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 Eime ria tenella to grow in primary chicken kidney cells (PCKCs) by selecti ng for characteristics of the parasite rather than modifying the cultu re and/or environmental conditions. Fourteen generations (F1 to F14) o f E. tenella were produced following repeated passages between PCKCs a nd chickens. Although F1 yielded only a 28% increase in oocysts in PCK Cs 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 F 1 to F14 demonstrated a greater propensity for multiple infections wit hin the same host cell than did FO. For example, it was not uncommon t o observe two, three, and occasionally four oocysts within a single PC KC. Chickens inoculated with F0 oocysts generally experienced greater pathogenesis by day 7 postinoculation than chickens inoculated with F1 4 oocysts as measured by decreased body weights, increased cecal lesio ns, and a higher mortality rate.