Immunoprotection against mixed Eimeria spp. infections in goat kids induced by X-irradiated oocysts

Abstract

Strategies to control goat coccidiosis traditionally rely on the use of management practices combined with anticoccidial treatments, and limited effort has been made, so far, to address immunological control of caprine Eimeria infections. Previously, we showed that monospecific immunization with X-Rad-attenuated Eimeria ninakohlyakimovae oocysts induced considerable immunoprotection upon challenge. In the present study, we conducted a similar vaccination trial but using a mixture of caprine Eimeria species typically present in natural infected goats. For immunization, sporulated oocysts were attenuated by X irradiation (20 kilorad). All infections were performed orally applying 10⁵ sporulated oocysts of mixed Eimeria spp. per animal. In total, 18 goat kids were grouped as follows: (G1) immunized + challenge infected; (G2) primary + challenge infected; (G3) challenge infection control; and (G4) non-immunized/non-infected control. Overall, goat kids infected with attenuated oocysts (= immunized) shed less oocysts in the faeces and showed a lower degree of clinical coccidiosis than animals infected with non-attenuated oocysts. Animals of both challenge groups (G1 and G2) showed partial immunoprotection upon reinfection when compared to challenge infection control (G3). However, the degree of immunoprotection was less pronounced than recently reported for monospecific vaccination against Eimeria ninakohlyakimovae, most probably due to the complexity of the pathogenesis and related immune responses against mixed Eimeria spp. infections. Nevertheless, the data of the present study demonstrate that immunization with attenuated Eimeria spp. oocysts may be worth pursuing as a strategy to control goat coccidiosis.

Keywords: Eimeria spp.; Goats; Immunoprotection; Vaccine; X-Rad attenuation.

Fig. 1

Log-transformed Eimeria oocyst counts per gram of faeces [Log (OPG+1)] (A) and raw OPG counts (B) in immunized goat kids and related control groups. The data are represented by mean ± SEM (A) or only mean values (B). For statistical differences: (1, 2, 3) P < 0.05 - P < 0.01 - P < 0.001 G1 vs G3; (a, b, c) P < 0.05 - P < 0.01 - P < 0.001 G2 vs G3. Day of challenge infection is indicated by an arrow

Fig. 2

Percentage of the Eimeria species found in faeces of immunized goat kids and related control groups: A “G1: Immunized + challenge infected”; B “G2: Primary + challenge infected”; C “G3: Challenge infection control”. Day of challenge infection is indicated by an arrow

Fig. 3

Faecal consistency in immunized goat kids and related control groups. The following score was used: (1) normal formed faeces; (2) unformed faeces of slightly reduced consistency; (3) faeces of moderately reduced consistency; (4) yellowish, greenish or brownish liquid faeces; (5) liquid faeces of reddish colour and/or presence of mucosa pieces. Data are expressed as means ± SEM. For significant differences: (1, 2, 3) P < 0.05 - P < 0.01 - P < 0.001 G1 vs G3; (a, b, c) P < 0.05 - P < 0.01 - P < 0.001 G2 vs G3. Day of challenge infection is indicated by an arrow

Fig. 4

Growth rates in immunized goat kids and related control groups. The data are expressed as means ± SEM. For significant differences: (a) P < 0.05 G2 vs G3. Day of challenge infection is indicated by an arrow