Adapting Eimeria tenella to grow in primary chicken kidney cells following repeated passages between cell culture and chickens.

The present study was undertaken to adapt a field isolate (F0) 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 F1 yielded only a 28% increase in oocysts, in PCKCs compared with F0, 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 F1 to F14 demonstrated a greater propensity for multiple infections within the same host cell than did F0. For example, it was not uncommon to observe two, three, and occasionally four oocysts within a single PCKC. Chickens inoculated with F0 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.