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

BACKGROUND: In 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. METHODS: We 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. RESULTS: The 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%). CONCLUSIONS: We 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.

Efficacy of nitroxynil against Fasciola hepatica resistant to triclabendazole in a naturally infected sheep flock.

The aim of this study was to compare the efficacy of triclabendazole (TCBZ) and nitroxynil against a TCBZ-resistant Fasciola hepatica strain in a naturally infected sheep flock. The efficacies were measured by the faecal egg count reduction test. The level of F. hepatica antigens was tested in faeces; and haematological indices such as total proteins (TP), albumin, hepatic enzymes and total IgG were also studied. The results confirmed the resistance of F. hepatica against TCBZ in the flock with an efficacy during the first month post-treatment between 59.4% and 73.8%. In the nitroxynil group, the efficacy during the same period ranged between 81.3% and 86%, likely because the efficacy of this drug against 7- to 9-week-old immature stages is only 50-90%. Anemia was showed in all groups and white blood cells were always higher than the reference range. The values of TP and albumin were within normal range in most of the sheep, and an increase in hepatic enzymes confirmed the liver damage. Regarding total IgG, some negative correlations were found with egg excretion, and in relation to the level of antigens in faeces, these ones decreased immediately after treatment. We conclude that nitroxynil could be an alternative in case of TCBZ resistance.