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diagnosis of poultrydisease Poultry Disease DiagnosisThe proper diagnosis of poultry diseases depends on three important factors: 1. Identification of vital organs and body structure. 2. Knowledge of disease symptoms and lesions. 3. A systematic plan fordiagnosis of poultrydisease Poultry Disease DiagnosisThe proper diagnosis of poultry diseases depends on three important factors: 1. Identification of vital organs and body structure.
2. Knowledge of disease symptoms and lesions.
3. A systematic plan for examining the bird's body.
This publication outlines a plan for examining sick birds. Become familiar with the normal
appearance of birds and their organs by following the procedure outlined in this
publication on one or more healthy birds. Examining a healthy bird can help you learn
what to look for in sick birds.
It is especially important that you identify affected organs and tissues before seeking a
diagnosis from poultry specialists. A treatment cannot be suggested unless an accurate
history and list of symptoms and lesions are known.
Poultry diseases must be considered as diseases of the flock rather than individual diseases.
Symptoms in a few individual birds are usually an indication of a more serious flock-wide
problem. It is important that an accurate flock history be recorded. The source of many
diseases can be determined from this flock history.
A complete flock history includes the following:
• name and address of the owner
• number of birds in the flock
• breed, strain, and age of the birds.
Management information consists of the following:
• hatchery source
• type of operation
• feeding program
• a complete vaccination history.
Information on the illness includes the following:
• the date the illness was first observed
• severity and number of birds affected
• number of birds dying
• medication history.
Final remarks of disease in previous flocks and any unusual problems or conditions should
Before examining the bird internally, observe and inspect the bird for external symptoms.
Note the general condition and fleshing (presence of meat on the bone) of the bird. Check
the condition of the skin, and all natural body openings (nasal openings, mouth, ears, and
vent). Examine the head, eyes, comb, and wattles for evidence of swelling, canker lesions,
unusual discharge or coloration.
Look for signs of lameness, paralysis, or general weakness. Inspect the affected areas for
abnormalities or swelling that can give a clue to the cause. If you observe a partial or
complete paralysis, note the position the bird assumes. It is often an indicator of the cause
of illness. Inspect the bird for external parasites such as mites, lice, ticks, and fleas.
Starting a flock treatment early often saves more birds than delaying treatment until the
first birds die. For disease diagnosis it is often best to kill a sick bird showing typical
symptoms of the flock. Healthy birds from a sick flock contribute nothing when examined.
The most humane methods of killing the bird are injecting sodium pentobarbitol,
electrocution, and dislocation of the head from cervical vertebrae. The first two methods
are usually too expensive or dangerous for common usage. Cervical dislocation is the most
practiced method of killing birds for examination.
To dislocate the head from the vertebra, direct the bird's head toward you. Grasp the
bird's head with a handshake grip. Place your thumb behind the head at the base of the
skull, all allow the remaining fingers to extend under the throat. Hold the bird's feet with
the other hand and stretch the bird until you feel the head separating from the neck
vertebrae. You will probably need to bend the head back slightly while stretching the bird.
Be careful to stop pulling when the spine separates or the head may be pulled off. The bird
dies immediately when the spine separates.
The killing of small birds such as chicks, poults, or parakeets is often difficult because their
heads are small and hard to grasp. The vertebrae may be separated by applying pressure
with scissor handles at a joint between two vertebrae. It is best to apply pressure on each
side of the neck rather than at the throat and back of the neck. This avoids unnecessary
damage to the gullet and windpipe. Large chickens and turkeys may be killed this same
way, using burdizzos instead of scissor handles. A burdizzo is a plier-like tool used when
castrating cattle and other farm animals.
It is important that you are familiar with the organs you will see. Become familiar with the
following anatomy before examining sick birds.
Each nasal opening leads into a nasal cavity that is connected to sinus cavities around each
eye. A split in the roof of the mouth provides an air passage between the nasal cavities and
the lower respiratory system. The nasal cavities filter the air before it enters the lungs.
The larynx is located at the rear of the mouth. It is the structure connecting the trachea
(windpipe) and gullet. The trachea is a tube that separates into two bronchial tubes, with
each tube attached to a lung. The trachea and bronchial tubes are supported by rings of
cartilage that prevent the tubes from collapsing.
The lungs are located near the vertebra and lay closely against the ribs. They resemble
bright red sponges because of the abundant blood supply. Bird lungs are smaller in
proportion to body size than other animals. Though small, the lungs are aided by an
extensive system of air sacs found only in birds.
The air sacs are thin membrane sacs that surround the internal organs. They are used as
reserve air space to increase lung capacity. When the bird's body is opened, the air sacs
appear as clear thin membranes among the body organs. They are among the first sites
affected by respiratory diseases.
The mouth is connected to the rest of the digestive system by a thin-walled tube called the
esophagus or gullet. The lower portion of the esophagus forms a pouch called the crop. It
functions as a temporary storage site for food. The lower end of the esophagus is attached
to the bird's stomach.
The bird stomach has two parts -- proventriculus and gizzard. The proventriculus is the
slightly enlarged area between the esophagus and gizzard. When opened it has a deeply
textured appearance. The gizzard has a tough membrane inner lining firmly attached to
the muscular outer part.
The lower end of the gizzard is attached to the upper end of the small intestine. The first
portion of the small intestine is the duodenum. It is held in a loop-like position by the
pancreas. The pink pancreas is located between and attached to the portions of the
intestine forming the loop.
The lower portion of the small intestine is attached to a membrane called the mesentery.
This mesentery is laced with many blood vessels that enter and exit the small intestine.
When opened, the lining of the small intestine has a soft, velvety texture.
Two large closed pouches called ceca are attached at the lower end of the small intestine.
Bacterial action in the ceca helps break down some of the undigested food passing through
the intestine. The ceca in adult chickens are usually about four or six inches long. When
opened they contain a darker brown, more pasty material than the intestines.
Following the ceca, the small intestine changes into the large intestine. This large intestine
is a short section of intestine that connects the small intestine and cloaca, or chamber where
the digestive, urinary, and reproductive systems meet. The external opening of the cloaca is
called the vent.
The liver is a large brown organ located in the front portion of the body cavity (thorax). It
is the largest organ in the body. It has two large lobes separated by a thin membrane. Its
function is to produce digestive fluids and filter toxic wastes from the blood. A digestive
fluid produced in the liver (bile) is stored in the gall bladder. This gall bladder is a small,
greenish pouch attached to the liver. A bile duct between the liver and small intestine
directs the bile to the intestine.
Urinary, Reproductive, and Vascular Systems
The urinary system in birds consists of kidneys and ureters. The kidney is a dark brown
organ located in a pocket of the pelvic bones. There are two kidneys in each bird, and each
kidney has a ureter. The ureter is a tube that passes the urinary wastes from the kidney to
The reproductive organs include the ovary and oviduct in the female and the testes in the
male. The hen usually has only one ovary and oviduct. The ovary is a group of egg yolks in
various stages of development and is located in the area of the kidneys. Some yolks may not
be seen, while some in the laying hen may be the size of normal egg yolks. The oviduct in
mature hens appears as a coiled tube extending from the area of the ovary to the cloaca. In
immature females the ovary and oviduct may not be easily seen.
The reproductive system of the male consists primarily of the two testes. The testes are oval
organs located between the lungs and kidneys. Ducts through which sperm pass (ductus
deferens) extend from each testis to the cloaca.
Vascular organs consist primarily of the heart and spleen. The four-chambered heart is
located above the liver. The spleen is a spherical, reddish-brown organ located between the
liver and gizzard. Its primary purpose is removing unhealthy blood cells, micro-organisms,
and debris from the blood system.
A necropsy is an examination of a dead animal. The only tool necessary to perform a
necropsy is a sharp cutting utensil, but several good quality tools are recommended. A
sharp pair of surgical type scissors and a scalpel, or knife, make it easier to cut the
necessary tissues. A pair of heavy shears help when cutting through bones. Although few
poultry disease can infect people, it is recommended that you wear disposable plastic gloves
during the necropsy procedure.
Begin the necropsy by washing the dead bird with detergent water. This removes any
foreign material and holds down the feathers. Place the wet bird on a flat surface with
breast side up and head directed away from you. The following steps are numbered to
make it easier to follow the procedures.
1. Remove upper portion of the beak by cutting through the nasal cavities and
turbinated bones. Turbinated bones are membrane-covered plates on the walls of
the nasal chambers. This lets you observe the upper respiratory areas for the
presence of infection. Squeeze the turbinate area and note if excessive matter oozes
from the area. Check the eyes for inflammation (unusual reddening), mucus, or
2. Insert one scissor blade into the mouth and cut through one corner of the mouth.
Extend the cut down the neck so the interior of the gullet is exposed. Examine the
mouth and larynx for abnormalities that indicate pox, mycosis, or other disease.
Scan the gullet for tiny nodules (bumps) or signs of injury by foreign materials.
3. Cut the larynx and trachea from the mouth and open the trachea lengthwise.
Examine its interior for excessive mucus, blood, or cheesy material.
4. Make an incision in the abdominal skin just below the tip of the breast cartilage.
Extend the cut around the body on each side. Grasp the upper edge of the cut skin
and bluntly peel the skin over the breast. This exposes the breast muscles. Examine
them for conditioning and the presence of hemorrhages (sites of prior bleeding in
5. Cut the skin on the abdomen where the legs join the body. Place a hand on each leg
and press down and out until the femoral joints dislocate and the legs lie flat on the
table. Tear the skin from the legs and check for small
6. Make an incision through the abdominal muscles just
below the tip of the breast bone. Do not cut too deep,
or you may cut internal organs. Extend the cut toward
the back and then angle toward the point of wing
attachment on each side. You must cut through the
ribs in order to complete this cut. Push the breast
toward the head and dislocate the shoulder joints. Cut
through the shoulder joints and remove the breast
from the carcass.
7. Observe the condition of the air sacs. The membranes
are often cloudy and covered with mucus in diseased
8. Examine the liver for unusual swelling, lesions,
hemorrhages, or abnormal coloration. Make incisions
into the liver and check for scar tissue and necrotic
(dead) tissue. Check the spleen for hemorrhages, lesions, and swelling. Check for a
cloudy, fluid-filled sac surrounding the heart.
9. Remove the liver, heart, and spleen so the digestive system is exposed. Check the
digestive system for abnormal nodules, tumors, or hemorrhages. Sever the gullet
near the mouth and remove the entire digestive system. You can cut the lower
intestine behind the ceca for complete removal.
10. Cut into the crop. Note if the contents are sour smelling. Wash contents from the
crop and examine the lining for thickened, patch-like areas or necrotic ulcers.
Check for capillary worms by making a small cut and slowly tearing the crop wall
as if it were a piece of paper. Capillary worms appear as small, hair-like fibers
extending across the base of the tear.
11. Open the proventriculus, the slightly enlarged area between the esophagus and
gizzard, and note any hemorrhages or a white coating on the lining.
12. Open the gizzard and examine the lining for unusual roughness or lesions.
Determine if the lining is separating from the underlying muscles.
13. Slit the intestine lengthwise and examine contents for the presence of worms, free
blood, and excess mucus. Check the lining for inflammation, ulcers, or hemorrhagic
areas. If unusual conditions exist, note in which one-third portion of the intestine the
conditions are located.
14. Open the ceca and examine the contents. Look for cheesy cores and small, cecal
worms. If you find blood, wash and examine the lining for scarring and cecal
15. Check the reproductive organs (ovary and oviduct in females, testes and ductus
deferens in males) for abnormalities before removing them from the body.
16. Examine the kidneys and ureters for unusual swelling or the presence of whitish salt
17. Check the sciatic nerve extending to each leg for swelling. Once you remove the
kidneys, you can see this nerve as a small white fiber stretching from the spinal cord
along the femur into the lower leg. Also check the brachial nerve extending from the
spine, along each humerus (upper wing bone), to the wing tip.
18. Observe the lungs and bronchial tubes for lesions and unusual accumulation of
You can make notes on history, symptoms, and lesions until you are familiar enough to
diagnose diseases without consulting references. It is recommended that you follow all the
procedures in this publication. Often two or more diseases can infect a bird and the
symptoms may be confusing. Check all affected areas before making a diagnosis and
administering a treatment.
Diagnosis and Treatment
After you have listed the symptoms and lesions, refer to a good poultry disease manual to
determine the proper diagnosis. You can get a disease manual and helpful advice from
your county agent or Extension poultry specialists.
When you or a specialist diagnose a disease, a specialist will recommend a treatment. Take
care to administer the medication using the proper dosage, method of application, and the
period of recommended time. Becoming familiar with disease symptoms and lesions and
following the proper diagnostic procedures will eliminate the difficulty of diagnosing many
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