Influence of vaccination of hens with attenuated oocysts of Eimeria tenella, E. necatrix, E. acervulina and E. maxima on protection of offspring against Eimeria infection

The feasibility of protection of offspring against Eimeria infection via maternal or passive derived immunity from hens (layers) vaccinated with attenuated oocysts of Eimeria acervulina, E. maxima, E. tenella and E. necatrix was investigated.Gross lesion scores on the basis of pathological changes and oocyst count methods were used in the experiment.Seven hens (layers) (Group A) and eighty hens (layers) (Group B) were orally vaccinated with 30,000 to 50,000 oocysts of attenuated Eimeria tenella, E. acervulina, E. maxima and 10,000 oocysts of attenuated E. necatrix.A second vaccination with the same dose was given to group B hens, and seven control hens (Group C) were not vaccinated.Offspring of three groups of hens (layers) were challenged with 10,000 oocysts of virulent lines of Eimeria tenella, E. acervulina, E. necatrix and E. maxima.Offspring of revaccinated hens showed significantly reduced lesion scores (p < 0.01) after challenge with E. tenella, E. necatrix, E. acervulina and E. maxima compared to offspring of non vaccinated hens.Offspring of vaccinated hens showed significant reduction in lesion scores (p < 0.01) with E. maxima and (p < 0.05) with E. necatrix compared to offspring of non vaccinated hens (layers).Progeny of revaccinated hens also showed reduced oocyst excretion with (0.3 ± 0.1) ×10 6 oocysts of E. tennella, (0.3 ± 0.1) ×10 6 oocysts of E. maxima, (0.3 ± 0.1) × 10 6 oocysts of E. necatrix and (0.3 ± 0.1) × 10 6 oocysts of E. acervulina compared to offspring of control hens that excreted (2.4 ± 0.1) × 10 6 oocysts of E. tenella, (2.5 ± 0.1) × 10 6 oocysts of E. maxima, (2.1 ± 0.1) × 106 oocysts of E. necatrix and (2.7 ± 0.1) × 10 6 oocysts of E. acervulina.The results demonstrate that revaccination of hens with attenuated oocysts of Eimeria may give better results than single vaccination in protection of offspring against Eimeria challenge infection.The results obtained in the experiment need further investigation. Chicken, coccidiosis, maternal immunity, lesion scores, oocyst countPoultry coccidiosis is an intestinal disease caused by protozoan parasites of the genus Eimeria.The disease causes serious economic loses to the poultry meat industry worldwide.As the world's poultry production continues to grow, so do concerns about the control of Eimeria infections that cause coccidiosis, which remains one of the most commonly reported diseases of chickens (Biggs 1982; X i e et al. 2001).Commercial chickens free from coccidia are extremely rare (Williams 1999).Furthermore, there is increasing concern about rising levels of drug resitance (Chapman 1997), consumer pressure to phase out the inclusion of anticoccidial drug additives in the diets of food animals (Young and Craig 2001), concerns about drug residues in poultry products (Young and Craig 2001) and a falling success rate in the discovery of chemical entities as well as high costs of development of new anticoccidial drugs.As a result, there has been in recent years a refocusing of research on biological rather than chemical control of coccidiosis.One approach to immune-based protection of chickens which should be considered is