By Joan Smyth, Ph.D.
University of Connecticut
Necrotic enteritis (NE), the subject of the current work, is a serious and often fatal disease of chickens and turkeys, with up to 50 percent mortality reported before effective control measures were introduced. A less severe, but economically important, form of this disease has also been identified and is frequently called subclinical NE. NE is caused by the bacterium Clostridium perfringens, which proliferates in the small intestine and produces potent exotoxins that damage the gut lining, leading to necrosis (death of tissue), ulceration and inflammation.
In affected birds, the C. perfringens may also invade the liver to cause acute or chronic hepatitis which results in either death, or subclinical disease, and condemnation of carcasses in the slaughter plant. Thus, NE is a disease which has a significant adverse impact on bird health and well-being, as well as on profitability for the producer.
The disease can be controlled by incorporation of antibiotic growth promoters (AGPs) in the feed. AGPs are effective in preventing NE, but they have been banned in many countries and their use is rapidly being phased out in the US. NE is expected to become a much bigger problem in the US, as has been the experience in other countries following the cessation of use of AGPs. Alternative preventative measures are needed, and vaccination is a good alternative strategy.
The objective of the present study was to test a non-virulent NetB and alpha toxin producing strain of C. perfringens as an orally administered vaccine. NetB and alpha toxin are two of the toxins produced by C. perfringens that are thought to be involved in producing NE.
The approach was to administer this unique NetB positive non NE producing strain of C. perfringens by the oral route, with or without mucosal adjuvants, and to test for protective effects by measurement of antibody response and by exposure to a challenge model for clinical NE.
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