Molecular Detection of Eimeria Species and Clostridium Perfringens in Poultry Dust and Pooled Excreta of Commercial Broiler Chicken Flocks

Necrotic enteritis (NE) and coccidiosis are the two major economically important enteric diseases of commercial broiler chickens. Coccidiosis predisposes birds to NE by causing physical damage to the gut epithelium and triggering inflammation and immunosuppression which enhances the growth and proliferation of pathogenic Clostridium perfringens (Park et al., 2008). This study was designed to investigate the association of flock performance and genome copies (GC) of five Eimeria species (E. acervulina, E. brunetti, E. maxima, E. necatrix and E. tenella), C. perfringens and the associated netB toxin plasmid in poultry dust and pooled excreta collected from the floor of commercial broiler flocks. Poultry house dust and pooled excreta from the floor were collected weekly from two Australian integrator companies at days 7, 14, 21, 28 and 35 from 8 farms (n = 2 flocks/farm). Nucleic acids were extracted from dust and excreta using commercial kits with an enhanced lysis step using bead beating to open the oocysts. The farms were ranked as low or high performers based on performance indexes used by the integrator companies. It was hypothesised that (a) Eimeria spp, C. perfringens and netB GC load would be higher in low-performance farms compared to high-performance farms, and (b) The GC levels of C. perfringens, netB and Eimeria spp in poultry dust and pooled excreta would have high agreement. The results showed that there was no association of Eimeria spp, C. perfringens and netB GC load with the production performance contrary to our first hypothesis. This is most likely because the pathogen GC load detected was low to moderate in all studied flocks regardless of ranking. All farms were positive for C. perfringens, E. acervulina and E. maxima but negative for E. tenella and E. necatrix. Eimeria brunetti was only detected in one low-performance farm while netB GC was detected only in one high-performance farm. The agreement of GC levels for dust and pooled excreta was excellent for E. maxima [Intraclass correlation (ICC) = 0.99], E. acervulina (ICC = 1.00), and netB (ICC = 0.98), while there was a poor agreement for C. perfringens (ICC = 0.08). In this study, the presence of these pathogens was not directly linked with farm performance suggesting that other factors influenced the production outcomes. Further studies on a larger number of farms are needed to determine whether these population level measurements of key pathogens based on PCR detection of nucleic acids are correlated with performance variables and to investigate other factors associated with production performance in commercial broiler farms.

ACKNOWLEDGEMENTS: This project was funded by AgriFutures Australia (grant PRJ-011908). Thanks to the poultry companies that participated in this study and to Danielle Smith for providing laboratorial assistance.