Irradiated oocysts in combination with inulin adjuvant-induced potent immune responses against Eimeria tenella infection in broiler chickens

Abstract

Coccidiosis is the leading parasitic disease in poultry. One of the most critical Eimeria species, Eimeria tenella, lives inside the cecal epithelial cells and induces bloody coccidiosis. The present study evaluated the effect of radiation-attenuated E. tenella oocytes mixed with inulin adjuvant on broiler chicken. Initially, the effect of irradiation on oocyst attenuation was confirmed. Then, one-day-old broilers (n = 90) were divided into nine groups on seven days of age as follow: Group 1 (400 attenuated oocysts + 1.00 mg of adjuvant), group 2 (400 attenuated oocysts + 0.50 mg adjuvant), group 3 (200 attenuated oocysts + 1.00 mg of adjuvant), group 4 (200 attenuated oocysts + 0.50 mg adjuvant), group 5 (1.00 mg adjuvant), group 6 (400 attenuated oocysts), group 7 (commercial vaccine), group 8 (negative control) and group 9 (blank). On day 21, we performed a challenge with E. tenella oocytes and investigated oocyst output and average weekly weight throughout the study. At the end of the study, we evaluated macroscopic lesion, histology, cytokine level and leukogram status. The results showed a statistically significant difference among groups. Furthermore, the optimal dose was 400 irradiated oocysts and 1.00 mg of inulin. Moreover, an X-ray could reduce the virulence of E. tenella oocytes. Inulin alone or combined with attenuated oocysts showed an acceptable effect on evaluated parameters.

Keywords: Broiler; Eimeria tenella; Inulin; X-ray.

Fig. 1

Cytokine induction. A) IFN-γ and B) IL-4 induction was evaluated as representative of T helper 1 and T helper 2 type immune responses, respectively, by RT-PCR

Fig. 2

Blood profile of treated animals. A) Atypical lymphocyte (yellow arrow), a monocyte (white arrow) and two granulocytes (blue arrow); B) thrombocytes (red arrow), and a granulocyte (blue arrow), C) thrombocyte (red arrow), small lymphocyte (green arrow) and atypical lymphocyte (yellow arrow), (Wright-Giemsa staining, 100×)

Fig. 3

Histological review of intestine epithelium. The presence of protozoa is shown in the epithelium of A) cecum and B) jejunum (Hematoxylin and Eosin staining, 100×)