Clinicopathological and immunological studies on Toxoid vaccine as a successful alternative in controlling clostridial infection in broilers

Three vaccination regimes based on Clostridium perfringens (C. perfringens) type A, C or combined AC toxoids were evaluated to detect if toxoid vaccines can prevent necrtotic enteritis (NE) caused by clostridial infection in broilers. The vaccines were administered two times at two weeks interval, then the birds were challenged with virulent strains of C. perfringens type A, C or combined AC. Blood samples were taken after both first and second vaccination doses as well as after challenge. Evaluating parameters included clinical signs, gross intestinal lesions, hemogram [red blood cell count (RBCs), packed cell volume (PCV), hemoglobin (Hb), total leukocytic count (TLC) and differential leukocytic count],serum biochemical assays [total protein (TP), albumin (Alb), globulin (Glob), albumin globulin ratio (A/G), serum activities of alanine amino transferase (ALT), aspartate amino transferase (AST), alkaline phosphatase (ALP) and uric acid (UA) values] and ELISA test for detecting serum antibody titers. Results revealed that affected birds showed marked depression, anorexia, reluctance to move, ruffled feathers and diarrhea. Numbers of chickens with intestinal lesions in immunized challenged groups were greatly fewer than the infected non immunized ones. There was an increase in RBCs, PCV and Hb. TLC decreased in infected non immunized birds and increased in vaccinated ones. Heterophils were increased in infected groups while, lymphocytes decreased. Prominent lymphocytosis was observed in immunized birds. Results of biochemical assays showed that there was a significant increase in TP, Alb, Glob, ALP, ALT, AST and UA and decrease in A/G. Results of ELISA test showed that there was a significant increase in antibody titer after immunization paricularly after the second dose of vaccination. The combined AC toxoid provided the greater antibody titer and best protection followed by toxoid A and finally toxoid C. We concluded that results provide an evidence that immunization of broilers with toxoid vaccines paricularly the combined type AC is safe, welltolerated and can protect broiler chickens against NE after the second booster dose of the vaccine.