EFFECT OF MERCURY-DOMINATED HEAVY-METAL E MISSION ON THE COURSE OF PASTURE HELMINTHOSES IN SHEEP

A group of 30 improved Valashka sheep, grazed in submontane pastures 3 and 6 km far from the emission source of mercury-dominated heavy meta ls (L1 and L2) and in pasture situated out of mercury emission fall-ou t (K), were investigated for the prevalence and mean intensity of past ure helminth infection. Hg concentration in the grass stand was determ ined by the distance of emission source. The amount of mercury was inc reasing in the direction from control locality to locality 1, lying 3 km from the emission source. With the mean concentration of 4.298 mg H g/kg in grass stand, 0.346 mg Hg/kg in the liver, 0.591 mg Hg/kg in th e kidneys and 0.030 mg Hg/kg in the muscles (Tab. I) a high prevalence of pasture helminths was recorded in sheep. This prevalence was incre asing in the direction from control locality to the nearest emission s ource (Tab. II). The only exception was Moniezia spp. and Strongyloide s papillosus, with values at locality 2 being lower than those at cont rol locality. Trichostrongylus spp. and Cooperia spp. were equally pre valent at all the localities studied. Mean infection intensity (Tab. I II) showed an increasing tendency from control locality towards locali ty 1. Only Dicrocoelium dentriticum and Strongyloides papillosus were an exception, with the highest mean infection intensity recorded at lo cality 2 (5.3 and 3.3 specimens, respectively). The highest mean inten sity at control locality was recorded for Cooperia spp. infection (4.5 specimens). Mean infection intensity at locality 2 (6 km from emissio n source) arid control locality showed proximate values in Moniezia sp p. (1.3-1.2 specimens), Nematodirus spp. (2.6-2.4 specimens) and Coope ria spp. (4.0-4.5 specimens). The highest differences in mean infectio n intensity between locality 1 and control locality were recorded in T richostrongylus spp. (24.3-13.3 specimens), Ostertagia spp. (15.4-7.4 specimens) and Nematodirus spp. (5.1-2.4 specimens). With high values of mercury in pasture, grass grazing animals cumulate mercury in their organisms, mainly in the parenchymatous organs (liver, kidneys). Cons equently, the immunity of animal organism is impaired, which is manife sted by an increased prevalence and mean infection intensity of most p asture helminths.