Population Genetics of the Northern Fowl Mite (Ornithonyssus sylviarum): Are wild host species a reservoir?

The northern fowl mite (NFM; Ornithonyssus sylviarum) is considered the most economically important ectoparasitic pest of poultry in the United States. Following the initial discovery of NFM on chickens in the 1920’s, the mite has been recovered from over 70 bird species, including peri-domestic species commonly associated with poultry operations (e.g. House sparrow and European starling). The association of NFM with wild birds has supported long-standing speculation that NFM are transferred to un-infested poultry flocks by wild birds. As part of an ongoing study of NFM population genetics, NFM collected from wild birds adjacent to commercial poultry operations have been compared to NFM from poultry using a NFM-specific microsatellite library. In addition, NFM collected from wild bird species have been experimentally inoculated onto domesticated chickens, to test for the ability of “wild” NFM to host-switch. Preliminary results show little gene flow between NFM populations on wild and domesticated host species. In addition, NFMs from wild hosts fail to establish infestations on chickens. These preliminary data cast doubt on the role of wild bird species as a reservoir for NFM found on poultry and raise questions about the host range of this ectoparasite.