Ultrastructural findings in natural canine hepatozoonosis.

The ultrastructure of several stages of Hepatozoon canis found in dogs with clinically and histologically diagnosed infections was determined using transmission electron microscopy. Merozoites, macro- and microschizonts and gamonts were found in spleen, liver, kidneys and lungs. Macro- and micromeronts were characterized by their size and by the presence of intracytoplasmic amylopectin granules. Gamonts, which provide the basis for clinical diagnosis of the disease, were observed within mononuclear cells (monocytes/macrophages); they were butterfly-shaped and exhibited varying electron densities. On the basis of the microscopic observations reported here, it is clear that the life cycle of H. canis is a complex one.