Adapting Eimeria tenella to Grow in Primary Chicken Kidney Cells Following Repeated Passages Between Cell Culture and Chickens

SUMMARY. The present study was undertaken to adapt a field isolate (FO) of Eimeria tenella to grow in primary chicken kidney cells (PCKCs) by selecting for characteristics of the parasite rather than modifying the culture and/or environmental conditions. Fourteen generations (F1 to F14) of E. tenella were produced following repeated passages between PCKCs and chickens. Although Fl yielded only a 28% increase in oocysts in PCKCs compared with FO, F2 to F5 produced from 259% to 277% more oocysts, respectively. There was no significant increase in the percentage of oocysts produced in PCKCs by F6 to F14 compared with F5. Generations Fl to F14 demonstrated a greater propensity for multiple infections within the same host cell than did FO. For example, it was not uncommon to observe two, three, and occasionally four oocysts within a single PCKC. Chickens inoculated with FO oocysts generally experienced greater pathogenesis by day 7 postinoculation than chickens inoculated with F14 oocysts as measured by decreased body weights, increased cecal lesions, and a higher mortality rate.