The comb is the red (sometimes purple), fleshy part on top of a chicken's head. Both male and female chickens have combs, but those of the male chickens are usually larger. Combs are important because they cool down chickens by circulating blood between the comb and the wattle, which is a fleshy red fold of skin hanging from the throat of the chicken. Chicken combs are susceptible to a number of diseases.
Fowl cholera, also known as avian cholera, avian pasteurellosis and avian hemorrhagic septicaemia, is a disease caused by the bacterial organism Pasteurella multocida that affects chickens. Symptoms include a purple comb, high temperature, swollen wattle, loss of appetite, ruffled feathers, coughing and lameness. Rodents and domestic pets can facilitate the spread of the disease by carrying the bacteria from one location to the other. Fowl cholera can be destroyed by the use of disinfectants, although they may persist for prolonged periods in the soil afterward. Some drugs like sulphonamides, tetracyclines, erythromycin, streptomycin and penicillin are used to treat fowl cholera.
Fowl pox comes in two varieties: the wet pox and the dry pox. The wet pox is spread by inhalation and affects the upper respiratory tracts. The prognosis for this type of fowl pox is very poor. On the other hand, dry pox is characterised by the appearance of small whitish foci, which develop into wart-like nodules on the featherless parts of the chicken including the comb. The nodules eventually turn to scabs, which lead to final healing. This disease is usually transmitted by mosquitoes that spread the virus from infected birds to non-infected ones through feeding. The virus can be highly resistant in dry scabs and has been known to survive for months on contaminated premises. There is no treatment for fowl pox, although a general vaccination against it when the birds are 6 to 10 weeks old results in immunity against the disease.
Avian influenza is a viral disease that affects most species of birds including chickens. This disease occurs as a result of improper disposal of manure and infected carcases and by rodents that carry the virus from infected poultry to non-infected ones. Avian influenza leads to facial swelling and blue combs and wattles in chicken. It also leads to the development of dark red and white spots on the combs and legs of chicken. There is no cure for avian influenza although proper hygiene and antibiotics might help prevent serious loss in mild infections.