New cause identified for necrotic enteritis in chicken
Researchers from Monash University and CSIRO Livestock Industries have demonstrated for the first time that alpha-toxin protein, long thought to be required for necrotic enteritis to develop, is not the main cause of the chicken disease. The study, published February 8 in the open-access journal PLoS Pathogens, provides insight into one of the world鈥檚 most common and financially crippling poultry diseases.
鈥淚t鈥檚 caused by Clostridium perfringens, a bacterium found in soil, litter, dust and in small quantities in the intestines of healthy chickens,鈥� said co-author Anthony Keyburn, 鈥淭he bacterium only causes disease when it proliferates to high numbers, producing extracellular toxins that attack the bird鈥檚 intestines, causing lesions.鈥� .
Poultry producers use antibiotics to treat and prevent the disease, which, when triggered, can cause mortality rates of up to 50 per cent. Necrotic enteritis costs the world鈥檚 poultry industries an estimated US$2 billion every year.
The disease was first described in 1961 and alpha-toxin was implicated as the major causative factor, although definitive proof has never been reported. As a result, for the last 30 years all vaccine development work has been based on the assumption that alpha-toxin was the key.
Mr Keyburn said the research team began to question the involvement of alpha-toxin when a survey showed that local disease-causing bacterial strains produced low levels of this toxin.
鈥淲e tested the importance of alpha-toxin by genetically altering the bacterium so it no longer produced any of the protein,鈥� he said. 鈥淒espite the toxin鈥檚 absence, our bacterial isolates still caused disease in chickens. This demonstrates that the development of necrotic enteritis in chickens is not dependent on C. perfringens producing a functional alpha-toxin.鈥�
This finding led the team to expand their search for the real cause of necrotic enteritis, finding a novel toxin 鈥� NetB 鈥� that is involved in the disease-causing potential of a high proportion of virulent C. perfringens strains.
The authors are now investigating NetB and other proteins produced by C. perfringens, with the aim of developing effective vaccines against the disease.
鈥淎round the world, poultry producers are waiting for vaccines against necrotic enteritis,鈥� said co-author Rob Moore. 鈥淭hanks to Anthony鈥檚 discoveries, scientists should now be able to develop the vaccines within a couple of years.鈥�
Source: Public Library of Science
