M gallisepticum is commonly involved in the polymicrobial chronic respiratory disease of chickens, in turkeys, it frequently results in swollen infraorbital sinues and is called infectious sinusitis. These diseases affect chickens and turkeys worldwide, causing the most significant economic losses in large commercial operations, and are commonly seen in noncommercial flocks. Infection also occurs in pheasants, chukar partridges, peafowl, pigeons, quail, ducks, geese, and psittacine birds. Songbirds are generally resistant, although M gallisepticum causes conjunctivitis in wild house finches (and some similar species) in North America.
