Fasciola hepatica: an unusual case of adaptation to a Moroccan population of Galba truncatula.
Parent snails, F1, and F2, originating from a Moroccan population of Galba truncatula, were experimentally subjected to sympatric miracidia of Fasciola hepatica at 20 degrees C to determine the mode of adaptation of this parasite to the local intermediate host via the study of redial burdens and by following cercarial shedding. In spite of an increase in the global prevalences of infections, the frequencies recorded for immature or mature infections in dissected snails did not show any significant variations from parents to F2. If the redial burdens in mature infections were mainly composed of first-generation rediae in parent snails, the numbers of rediae belonging to subsequent generations significantly increased in the F1 and F2 generations. In mature infections, the lengths of first-generation rediae and their contents significantly decreased from parent snails to F2. Conversely, in the first redial cohort of the second generation (R2a rediae), only the intraredial contents increased significantly with snail generation. In mature infections, daughter redia production was ensured by all mother rediae of the first generation in parent snails, whereas it was progressively effected by the first mother redia in the F1 and F2 infections. The numbers of cercariae shed by snails increased significantly from parents to F2. If the cercariae produced by first-generation rediae decreased with snail generation, an inverse finding was noted in the case of R2a rediae. We suggest that snails impose a bottleneck on the development of the first mother redia, so that other mother rediae of the first generation react with greater growth (until 3.9 mm in parent snails), an important daughter redia production and a high cercarial production. As the first mother redia remained alive until day 49 post-exposure but without growth after week 2, this mode of development must be considered as a new developmental pattern of redial generations, and it is useful to determine its frequency in snails, as it has never been found in naturally or experimentally infected snails in central France.
Belfaiza
M
M
Laboratoire d'Hydrobiologie, Département de Biologie, Faculté des Sciences, Université Chouaïb Doukkali, BP 20, 24000, El Jadida, Morocco.
Moncef
M
M
Rondelaud
D
D
D000222:Adaptation, Physiological; D000818:Animals; D005210:Fasciola hepatica / Q000254:growth & development* / Q000502:physiology; D006790:Host-Parasite Interactions; D009018:Morocco; D012908:Snails / Q000254:growth & development / Q000469:parasitology*
Parasitol Res. 2004 Feb;92(3):242-5
14714176
Parasitol Res. 2003 Dec;91(6):458-61
14564511
Adv Parasitol. 1969;7:95-210
4935272
Parasitol Res. 2004 Jan;92(1):12-7
14586643
Ann Parasitol Hum Comp. 1982;57(6):639-42
7168535
Parasitol Res. 2004 Oct;94(3):183-7
15338285
Ann Parasitol Hum Comp. 1978 Mar-Apr;53(2):201-13
677721
Parasitol Res. 1995;81(3):265-7
7770435
Vet Rec. 1971 Feb 6;88(6):152-64
5102169
J Helminthol. 1999 Mar;73(1):27-30
23745981
Parasitol Res. 2001 Dec;87(12):1016-9
11763431
J Helminthol. 2002 Jun;76(2):179-83
12015832
Parasitol Res. 2001 Aug;87(8):631-3
11510999