Aspergillosis is usually a disease of the respiratory system, of chickens, turkeys, and less frequently other wild and pet birds. In chickens and turkeys, the disease may be endemic in some cases. In wild birds, it appears to be sporadic, frequently affecting only an individual bird. It is usually seen in birds 7-40 days old.

Etiology and Epidemiology :

Mainly Aspergillus fumigatus is a common cause of the disease,some times other Aspergillus spp may be involved.
Chicks and growers may get infected during hatching by inhaling spores from contaminated hatching machines or from contaminated litter. In older birds, infection is caused  by inhalation of spore-loaded dust from contaminated litter or feed or dust from surroundings.

Clinical Findings and Lesions :

Aspergillus granulomas, lungs, chicken
Dysponea, hyperpnea, somnolence, other symptoms of nervous system involvement.Inappetence, emaciation, and more thirst may be there. The encephalitic form is most common in turkeys. In chicks or growers up to 6 wk, the lungs are  usually involved. Pulmonary lesions which can be characterized by cream-colored plaques which can be  a few mm to several cm in diameter.
Occasionally, mycelia masses may be seen within the air passages. The plaques also may be found in the syrinx, air sacs, liver, intestines, and sometimes brain. In chickens an ocular form has been seen, in which large plaques may be expressed from the medial canthus.

Diagnosis :

The fungus can be detected by culture or by microscopic examination of fresh samples taken from One of the plaques. Histopathologic examination using a special fungus stain reveals granulomas containing mycelia. Pathogenicity of the isolate is confirmed by injecting it into the air sacs of susceptible 3-wk-old chicks.

Differential diagnoses include, Newcastle disease, infectious bronchitis, infectious laryngotracheitis, Dactylariainfection, and nutritional encephalomalacia.

Treatment and Control :

Treatment of affected birds is not of much use . Strictly following  the sanitation procedures in the hatchery reduces chances of early outbreaks. Highly contaminated eggs should not be set for incubation because they may explode and release spores in the hatching machine. Contaminated hatchers should be fumigated with formaldehyde or thiabendazole (120-360 g/m3). Preventing mold development in litter or surroundings helps to prevent outbreaks in older birds. Pens should be sprayed with nystatin. All equipment cleaned and disinfected.
Reference :- Merck Veterinary Manual
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