Aspergillosis has been observed in
almost all birds and animals, including man. The disease is observed
in one of two forms; acute outbreaks with high morbidity and high
mortality in young birds, and a chronic condition affecting adult
birds. It is more of a problem in turkeys than in chickens.
The condition is caused by Aspergillus
fumigatus, a mold or fungus-type organism. Occasionally other
types of molds are involved. These organisms are present in the
environment of all poultry. They grow readily on many substances
such as litter, feed, rotten wood and other similar materials.
The bird comes in contact with the
organisms through contaminated feed, litter or premises. The disease
is not contagious and does not spread from one bird to another.
Most healthy birds can withstand repeated exposure to these organisms.
Inhalation of large amounts of the infectious form of the mold
or reduced resistance of the bird apparently results in infection.
In adult turkeys, the disease more often affects the male.
In the acute form in young birds, main
symptoms are gasping, sleepiness, loss of appetite and sometimes
convulsions and death. Occasionally the organism invades the brain,
causing paralysis or other forms of nervous symptoms. The more
chronic form in older birds usually results in loss of appetite,
gasping or coughing and a rapid loss of body weight. Mortality
is usually low and only a few birds are affected at one time.
The disease produces hard nodular areas
in the lungs and an infection of the air sacs. Sometimes the air
sac lesions are similar to those produced by infectious sinusitis
or CRD. In some birds, colonies of mold growth can be seen on
the air sac membranes.
Diagnosis is usually made from history,
symptoms and lesions. It may be necessary to base diagnosis on
microscopic lesions.
The disease can usually be prevented
by avoiding moldy litter, feed or premises. There is no treatment
for the affected flock. Cleaning and disinfecting the equipment
is often helpful.
It is known that certain strains of
fungi (molds) growing in feed or feed ingredients can produce
toxins that, when eaten by man or animals, can cause a very lethal
disease called mycotoxicosis. The toxins produced by these fungi
are very toxic and rivals the botulism toxin for toxicity.
Mycotoxicosis is caused by ingestion
of toxic substances produced by molds growing on feed, feed ingredients
and possibly litter. Several types of fungi produce toxins that
may cause problems in poultry, but of primary concern are substances
produced by the Aspergillus flavus fungi and are thus called
alfatoxins. Aspergillus flavus is a common mold that grows
on many substances, and grows especially well on grain and nuts.
Several other fungi also produce toxins that cause the disease.
The alfatoxins include four closely
related metabolites of A. flavus known as B1,
B2, G and G2. The B1 toxin is
the most toxic and is of greatest concern to the poultry industry.
Mold toxins cause a wide variety of
signs, many difficult to recognize. The alfatoxins under certain
conditions cause death, reduced growth, reduced egg production,
reduced hatchability, signs associated with "physiological
stress" and impaired ability to develop immunity to infectious
agents. Diagnosis is difficult because characteristic lesions
usually are not present, and detection of the toxin is not conclusive.
Molds are widespread in nature. Standing
grains and other feed substances are frequently infected with
toxin-producing molds prior to harvest. The key is proper storage
to control moisture and temperature to reduce growth of the molds
while in storage. Although the mold is present, it cannot produce
toxic products unless allowed to grow freely. Alfatoxins in feeds
can be detected by chemical tests. Once the toxin is produced
there is no known method for removing it from the feed or cancelling
its harmful effects. Providing a diet containing high fat and
high protein levels and augmenting the ration with vitamin supplements
may be of value.
This is a disease that primarily affects
the upper digestive tract of all birds and is characterized by
whitish thickened areas of the crop and proventriculus, erosions
in the gizzard, and inflammation of the vent area. It is caused
by a yeast-like fungus (Candida albicans).
Poultry of all ages are susceptible
to the effects of this organism. Chickens, turkeys, pigeons, pheasants,
quail and grouse are species most commonly affected as well as
other domestic animals and humans. The Candida organism is widely
spread throughout the poultry producing areas of the world.
Moniliasis is transmitted by ingestion
of the causative organism in infected feed, water or environment.
Unsanitary and unclean water troughs are an excellent reservoir
of the Candida organism. The disease does not however, spread
directly from bird to bird. The organism grows especially well
on corn, so infection can be introduced by feeding moldy feed.
This malady produces no specific symptoms.
Young birds become listless, pale, show ruffled feathers and appear
unthrifty. Affected caged layer hens become obese and anemic.
Some birds exhibit a vent inflammation that resembles a diarrhea
induced condition having whitish incrustations of the feathers
and skin around the area. Feed consumption may increase by ten
to twenty percent.
Gross lesions are mostly confined to
the crop, proventriculus and gizzard. The crop and proventriculus
have whitish thickened areas that are often described as having
a "turkish towel" appearance. Erosion of the lining
of the proventriculus and gizzard is commonly observed, as well
as an inflammation of the intestines. Diagnosis is based on history
and typical lesions in the flock. Confirmation of the condition
is by isolation and laboratory identification of the C. albicans
organism.
Treatment of the flock with an antimycotic
drug will control the infection. Many broad spectrum antibiotics
will enhance this disease; therefore they should not be used until
after control of this condition is completed. Addition of Nystatin
(100 g/Ton) or copper sulfate (2-3 lb/Ton) to the feed for seven
to ten days should control moniliasis.
Once introduced into the flock, moniliasis
is perpetuated by suboptimal management conditions. Preventative
measures include the continual use of mold inhibitors in the feed,
proper feed handling and storage, daily cleaning and sanitizing
of the watering system and periodic stirring and/or replacement
of wet litter areas to prevent caking. An inexpensive, yet effective,
water treatment is the continuous addition of household chlorine
bleach to the drinking water at the rate of five parts per million
(ppm).