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Avian Mycobacteriosis, Mycobacterium Infection
Avian mycobacteriosis, also known as avian tuberculosis (ATB), is an important chronic, contagious disease that affects both domestic and wild birds worldwide. The disease is caused by infection with Mycobacterium avium or M. genavense. M. avium is capable of infecting any species of bird, as well as other mammals, including humans. In cattle and goats, M. avium subsp. paratuberculosis (MAP) is responsible for causing paratuberculosis (PTB), also known as Johne's disease.
Often, chickens with avian mycobacteriosis may not show any clinical signs of infection until death. However in those that do, the classical presentation is characterized by chronic and progressive emaciation with a prominent keel bone apparent, as a result of muscle atrophy, and weakness. Chickens that are stressed or have poor immune systems are more susceptible to infection with M. avium. Possible stresses may be related to overcrowded living conditions, inadequate or unbalanced nutrition, adverse weather or environmental conditions such as drought, extreme cold or heat, chronic inflammation, internal or external parasites, or infection with an existing disease.
The most commonly reported clinical signs of the disease include progressive weight loss and muscle atrophy along the keel bone. More specific, additional signs exhibited by an infected white-crested Hollard dwarf rooster were hoarse attempts at crowing during it's last three weeks in the disease course. Over the course of the final week, the rooster showed dramatic loss of condition and depression.
Transmission M. avium is transmitted primarily by infected wild birds or newly introduced, older adult domesticated poultry, which shed the organism into the environment through their droppings. Susceptible chickens become infected by ingesting or inhaling the organism.
Avian mycobacteriosis has a long incubation period and a slow course, with symptoms prolonging in birds for weeks or months.
Firm, grayish-yellow to white granulomatous lesions in the intestines, liver, and spleen, and bone marrow.