CPRC Update: Research study conducted on necrotic enteritis in broiler flocks raised without antibiotics
A novel necrotic enteritis vaccine strategy
Increased pressure on the poultry industry to produce antibiotic-free chickens remains a challenge, as rearing birds without antibiotics results in an increased risk of pathogen contamination. The Canadian poultry industry is faced with an increased risk in the development of necrotic enteritis, known to be caused by Clostridium perfringens bacterium.
Dr. Martine Boulianne, poultry research chair with the University of Montreal’s Faculty of Veterinary Medicine, conducted a large-scale commercial study in which the incidence of development of necrotic enteritis was monitored in broiler flocks raised without antibiotics. This study demonstrated 25 per cent of antibiotic-free flocks experience necrotic enteritis outbreaks, while 50 per cent of the flocks experienced various levels of sub-clinical enteritis and 25 per cent of the flocks were classified as clinically healthy. This is not only a bird health and welfare concern, but also an economic concern for the industry as it reduces antibiotic use. This on-farm broiler trial showed cost increased 10 cents per kilogram of chicken produced for antibiotic-free birds compared to conventionally raised chickens.
A Clostridium perfringens culture collection, covering a full spectrum of chicken intestinal health from healthy birds to those infected with necrotic enteritis, will be used in Boulianne’s research project, with the aim of developing a novel necrotic enteritis vaccine strategy.
The pathogenicity and genetic characteristics of Clostridium perfringens able to cause necrotic enteritis are unknown. Recent evidence suggests attachment of the bacteria could play an important role in the development of necrotic enteritis. Virulence factors conferring them a competitive advantage in the presence of other predisposing factors have recently been discovered. Capacity to attach to some intestinal mucosal cells’ molecules following coccidial damage has been demonstrated in some Clostridium perfringens isolates.
Boulianne and her research team have developed a unique method to compare the virulence of both commensal and pathogenic Clostridium perfringens strains using a surgical model. Additionally, recent observations from her laboratory suggest intestinal mucosa attachment by the bacteria could play a role in the pathogenesis of necrotic enteritis. A specific hair-like appendage found on the surface of bacteria plays a predominant role in the attachment by bacteria found within the Clostridium perfringens genetic code. Thus, the research approach will be to compare the organization of genes encoding for this pilus in both commensal and virulent strains to evaluate the role of bacterial attachment mediated through this specific hair-like appendage.
Post-doctoral students Dr. Marie-Lou Gaucher and Dr. Audrey Charlebois are working on the project in collaboration with Dr. Marie Archambault and Dr. John Prescott.
FINDINGS AND OUTCOMES
The researchers have identified and localized regions encoding for type IV pilus using bioinformatics and molecular biology techniques. Researchers are currently conducting tests of the genetic variability within the regions from commensal and virulent strains to establish a “profile pilus” specific to each strain. The role of these different regions encoding the pilus in the attachment of the bacterium to intestinal cells will be evaluated to understand the role of the pilus in strains causing necrotic enteritis. The researchers plan to further the experiments in order to better understand the pathogenic mechanisms underlying necrotic enteritis. Such understanding will improve the development of better control methods. The planned outcome of this research group is to develop a novel vaccine strategy against necrotic enteritis.
This research is funded by the Canadian Poultry Research Council (CPRC), Mitacs, Quebec Poultry Associations and the University of Montreal.
The membership of the CPRC consists of Chicken Farmers of Canada, Canadian Hatching Egg Producers, Turkey Farmers of Canada, Egg Farmers of Canada and the Canadian Poultry and Egg Processors’ Council. CPRC’s mission is to address its members’ needs through dynamic leadership in the creation and implementation of programs for poultry research in Canada, which may also include societal concerns.