The project aimed to provide new insight into controlling necrotic enteritis in broilers, and was funded by USPOULTRY and the USPOULTRY Foundation.

Necrotic enteritis is a disease in broilers that is increasing in incidence as companies reduce the use of antibiotics in feed. It 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 necrotic enteritis.

Little is known about the causative organism, Clostridium perfringens, and new effective control measures are needed. C. perfringens, which proliferates in the small intestine and produces potent toxins that damage the gut lining, leading to necrosis (death of tissue), ulceration and inflammation.

In affected birds, the C. perfringens bacteria 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.

Using growth-promoting antibiotics to prevent disease has saved producers money in the US, but more and more countries and brands are banning this practice, leading to increased disease risk. More knowledge is needed to develop alternative strategies.

Researchers led by Dr Joan Smyth performed basic research on the organism to determine the factors which allow it to cause the disease.

The approach was to comprehensively examine the entire proteome (all of the proteins expressed by the bacteria) of four severe necrotic enteritis-producing strains as well as a non necrotic enteritis-producing strain of C. perfringens.

The proteins produced by the strains were compared both qualitatively and quantitatively, for differences between the disease producing and non-disease producing strain.

They discovered previously unknown bacterial proteins which may be important factors involved in the disease. The scientists found 35 proteins out of a total of 2,424 identified that were produced in significantly higher amounts by the disease-producing strains of the bacterium.

According to the scientists, none of these proteins have been previously considered as potential virulence factors in necrotic enteritis. Among them are proteins resembling those associated with virulence in some other pathogenic bacteria, including proteins associated with adhesion, which seems to be related to the ability of bacteria to produce disease.

Further study of these proteins is underway and may lead to new vaccines or other methods to control necrotic enteritis.