1. The staining and morphology of E. parvum were characteristic of the genus Eperythrozoon. The diameter of the organism was approximately 250 mμ.2. Visible eperythrozoa disappeared in 20 min. from infected blood incubated at 56° C., and in 12 hr. at 37° C. They persisted for several days at room temperature.3. E. parvum was preserved for short periods at 5° C. and for longer periods at −30 and −79° C.4. Splenectomized early-weaned piglets were experimentally infected by the parenteral and oral routes, and by means of the pig louse Haematopinus suis.5. The mean prepatent period of 103 primary infections in splenectomized pigs was 9·7 days. Patent infections sometimes persisted for at least 36 days. One pig remained a carrier of E. parvum for 23 months.6. A severe anaemia occurred in splenectomized piglets affected with E. parvum, but intact piglets were apparently unaffected.7. E. parvum was susceptible in vivo to neoarsphenamine and oxytetracycline, but not to sulphadimidine, penicillin or streptomycin.
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