Aspergillosis is a disease, usually of the respiratory system, of chickens, turkeys, and less frequently ducklings, pigeons, canaries, geese, and many other wild and pet birds. In chickens and turkeys, the disease may be endemic on some farms; in wild birds, it appears to be sporadic, frequently affecting only an individual bird. Instances of severe outbreaks are usually seen in birds 7–40 days old. (Also see Fungal Infections: Aspergillosis and see Pet Birds: Aspergillosis.)
Etiology and Epidemiology
Aspergillus fumigatus is a common cause of the disease. However, several other Aspergillus spp may be incriminated.
High mortality rates are seen in chicks and poults that inhale large numbers of spores during hatching in contaminated incubators or when placed on mold-bearing litter. In older birds, infection is caused primarily by inhalation of sporeladen dust from contaminated litter or feed or dusty range areas. Morbidity can be underestimated in finishing flocks until slaughter inspection reveals pulmonary lesions.
Clinical Findings and Lesions
Dyspnea, hyperpnea, somnolence and other signs of nervous system involvement, inappetence, emaciation, and increased thirst may be seen. In chicks or poults up to 6 wk, the lungs are most frequently involved. Airsacculitis in young mature turkeys is a leading cause of postmortem condemnation. Pulmonary lesions are characterized by cream-colored plaques a few mm to several cm in diameter; occasionally, mycelial masses may be seen within the air passages on gross examination. The plaques also may be found in the syrinx, air sacs, liver, intestines, and occasionally the brain. The encephalitic form is most common in turkeys. An ocular form, in which large plaques may be expressed from the medial canthus, has been seen in chickens and turkeys.
The fungus can be demonstrated by culture or by microscopic examination of fresh preparations. One of the plaques is teased apart and placed on a suitable medium, usually resulting in a pure culture of the organism. 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 infectious bronchitis, Newcastle disease, infectious laryngotracheitis, mycobacteriosis, colibacillosis, Dactylaria infection, and nutritional encephalomalacia.
Treatment and Control
Treatment of affected birds is generally ineffective. Spontaneous recovery from pulmonary aspergillosis can occur if reexposure to the mold is prevented. Strict adherence to sanitation procedures in the hatchery minimizes early outbreaks. Grossly contaminated eggs should not be set for incubation because they may explode and disseminate spores throughout the hatching machine. Contaminated hatchers should be fumigated with enilconazole or formaldehyde. Avoiding moldy litter or ranges serves to prevent outbreaks in older birds. Cleaned pens should be sprayed or fumigated with enilconazole, and all equipment should be cleaned and disinfected.
Last full review/revision March 2012 by Robert A. Kunkle, DVM, PhD