Dispersal of northern fowl mites, Ornithonyssus sylviarum, among hens in an experimental poultry house

Northern fowl mites were introduced in the center of each of four rows of c ages in a poultry house containing uninfested White Leghorn hens. individua lly housed hens (seven per row) were separated by empty cages. The vent reg ions of all hens were examined every 2 to 4 days for 11 weeks. Light infest ations were noted in all four rows within the first 14 days, but mites appa rently disappeared from two of the four rows (Rows 1 and 2) in the first 4 weeks. Infestations in the remaining two rows (Rows 3 and 4) increased firs t on the nearest hens and were detected on more distant hens only after mit es had increased to moderate-to-high populations on closer hens. Within 8 t o 9 weeks, infestations were heavy fur all hens in Rows 3 and 1. By 8 weeks , mites again were evident in Rows 1 and 2; all hens in the house were infe sted by Week 11. Results demonstrate rapid spread of mites achieved by mite movement across open cage areas rather than direct hen contact. The repeat ed pattern of mite spread (appearance on a hen after mites on an adjacent h en reached moderate-to-high levels) suggests that movement within a row was probably due to mites walking on cage wires rather than dispersal on roden ts or wild birds.