To study the possibility of immunization against Cryptosporidium baileyi Current, Upton et Haynes, 1986 with the attenuated anticoccidial vaccine, Paracox™ and oocysts of C. parvum Tyzzer, 1912, chickens were inoculated orally with either 3 x 10’ vaccine oocysts or 8 x I O5 C, baileyi or C. parvum oocysts at 1 week of age. The inoculation with Paracox™ vaccine and C. parvum oocysts was repeated at 2 and 3 weeks of age. Uninfected birds served as controls. All animals with the exception of one uninfected group were challenged orally with either 8 x 105 C. baileyi or 3 x 10s Eimeria tenella Railliet et Lucet, 1891 oocysts at 4 weeks of age. Sera were collected at 4 weeks of age, and were examined by ELISA using C. baileyi antigens. Birds inoculated with C. parvum oocysts did not shed C. parvum oocysts in their faeces, but anticryptosporidial antibodies could be detected in the sera. The total oocyst output of C. parvum inoculated chickens was 17% of that of previously uninfected birds after the oral challenge with C. baileyi. Considering that antibodies play no or only a minor role in resistance to C. baileyi, these results suggest that inoculation of chickens with C. parvum oocysts stimulated also cellular immune response. Based on the relative body weight gain, faecal scores, oocyst output, mortality, and caecal lesions in the birds immunized with Paracox™ vaccine and challenged with E. tenella, the vaccination induced only a moderate protection against the reinfection. The results of crossimmunization of chickens with Eimeria spp. and C. baileyi suggest that attenuated anti-eimerian vaccines do not induce any protection against cryptosporidial infection.
Anticoccidial efficacy of a drug combination containing monensin at 8 p.p.m. plus the new antioxidant duokvin at 120 p.p.m. in the feed was compared with that of monensin alone at the recommended level of 100 p.p.m. against a field isolate of the coccidium Eimeria acervulina Tyzzer, 1929 in a battery study. Both monensin and monensin duokvin combination were effective against E. acervulina when judged by weight gain, feed conversion and faecal scores. There was no significant difference in the chemoprophylactic activity of either treatments. Neither monensin at 100 p.p.m. nor the combination proved effective in terms of oocyst production. In accordance with the earlier findings with E. lenella, the combination seems appropriate for field trials.