Eperythrozoon suis in naturally infected pigs: a light and electron microscopic study.

The light and electron microscopic characteristics of natural infections with Eperythrozoon suis are reported. E. suis are enclosed by a single membrane, and they reach a length of up to 600 nm and a diameter of 375 to 500 nm. Neither distinct organelles nor nuclear structures appear in the parasites cytoplasm. They replicate by binary fission, and have close contact with red blood cells without showing any signs of membrance alteration. Massive phagocytosis of whole red blood cells not parasitized by E. suis in spleen and lymph nodes.