram capturados em diversos ecossistemas aquáticos do lugar e sua infecção estabelecida mediante dissecção. Os ovos e os estádios intramolusco do parasito foram descritos e fotografados. A freqüência do paramfistómido foi de 100% nos 71 bovinos avaliados, de estes, o 80% (51 bovinos) apresentaram ademais um fasciólido. Os ovos de ambos digêneos diferenciaram-se mediante sua coloração e a família se confirmou mediante a eclosão dos miracidios. Foram coletados 1.146 caracois catalogados como Lymnaea truncatula e 335 catalogados como Lymnaea columella, cujas freqüências de infeção pelo paramfistomido foram 25, 47 e 1.79%, respectivamente. A morfologia dos estádios intramolusco obtidos foi compatível com as familias Paramphistomidae e Fasciolidae. Isto constitui o primeiro registro de um foco de paramfistomosis bovina numa região alto andina, no ocidente da Colômbia, donde destaca-se a presença em simpatría com Fasciola hepatica e duas espécies de moluscos hospedeiros de ambos digêneos. As freqüências de infecção nos caracóis, sugerem L. truncatula como hospedeiro intermediário principal do paramfistómido e L. columella como hospedeiro intermediário alternativo do mesmo. A alta freqüência do paramfistomido pode obedecer ao desconhecimento de sua presença no rebanho e por tanto à ausência de medidas para seu controle. COL0040189 COL0015099

We report on abundance and natural infection rates of Fasciola hepatica in Lymnaea truncatula snails from endemic rural areas of the Moscow Region. Field surveys were carried out monthly between May and October 2002, in two cattle farms of the Naro-Fominsk district and two of the Dmitrov district. Snail abundance was maximum in May (189 snails in spring) and minimum in July (5 snails in summer), probably due to more suitable microenvironmental conditions for snail development during spring. The prevalence registered during the studied period was 14.3%, with the highest (12.5%) and lowest (0.5%) estimates in September and May, respectively.

In April 2002, five cases of fascioliasis were diagnosed in Tourcoing. A case-finding and a case-control study were carried out to identify the source of the outbreak and take appropriate control measures. Eighteen cases were identified through the medical laboratories carrying out serology for fascioliasis. Fourteen cases and 23 controls, identified by the physicians of the cases, were interviewed on symptoms of the disease and their consumption of uncooked plants. Cases were more likely than controls to have eaten commercialized raw watercress (OR 86·7, PLymnaea truncatula. This outbreak of fascioliasis due to commercialized watercress indicates that actual sanitary regulations do not allow for the efficient prevention of infestation of watercress production in France.

Department of Veterinary Pathology, Agrary Faculty, Russian People’s Friendship University. Russian. The All-Russian Skryabin Institute of Helminthology. Russian. Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Núcleo de Biologia e Controle de Endo e Ectoparasitas de Interesse Médico e Veterinário, Departamento de Biologia. Rio de Janeiro, RJ, Brasil. We report on abundance and natural infection rates of Fasciola hepatica in Lymnaea truncatula snails from endemic rural areas of the Moscow Region. Field surveys were carried out monthly between May and October 2002, in two cattle farms of the Naro-Fominsk district and two of the Dmitrov district. Snail abundance was maximum in May (189 snails in spring) and minimum in July (5 snails in summer), probably due to more suitable microenvironmental conditions for snail development during spring. The prevalence registered during the studied period was 14.3%, with the highest (12.5%) and lowest (0.5%) estimates in September and May, respectively.

International audience

Fasciola hepatica mother rediae belonging to the first generation and the first cohort of the second generation were extracted from their snail intermediate host (Lymnaea truncatula) and maintained in vitro for 16 days to determine the quantity of daughter rediae and cercariae produced by each generation. L-15 Leibovitz medium with a saline fraction adjusted to that of the L. truncatula hemolymph was used for experiments. A total of 35 daughter rediae exited from the 21 mother rediae of the first and second generations, which were 14-32 days old at the onset of culture. Microscope examination of the mother rediae demonstrated the presence of numerous redial embryos and differentiating daughter rediae, whereas no cercaria was seen within their body. A total of 49 cercariae exited from the 17 mother rediae of the first and second generations, which were 29-50 days old at the onset of culture. No differentiating daughter redia was seen in these last mother rediae. The productivity of the first or second generation (first cohort) was nearly identical in terms of cercariae.

4 pages, 2 figures., The chaetotaxy of cercariae of the species Fasciola hepatica (Linnaeus, 1758), obtained from naturally infected snails of the species Lymnaea truncatula collected in Spain (Iberian Peninsula) was studied. Tbe results obtained were compared with the chaetotaxy of cercariae of the same species obtained from the same snail host species L. truncatula collected in Bulgaria (Balkan Peninsula). Papillae O-7DL and O-1PIIIL, which have not been observed in cercariae from Bulgaria, were identified in the cercariae from Spain. These differences are discussed with respect to the present day concept of the species, subspecies, variations and adaptive forms of F. hepatica., This study was sponsored by the Bulgarian Academy of Sciences, Fund National Scientific Investigation (Bulgaria), Grant No. NI B-23 1, B-526, and the Spanish Consejo Superior de Investigationes Científicas, within the Programme of Scientific Cooperation between Bulgaria and Spain.

Lymnaea truncatula, 4 mm in height, were subjected to infection by a single miracidium of Fasciola gigantica, then raised at 23°C until day 60 of the experiment. Histological study of these snails demonstrated a mean redial burden of 34 parasites at day 60, of which one third were degenerating forms. The mean number of living independent rediae did not exceed 5 for the first and second generations. Conversely, in subsequent generations there were as many as 18 rediae per snail at day 60. The first living redia of the first generation in particular gave rise to daughter rediae. Mature rediae appeared at day 35 and especially concerned the first and second generations at day 60. The authors conclude that development of the first and second redial generations occurs during the same period, and that the forms of the first cohort of the second generation are produced from the first redia of the first generation which originated from the sporocyst.

http://www.ncbi.nlm.nih.gov/pubmed/2050981, For two years fortnightly malacological samplings were carried out to collect Lymnaea truncatula (Mollusca; Basommatophora) at five points in the upper and middle Porma river basin, León, Spain. The highest numbers of snails were collected in September, May and November. Of the 5486 molluscs examined, 11.41% harboured F. hepatica (Trematoda; Digenea) with an average intensity of 20.14. In general, the values of both infection prevalence and intensity increased with the size of the snails. It was in October when the highest figures for each parameter mentioned above were detected (18.73% and 28.48, respectively). The chi-square test showed statistically significant differences in relation to the infection prevalence among the groups of molluscs established according to: their length; the months in which they were collected; the sampling localities; monthly average ambient temperature; precipitation during the collection. Similarly, statistically significant differences were detected in the intensity of the infection among the groups of molluscs previously established, except for that based on the values of precipitation. Generally, parasites were found in the same snail at different stages of development. It seems that most mollusc infections occur in February-March and at the end of summer-beginning of autumn periods. The highest rate of rediae with mature cercariae ready to be shed were detected between September and December. Metacercariae in the grass samples were also observed at the end of autumn. For this reason, this period could be considered as the most suitable for infection of the definitive hosts to take place., This study was supported by the Spanish CSIC (Project No ID-608) and DGICYT (Project GAN89-0525).

The authors study the influence of several factors: temperature, drying up of ground, bodily volume of intermediary host on development of the redial generations of Fasciola hepatica in Lymnaea truncatula. Three redial generations are seen in Lymnaea truncatula, whatever environmental factors. The number of rediae of generations 2 and 3 is correlated with bodily volume of the snail host. The temperature affects synchronism of cercarial maturation in rediae of generations 1 and 2.

SUMMARY It has been shown that the presence of active surface populations of Lymnaea truncatula in central highland Ethiopia is determined by adequate rainfall, and that associated transmission of Fasciola hepatica is mainly in the ‘overwintering’ variety, except in those years of above average rainfall when ‘summer’ infection may occur, leading to outbreaks of acute fascioliasis.

The principle of using mathematical modesl, based on temperature data, to predict the development times of the extra-mammalian stages of the liver fluke is described. The effect of temperature on survival of those stages are also modelled. The effect of temperature is also examined in relation to its effect on predation efficiency.

The duration of larval and pupal stages of two species of predatory flies was investigated at five constant temperatures. Ilione albiseta (Scopoli): Mean duration of first and second instars was shortest at 23 °C and there was 100% survival of first instar larvae at all temperatures. Mean third instar larval duration decreased from 104 days at 17 °C to 27.5 days at 26 °C. Total percentage larval survival was greatest at 17 °C and least at 26 °C. Mean pupal duration decreased as temperature increased and this occurred also under outdoor conditions. Pherbellia cinerella (Fallen): As temperature increased mean larval duration decreased but the percentage of larvae pupating also decreased (100% at 14 °C, 33.3 % at 26 °C). There was a trend for shorter mean pupal durations at higher temperatures. RESUME Action de la temperature sur les durees des developpements larvaire et nymphal de deux mouches Sciomyzidae: Ilione albiseta et Pherbellia cinerella, predatrices de Lymnaea truncatula. L'action de la temperature a ete examinee a 14, 17, 20, 23 et 26 °C. Les 2 especes sont predatrices de L. truncatula, vecteur de la douve du foie en Irlande, ou elle provoque a l'agriculture une perte evaluee a 10 millions de livres par an. Les donnees recuellies en conditions controlees du laboratoire doivent permettre de definir les conditions optimales pour l'elevage continu de ces especes. Ceci est indispensable pour evaluer, dans la nature leurs potentialites pour la lutte biologique. Ilione albiseta: C'est a 23 °C que le developpement des larves de premier et second stades sont les plus brefs; la survie du premier stade est totale a toutes les temperatures constantes examinees. La duree moyenne du 3eme stade decroit de 104 jours a 17 °C jusqu'a 27,5 jours a 26 °C. Le taux de survie total est plus ele a 17 °C qu'a 26 °C. La duree moyenne de la nymphose diminue quand la temperature croit, et ceci se produit aussi a la temperature ambiante exterieure. On reduit de moitie la duree du developpement de l'eclosion de l'oeuf a l'apparition de l'adulte, entre la nature et le laboratoire, en utilisant respectivement: 23°, 17° et 26 °C pour les premier et second stades, le troisieme stade, la nymphe. Cela devrait aider a multiplier la souche pour la lutte biologique. Pherbellia cinerella: Avec elevation de la temperature la duree du developpement larvaire diminue, mais aussi le nombre de larves parvenant a la pupaison (100% a et 14° et 33,3% a 26 °C). La nymphose tendait a etre plus breve aux temperatures les plus elevees.

SUMMARYExperimental studies on the dynamics of infection of Lymnaea truncatula by the miracidia of Fasciola hepatica show that there is a linear relationship between the net rate of attachment of miracidia to snail epithelium and the density of infective stages. The probability of a snail remaining uninfected after exposure to a single miracidium varies with the size class of the snail. Under the conditions of the experiment (temperature, 15° C; exposure period, 30 min; water volume, 8 ml), the probability was 0·46–0·48, 0·27–0·26 and 0·13–0·19 for snail size classes, 0·5–2·9, 3·0-5·9 and 6·0-8·9 mm respectively.

The different rediae of Fasciola hepatica were counted in 398 snails individually exposed to single miracidium and then killed at day 30 post-exposure at 20 degrees C. When the redia n degree 1 of generation 1 was alive (327 snails), it produced rediae of generation 2 with high numbers (until 19): these rediae were precocious and could be followed by differentiation of cercariae. When the redia n degree 1 of generation 1 was degenerated (71 snails), an other redia--redia n degree 2 of generation 1 or redia n degree 1 of generation 2--produced daughter rediae with low numbers (until 9): these latter rediae differentiated in the same time as cercariae. The significance of these observations is discussed.

Cette etude traite des resultats positifs et negatifs obtenus apres une annee d’application d’une technique de lutte biologique sur 49 stations de la Haute-Vienne, France. Les resultats negatifs peuvent s’expliquer par les effets de 6 facteurs naturels :1 -la hauteur de l’eau pluviale recue par les habitats durant les 10 premiers jours de l’experimentation. Le taux de mortalite naturelle et de predation des limnees diminue lorsque la hauteur de l’eau recue depasse 8 mm. Les predateurs fuient le sediment detrempe et n’y consomment pas de limnees ;2 -la presence de blocs de pierre sur l’habitat. Ces blocs constituent des abris pour les limnees ;3 -la qualite de la couverture vegetale. Il faut utiliser les joncs et les graminees de preference ;4 -le traitement prealable de l’habitat par voie chimique (sulfate de cuivre) juste avant l’application de la lutte biologique. Les predateurs consomment de preference les limnees les plus intoxiquees et delaissent les plus saines ;5 -la presence d’acariens phoretiques sur les predateurs qui en meurent ;6 -le comportement des ovins sur les habitats situes sur les pâtures a forte declivite. Leurs passages repetes entrainent l’ecrasement de la plupart des predateurs.Les solutions adoptees sont discutees en fonction de la region d’experimentation.

Les limnees tronquees recoltees sur le terrain montrent l’existence d’une reaction amibocytaire generalisee lorsqu’elles sont infestees par Fasciola hepatica. Cette reaction cellulaire se retrouve chez les mollusques eleves dans les conditions standard du laboratoire (20° C) avec une infestation fasciolienne evolutive ou abortive.L’intensite de la reaction est identique chez les limnees exposees chacune a un seul miracidium au laboratoire, que l’infestation soit evolutive ou abortive ; par contre la reaction est quasi-nulle chez les limnees non infestees ou les temoins. L’intensite de la reaction varie en fonction de l’origine geographique des limnees ou des miracidiums utilises.L’intensite de la reaction croit chez les limnees a infestation evolutive si le nombre de miracidiums presents par exposition ou le nombre d’expositions augmentent. Elle est par contre toujours equivalente chez les individus a infestation abortive de la meme population, quels que soient les nombres de miracidiums et d’expositions.La signification de ces resultats est discutee.

The kidney of Lymnaea truncatula showed structural changes when infected by Fasciola hepatica. These changes first occurred at day 21 postexposure at 20 degrees C and concerned a destruction of renal epithelial cells followed by an epithelial hyperplasia. These hyperplasied epithelial cells again showed a destruction at days 49 and 70 post-exposure. The significance of these results is discussed.

Lymnaea truncatula infestee par Fasciola hepatica presente une succession de trois generations rediennes lorsque des mollusques de 4 mm de hauteur sont exposes chacun a un seul miracidium et eleves ensuite a 20° C jusqu’au 30e jour post-exposition. L’origine geographique de L. truncatula ne retentit que sur le nombre de redies des generations 2 et 3. L’origine geographique des miracidiums n’a pas d’influence sur le developpement de ces generations rediennes. La succession de ces generations est par contre modifiee chez les mollusques soumis a des infestations plurimiracidiennes. A partir de 5 miracidiums pour une seule exposition, s’observe une chute du nombre moyen des redies affectant surtout les generations 2 et 3 ; pour les redies des generations 1 et 2, il existe un retard de maturation d’autant plus grand que le nombre de miracidiums est plus eleve. A partir de 4 expositions monomiracidiennes successives, on retrouve les resultats precites.La signification de ces observations est discutee.

SUMMARY The prevalence of infection with Fasciola hepatica in both primary and intermediate hosts was monitored on two farms for a period of three years. A succession of increasingly prolonged and intense droughts in the spring and early summer of each year was associated with a progressive decline in the proportion of hosts affected. The exceptional pattern of infection in one of the populations of Lymnaea truncatula was explained in terms of the microclimate at the soil surface of the habitat.