STUDIES OF GIARDIA SPP AND CRYPTOSPORIDIUM SPP IN 2 ADJACENT WATERSHEDS

Two adjacent British Columbia, Canada, watersheds with similar topogra phical features were studied, Both the Black Mountain Irrigation Distr ict (BMID) and the Vernon Irrigation District (VID) serve rural agricu ltural communities which are active in cattle ranching. The present st udy was carried out in five phases, during which a total of 249 surfac e water samples were tested in the study watersheds, The aims of these phases were to determine levels of parasite contamination in raw wate r samples collected from the intakes as well as from other sites in ea ch watershed and to investigate cattle in the watersheds as potential sources of parasite contamination of surface drinking water supplies, Giardia cysts were not detected in the raw water samples collected fro m lake sources at the headwaters of both watersheds but were found in 100% (70 of 70) of water samples collected at the BMID intake and 97% (68 of 70) of mater samples collected at the VID intake. Significantly higher levels (P < 0.05) of Giardia cysts mere found at the BMID inta ke (phase 1, 7 to 2,215 cysts per 100 liters; phase 3, 4.6 to 1,880 cy sts per 100 liters) when compared with that of the VID intake (2 to 11 4 cysts per 100 liters). The BMID watershed has a more complex system of surface water sources than the VID watershed, Cattle have access to creeks in the BMID watershed, whereas access is restricted in the VID watershed. Collection of raw crater samples from a creek upstream and downstream of a cattle ranch in the BMID watershed showed that the do wnstream location had significantly higher (P < 0.05) levels (0.6 to 4 2.9 cysts per 100 liters and 1.4 to 300.0 oocysts per 100 liters) of b oth Giardia cysts and Cryptosporidium oocysts than those of the upstre am location (0.5 to 34.4 cysts per 100 liters and 0.5 to 34.4 oocysts per 100 liters), Peak concentrations of both parasites coincided with calving activity. Fecal samples, collected from cattle in both watersh eds, showed 10% (3 of 30) in the BMID and 50% (5 of 10) in the VID wat ersheds to be Giardia positive. No Cryptosporidium-positive fecal samp les were found, Giardia cysts isolated from the BMID watershed were re peatedly infective to gerbils in contrast to those from the VID waters hed. The 10 BMID drinking water Giardia isolates retrieved into cultur e and biotyped showed zymodeme and karyotype heterogeneity, The differ ences in patterns of parasite contamination and cattle management prac tices contribute to the unique watershed characteristics observed betw een two areas which are topographically similar and geographically adj acent.