Young broiler chickens at the poultry farm [iStockphoto]
Aspergillosis is a disease of all animals including human beings. In farmed chickens, it is a respiratory infection caused by a type of mould called Aspergillus fumigatus, in fact it is caused by spores produced by this organism and spread in the vicinity of young chicks soon after hatch or during hatching. It is primarily a disease of young juvenile birds and presents signs like difficulty in breathing, chicks gasping for air, off-feed, weak and reluctant to move and even death.
How does a chick get infected?
Most infections are spread through dirty hatcheries (where chicks are hatched). Like all types of moulds, they prefer dark, humid and warm environment to grow, multiply and complete their life cycles. The spores of A. fumigatus are then released into the ventilation system in the hatchery and ultimately lodge on hatching eggs in the incubators. With time these contaminated eggs explode and release thousands of spore particles that are eventually taken in as chicks hatch out of eggs in the hatcher room. If embryos are infected before hatching they die and this is seen as drop in hatchability. But in most cases, chicks are hatched already infected. Mortality can reach up to 50 per cent in worse cases. It is not strange to hear farmers complaining of losing a brood of chicks with respiratory distress. If the hatcheries are clean, the healthy chicks can pick infection from mouldy growth on stale feed, litter or feeding equipment in the farm.
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signs and symptoms of Aspergillosis
This disease is common in warm and humid environment and outbreaks are associated with young chicks or poults. For years, it has been referred to as brooder pneumonia. The chicks have increased respiration rates, gasp for air with open-mouth breathing quite common occurrence, lachrymation, tearing and wasting. The growth rate is retarded as the disease spreads affecting visceral organs like liver and kidneys and in extreme cases the eyes.
On further examination by a vet on dead birds, the common lesions are seen in the respiratory system showing white nodular growths in lungs, air sacs and airways. The organisms can be isolated from affected tissues and identified through further laboratory procedures.
Can sick chicks be treated?
Sadly, affected chicks cannot be treated and once a confirmed diagnosis is done, the best option is to destroy the affected flock. It is important that the chick supplier is adequately informed so that proper cleaning and disinfection of the hatching facilities is done to stop broadcasting infections to non- suspecting farms.
How do you get rid of Aspergillus in the hatchery or farms?
At the breeder farm level, it is important to make sure the litter is kept dry and friable all the time by frequent turning, at least once daily. Hatching eggs must be clean all the time and must be more frequently collected, say five times a day. Do not collect floor eggs for purposes of hatching as this habit is likely to introduce the offending organisms into the hatchery.
In the hatchery, the ideal hatching conditions also help propagate the growth and multiplication of moulds. So, to reduce the load of spores, it is important to fumigate all the ventilation system, corridors, hatch bays and incubators with appropriate antifungal agents on a regular basis. Products like Triazolol are good if well applied in the egg storage and incubation facilities.
At the farm level, ensure the units are well ventilated, the litter must always be kept dry and friable. The feed should be kept in a dry environment and moist bins and troughs should be avoided.
Economic impact
The farmer is the greatest loser in the event of this condition, a whole brood will be lost especially in severe cases. The hatchery will lose on hatchability and get backlash from affected farmers unless the situation is identified, and cleaning and decontamination protocols are immediately implemented. In case affected birds survive, the impact on the immune system of the birds doesn't allow for peak performance and such birds will rarely meet target weights.
[watsonmesso@yahoo.com or vet@kenchic.com]
