Seasonality of QPX disease in the Raritan Bay (NY) wild hard clam (Mercenaria mercenaria) population

Quahog Parasite Unknown (QPX) is a potentially lethal pathogen of the hard clam Mercenaria mercenaria along the northeastern coast of the United States. In the Raritan Bay wild clam population, QPX prevalence and infection intensity at three sites were examined by both histology and quantitative PCR in 2006. At two of three sites, QPX infection showed a seasonal pattern, with prevalence and weighted prevalence increasing through the spring, peaking in the summer and declining in the fall, while at the other site, the highest QPX prevalence and infection intensity were observed in the spring although overall prevalence at this site was generally low. Our data suggested that temperature may be an important environmental factor regulating the seasonal pattern of QPX disease in wild clams but also demonstrated that seasonal patterns vary from site to site, possibly linked to the clam density or other environmental factors. Over-winter sampling and further investigations focusing on environmental factors, clam density and clam mortality as related to QPX infection are needed to better characterize and understand the seasonality of QPX disease.