Development of Eimeria alabamensis from cattle in mammalian cell cultures

SYNOPSIS. Monolayer primary cultures of cells from bovine embryonic intestine (BEInt), kidney (BEK), spleen (BES), and thyroid (BETy) and cell line cultures of embryonic bovine trachea (EBTr) and synovium (BESy) as well as established cell line cultures of bovine kidney (Madin‐Darby, MDBK), human intestine (Int 407) and Syrian hamster kidney (BHK) were inoculated with freshly excysted sporozoites of Eimeria alabamensis and observed for 4–5 days. Sporozoites penetrated all cell types; during the 1st 24 hr, intracellular sporozoites, trophozoites and binucleate schizonts were seen in all cell cultures. Mature schizonts were more numerous in BES and MDBK cells than in the others. Large schizonts, 14.2 (11–18.5) by 10.2 μ (8.5–11), with 6–14 short, stubby merozoites (each with 2 refractile bodies) occurred at 2 and 3 days in all cells except BESy, Int 407, and BHK. Small schizonts, 9.7 (5.5–13) by 6 μ (5–8.5), with 6–10 long, slender merozoites (each with 2 refractile bodies) were found 3 days after inoculation in all cell types. At 4 days, some intracytoplasmic merozoites and a few intranuclear 2nd generation trophozoites were found. After 4 days post‐inoculation, intracellular parasites were rarely seen and these were apparently degenerate. Development within the host cell nucleus, the normal site of development in the host animal, was observed infrequently in cell cultures. Intranuclear sporozoites, found no earlier than 2 days after inoculation, developed similarly to those in the cytoplasm, and small intranuclear schizonts with 6–10 merozoites (each with 2 refractile bodies) occurred after 3 days in culture.