Observations on the course of Eperythrozoon coccoides infections in mice, and the sensitivity of the parasite to external agents

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Abstract
Non-splenectomized mice developed acute infections of Eperythrozoon coccoides after inoculation, but were then immune to re-infection. Splenectomy evoked acute infections that were heavier and longer in duration than the primary infection; during this phase, the parasites doubled in number in about 5 hr. The presence of splenic tissue transplanted subcutaneously did not prevent this evocation by splenectomy.The number of eperythrozoa decreased rapidly after the peak of infection had been reached, but no immune factor was detected in the blood. No immune factor or infection was transmitted from mother to offspring through the milk.Citrated blood remained infective for 11 days at 3° C., for 17 hr. at 16–17·7°C. and for 3 hr. at 37° C. It was not infective after 24 hr. at either 24° C. or 16–17·7°C., or after 5 hr. at 37° C. Parasitized blood was not infective after drying.Citrated blood was infective to mice when given by mouth, but was not infective when applied externally. Urine and faeces were non-infective.Eperythrozoa remained infective when infected blood was diluted with twice its volume of water and left for 24 hr. at 3° C. Phenol, 0·5%, rendered citrated blood non-infective in 1 hr. Neoarsphenamine, 0·1%, reduced the infectivity of citrated blood in 16 hr., and rendered it non-infective in 26 hr.Cortisone did not affect the course of infection of E. coccoides in mice when given subcutaneously, 1·0 mg. per 20 g. mouse, once daily for 6–9 days.Concurrent infection with Plasmodium berghei evoked relapses of E. coccoides during the terminal stages of the P. berghei infection.