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The quantification of the different sizes and shapes of Fasciola hepatica and Fasciola gigantica from bovines has been achieved for the first time in natural allopatric populations. Linear measurements, areas and ratios of gravid adults and eggs of F. hepatica (from France and Spain) and F. gigantica (from Burkina Faso) were analysed using a computer image analysis system and an allometric model: (y2m - y2)/y2 = c[(y1m - y1)/y1](b), where y1 = body area or body length, y2 = one of the measurements analysed, y1m, y2m = maximum values towards which y1 and y2, respectively, tend and c, b = constants. All the measurements overlap in the two fasciolids, apart from the distance between the ventral sucker and the posterior end of the body, body roundness and body length/body width ratio. The results obtained may be useful in Fasciola species identification in countries where both species coexist.

Knowledge of the morphological phenotypes of the liver fluke Fasciola hepatica (Trematoda: Digenea) is analysed. The influence of parasite age on its dimensions, the adult fluke growth model, variation in a biometric variable versus time, and variation in a biometric variable versus another biometric variable (allometric model) are revised. The most useful allometric model appears to be (y2 m-y2)/y2=c [(y1 m-y1)/y1](b), where y1=body area or body length, y2=one of the measurements analysed, y1 m, y2 m=maximum values towards which y1 and y2, respectively, tend, and c, b=constants. A method based on material standardization, the measurement proposal and allometric analysis is detailed. A computer image analysis system (CIAS), which includes a colour video-camera connected to a stereomicroscope (for adult studies) and a microscope (for egg studies), facilitates the processing of digital imaging. Examples of its application for the analysis of the influence of different factors on the liver fluke phenotype are shown using material from the Northern Bolivian Altiplano, where human and domestic animal fascioliasis is caused by F. hepatica only. Comparisons between the development of livestock fluke populations from highlands and lowlands are discussed and the relationships between host species and liver fluke morphometric patterns is analysed.

Using samples collected on the island of Corsica, a comparative study was done of the morphometry of Fasciola hepatica eggs shed by cattle and by naturally and experimentally infected murid rodents (wild Mus musculus and Rattus rattus and Rattus norvegicus Wistar laboratory strain). Eggs shed by murids are smaller in size than those shed by naturally infected cattle. A second study analyzed the number of F. hepatica eggs shed in murid feces at different time intervals, i.e., months, days, and 6-hr periods, by the Kato-Katz technique. Both experimentally and naturally infected black rats (R. rattus) were used, and Wistar rats were experimentally infected and included for comparison. The present studies prove that black rats R. rattus are able to shed eggs independently from the liver fluke isolate and that egg shedding occurs throughout the life of this host species, uninterrupted during all the months analyzed in a 2-yr period. Moreover, the results suggest that this shedding is continuous, with eggs appearing in the feces daily. The results on egg shedding by wild black rats R. rattus reach their maximum shedding in spring and autumn and a maximum during twilight hr. These chronobiological patterns appear to favor parasite transmission, both seasonally and daily.