Cervical scoliosis and torticollis: a novel skeletal anomaly in broiler chickens

Andrew Olkowski, Chris Wojnarowicz, Boguslaw Olkowski, Bernard Laarveld

Among the most prominent health problems marring the global poultry industry for several decades are skeletal abnormalities. The aim of this study was to investigate a recent emergence of a novel form of skeletal deformity affecting cervical spine in broiler chickens. This work presents the natural history of this newly emerging skeletal anomaly along with long term observations of epidemiological trends in commercial broiler flocks, and clinical and pathological features. In distinction from other forms of skeletal deformities commonly reported in broiler chickens, this new form of cervical spine anomaly have been observed in newly hatched chicks and in fully developed embryos that died in the shell. On clinical and post mortem examination this condition presents characteristic features consistent with congenital cervical scoliosis and torticollis (CCST). The pathogenesis of CCST appears to be linked to pathological remodeling of the cervical vertebrae bone associated with excessive activity of osteoclasts. Long term observations indicate that the incidence of CCST showed increasing epidemiological trends over time. More recently CCST has been observed in newly hatched chicks with incidence ranging from 0.1 to > 1%, and in fully developed embryos that failed to hatch about 4 to 5%. The increasing trends in incidence of CCST in commercial broiler flocks are of concern from an economic perspective, and also represent a very specific and important aspect of animal welfare.