Eimeria: immunisation of young chickens kept in litter pens

Infection of chickens with an attenuated strain of Eimeria tenella gave good protection against challenge with the parent strain of this species. Chickens given an attenuated strain of E. acervulina var. mivati were protected against challenge with other pathogenic cultures of E. acervulina when kept in litter pens under conditions allowing reinfection. Two-week-old chickens, kept in litter pens, were given attenuated strains of E. tenella and E. acervulina and small numbers of oocysts (50-100) of E. brunetti, E. maxima and E. necatrix. Body weight gain was unaffected and resistance to challenge infection was demonstrated at 6 and 9 weeks after inoculation. In other experiments only a small proportion of 1 to 3-week-old chickens in each pen were given oocysts. Chickens placed in contact with these 'seeder' chickens were immunised against five species of Eimeria within a 2 to 4 week period. Similar experiments with 1-week-old chickens showed that these could also be immunised but the degree of parasitism during immunisation caused some weight gain depression. These results suggest that controlled immunisation against several species of Eimeria may be possible and further experiments are needed under conditions which more closely resemble those operating in the field.