Confirmation of the safety of Lagenidium giganteum (Oomycetes: Lagenidiales) to mammals.

Lagenidium giganteum Couch, a fungal parasite of mosquito larvae, is considered a promising agent for operational control. Quantitative reisolation of the fungus from rodent blood and tissue is easily accomplished because the cell walls are much more persistent than those of mammalian cells. The mycelium forms discrete, septate cells very early in its development, in marked contrast to filamentous fungi. The fungus is rapidly cleared from mice following intraperitoneal injection of large quantities of mycelium and oospores. More than 95% of viable cells are cleared within 24 h. Mortality following intravenous injection of mycelium in tail veins of mice is caused solely by embolism of heart and lung tissue. Recently revised U.S. Environmental Protection Agency protocols for testing of microbial pest control agents may have to be altered further to accommodate physically large microbial agents such as L. giganteum.