Eperythrozoon coccoides: influence on course of infection of Plasmodium chabaudi in mouse.

Mice infected with Plasmodium chabaudi obtained from two sources were found to be contaminated with Eperythrozoon coccoides. At each transfer of blood parasitized with plasmodia, eperythrozoa were also passed. In the presence of these organisms, the malarial infection assumed a low-level, chronic course infrequently resulting in death of the mice. When the eperythrozoa were eliminated through treatment with oxophenarsine hydrochloride, the malarial infection took an acute course always ending in death.