January 2013
Contact: Margaret Sexton (08) 8207 7866
Poultry Diseases - Coccidiosis
Poultry coccidiosis is caused by a number of different species of coccidia. These are
members of the simple, single-celled animal form called protozoa.
Each species has its own coccidia, so chooks are not affected by coccidia from other
birds or vice versa. The chook has at least 7 species of coccidian and each damages
the wall in different parts of the gut. Symptoms depend on which part of the gut is
affected. All have about a 5 day life cycle so numbers can build up quickly.
THE DISEASE
Caecal Coccidiosis
The most severe form is caecal coccidiosis, mostly
found in chickens up to eight weeks of age.
Affected birds typically have a dirty appearance,
are depressed, not eating and stand with eyes
closed, wings hanging down and feathers ruffled.
In severe cases, pure blood is passed in the
droppings. Caecal coccidiosis has a rapid onset
and results in mortalities up to 50% unless treated
immediately.
The picture (left) shows the blood present in a
severe case of caecal coccidiosis
Intestinal Coccidiosis
Intestinal coccidiosis is most likely to occur between six and 16 weeks of age. The
intestinal form is more difficult to detect and usually more insidious. It can still cause a
heavy economic loss, often with a low but steady mortality. Birds eat but lose weight
and have a staggery gait. Their head feathers are raised, and they have a dirty, ruffled
appearance. A whitish soiling is often present around the vent.
Intestinal and caecal coccidiosis can occur together.
DIAGNOSIS
The disease can be confirmed by necropsy and looking for the typical lesions of
coccidiosis.
With caecal coccidiosis, there will be blood or blood stained fluids in the caecum and
possibly lower intestine.
With intestinal coccidia, the organisms are seen as
white spots sometimes with spotty bleeding seen
within the gut wall when looked at externally. Inside,
there may be orange coloured mucus. In severe
cases, the gut is grossly distended.
The picture to the left shows three levels of intestinal
coccidiosis. The left gut is normal, the middle gut is
mildly affected, the right one shows the distension,
white spots and bleeding.
The picture to the
right are the same
pieces of gut opened
to show the internal
appearance.
TRANSMISSION
Coccidiosis is transmitted through bird droppings
containing fertile coccidial oocysts. These need
moisture and warmth to mature to the infective stage.
This stage is picked up when birds scratch and peck
in the litter. On ingestion, the infective organisms are
released from the oocyst and penetrate the gut wall
cells and so begin the infection.
PREVENTION
Management
It is better to try and achieve prevention through good management than rely on drugs
to cure an outbreak. As coccidia require moisture to become infective, litter must be
kept dry. Ventilation must be good, and overcrowding should be avoided.
Birds develop immunity to coccidia after infection and the aim is to ensure that some
infection takes place during rearing. If the challenge develops too far though, a disease
outbreak will occur. Immunity is temporary and repeated exposure is necessary.
Immunity to one species does not protect the bird from its other coccidial species.
Medication
Coccidiostats are drugs used at low rates, usually in feed, as preventative medication.
The very effective coccidiostats, like ionophores, completely inhibit the coccidia from
developing if ingested and are used in meat chickens where, because they are
marketed at an early age, it is not desirable to expose them to any challenge.
The less effective coccidiostats, like diethyl o toluamide (DOT), are used in layers to
help develop immunity by allowing a challenge to occur but inhibiting a major build-up
of coccidia and so prevent outbreaks.
TREATMENT
When coccidiosis has been diagnosed, treatment should be started immediately.
Several drugs are available and the choice will depend on age, flock type and coccidial
type. Whichever drug is used, the maker's instructions must be followed exactly.
Product may be difficult to obtain for small flocks as they are often only sold in large
volume packages. There are some aviary bird products sold that may suit small flock
needs.
Many of the drugs do not work quickly and deaths may continue for a few days after
commencing treatment.
Sulpha drugs must not be used in metal drinkers or drinking systems because rust in
the systems reacts with the chemicals in the drugs rendering them toxic.
Toltrazuril (Baycox) works quickest but is very expensive and may need the water pH to
be adjusted to ensure efficacy.
Some causes of coccidial outbreaks:
1.
2.
3.
4.
Incorrect coccidiostat level in rations.
Failure to include extra coccidiostat during a restrictive feeding period.
Withdrawing coccidiostat too early, before immunity has built up.
Leakage from waterers and hose joints producing litter damp spots.
Author: Dr Kim Critchley, Poultry Health, PIRSA
FOR FURTHER INFORMATION:
Contact your local veterinary practitioner.
IF YOU HAVE SIGNS OF UNUSUAL OR SERIOUS ANIMAL DISEASE*, phone
Biosecurity SA Animal Health at Glenside on 82077900, contact your local PIRSA
Animal Health officer, call your local veterinary practitioner
OR RING THE DISEASE WATCH HOTLINE: 1800 675 888.
*Signs such as mass mortality events, sudden onset of multiple ill birds, rapid spread of
a problem or a noticeably unusual illness in birds.