Prevalence of gastrointestinal nematodes and Fasciola hepatica in sheep in the northwest of Spain: relation to climatic conditions and/or man-made environmental modifications

BackgroundIn the present study we studied and updated the prevalence of the infections caused by gastrointestinal nematodes (GIN) and Fasciola hepatica in grazing sheep in the northwest (NW) of Spain for the last six years (2006–2011), and its relationship with the current climatic conditions.MethodsWe analyzed faecal samples from 110 flocks located in four different provinces of the Autonomous Community of Castilla y León: 76.4% of them were situated in León, 12.7% in Zamora, 9.1% in Palencia and 1.8% in Valladolid.ResultsThe prevalence of GIN was 100% and the mean of eggs per gram (epg) in faeces was 237.2 (± 375.9) per flock. Regarding climatic conditions, we found a direct relationship between the GIN infection level and the maximum humidity (p<0.05) but inverse with the degree of solar radiation (p<0.05). The prevalence of fasciolosis was 59.3%, with a mean epg of 17.5 (± 33.9) per flock; these values were correlated with the minimum humidity and precipitations (p<0.05). Comparing our results in León with previous studies during the early 1990s, the mean epg of GIN was increased slightly (134.3 epg); regarding fasciolosis, the prevalence rose significantly, from 26.7% to 60.5%. Since the 1990s we observed that the maximum temperature is nowadays 0.45°C higher (17.0°C) and the minimum 0.5°C lower (5.2°C); the rainfall values were very similar in both decades but at the present time the humidity is higher (75.9%).ConclusionsWe found that the prevalence of GIN and F. hepatica infections was directly influenced by the humidity and also by precipitations in the case of F. hepatica. Comparing the current prevalence with studies carried out in the same area for the early 1990s, we observed that nowadays the mean epg of GIN is higher with a possible cause being the differences in climatic conditions depending on the sampling year. Regarding F. hepatica infection, its prevalence rose significantly probably favoured by an increase in irrigated areas in the area of study.

[1]  I. Fairweather,et al.  Fasciolicides: efficacy, actions, resistance and its management. , 1999, Veterinary journal.

[2]  F. Roberts,et al.  Methods for egg counts and larval cultures for strongyles infesting the gastro-intestinal tract of cattle. , 1950 .

[3]  Peter J. Hudson,et al.  system: Trichostrongylus tenuis in red grouse. II. Population models , 1992 .

[4]  S. Walkden-Brown,et al.  Ecology of the free-living stages of major trichostrongylid parasites of sheep. , 2006, Veterinary parasitology.

[5]  E. Morgan,et al.  Back to the future: developing hypotheses on the effects of climate change on ovine parasitic gastroenteritis from historical data. , 2008, Veterinary parasitology.

[6]  R. Besier,et al.  The ecology of Haemonchus contortus in a winter rainfall region in Australia: the development of eggs to infective larvae. , 1993, Veterinary parasitology.

[7]  F. Rojo-Vázquez,et al.  An epidemiological study of gastrointestinal parasitism in dairy sheep flocks in León (NW Spain) , 1998 .

[8]  H. Ploeger,et al.  Consequences of the unusually warm and dry summer of 2003 in The Netherlands: poor development of free living stages, normal survival of infective larvae and long survival of adult gastrointestinal nematodes of sheep. , 2005, Veterinary parasitology.

[9]  P. Díaz,et al.  Prevalences of gastrointestinal parasites in sheep and parasite-control practices in NW Spain. , 2006, Preventive veterinary medicine.

[10]  R. Hidalgo,et al.  Kinetics of Fasciola hepatica egg passage in the faeces of sheep in the Porma basin, Spain. , 1990 .

[11]  S. Mas‐Coma,et al.  Climate change effects on trematodiases, with emphasis on zoonotic fascioliasis and schistosomiasis. , 2009, Veterinary parasitology.

[12]  M Edwards,et al.  Impacts of Europe's changing climate - 2008 indicator-based assessment , 2008 .

[13]  J. Pérez-Garcia,et al.  Anthelmintic resistance in trichostrongylid nematodes of sheep farms in Northwest Spain , 2006, Parasitology Research.

[14]  K. Friedhoff.  Manual of veterinary parasitological laboratory techniques: Ministry of Agriculture, Fisheries and Food, Agricultural Development and Advisory Service, Technical Bulletin No. 18, 2nd edition, 1977, iii + 129 pp., 16 figs., XI plates, 9 tables, Price £3.50 , 1978 .

[15]  J. Esteban,et al.  High fascioliasis infection in children linked to a man‐made irrigation zone in Peru , 2002, Tropical medicine & international health : TM & IH.

[16]  P. Skuce,et al.  Sheep helminth parasitic disease in south eastern Scotland arising as a possible consequence of climate change. , 2009, Veterinary parasitology.

[17]  A. Dobson,et al.  Climate disruption and parasite–host dynamics: patterns and processes associated with warming and the frequency of extreme climatic events , 2006, Journal of Helminthology.

[18]  L. Ortega-Mora,et al.  Seroprevalence ofFasciola hepatica infection in sheep in northwestern Spain , 2004, Parasitology Research.

[19]  M. Martínez-Valladares,et al.  Efficacy of a moxidectin/triclabendazole oral formulation against mixed infections of Fasciola hepatica and gastrointestinal nematodes in sheep. , 2010, Veterinary parasitology.

[20]  L. Ortega-Mora,et al.  Excystment of Paragonimus westermani metacercariae by endogenous cysteine protease. , 1995 .