Investigation into the potential of using UV-treated sporulated oocysts of Eimeria tenella as a local solution to immunization of chickens against caecal coccidiosis.

In this study, we aim to evaluate the immune response of chickens to UV-treated sporulated oocysts as a means of protection against caecal coccidiosis caused by field strains of Eimeria tenella . Two groups of chicks were immunized using prepared UV-treated oocysts of E. tenella and challenged at day 20 post hatching. The first group was immunized only once at day 1 post hatching, the second group was immunized twice (day 1 and day 8 post hatching). Two non-immunized control groups were used: the first group was challenged with E. tenella , while the second group remained uninfected. The effectiveness of immunization on production and animal health was evaluated by the following criteria: body weight, feed conversion ratio, blood in faeces, mortality, lesion scores and oocyst output. The two immunized groups showed a significantly better performance in body weight, weight gain and lesion scores than the non-immunized group. However, all three groups performed significantly worse than the unchallenged group. The mortality of the non-immunized infected group was high (70%) while mortality in both immunized and unchallenged groups of chickens was significantly lower (range 2.2 to 4.4%) than the infected group ( p  < 0.05). The production of oocysts in faeces, post-infection, was significantly higher in the non-immunized group compared to the immunized group ( p  < 0.05) and both were significantly higher than the uninfected group ( p  < 0.05). In conclusion, immunization by prepared UV-irradiated oocysts is effective in stimulating at least a partial protective immunity in immunized chickens against caecal coccidiosis.