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FAQ: Clostridium perfringens type A toxoid
- What is Clostridium perfringens type A toxoid?
- What is a toxoid?
- How does Clostridium perfringens type A toxoid work?
- What’s unique about Clostridium perfringenstype A toxoid?
- How can passive maternal protection against NE help my flocks?
- How long does the protection afforded by Clostridium perfringens type A toxoid last in progeny chicks?
- What is a good or protective titer?
- Will Clostridium perfringens type A toxoid protect the hens as well as the progeny against NE outbreaks?
- Will Clostridium perfringens type A toxoid have a negative impact on pullet mortality, egg production, fertility and hatchability?
- Do I need to vaccinate roosters as well as the hens?
- My operation uses Coccivac®-B coccidiosis vaccine to control coccidiosis in broilers.
- Can I use Clostridium perfringens type A toxoid to help protect broiler flocks against NE outbreaks?
- Can I use Clostridium perfringens type A toxoid to help protect broiler flocks that will be medicated with ionophore anticoccidial drugs?
- If I vaccinate my pullet flocks with Clostridium perfringens type A toxoid, do I still need to use water acidifiers, probiotics, enzymes and prebiotics to keep my antibiotic-free flocks free from NE?
- Is Clostridium perfringens type A toxoid cost effective?
- How much does Clostridium perfringens type A toxoid cost?
- The price of Clostridium perfringens type A toxoid seems high. How can I justify this investment?
- I have to add one more person to the vaccination crew to inject Clostridium perfringens type A toxoid in my pullets. How much will that cost me?
- Necrotic enteritis occurs only seasonally or sporadically. How can I justify vaccinating pullet flocks that will lay most of their eggs during low incidence
periods?
Q1. What is Clostridium perfringens type A toxoid?
Clostridium perfringens type A toxoid is an innovative clostridial vaccine conditionally licensed in the United States for use in chickens. It is a non-antibiotic, biologic product that can be used in broiler chickens as an aid in the control of necrotic enteritis (NE) caused by the alpha toxin of Clostridium perfringens.
A toxoid is a vaccine made from an inactivated toxin. Although it stimulates immunity to protect against disease, it cannot cause disease.
Q3. How does Clostridium perfringens type A toxoid work?
Clostridium perfringens type A toxoid is administered to hens at 10 to 15 weeks of age, followed by revaccination at 17 to 20 weeks of age. The toxoid initiates high antibody titers against the alpha toxin of C. perfringens, which is the cause of NE. The antibodies are transferred to progeny chicks via the egg yolk. Antibody titers in hens are maintained throughout the laying period of 65 weeks.
Q4. What’s unique about Clostridium perfringenstype A toxoid?
Clostridium perfringens type A toxoid is the first toxoid for NE in poultry, although toxoids have been used in other species for years. The transfer of antibodies from hens to chicks, which is known as passive immunity, enables broiler flocks to be protected against NE without having to vaccinate large numbers of individual broilers.
Q5. How can passive maternal protection against NE help my flocks?
Vaccination of replacement pullets to protect progeny chicks is a widely used preventive measure against many infectious poultry diseases. Alpha toxin produced by C. perfringens types A and C is the leading cause of the typical intestinal mucosal lesions that develop in chickens with NE. Specific antibodies have been used to protect other animal species against diseases caused by various C. perfringenstoxin types; they may also protect broilers against NE.
In a study of naturally occurring specific antibodies against C. perfringens alpha toxin in broiler chickens, Heier et al. (Avian Diseases, 2001) found that flocks with high blood titers of specific maternal antibodies against the alpha-toxin had lower mortality during the grow-out period than flocks with low titers.
Q6. How long does the protection afforded by Clostridium perfringens type A toxoid last in progeny chicks?
To date, no specific data on the duration of protection has been generated. Review of scientific literature on the subject indicates that passive maternal protection against other infectious diseases can be expected to last from 2 to 3 weeks.
In laboratory trials performed by Schering-Plough Animal Health to test the efficacy of Clostridium perfringens type A toxoid vaccination, 21-day-old broilers were challenged with a high dose of C. perfringens that resulted in lesions and mortality in control birds. Broiler chicks from hens vaccinated with Clostridium perfringens type A toxoid showed a significant reduction in the incidence and severity of typical NE lesions compared to the controls.
Q7. What is a good or protective titer?
A minimum protective antibody titer has not been established for Clostridium perfringens type A toxoid. A hemolysis inhibition test, however, was developed to test the antibody response of pullets following vaccination. Antibody titers were evaluated in SPF White Leghorn pullets following immunization with Clostridium perfringens type A toxoid vaccine administered subcutaneously. The pullets were vaccinated at 15 weeks of age with 0.5 mL of the vaccine and a booster dose was administered 4 weeks later. Blood samples were collected 6 weeks after the booster. Serum from each individual bird was evaluated for antibody titer by the hemolysis inhibition assay and ranged from 512 to 8,192, with a GMT of 1,290.
In contrast, serum samples from control birds showed a GMT of ≤ 2, with a maximum value of 4. The antibody titer in eggs collected at 25 weeks of age from the White Leghorn layers were also evaluated and showed a pooled value of 512, whereas eggs from control birds showed a pooled value of < 2.
Q8. Will Clostridium perfringens type A toxoid protect the hens as well as the progeny against NE outbreaks?
The efficacy of Clostridium perfringens type A toxoid in protecting hen flocks against NE has not been measured. As more flocks are vaccinated, SPAH will be able to collect more data and measure the possible beneficial effect of Clostridium perfringens type A toxoid in hens.
Q9. Will Clostridium perfringens type A toxoid have a negative impact on pullet mortality, egg production, fertility and hatchability?
No. In field safety trials conducted in the United States, vaccination with Clostridium perfringens type A toxoid had no negative impact on pullet mortality, egg production, fertility or hatchability.
Q10. Do I need to vaccinate roosters as well as the hens?
No. The transfer of specific maternal antibodies against the alpha toxin to progeny chicks via the egg yolk that is initiated by Clostridium perfringens type A toxoid does not depend in any way on the immune status or serologic titers of roosters.
Q11. My operation uses Coccivac®-B coccidiosis vaccine to control coccidiosis in broilers. Can I use Clostridium perfringens type A toxoid to help protect broiler flocks against NE outbreaks?
Yes. Clostridium perfringens type A toxoid represents an important innovation in poultry production because it is the first non-antibiotic product that helps control NE caused by C. perfringens types A and C. In addition, vaccination with Clostridium perfringens type A toxoid may help poultry companies achieve important marketing advantages by better enabling them to promote their poultry products as “raised without antibiotics,” especially when the new vaccine is combined with vaccination against coccidiosis.
In a field trial carried out in the United States by Schering-Plough Animal Health, broiler flocks vaccinated with Coccivac-B that were from breeder hens vaccinated with Clostridium perfringens type A toxoid showed a better mortality trend line compared to comparable flocks from non-vaccinated breeder hens in the same company that were processed at the same time. Mortality trend lines were assessed at four times:
- 8-14 days
- 15-21 days
- 22-27 days
- Total mortality
Q12. Can I use Clostridium perfringens type A toxoid to help protect broiler flocks that will be medicated with ionophore anticoccidial drugs?
Yes. Ionophore anticoccidials help prevent clostridial infections in two ways. First, they control coccidiosis, which predisposes birds to clostridial overgrowth and NE. Second, these drugs have a direct anticlostridial effect when administered at the recommended doses for anticoccidial activity.
Ionophores, however, may become less effective if bacteria and coccidial parasites develop resistance. To achieve optimal anticoccidial protection, ionophore anticoccidials need to be used in shuttle or combination with other, non-ionophore anticoccidials such as nicarbazin or diclazuril, which have no anticlostridial activity, thus diluting the beneficial effect of ionophore drugs against clostridial bacteria.
Clostridium perfringens type A toxoid may complement the partial protection provided against NE afforded by ionophore anticoccidials. In field trials carried out in the United States by Schering-Plough Animal Health, broiler flocks from hens vaccinated with the toxoid that were treated with ionophore anticoccidials had significantly better livability, feed conversion, standard cost, calorie conversion and adjusted calorie conversion compared to paired flocks from hens that were not vaccinated with the toxoid.
Q13. Can I use Clostridium perfringens type A toxoid to help protect broiler flocks that will be medicated with a full level of in-feed antibiotic growth promoters?
Yes. Antibiotic growth promoters are effective in preventing clostridial bacteria overgrowth and at the same time, promote bird growth and improve feed efficiency. As with ionophore drugs, however, clostridium and other bacteria may acquire resistance to in-feed antibiotic growth promoters, minimizing or eliminating their effectiveness.
Clostridium perfringens type A toxoid can be used to complement NE protection in high-challenge situations, such as that of broilers vaccinated with coccidiosis vaccines that are raised on a wheat-based diet, which has been associated with an increased risk for NE.
In an ongoing series of field trials conducted by a Canadian veterinarian, passive immunity against the C. perfringens type A alpha toxin appeared to successfully augment the effect of in-feed medication for preventing NE when a non-attenuated coccidiosis vaccine (Coccivac®-B) was used in concert with a wheat-based ration. The broiler flock achieved growth performance that met breed standards. No loss in performance due to coccidiosis or NE was detected, whereas previously, six consecutive flocks on the same farm suffered high mortality and low performance due to clinical NE outbreaks.
Q14. If I vaccinate my pullet flocks with Clostridium perfringens type A toxoid, do I still need to use water acidifiers, probiotics, enzymes and prebiotics to keep my antibiotic-free flocks free from NE?
There are no known conflicts for the concomitant use of Clostridium perfringenstype A toxoid and other non-antibiotic products for the control of NE. Most alternative compounds do not have a specific claim or direct effect on the incidence or severity of clinical and subclinical NE. Instead, they alter the profile of gut micro flora by limiting the colonization of unfavorable bacteria while promoting the growth of more favorable species. Strategic use of these alternative compounds may help optimize growth, provided they are used in a manner that complements their modes of action.
Clostridium perfringens type A toxoid, on the other hand, provides specific protection via passive maternal antibodies against the alpha-toxin produced by C. perfringens types A and C and, therefore, can be used as an aid in the control of NE caused by these bacteria.
Q15. Is Clostridium perfringens type A toxoid cost effective?
One 500 mL bottle of Clostridium perfringens type A toxoid treats 500 pullets on a two-shot treatment schedule. Since one broiler breeder hen may produce up to 130 broiler chicks or more, one bottle of Clostridium perfringens type A toxoid is enough to protect at least 65,000 broilers. A toxoid vaccine such as Clostridium perfringens type A toxoid that provides passive immunity is more cost effective and practical than a vaccine that would have to be administered to every broiler chick. Schering-Plough Animal Health has developed a Return on Investment calculator to help individual producers determine the cost effectiveness of Clostridium perfringens type A toxoid for their operation.
Q16. How much does Clostridium perfringens type A toxoid cost?
A two-shot treatment with Clostridium perfringens type A toxoid in the United States will cost approximately $0.34 per pullet. Since the vaccine is administered to protect broiler chickens that are the progeny of vaccinated hens, it is important to estimate the cost of Clostridium perfringens type A toxoid in a broiler flock.
If we assume that each vaccinated hen will produce 156 fertile eggs (13 dozen eggs — a common industry average) with an average hatchability rate of 84% or 131 chicks per hen, then the cost of Clostridium perfringens type A toxoid can be estimated at about $0.003, or a quarter of a penny per broiler chicken.
Q17. The price of Clostridium perfringens type A toxoid seems high. How can I justify this investment?
The cost of NE in either its clinical or subclinical forms far exceeds the investment in vaccinating breeder flocks with Clostridium perfringens type A toxoid. It has been estimated by industry experts that NE costs on average $0.05 per bird, which is more than 10 times greater than the cost of vaccination. In field trials conducted in the United States by Schering-Plough Animal Health, improvement in livability and reduced production costs among flocks that received Clostridium perfringens type A toxoid at three large-bird complexes resulted in an estimated return on investment of 8:1.
Q18. I have to add one more person to the vaccination crew to inject Clostridium perfringens type A toxoid in my pullets. How much will that cost me?
Clostridium perfringens type A toxoid was designed to coincide with current management practices. Pullets are handled anyway at ages 10 to 15 and 17 to 20 weeks to receive other vaccinations. In the United States, the cost of additional labor required to inject Clostridium perfringens type A toxoid in pullet flocks has been estimated to range from $0.015 to $0.03 per pullet. For a two-shot treatment, the total cost of additional labor would be an estimated $0.03 to $0.06 per pullet.
Q19. Necrotic enteritis occurs only seasonally or sporadically. How can I justify vaccinating pullet flocks that will lay most of their eggs during low incidence periods?
The incidence of clinical NE outbreaks can be associated with seasonal factors such as the quality of litter, which can be hard to maintain in cold weather, feed ingredient quality, coccidiosis and other diseases that damage the intestinal tract. At one poultry operation where sporadic outbreaks of NE resulted in increased mortality during colder months of the year, vaccination with Clostridium perfringens type A toxoid appeared to be beneficial.
On the other hand, little is known about the incidence of subclinical NE, and it appears that this condition can occur throughout the year. In another series of trials involving four broiler operations with NE outbreaks during different seasons, vaccination with Clostridium perfringens type A toxoid appeared to benefit overall performance parameters, resulting in significantly better livability, feed conversion, calorie conversion, adjusted calorie conversion and lower production costs, although no reduction in the incidence of clinical outbreaks were recorded.
In summary, Clostridium perfringens type A toxoid may help reduce the incidence and severity of both clinical and subclinical NE. Since most cases of subclinical NE go undetected, vaccination with Clostridium perfringens type A toxoid may help improve protection even during apparently low incidence periods.
