Fasciola hepatica: epidemiological surveillance of natural watercress beds in central France

Abstract

A total of 59 natural watercress beds in the Limousin region (central France) was surveyed over a 15-year period (1990-2004) to detect the contamination of watercress by the metacercariae of Fasciola hepatica and to determine the presence of larval forms in the two species of lymnaeids which live in these waterholes in June and July. The number of beds contaminated with F. hepatica metacercariae varied over the years, and the burden of the larvae on plants was low: a mean of 2.6-6.3 per bed. The same variability was also noted for natural infections of Galba truncatula with F. hepatica, as the annual prevalences ranged from 1.2% to 2.4%. Natural infections of Omphiscola glabra with F. hepatica were only detected from 1996 and the annual prevalences subsequently increased up to 1.4-1.8% between 2001 and 2004. However, for both lymnaeids, the variations in these prevalences with year were insignificant. The contamination of these beds with F. hepatica over the past 15 years was similar to that recorded in the same sites between 1970 and 1986. The main changes were the appearance of another digenea, Paramphistomum daubneyi, in the beds, and the possibility for O. glabra to naturally sustain the larval development of F. hepatica.

Epidemiological studies onFasciola hepaticain Gafsa oases (South West of Tunisia)

“…Oxalis cernua and Apium nodiflorum were appreciated for their acidic taste by few oases inhabitants. Apium nodiflorum was described as a plant that contaminated natural watercress beds from the Limousin region in Central France (Dreyfuss et al, 2005). Oxalis cernua, Apium nodiflorum and Sonchus maritimus were suspected to be at the origin of animal contamination.…”

An optimized DNA extraction and multiplex PCR for the detection of Fasciola sp. in lymnaeid snails

“…Indeed, the prevalence of a natural infestation in 52,000 G. truncatula collected in the United Kingdom was estimated through microscopy to be under 2% (Ollerenshaw, 1971). Most recently this prevalence was estimated at 1.7% in France (Dreyfuss et al, 2005). Among more recently developed techniques, PCR provides the most accurate information and shows high sensitivity and specificity levels (Caron et al, 2008).…”

Omphiscola glabra(Gastropoda, Lymnaeidae): Changes occurring in natural infections withFasciola hepaticaandParamphistomum daubneyiwhen this snail species is introduced into new areas

“…Natural infections of this latter snail with F. hepatica and/or another digenean, Paramphistomum daubneyi were reported from the 2000s by several authors (Mage et al, 2002;Dreyfuss et al, 2003Dreyfuss et al, , 2005 on the acid soils of Haute-Vienne. If miracidia of both digenean species penetrate O. glabra during the same time interval (4 h) at exposure, the first parasite which enters the snail favours the development of the other digenean (Augot et al, 1996) so that natural infections with F. hepatica, P. daubneyi, or both can be noted.…”