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Research summaries
Clostridium perfringens type A toxoid is based on strong scientific evidence and extensive experience with clostridial vaccines for other animals.
It has also been tested in field trials, demonstrating that the vaccine can help control necrotic enteritis in commercial broiler chickens.
Following are summaries of key studies to date, using the Clostridium perfringens type A toxoid in a variety of commercial situations:
Toxoid in antibiotic-free birds
AGP = Antibiotic growth promoter.
Initial trials with toxoid
The first studies with Clostridium perfringens type A toxoid were designed to determine if the vaccine could protect birds from exposure to necrotic enteritis.
Schering-Plough Animal Health scientists vaccinated broiler breeder pullets with the toxoid vaccine and additional pullets remained unvaccinated and served as controls.
Eggs were collected from all pullets in the study at 32, 52 and 65 weeks of age. Each hatched chick was then orally challenged with virulent C. perfringens type A at 21 days of age.
Most chicks in the control group developed necrotic enteritis (NE) lesions, which demonstrated that the exposure to C. perfringens was enough to cause disease and evaluate the ability of the NE toxoid to protect against NE.
Results
- Chicks from hens vaccinated with Clostridium perfringens type A toxoid had significantly lower NE lesion scores compared to the unvaccinated group (Figure 1).
- Clostridium perfringens type A toxoid provided protection throughout the typical 65-week laying period.
- Sera and egg yolk from vaccinated hens had significantly higher antibody titers for C. perfringens compared to controls.
- Similar results occurred when the studies were repeated and Clostridium perfringens type A toxoid was administered via the intramuscular route.
- Clostridium perfringens type A toxoid was found to be safe for breeder hens.
Figure 1. The offspring of chicks from hens vaccinated with Clostridium perfringens type A toxoid had significantly lower median NE lesion scores than chicks from unvaccinated controls.
Toxoid in antibiotic-free birds
A US poultry company growing 4.60- to 5.50-pound antibiotic-free birds was having NE outbreaks, resulting in mortality ranging from 2% to 10% among affected flocks. The adverse effects of subclinical NE were not known.
Investigators administered Clostridium perfringens type A toxoid at 10 and 18 weeks to nearly 79,900 pullets producing 100,000 offspring weekly. Offspring also received Coccivac-B at the hatchery to prevent coccidiosis.
In control flocks from hens not vaccinated with the NE toxoid, high mortality from NE developed and standard treatment for NE was administered.
Results
- Mortality was significantly less in the group from hens that received Clostridium perfringens type A toxoid compared to controls (Figure 2). The reduction in mortality was as high as 2.5% by the end of the observation period.
- Lowering mortality by even 1% can have a significant impact on production costs.
Figure 2. Clostridium perfringens type A toxoid significantly lowered mortality in antibiotic-free birds experiencing NE outbreaks. 
Toxoid + ionophore + AGPs + wheat-based diet
A commercial broiler farm in Western Canada using a wheat-based diet, which is considered a risk factor for NE, tried Clostridium perfringens type A toxoid to reduce the incidence of NE.
In 2005, the company had used Coccivac-B and an antibiotic growth promoter in six flocks; three of the flocks had also received salinomycin, but NE remained a problem.
In 2006, the company raised two flocks from hens vaccinated with the NE toxoid. The chicks received Coccivac-B as well as the growth promoter bacitracin in the starter, grower and finisher rations.
Results
- There was no evidence of NE after the first production cycle based on examination of mortality, culls and random birds.
- The growth rate for birds in the Clostridium perfringens type A toxoid group was greater than the 2005 flocks and met breed standards.
Passive immunity against C. perfringens type A alpha toxin appeared to successfully augment in-feed medication to prevent lesions of NE when a non-attenuated coccidiosis vaccine was used in concert with a wheat-based ration, the company’s director of veterinary services concluded.
Toxoid + ionophore
A major US poultry company administered the NE toxoid to more than 1.1 million hens at 10 to 15 weeks and again at 17 to 20 weeks of age.
The flocks, from six pullet operations, received an ionophore anticoccidial but no antibiotic growth promoter.
For the purpose of the study, flocks were considered to be “vaccinated with Clostridium perfringens type A toxoid” when over 70% of broilers came from hens that had actually received the vaccine.
Results
- Chicks from hens vaccinated with Clostridium perfringens type A toxoid showed significantly better livability, feed conversion, standard cost, calorie conversion and adjusted calorie conversion than birds from unvaccinated hens.
- Clostridium perfringens type A toxoid flocks also had numerically better average weight and daily gain compared to controls.
The results demonstrate that Clostridium perfringens type A toxoid can benefit broiler flocks raised with ionophore anticoccidials but without an antibiotic growth promoter.
Coccivac is a registered trademark of Schering-Plough Animal Health Corporation.
BMD is a registered trademark of Alpharma Inc.
