Electrophoretic characterization of Giardia isolated from humans, cattle, sheep, and a dog in Switzerland.

Nine isolates of Giardia lamblia from humans, cattle, sheep, and 1 dog were compared by employing agarose gel isoenzyme electrophoresis and isoelectric focusing of total soluble cell protein on polyacrylamide gels. The banding patterns of the 14 enzymes examined showed remarkable similarities among the Swiss Giardia isolates. This was true also of the total soluble trophozoite proteins. The electrophoretic mobilities of most enzymes and other proteins obtained for the Swiss isolates were the same as those of 2 isolates from humans in other geographical areas, the WB and the Portland-1 strains. Only the human isolate CH-H2 could clearly be distinguished from all other isolates analyzed. The great biochemical similarities observed among the Swiss isolates contrast with the extensive heterogeneity previously demonstrated for G. lamblia by other investigators who used similar analytical techniques. These data are consistent with recent transmission studies of Giardia and suggest that in Switzerland domestic animals may serve as a reservoir of human Giardia infections and that cross-transmission between humans and animals is likely to occur.