Immunisation of chickens with commercial anticoccidial vaccines Immucox® and Livacox® showed varied protection against a virulent Eimeria tenella local isolate and Houghton strain

Coccidia is an ubiquitous intestinal protozoan of poultry that invade the mucosa and induce epithelial cell necrosis and inflammation. To assess the pathogenicity of two commercial anticoccidial vaccines against a local isolate of Eimeria tenella, ninety (90) day-old dominant black chicks were assigned to 9 groups of 10 birds each. Immunisation was done at 5 days of age by oral gavage. Infection was done with 1.7×104 E. tenella of either Houghton strain (H-strain) or local isolate (L-isolate) at 4 weeks of age. Increased pathogenicity of the local isolate was observed, as it produced a more severe gross pathologic lesion score than the Houghton strain in unvaccinated but infected groups of chickens 6 days post-infection (dpi). The high virulence and pathogenicity of the local E. tenella was responsible for the differences in the severity of clinical signs, gross and microscopic lesions observed between the H-strain and L-isolate infected groups. The histopathology showed that the vaccinated groups, infected with the H-strain of E. tenella, did not show presence of oocysts or schizonts by 6 dpi. The successful immunogenicity and effectiveness of these two vaccines as measured by the histopathologic lesions and the presence of oocysts in the enterocytes of the caecal crypts of these chickens were reduced in vaccinated and L-isolate infected groups. The findings in the L-isolate groups were setbacks to the use of live attenuated and non-attenuated anticoccidial vaccines for control of coccidiosis and in particular, caecal coccidiosis in chickens reared in environments dominated by virulent E. tenella.