2005 - 2006
Molecular epidemiology of necrotic enteritis
Principal Investigator: Patrick Boerlin, University of Guelph
Co-investigator: John Prescott, Bruce Hunter, Wayne Martin, Gabhan Chalmers (MSc student), University of Guelph
BackgroundClostridium perfringens is a bacterium commonly found in the gut of a variety of healthy animals, including chickens. However, it is also linked to necrotic enteritis (NE). There is relatively little information on how NE develops, especially in terms of the role that C. perfringens plays and why certain strains of the bacterium can cause the disease. The main objectives of this project were to look at the C. perfringens strains present in chickens and compare their diversity both within individual birds and among different birds on commercial broiler farms, and to see if that diversity changes in birds suffering from NE.
Research ProgressThe techniques traditionally used to determine strain diversity are very laborious. Dr. Boerlin’s team therefore developed techniques that are less work intensive and can be largely automated. These new techniques were used throughout the current project and will part of related studies in the future.
In the first phase of the project, Dr. Boerlin’s team looked at the diversity of C. perfringens strains in two barns in a commercial broiler farm. It was unexpectedly low. Similar studies in Europe, where antimicrobial use is restricted, show higher strain diversity. Dr. Boerlin suggests that the use of bacitracin on the farms in his study may have skewed the C. perfringens population towards a few resistant strains.
Strains isolated from field cases of NE (these birds did not receive antimicrobials) were then compared to those from flocks with no known history of the disease. C. perfringens strains from the same NE-positive birds, or from different healthy birds from the same barn, were generally the same genetic type. However, different NE outbreaks were associated with genetically diverse strains. Almost all these isolates tested positive for the NetB toxin, which was recently implicated as a contributing factor in NE. Collectively, these results suggest that an element(s) that can be transferred from one strain to another (such as the netB gene) can affect a strain’s ability to cause NE.
Samples were also taken from a different research project during which birds were challenged with C. perfingens to artificially cause NE. All the strains tested were netB positive, but the degree to which they caused disease varied. The implication here is that netB may only contribute to NE and that other factors (such as management practices) are involved in development of the disease. Further studies are being planned to determine the effects of different management practices on C. perfringens populations.
Funding$107,000 (CPRC $70,000, PIC $37,000)
PublicationsChalmers, G., S. W. Martin, D.B. Hunter, J.F. Prescott, I. J. Weber, and P. Boerlin. 2008 Genetic diversity of Clostridium perfringens isolated from healthy broiler chickens at a commercial farm. Vet. Microbiol. 127:116-127.
Chalmers, G., S.W. martin, J. F. Prescott, P. Boerlin. 2008. Typing of Clostridium perfringens by multiple-locus variable number of tandem repeats analysis. 128:126-135.
Chalmers, G., H. L. Bruce, D. L. Toole, D. A. Barnum, and P. Boerlin. 2007. Necrotic enteritis potential in a model system using Clostridium perfringens isolated from field outbreaks. Av. Dis. 51:834:839.