The Effects of Variable Dosages of Sporulated Eimeria Acervulina Oöcysts on Chickens

ONE of the most important factors in the development of clinical or fatal coccidiosis in susceptible chickens is the dosage of sporulated oöcysts ingested at one time. Since Johnson (1927) drew attention to “the relationship of the number of sporulated oöcysts ingested to the severity of the disease,” only very limited information has been available regarding this important factor. Further, Johnson (1931) reported “complete temporary cessation of (egg) production” when susceptible birds were inoculated “with large doses of pure cultures” of Eimeria acervulina. He did not reveal, however, what was considered as a large dose. Tyzzer (1929) also drew attention to the effect of the size of the dose of E. acervulina, but did not mention what approximate dosages were used. In a comparison with Eimeria tenetta his statement that “while with E. tenella a single feeding of a relatively moderate number of oöcysts may produce serious or fatal results . . .