Epizootiology of coccidia in organic poultry: Management, risks, and future research

Kevin A. Cornell

doi:10.7273/000004198

Coccidia (Eimeria spp.) is a protozoan intestinal parasite that causes coccidiosis in chickens and is an enormous burden to the poultry industry. However, it is unknown if Eimeria has a large impact on organic free range poultry. Traditionally, conventional growers are required to have strict biosecurity standards, such as physical barriers from the outside environment, standardized vaccinations, and have access to antibiotics and chemical treatments. In recent years, growers have increasingly been switching over to organic, free range, and pastured practices to match a growing demand for more ethical and higher quality products. USDA organic standards require that poultry have access to the outdoors and restrict the use of antibiotics and anticoccidials. Small organic growers may not have financial access to costly vaccinations. Additionally, many smaller organic growers raise flocks completely outdoors. Flocks reared in free range and pastured conditions can be thought of as integrated into the greater agroecology, creating unique and unknown risks to coccidia transmission, host susceptibility, morbidity and production loss. To address this, we surveyed 30 free range, pastured, and organic farms to understand how management practices, ecological factors, and parasite abundance may contribute to disease risk. Farms that were either certified organic or used organic methods (i.e. no chemicals and antibiotics) and provided complete outdoor access were chosen: commercial organic, free range, pasture raised, and backyard flocks. Gastrointestinal parasite oocysts/eggs and pathogens were quantified in 1040 individual fecal samples across 77 flocks. Eimeria spp. was detected in 97.4% of flocks sampled, with a prevalence of 62.8% of all individuals, and a mean intensity of 210.04 ± 37.05 (SE) oocysts per gram. We used negative binomial generalized linear mixed models and univariate AICc comparison to determine parameters that affected Eimeria abundance within a flock. Layers contained an average of 1.3 more oocysts per gram than broilers. Age was negatively associated with average Eimeria oocysts per gram. Capillaria spp. and tapeworms were positively and negatively associated with Eimeria spp., respectively. We found no evidence that spatial management, flock demographics, soil organic matter and water retention, and other coinfectious parasites affected the abundance of Eimeria within flocks.

Epizootiology of coccidia in organic poultry: Management, risks, and future research

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