Immunization by irradiated Eimeria acervulina

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.

Identification of immunodominant surface antigens of Eimeria acervulina sporozoites and merozoites

Immunodominant surface antigens of Eimeria acervulina sporozoites and merozoites were identified by 125I-labeling and immunoblotting studies. Using these methodologies 60% of the immunodominant sporozoite antigens and 90% of the immunodominant merozoite antigens were observed to be 125I-surface labeled. However, several major 125I-labeled sporozoite and merozoite proteins did not represent prominent antigens as measured by immunoblotting. Immunodominant surface antigens were found over a wide size range for sporozoites (21-110 kDa) and for merozoites (20-250 kDa). In order to relate these findings to a 'natural' infection, two groups of 3-week old chickens were inoculated 5 times over a 2.5 week period with either a low or high dose of E. acervulina oocysts. The serum response to sporozoites and merozoites, indicated by enzyme-linked immunosorbent assay titers, was rapid; less than or equal to 7 days post-infection with 10(4) oocysts and less than or equal to 3 days with 10(5) oocysts. Many of the antigens identified by immunoblotting of sera from sporozoite- and merozoite-immunized animals were recognized by sera from both high dose and low dose E. acervulina-infected chickens. Furthermore, the sporozoite and merozoite antigens could be grouped into those constituents which induced a serum response early or late in the infection.

The effects of heat and cobalt-60 gamma-radiation on excystation of the rat coccidium, Eimeria nieschulzi Dieben, 1924

Sporulated oocysts of Eimeria nieschulzi Dieben, a rat coccidium, were exposed for 1 hr to Cobalt-60 gamma-radiation (15, 30, or 60k-rads), to heat (35, 40, or 45 C) , or to both concurrently (15, 30, OR 60 K-RADS AT 35 C) to compared the excystation capabilities of treated vs nontreated parasites. Intact treated oocysts appeared structurally unaltered when viewed with the light microscope. Excystation of sporozoites occured in all treated groups when their sporocysts were exposed to a trypsin-sodium taurocholate (TST) fluid, but after 150 min in TST the excystation rate was significantly lower than in nontreated sporocysts. Sporozoites which excysted from treated sporocysts were abnormal both in the excystation process and in their form and movement once outside the sporocysts.

Effect of gamma-irradiation on oocysts of Eimeria necatrix

Effect of gamma radiation on oocysts of Eimeria necatrix was investigated. It was observed that oocysts exposed to 200 kR or above did not sporulate. Irratiation at 10-150 kR caused a progressive decrease in sporulation. Irradiation affected normal development of unsporulated oocysts as the zygote protoplasm divided into unequal masses or was shattered into granules. Increase in the intensity of irradiation of sporulated oocysts resulted in the progressive decrease in severity of the resultant infections in chicks and their effects - mortality, type of lesions developed, total oocyst production and immunity produced - were comparable with infections induced by decreasing the number of unirradiated oocysts. Infection produced by 1000 unirradiated oocysts was comparable with that resulting from 50 000 oocysts irradiated at 25 kR. Infection obtained with 20 000 unexposed oocysts approximated to that produced by 50 000 oocysts irradiated at 2-5 kR. It was concluded that irradiation abolished infectivity of the oocysts/sporozoites rather than bringing about attenuation of the parasite.