In the present study, we describe the investigation of Echinostoma friedi excretory/secretory products using a proteomic approach combined with the use of heterologous antibodies. We have identified 18 protein spots corresponding to ten proteins, including cytoskeletal proteins like actin, tropomyosin, and paramyosin; glycolytic enzymes like enolase, glyceraldehyde 3P dehydrogenase, and aldolase; detoxifying enzymes like GSTs; and stress proteins like heat shock protein (Hsp) 70. Among these proteins, both actin and, to a lesser extent, Hsp70, exhibited differential expression patterns between chronic and acute infections in the Echinostoma-rodent model, suggesting that these proteins may play a role in the survival within the host.

The aim of the present study was to compare the development of Echinostoma caproni (Trematoda: Echinostomatidae) adults in two host species displaying different degrees of compatibility with this parasite. For this purpose, the variability in the worm recovery, egg output, and morphology of E. caproni adults during the course of experimental infections in hamsters and rats was analyzed. Student's t-tests and two-factor ANOVA analysis with the time post-infection and the host species as independent variables, and Bonferroni t-tests as post hoc analysis were used for the study. Worm recovery and egg output were host species dependent. The values were significantly higher in the worms established in hamsters than those in rats. The oral sucker area, pre-pharynx length, and pharynx area were the most conservative features, and no significant variability related to the host species was detected. In contrast, body area, collar width, esophagus length, cirrus sac area, ventral sucker area, ovarian area and anterior and posterior testicular areas were significantly higher in those worms collected from hamsters. Moreover, significant worm age-host species interactions were found for body area, ovarian area, ventral sucker area, and anterior and posterior testicular areas.

Viable eggs produced weekly per infective stage was used as a measure of the reproductive success of Echinostoma friedi during the first 12 weeks of infection in hamsters. The weekly reproductive success was not constant during the experiment in relation to the egg output and the proportion of viable eggs produced. The egg release started during week 2 post-inoculation, attaining a maximum during week 3. A decline in egg output was observed from week 9. Viable eggs were only produced from week 3 post-inoculation and a maximum was attained at week 4 of the experiment. A decline in egg viability was observed from week 9. Considering together the egg output and the egg viability, the maximum weekly reproductive success was obtained during week 4 post-inoculation. The changes in the weekly reproductive success were not reflected in variations in worm numbers and body sizes during the course of the infection. The humoral immune response of golden hamsters during the infection with E. friedi was determined. Increases of IgG levels against somatic and excretory/secretory products of E. friedi were detected coinciding with the reduction in the reproductive success.

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Using a range of parameters, the ability of rats (Rattus norvegicus) to successfully transmit Echinostoma friedi to the next host was examined under experimental conditions. The concept of Experimental Transmission Success (T M ), defined as the number of hosts that become successfully infected after exposure to a number of infective stages produced by a previous host per unit of inoculation at which this latter host was exposed, was introduced. Using data for the egg output and miracidium hatching and infectivity, the T M permits us to estimate the ability of a particular defintive host species to successfully transmit a parasite species. This concept may be also useful to compare the transmission fitness of a parasite in different definitive host species. Moreover, variations of the Experimental Transmission Success over the course of the infection were calculated by the use of the Weekly Experimental Transmission Success (T MW ). Overall, considering the complete duration of the experiment, the T M of E. friedi using rats as definitive hosts was 0.68 infected snails/metacercaria. However, positive values of the T MW were only obtained from 2 to 4 wk post-infection, with a maximum during the third wk post-infection. When comparing the T M values of E. friedi in rats with those calculated in hamsters on the basis of previously published data, E. friedi appears to be more appropriate to move through this portion of its life cycle when using hamsters (Mesocricetus auratus) as the final host than rats.