Patterns in Size and Shedding of Fasciola Hepatica Eggs by Naturally and Experimentally Infected Murid Rodents

Abstract

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.

A dual anthelmintic treatment strategic scheme for the control of fasciolosis in dairy sheep farms

“…A similar lack of total effectiveness has been reported in previous studies (Torgerson and Claxton 1999). In the present study, the residual presence of this parasite was probably due to contamination of the pasture by infected hares, which may act as competent reservoirs, as found for the nutria (Myocastor cypus) by Ménard et al (2001) in France and for the black rat (Rattus rattus) by Adela Valero et al (2002) in Corsica.…”

Phenotypic comparison of allopatric populations of Fasciola hepatica and Fasciola gigantica from European and African bovines using a computer image analysis system (CIAS)

“…For an accurate morphometric comparison, increases in the different biometric parameters which occur during digenean development within the definitive host according to growth laws (Dawes and Hughes 1964;Valero et al 1996Valero et al , 1998Valero et al , 2002 must be taken into account. If adult populations of different ages are studied, morphometric differences attributable to age can appear.…”

Physiological responses of insular wild black rat (Rattus rattus) to natural infection by the digenean trematode Fasciola hepatica

“…Their small size may account for the numerous constraints and adjustments reported for the digenean. Parasite eggs shed by murids are smaller than those shed by naturally infected cattle (Valero et al 2002). The biometric study of the parasite revealed that adult body size (at sexual maturity) is smaller in wild Corsican black rat than that in Bos taurus (Valero et al 1996).…”

“…Although rats are only occasionally infected by the liver fluke on a worldwide basis (Li 1952; Molan and Hussein 1988), high prevalence has been reported in black rats (Rattus rattus) on the Mediterranean island of Corsica (Mas-Coma et al 1988). A series of studies demonstrated that the murid rodent may play an important role in the transmission of the disease on this island (Mas-Coma et al 1987, 1988Valero et al 1998Valero et al , 2002.…”