Leucocytozoonosis in Canada geese in upper Michigan,. 1. Strain differences among geese from different localities.

Geographic variation in pathogenicity of Leucocytozoon simondi in Canada geese (Branta canadensis maxima) was investigated by exposing goslings to natural infection at three locations in the upper peninsula of Michigan. Examination of blood smears and tissue sections revealed two patterns of development. Hepatic schizogony and secondary megaloschizogony occurred in cells of the reticuloendothelial system, with round and elongate gametocytes, or only hepatic schizonts and round gametocytes. The evidence for strain differences in L. simondi and its implications in wildfowl management practices are discussed.