Dispersion of northern fowl mites, Ornithonyssus sylviarum, between poultry facilities via infested eggs from layer and breeder flocks

Two potential ways that northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), initiate infestations in poultry flocks were investigated: between-farm collection of eggs and transfer of egg flats, and the transfer of mites via eggs from breeder flocks to pullet growing operations. Under laboratory conditions designed to simulate the interior of an egg collection truck, 2% of the mites (n = 5 trials, 150 to 300 mites per trial) placed on full egg carts successfully transferred to adjacent empty carts. This transfer occurred in 1 to 2 h. Observations at commercial facilities confirmed cross-contamination of clean, empty egg carts from full egg carts. Northern fowl mites (n = 179) did not survive the 23 d required to hatch chicken eggs in a commercial setter and hatcher. In simulated conditions required to hatch chicken eggs (37°C, 55% RH), 50% of the mites (n = 140) were dead within 24 h and 100% mortality occurred by 96 h. Therefore, vertical transmission of mites on the eggs from breeder flocks to the subsequent pullet growing operations appears to be unlikely.