Coccidiosis is a disease of fowl caused
by a microscopic animal or protozoa and is characterized by diarrhea,
unthriftiness and variable levels of mortality. In spite of much
research to advance the control and treatment of this disease,
it remains the most costly disease of the poultry industry.
Coccidiosis is caused by microscopic
animals called coccidia. There are many species of coccidia that
can infect fowl, domestic animals and humans. Each species of
coccidia is host specific and does not infect a wide variety of
animals. After an outbreak of a specific species of coccidia,
the flock will develop a resistance to the exposed coccidia species
but remain resistant to other infective species. This means that
a flock may experience several outbreaks of coccidiosis, each
being caused by a different species of coccidia. Chickens are
susceptible to any of nine coccidia species, turkeys are susceptible
to seven species and quail are susceptible to at least four different
species of coccidia.
Coccidiosis is transmitted by direct
or indirect contact with droppings of infected birds. When a bird
ingests coccidia, the organisms invade the lining of the intestine
and produce tissue damage as the undergo reproduction. Within
a week after infection, the coccidia shed immature descendants
that are referred to as oocysts. The oocysts shed in the droppings
are not capable of infecting another bird unless they pass through
a maturation process (sporulation) in the litter. This sporulation
occurs within a one to three day period if the litter is warm
and damp but can take much longer if the conditions are cool and
dry. After sporulation the coccidia are infective if consumed
by a new host bird.
The number of infective coccidia consumed
by the host is a primary factor as to the severity of the resulting
infection. An infection may be mild enough to go unnoticed while
a large infective dose of coccidia may produce severe lesions
that can cause death. Coccidia survive for long periods outside
the bird's body. They are easily transmitted from one house to
another on contaminated boots, clothing, free-flying birds, equipment,
feed sacks, insects and rodents.
Coccidiosis usually occurs in growing
birds and young adults. It is seldom seen in birds under three
weeks or in mature birds. Signs of an outbreak include birds that
are pale, droopy, tend to huddle, consume less feed and water,
have diarrhea, and may become emaciated and dehydrated. Laying
hens will experience a reduction in rate of egg production.
Cecal coccidiosis may produce bloody
droppings and anemia that is often followed by death. Intestinal
coccidiosis is not as acute and is more chronic in nature. It
produces less mortality than the cecal form.
Lesions of the infection depend on
the species of coccidia causing the problem, its severity and
stage of the disease. Cecal coccidiosis may produce a ballooning
of the cecal pouches that is filled with free blood. A later stage
is characterized by cecae that are filled with a material with
a cheesy consistency and being tinged with variable amounts of
blood. Lesions of intestinal coccidiosis vary from a rather mild
enteritis to a severe necrotic or hemorrhagic type.
Cecal coccidiosis may be confused with
blackhead and salmonellosis due to their similar lesions. Intestinal
coccidiosis may be confused with hemorrhagic anemia syndrome and
other enteric diseases. Definite diagnosis is made from the microscopic
examination of scrapings of the digestive tract and identification
of the coccidia organisms. Since it is common for healthy birds
to possess some coccidia, consideration of flock history and lesions
must be considered before making diagnosis and treatment recommendations.
It is difficult, if not impossible,
to prevent coccidiosis by sanitation alone. It is best prevented
by addition of a drug (coccidiostat) to the feed that controls
the growth of coccidia in the digestive tract. Many coccidiostats
are available commercially. Coccidiostats should not be indiscriminately
used and recommendations must be followed precisely
A coccidiosis vaccine is also available
commercially. The product is useful only in certain types of poultry
operations and must be used as recommended. Seek expert advice
before using the vaccine.
Blackhead is an acute or chronic protozoan
disease of fowl, primarily affecting the cecae and liver. The
disease is present wherever poultry are raised. Blackhead is one
of the critical diseases of growing turkeys and game birds. It
may cause stunted growth, poor feed utilization and death. It
is of lesser economic importance in chickens since they are more
resistant, but the incidence in chickens apparently is increasing.
Blackhead is caused by a protozoan
parasite called Histomonas meleagridis. The organism in
passed in the fecal material of infected birds. In many instances,
the organism is shed within the eggs of the cecal worm of chickens,
turkeys and game birds. Free-living blackhead organisms do not
survive long in nature, but those in cecal worm eggs may survive
for years. Therefore, most blackhead transmission is considered
due to ingesting infected cecal worm eggs. Transmission may also
occur by the earthworm.
Chickens are frequently infected without
showing signs of the disease. These chickens may shed enormous
numbers of blackhead organisms, many of which are protected by
cecal worm eggs. Outbreaks in turkeys can often be traced to direct
or indirect contact with ranges, houses or equipment previously
used by chickens. Free-flying birds may also contribute to an
infection.
Most blackhead losses occur in young
birds (six to sixteen weeks). Among the symptoms are loss of appetite,
increased thirst, droopiness, drowsiness, darkening of the facial
regions and diarrhea. Morbidity and mortality are variable, but
mortality seldom exceeds fifteen percent; however, it may approach
one-hundred percent in uncontrolled turkey outbreaks. Losses are
usually low in chickens.
Lesions of uncomplicated blackhead
are confined to the cecae and liver, thus the reason for the synonymous
term, enterohepatitis. The cecae are ballooned and walls may be
thickened, necrotic and ulcerated. Caseous (cheesy) cores within
the cecae may be blood tinged. Peritonitis may be present if ulcers
have perforated the ceca walls. Livers are swollen and display
circular depressed areas of necrosis about one-half inch in diameter.
Smaller lesions coalesce to form larger ones. Lesions are yellowish
to yellow-green and extend deeply into the underlying liver tissue.
Healing lesions may resemble those seen in visceral leukosis.
Blackhead diagnosis is made readily
on the basis of the lesions. Atypical forms, particularly in chickens,
must be differentiated from cecal coccidiosis and Salmonella infections
in particular. Medications may interfere with atypical lesions.
Laboratory tests may be required for positive diagnosis in such
cases.
Good management practices can do much
to control the blackhead problem. Do not keep birds of different
species on the same premises. Do not range turkeys on ground
previously used by chickens unless several years have elapsed.
Rotate ranges periodically if possible. Cecal worm control
is necessary to reduce blackhead incidence. Wire or slatted
floors reduce exposure.
Good management is the only effective
method of preventing this disease since many of the effective
drugs used in past years are no longer available commercially.
Drugs that reduce the presence of cecal worms, and thus reduce
the infection rate, are available but do not have an effect on
the Histomonas organism. Refer to the cecal worm section for recommended
control practices.
Hexamitiasis is an acute infectious
disease of turkeys, quail, ducks, chukar partridges and pigeons.
Heavy losses have been reported in one outbreak in ring-necked
pheasants. Chickens apparently are not affected.
Hexamitiasis is a problem in every
commercial turkey-producing area. It may be a major problem in
localized areas during a particular year, followed by one or more
years in which incidence is low.
Hexamitiasis is caused by a one-celled
parasite of the genus Hexamita. Hexamita meleagridis is
the cause in turkeys; in pigeons it is Hexamita columbae.
Experimentally, the Hexamita of turkeys can be transmitted to
young quail, chicks and ducklings, and that of quail and partridges
can be transmitted to poults. However, poults cannot be infected
with the organism isolated from pigeons.
This disease is found primarily in
young birds, and outbreaks seldom occur in poults past ten or
eleven weeks. Losses are most severe in birds three to five weeks
old. Apparently, resistance develops rapidly with increasing age,
regardless of previous exposure.
The primary infection source is droppings
from carrier birds. About a third of recovered birds become carriers.
Most outbreaks result from a buildup of organisms through several
broods of poults, making exposure of the following brood overwhelming.
Indirect transmission may result from fecal material carried from
one location to another on shoes or equipment. Free-flying birds
also may be carriers.
Primary symptoms are listlessness and
foamy or watery diarrhea with rapid weight loss due to the dehydrating
effect. Birds often huddle together near the heat source and cry
or "chirp" constantly as though in pain. Convulsions
due to lowered blood sugar levels shortly precede death. Affected
birds suffer losses in weight and survivors remain stunted.
Dehydration and emaciation are the
principal gross lesions. Muscles are dark and dry. The intestine
usually appears to have lost muscle-tone. Intestinal contents
are usually thin and watery, or may contain mucus.
Diagnosis depends upon history, symptoms
and microscopic examination of intestinal contents. A definite
diagnosis cannot be made unless typical flagellated organisms
can be detected in intestinal contents of the duodenum. Most flagellate
organisms in the cecae are not disease producers.