Poultry parasites are grouped into external and internal parasites. The parasites cause harm to the animals and economic losses to the poultry farmers. These parasites include
External parasites (ectoparasites)
These are very common in scavenging poultry, and include:
Lice: these live on the skin of the birds, especially around the cloacae and under the wings.
The irritation they cause can lead to reduced production. Lice species commonly found on poultry are Menacanthus straminens, Lipeurus caponis, Monopon gallinae, Goniodes gigas and Chelopistes meleagride.
Mites: these are troublesome ectoparasites, which hide in the cracks of housing and perches, and come out only at night. They are bloodsuckers and lower egg production.
Mites such as Dermanyssus gallinae can also transmit the bacteria Borrelia, which causes fever, depression, cyanosis and anaemia (spirochaetosis).
Ticks: a heavy infestation can produce severe anaemia and, in extreme cases, death due to blood loss. Argas persicus is particularly dangerous, being the vector of several blood parasites such as the haemoprotozoa and microfilaria.
Internal poultry parasites (endoparasites)
The more important internal parasites are:
Helminths (worms): these are common in scavenging poultry, especially nematodes and cestodes. worms are a major cause of lowered egg production of scavenging poultry, the most commonly found being Ascaridia galli (Round Worm), Heterakis gallinae (Caecal Worm), Syngamus trachae (Tracheal Worm) and Raillientina spp. (Tape Worm).
Protozoa: the most pathogenic are the coccidiosis disease species of Eimeria tenella and E. necatrix. Coccidiosis is a common parasitic infection in scavenging poultry. It affects mostly young birds, and the most important signs are emaciation, thirst, listlessness, ruffled plumage, bloodstained faeces and birds huddling together.