Avian lice, which belong to the order Mallophaga, have a life cycle of ~3 wk and normally feed on bits of skin or feather products. Lice may live for several months on the host but only remain alive for ~1 wk off the host. People and other mammals may harbor avian lice, but only temporarily.
In intensive poultry systems, the most common and economically important louse to both chickens and turkeys is Menacanthus stramineus, the chicken body louse, which typically is found on the breast, vent, and thighs. It punctures soft quills near their base or gnaws the skin at the base of the feathers and feeds on the blood. Chickens are less commonly infested with Menopon gallinae (on feather shafts), Lipeurus caponis (mainly on the wing feathers), Cuclotogaster heterographus (mainly on the head and neck), Goniocotes gallinae (very small, in the fluff), Goniodes gigas (the large chicken louse), Goniodes dissimilis (the brown chicken louse), Menacanthus cornutus (the body louse), Uchida pallidula (the small body louse), or Oxylipeurus dentatus. Turkeys may also be infested with Chelopistes meleagridis (the large turkey louse), and Oxylipeurus polytrapezius (the slender turkey louse).
Because lice transfer from one bird species to another when the hosts are in close contact, other domestic and caged birds may be infested with species of Mallophaga that are usually host-specific. Lice also sometimes reach new bird hosts by using louse flies (Hippoboscidae) for transportation. Some lice of geese and swans are vectors of filarial nematodes.
Heavy populations of the chicken body louse decrease reproductive potential in males, egg production in females, and weight gain in growing chickens. The skin irritations are also sites for secondary bacterial infections. Other species of lice are not highly pathogenic to mature birds but may be fatal to chicks. Examination of birds, particularly around the vent and under the wings, reveals eggs or moving lice on the skin or feathers.
Lice are usually introduced to a farm through infested equipment (eg, crates or egg flats) or by galliform birds. Lice are best controlled on caged chickens or turkeys by spraying with pyrethroids, carbaryl, coumaphos, malathion, or stirofos. Birds on the floor are more easily treated by scattering carbaryl, coumaphos, malathion, or stirofos dust on the litter. Eggs are not killed, so insecticide treatment should be repeated after 10 days.