Hi
Aspergillosis
Scientific name
Aspergilla flavus
Description
The disease aspergillosis is caused by a fungus from the genus Aspergilla. Aspergilla has the potential to infect a wide range of mammalian, avian and reptilian species including man and is probably the most common fungal infection found in birds.
The most common species of Aspergilla causing disease in birds are A. fumigatus, A. flavus and A. niger. There are numerous other species of aspergilla present in the environment but these rarely appear as a cause of the disease.
A. flavus has been isolated as a cause of aspergillosis in emus in Queensland.
Aspergilla is widespread throughout the environment and where conditions are suitable it will grow and multiply to give a localised high concentration of the fungus.
Favourable conditions include:
warm, moist areas eg in litter around waterers and in some types of deep-litter and
mouldy or rotting areas eg spoiled or damp feed, rotting vegetation.
As with other fungi, aspergilla has a growing phase where hyphae (appearance of white strands/lumps) grow. This is followed by the production of spores. Spores are resistant to environmental conditions and are very small, allowing them to be easily transported by wind and in dust particles. Where conditions are favourable large numbers of spores are produced.
Birds get infected usually through inhalation of spores. The infection is not transferred from bird to bird. The bird's immune system is able to control infection where relatively small numbers of spores are inhaled. Infection results if the immune system is deficient eg in very young chicks where the immune system is still developing or in birds that have been stressed through other disease problems, overcrowding, insufficient food and water etc. Infection can also result in normal birds where massive numbers of spores are inhaled and the immune system is overwhelmed.
In Queensland at the time of writing, aspergillosis has only been found in young chicks and has caused deaths in the 3-8 week age group. There appears to be a strong association between infection and the presence of dust from the litter in the atmosphere of the brooder shed. This dust can be raised when the litter is shovelled out or raked over or even where the passage of older chicks raises dust from the litter.
Prevention
At this stage, prevention is the only effective method of controlling aspergillosis in emus.
Prevention should be aimed at three broad areas:
1. Removal or control of favourable areas for fungal growth
This would include such things as removing wet litter, not using damp or mouldy straw/hay as litter or food, not using or removing spoiled grain and regular provision of fresh non-dusty litter.
2. Dust control in brooder sheds
This is an important area as dust in the air of brooder sheds appears closely associated with infection of young chicks.
Dust is most likely to be raised when litter is being removed or raked over. In these cases it would be worth lightly damping down the litter so dust is not raised when it is moved.
Good quality litter will also help. A coarse litter of wood chips or pine wood shavings appears to work well. Litter that is already dusty may only contribute to the problem.
3. Hygiene
Attention to hygiene can prevent aspergilla numbers building up to a point where problems occur. This needs to be done in all stages to the end of the brooder stage.
Eggs should be fumigated and/or washed in a recognised egg sanitiser used according to directions.
The cold storage room, the incubator and the hatcher should be fumigated or cleaned regularly with a recognised disinfectant active against fungi.
The brooder house should be cleaned and disinfected before the hatching season begins. If individual pens are cleaned out during the breeding season they should be disinfected as well each time.
Disinfectants that are active against aspergilla include those containing gluteraldehyde as an active constituent, Antec Virkon S and Antec Farm Fluid S.
The above procedure will also control other diseases that may cause problems during incubation, hatching and brooding.
2. Salmonellosis (paratyphoid)
Scientific name
Salmonella spp
Description
Salmonellosis can be caused by any one of the salmonella group of bacteria. There are a large number of salmonella species spread widely throughout the environment.
Two individual salmonella species S. pullorum and S. gallinarum cause pullorum disease (S. pullorum) and fowl typhoid (S. gallinarum) in poultry. In the past these two diseases have caused significant problems, and both diseases are now very well controlled in the poultry industry. However, these diseases may still exist in backyard poultry. It would appear that there is little risk of emus being exposed to these two types of salmonella.
Of more significance to the emu industry are the large number of remaining salmonella species that are capable of infecting a wide range of hosts including man. Infection and disease caused by these salmonella is given the general term paratyphoid.
Distribution and transmission
Paratyphoid occurs worldwide.
Salmonella are widespread in the environment and a property can be infected from a number of sources including wild birds, other emus, feed sources and other animals.
The organisms are reasonably resistant and can survive for several weeks or months in the environment in favourable conditions. They are susceptible to sunlight and drying out.
In poultry, carrier birds are the main reservoir of infection once the organism has established in a flock. These birds have been infected and have survived but the organism has established itself in the intestine where it causes the bird little problem but is regularly passed out in faeces. This then acts as a source of contamination. Some rodents and insects also have a potential to act as reservoirs.
Paratyphoid has been detected on some emu farms in Queensland but the full extent of the problem is not known. Problems have occurred in young chicks less than 2 weeks of age, but further research is required to determine the full impact and size of the problem. It is not known whether adult emus can become carriers, but as it is known that paratyphoid affects a wide range of animals it is probable that infection could become established in emu flocks.
Transmission between birds occurs mainly by ingestion. Sick birds and carriers excrete salmonella in their faeces which then has a potential to contaminate food, water, litter etc.
Females can also lay eggs with contamination on the outside of the shell. The paratyphoid organisms are mobile and can penetrate the pores of the shell while it is still warm and moist. If these organisms are not killed during egg disinfection procedures, infected eggs will reach the hatcher. If these eggs hatch, large numbers of salmonella are released into the hatcher. Other chicks can become infected by inhalation of organisms or by eating contaminated fluff circulating round the hatcher. This can result in sickness, deaths and carrier birds from this batch of chicks.
Clinical signs
In poultry, mature and semi-mature birds rarely have problems even though they may be infected. However, if these birds are stressed the infection can flare up and cause clinical disease.
Most problems are seen in chicks and the disease has a potential to cause significant mortalities.
These mortalities may include a high proportion of dead embryos in-shell in both the pipped and unpipped stages.
Prevention
It is unlikely that salmonella paratyphoid could be eradicated from a property and it would not be worth trying.
If it becomes established on a property then a control program can be drawn up. This program would concentrate on the areas where this disease causes the most damage ie the incubation, hatching and brooder stages.
Regards
ashwini
