Study of the pathogenicity in chickens of Eimeria praecox alone or associated with Eimeria acervulina

Répérant, J. M.; Dardi, M.; Pagès, M.; Thomas-Hénaff, M.

Among the seven species of coccidia that are able to infect chickens, Eimeria praecox is described as the less pathogenic. Its effect on growth and health is even controversial and its interest for vaccination has been questioned (Williams 2000 and 2002). When a side effect due to the infection with E .praecox is described, it is only noticed with high levels of infection (Long 1968; Jorgensen et al. 1997; Williams 1998).

Pathogenicity of Eimeria praecox was clearly demonstrated in this study, and the negative effect on weight gain was observed from the lowest infective dose. When it was inoculated with E. acervulina with lowest infective dose, its side effect on growth was additive to the later and it was significantly raised compared to an infection with E. acervulina alone. Although it was not possible to measure the impact of an infection with E. praecox in field conditions, because of the absence of typical lesions reflecting the intensity of infection, this species should be taken into account in a prophylactic approach to perform an optimal protection of poultry.

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