refers to any disease caused by the spores of Aspergillus spp
fungus commonly found in the environment, especially in soi,. grains, and decaying vegetative matter including litter. These moulds are capable of infecting all birds. They produce a form of pneumonia that is usually acute in chicks and chronic in mature birds. The key to preventing it is good sanitation (especially in the incubator and brooder), avoiding mouldy grain and litter, periodically moving feeders and waterers or placing them on droppings boards, providing good ventilation to minimize dust, and keeping stress to a minimum.
Generally, a bird that develops a problem has some predisposing factor
- perhaps it is malnourished, the environment might be poor, it may have another disease or be stressed in some way. Interestingly, stress-induced aspergillosis is seen in birds subjected to oil contamination and other stressful situations.
Aspergillus and other fungi grow readily in decaying organic matters. Conditions that favour mould growth include damp
feed, feed utensils or litter, dry feces, and dark, damp conditions with poor ventilation. If a bird breathes in an overwhelming number of spres it can result in an accute aspergillosis.
Aspergillosis is predominantly a disease of the lower respiratory tract
in birds and can occur as an acute or chronic disease. Acute aspergillosis is a fatal respiratory disease. Lesions can appear as white mucoid exudation in the respiratory tract, marked congestion of the lungs, thickening of the air sacs, or acute pneumonic nodules surrounded by areas of hyperemia. Chronic aspergillosis is the more common form with typical granulomatous lesions. Multiple plaques or nodules may be seen diseminated throughout the lungs and air sacs. The lesions appear as white, yellow, or green caseous granulomatous nodules that often exhibit sporulating fungal colonies. In severe cases, extensive adhesions between the air sac lesions and the abdominal viscera may occur. Rarely, large tumor-like aspergillomas may occur. Clinical Signs
Birds with this disease look like they have a respiratory disease or other chronic debilitating diseases. The acute form comes on very quickly and may include anorexia, dyspnea, or sudden death without signs. The chronic form varies in symptoms, but often the disease has spread extensively before it is detected. Lesions can involve the upper respiratory tract, there can be voice changes, a gurgling noise, weight loss, lethargy and dyspnea. Avian aspergillosis involving the central nervous system is often associated with ataxia or paralysis. Frequently the first sign is that the bird takes a very long time to recover normal breathing after only moderate exertion. Acute aspergillosis
-This typically occurs in very young birds and may be associated with considerable losses. Watkins (1940), for instance, estimated that 10% of all deaths in chicks under 14 days old were caused by this disease. Typically there is loss of appetite, increased respiration, a rise in temperature, listlessness, foetid diarrhoea and rapid loss of condition. Convulsions sometimes occur and affected birds often die within 24-48 hours of the onset of symptoms. Epidemic outbreaks in young birds frequently have a very high death rate before control measures can be taken. Similar symptoms may occur in pullorum disease (Salmonella pullorum), from which this form of aspergillosis must be distinguished.Chronic aspergillosis
-The onset of this form is insidious and the affected birds may survive for long periods in a gradually declining state. The symptoms of the acute disease are often present in a milder form together with anaemia, yellowing of the faeces and the presence of a respiratory rattle. The chronic disease generally occurs sporadically and is the usual form in adult birds.Treatment
A variety of treatments have been used with varying results. In the general this disese is given a poor to grave prognosis with or without therapy. Treatments may include:
* Supportive care such as forced feeding and fluid therapy
* Antifungal medications
* Surgical removal of the mycotic lesions
Treatment is difficult and takes a long time. A vet may prescribe a number of different oral anti-fungal medications and they usually need to be given for an extended period of time, perhaps up to 3 months. One possible medication is Terbinafine 250mg (trade name Tamsil) which is normally used to treat athlete's foot in humans. The dosage given is 1/4 tablet once a day for a 2 kg bird. It is quite expensive. A pack of 42 tablets costs around $90.
It is possible to nebulize with F10SC at a rate of 2 ml/L, twice a day. Some birds seem to respond to this and others don't. It is also important to keep the bird warm and free of drafts, but in a well ventilated environment. The birds have less difficulties to breathe when a humidifier (or just a pot of water) is used in their room. This is the case for any respiratory infection but it can have an an even larger impact with aspergillosis.
Secondary respiratory infections are a big problem and any recurring bacterial infections require treatment with something like Amoxycillin in combination with Clavulanic Acid (e.g. Clavulox), so far. Dosage: 125 mg/kg bird, one half of that in the morning, on half at night.
Prevention is better than cure with aspergillosis. Limit the fungal growth in the environment and reduce stressful conditions. Good hygiene practices should be applied to the daily care of the birds. Incubators and brooders should be kept clean to prevent fungal contamination. Egg Infection
Aspergillus fumigatus can readily attack both fresh and incubating eggs once it has gained entry through the shell. Infection does not seem to occur in the oviduct but results from the external contamination of the shell after laying. Penetration occurs through the pores of the shell and the fungus grows well on the shell membranes, killing the embryo if present and occasionally penetrating into the white. Eventually conidiophores and spores are formed in the air-space and affected eggs can be detected by candling. On breaking open the air-space the greenish felt of hyphae and spores is seen.
The chief fungus reported from eggs in incubation is A.fumigatus but several others have been obtained from stored eggs. Of these probably Cladosporium herbarum is the most important in causing the "black spot" discoloration reported by Weston & Halnan (1927). Lucet (1897) demonstrated that clean eggs cannot be infected by direct application of the spores of A.fumigatus and that it was necessary to put a thin layer of butter or other grease on the shell before infection would take place. Hence he concluded that dirty eggs were more liable to infection than clean, and cited an outbreak of egg infection in ducks in which the nests were heavily contaminated with A.fumigatus.
Here we have post mortem examination pictures from a bird with aspergillosis:http://www.aspergillus.org.uk/secure/veterinary/chap1avian.htmHarrison & Harrison (1986) Clinical Avian Medicine and Surgery. W.B. Saunders Company.
Damerow, G. (1994) The Chicken Health Handbookhttp://www.aspergillus.org.uk/secure/veterinary/chap1avian.htm