Poultry Husbandry Chapter
V: Diagnosis of Poultry Disease
History. A good history will often
provide clues that will help solve a problem. Get information on the type of
bird, age, feed and water source and consumption rate, growth, production,
morbidity and mortality, the description of the case, previous problems,
vaccination program, medicine being used etc.
The problems may relate to
management, environmental factors, and stress rather than to infection so
examine the yard and housing conditions. Is the ventilation adequate? Are
ammonia fumes a problem? Is it too hot or too cold? Is the litter wet or is
it too dry and dusty? Is the pen too light or too dark? Are there sufficient
hours of light for best production? Is the nest area darkened? Are the roosts
too high? Do the birds appear comfortable? Chickens can talk and the sounds
they make can indicate comfort, hunger, pain, panic, or disease.
Examination of Live Birds. Check the general appearance
of the individual or group and try to determine which organ or system is
involved in the illness. Note any signs or lesions that might point to a
diagnosis, such as small size with poor feathering that suggests infectious
stunting (malabsorption syndrome). If the birds show lameness or paralysis,
is the lesion in the nervous system, bones, joints, muscles or skin? Some
conditions, particularly those affecting locomotion, are easier to diagnose
in live birds. Botulism which produces neck paralysis in chickens (leg and
wing paralysis are more obvious in turkeys, ducks and pheasants) is an
Examine the skin of the head,
body and legs for lice and mites, injury (particularly cannibalism), blood,
mottling, swellings, anemia, cyanosis, or dermatitis. Listen for unusual
breathing sounds (snicking, gurgling) and look for gasping or head-shaking
that might indicate respiratory distress. Mouth-breathing (panting) is normal
in chickens in hot weather. Exudate from nostrils and eyes and dirty feathers
also suggest respiratory infection, or if just the eye, ammonia burn, ILTor
eyeworm. Examine the droppings for evidence of diarrhea or other
abnormalities. Take a blood sample for hematology or serology if indicated.
Necropsy. If a postmortem examination
is to be carried out, birds that are representative of the problem in the
flock must be selected. If birds have died, both sick and dead birds should
be opened. Cull birds will not provide the answer. If the problem is a drop
in production, try to find birds that look like they have recently stopped
laying. It is important to do both an external and internal examination and
to follow a specific routine to avoid missing important lesions.
CRD - chronic respiratory
IB(V) - infectious bronchitis
ND - Newcastle disease
AI - avian influenza
CA(V) - chicken anemia (virus)
EDS - egg drop syndrome
IBH - inclusion body hepatitis
ILT - infectious
IBD - infectious bursal disease
Live birds may be killed by
cervical dislocation except when anemia or respiratory disease is suspected.
1. Examine the head, including
the eyes, ears, nostrils, comb, wattles, mouth and beak.
Infected eyes and
conjunctivitis are seen in CRD, sinusitis, Bordetella and Orthobacterium
infection, infectious coryza and in ILT, IB and ND.
central corneal ulcers suggest ammonia burn.
Swollen sinuses are seen in
infectious coryza (Parahaemophilus infection) in chickens, sinusitis
(mycoplasma), cryptosporidia and Bordetella infection in turkeys and
pheasants. They may also be seen as the result of other infections such as
Chronic fowl cholera causes
swollen wattles and sinuses in adult chickens.
Fowl pox causes scabs on the
comb, eyelid, and wattle, but must be differentiated from injury. Pox also
occurs in turkey, pigeons, doves, canaries and other birds.
If the bird has had its beak
trimmed, check for proper healing, overgrowth of the lower beak or
over-trimming (cut too short).
Injury on the head, neck or
breast or back may indicate predators. Dermatitis and scabby or crusty
lesions around the mouth and eyes suggest vitamin B deficiency.
2. Cut across the upper beak
and back into the sinuses; then through the mandible and down the esophagus
into the crop.
White plaques in the mouth,
esophagus, or crop may be caused by capillaria worms, yeast infection
(candidiasis, moniliasis), or possibly trichomoniasis or vitamin A
deficiency, but most frequently by fowl pox (wet form). White plaques
beside the tongue in the mouth are common in hens and turkey breeders and
may be caused by mycotoxin or low humidity. Vomitoxin may produce similar
lesions in young chickens and turkeys.
If the crop is enlarged and
full, it may be an impacted or a sour crop (pendulous crop). The problem
may be caused by excess water intake, defects in the crop itself, partial
blockage of the proventriculus or gizzard or Marek's disease. Necrosis of
the crop in wild birds is caused by Salmonella infection.
3. Examine the soft palate and
larynx and cut down the trachea.
Wet fowl pox lesions are seen
on the roof of the mouth, pharynx and larynx.
Granulation, congestion and
mucus in the trachea are seen in CRD, IB, coryza, ILT, Orthobacterium,
Bordetella, and E. coli infection, or with dust and
Hemorrhage and blood clots
may occur in ILT and in ND or coryza and may cause severe gasping.
Gapes (gape worms) in
pheasants, quail, and other birds is caused by Syngamus infection which
also causes gasping. Cyanthastoma cause similar infection in water fowl and
tracheal flukes may be found in waterfowl. Tracheal and air sac mites occur
in cage birds.
4. Check the abdomen for lice
and mites, and the vent for injury and prolapse of the oviduct.
Cut down between the abdomen
and the legs and dislocate the hip joints. Peel the skin off the abdomen
and breast. Tightly adhering skin and dark tissues indicate dehydration.
Remove the breast carefully by cutting through the abdominal muscles, ribs
At this point, examine the
thoracic and abdominal organs, paying particular attention to the air sacs,
lungs, and liver. Carefully raise the gizzard and intestines and examine
the abdominal air sacs, peritoneum, spleen and the ovary in laying birds.
The air sacs are cloudy in
respiratory disease such as E. coli infection, Mycoplasma,
Aspergillus, IB or early CRD in chickens. If there is also fibrin on the
liver and in the pericardial sac, suspect E. coli or
Salmonella infection. These lesions in turkeys and other birds might also
be due to Chlamydia, or in ducks Anatipestifer infection.
Pneumonia in turkeys is
caused by fowl cholera (Pasteurella multocida infection), and the lungs are
quite solid. Aspergillosis, ND, AI, E. coli and Ornithobacterium infection
can also cause pneumonia.
Peritonitis in layers is
usually "egg peritonitis" caused by E. coli infection
from the oviduct, although acute fowl cholera also causes peritonitis.
White crystals on the heart,
liver and other tissues and organs are uric acid crystals (visceral gout)
and are caused by hyperuricemia from urate nephrosis secondary to water
deprivation, urolithiasis or other kidney disease.
Large blood clots in the
abdomen or hemorrhage and hematoma on the liver are the result of trauma or
fatty liver hemorrhage syndrome in chickens, or ruptured aorta in turkeys.
Tumors in or on the organs
may be Marek's disease, lymphoid leukosis, or other varieties of tumors.
Multiple small tumors on the organs and peritoneum in adult hens are
metastasis from a carcinoma of the oviduct. This may result in ascites.
Ascites may also result from
heart or liver disease or from ingestion of some toxic material. Right
ventricular failure occurs most frequently in meat-type chickens after 4
weeks. It occurs secondary to pulmonary hypertension causing right
ventricular hypertrophy and valvular insufficiency.
Focal white lesions on the
organs may be tumors or they may be tuberculosis or coli-granuloma or, if
just on the liver, blackhead. Turkeys, pheasants, and peacocks are all
quite susceptible to blackhead; chickens are less susceptible. There are
prominent cecal cores in blackhead (Histomoniasis) and occasionally in
salmonella infection or coccidiosis.
In chicks, turkeys and
waterfowl, examine the lungs and air sac for yellow-white foci or plaques
caused by brooder pneumonia (Aspergillosis). Gasping in young birds is a
sign of tracheal or bronchial epithelial injury, or obstruction and can be
caused by irritating fumes or by infection (often IB plus E. coli or
In young chicks, look for an
infected navel and for yolk-sac infection or peritonitis (mushy chick,
omphalitis) in which the abdomen is swollen, wet, and discoloured, and the
yolk-sac is infected (due to E. coli, Salmonella, Staph.,
Young birds also die because
they don't start to eat (starve-outs) or drink (dehydration). Deaths occur
mainly at 3, 4, and 5 days. This may be a management problem (chilling,
feed and water not available, etc.) or the chicks/poults may be weak or
defective when hatched.
Broiler chickens that die
suddenly from sudden death syndrome (dead in good condition) or from heat
stroke, or suffocation (piling-up) have congested, edematous lungs, a full
digestive tract and congested mottled breast muscle.
5. Examine the circulatory and
immune systems, the heart, pericardial sac, blood, spleen, bursa, thymus, and
lymphoid tissue of the thigh and intestine.
Birds that die from anemia
are pale and the blood is watery. With CAV the thymus is small and bone
marrow may be pale. Birds that bleed to death (pick-outs, ruptured fatty
liver, acute cecal coccidiosis, ruptured aorta, hemorrhagic enteritis in
turkeys, etc.) are also pale.
Sulfa poisoning produces
anemia and widespread hemorrhage in the tissues. Chicken anemia virus (CAV)
produces similar lesions and is the agent responsible for infectious anemia
associated with IBH. Lead poisoning may also cause anemia.
To identify anemia from
parasites in blood cells (Plasmodium or leukocytozoon in ducks, turkeys and
chickens), blood from a live, sick bird must be examined.
IBD (Gumboro disease) is
caused by a virus that damages the bursa causing illness in 2-4 week old
chickens or in younger chickens destroys part of the immune system, making
birds more susceptible to other infections.
Swelling, congestion and
hemorrhage with or without focal necrosis in the spleen, liver and lymphoid
tissue suggest septicemia (fowl cholera, fowl typhoid, streptococcosis, or
erysipelas) or viremia (ND and duck virus enteritis also affect the
lymphoid tissue in the intestine).
Marek's disease and lymphoid
leukosis produce tumors in lymphoid tissue and organs except for the bursa
which is mainly affected by lymphoid leukosis (occasional Marek's lesions
may occur in the stroma of the bursa).
Skin leukosis is Marek's
disease virus causing viral dermatitis in the feather follicles. At
processing this can be confused with scabby hip or other causes of
dermatitis. Marek's disease can also cause lymphoid neoplasia in the skin.
6. Cut through the
proventriculus and remove the digestive tract and liver. Open the
proventriculus, gizzard, and small and large intestines to the cloaca. Check
the cloaca carefully for evidence of picking injury.
If hens are not properly
beak-trimmed or are too fat, mortality from "pick-out" is common.
The whole intestine may be picked out through the cloaca. Prolapse of the
vagina (and cloaca) (blow-out) may occur from excess fat or straining,
secondary to injury or inflammation. Injury is common in flocks that
produce large eggs before they become mature.
Examine the digestive tract
for lesions and the various kinds of enteritis (hemorrhagic, necrotic,
ulcerative, etc.), parasites (tetrameres, roundworms, capillary worms,
tapeworms, cecal worms, and coccidia), and gastrointestinal accidents. A
large proventriculus in broilers is from lack of fibre in the diet
resulting in poor development of the gizzard. A thickened proventriculus
sometimes with ulcers or hemorrhage may be Marek's disease or infectious
Green staining of the
digestive tract is just bile and indicates that the bird is not eating. The
liver and spleen may be small (if the bird is thin) and the gallbladder
Salmonella pullorum (pullorum
disease, bacillary white diarrhea) causes enteritis, diarrhea and death in
chicks. It has been eradicated in many countries.
Check the ceca, intestine and
liver for lesions of blackhead, TB, coccidiosis or tumor, the liver for
other varieties of bacterial, viral or protozoal hepatitis,
cholangiohepatitis etc., and the pancreas for tumors.
A large liver may be lymphoid
leukosis or Marek's disease, or it may be caused by bacterial hepatitis (E.
coli, campylobacter) or fowl typhoid (Salmonella gallinarum).
Hepatitis with necrosis and
hemorrhage that looks like bacterial (vibrionic) hepatitis may be immune
damage to veins (vasculitis) from amyloid.
A large, yellow liver may be
normal fat storage in a laying bird (estrogen stimulation) but layers die
from fatty liver hemorrhage syndrome. This occurs when the liver ruptures
because it has become fragile due to excess fat and free radical damage
A yellow or hemorrhagic liver
particularly with focal necrosis may be viral hepatitis (IBH) which is seen
in broilers, pigeons, raptors, owls and psittacine (but IBH does not cause
7. Examine the testes or ovary
and open the oviduct. Shrinking ova indicate illness of 2-7 days' duration or
one from which the bird may be recovering. Small, sac-like ova indicate that
the bird has been out of lay for a week or more and may be in a molt.
Semi-solid (cooked) ova
indicate bacterial infection (such as salmonella).
An impacted oviduct may be
secondary to vent-picking, egg-material left in the oviduct, or the bird
may be egg-bound. Infection (Mycoplasma, IB, E. coli) can cause
salpingitis as well.
A large or small fluid-filled
cyst in the right abdomen beside the cloaca is the cystic remnant of the
right oviduct (may be normal, but increased by IBV).
A drop in production may be
related to clinical or subclinical disease (EDS, IB, MG, AE, AI, ND, etc.)
or management faults (lack of light, temperature change, lack of water) or
nutritional problems etc.
Deformed shells suggest
management faults, superovulation, EDS, IB and soft shells (higher than
1-2%) calcium or vitamin D3 deficiency.
A normal-appearing dead bird
with an egg in the shell gland, or just laid has likely died from acute
hypocalcemia. These birds often have fragile bones (particulary the femur),
lack of medullary bone and rib infolding (osteoporosis, osteopenia,
Hard (fibrotic) or swollen
testes indicate bacterial infection (salmonella).
8. Examine the kidneys and
Swollen, pale or white
spotted kidneys indicate hyperuricemia from urate nephrosis and may be due
to lack of water or other kidney disease. Swollen. pale kidneys are also
seen in IBH, IBD and fatty liver and kidney disease. Ureters plugged with
hard stony material (urolithiasis) indicates a previous low phosphorus
Swollen kidneys and nephritis
may be due to IBV (nephrotrophic strain) or E. coli infection
and usually causes death from dehydration. Newcastle's disease causes
lympholytic foci in the kidney in pigeons.
9. Examine the skin,
integument, muscles, bones and joints.
Emaciation, along with small
organs, suggests malnutrition, stunting syndrome, beak injury (poor
trimming), peck order (psychological) problems, chronic disease
(coccidiosis), bumblefoot or other lameness, or chronic poisoning (lead,
Muscular degeneration due to
vitamin E-selenium deficiency can cause lameness, particularly in ducks.
Ionophore toxicity causes muscle damage and paralysis in turkeys.
Granulomas in the breast muscle are usually a vaccine reaction.
Sarcosporidial cysts produce
small, white lesions in the muscle of water fowl.
Examine bones and joints for
abnormality and deformity. Angular bone (valgus-varus) deformity of the
intertarsal joint is caused by lateral or medial bending of the
tibio-tarsal and metatarsal bones and is a common problem in meat-type
poultry. It has a variety of possible causes (nutritional, rapid growth,
management, etc.). Tibial dyschondroplasia causes backward bending or
fracture of the top of the tibia. Slowing growth in young birds will help
prevent leg deformity.
Other types of hock and
stifle lameness and ruptured tendons are frequent in heavy roaster and
turkeys and may be mainly due to injury as the result of heavy weight and
fast growth, but some respond to added selenium or B vitamins.
Check for poor bone-breaking
strength (osteoporosis) and, in young birds for rubbery bones, soft beaks,
and beaded ribs which indicate calcium or Vit. D3 deficiency (rickets).
Cage layer fatigue because of fragile bones may be due to phosphorus
deficiency. Calcium and Vit. D3 deficiency also cause fragile bones
(osteoporosis) in adults, but the most common cause is continuous high
Infectious stunting syndrome
(malabsorption syndrome, fragile bones, osteoporosis) in young broilers is
caused by intestinal damage from viral infection in young chicks. The
chickens are small, poorly feathered and there is poorly digested food in
the lower intestine. Osteomyelitis also causes fragile bones.
Curly-toe paralysis in young
birds may be riboflavin deficiency, but in older birds and turkeys may be
genetic or due to lack of roosts.
Cracked feet and foot
dermatitis may be pantothenic acid or biotin deficiency, but scaly leg is
caused by mites.
Footpad dermatitis and hock
lesion are often caused by poor litter conditions.
Toe injury in young birds may
be cannibalism or mechanical injury.
Arthritis in the feet or
hocks or other joints suggests infectious synovitis (Mycoplasma synoviae)
or E. coli or Staph. infection often with osteomyelitis.
Infection in the wing joints in
pigeons is usually due to salmonella.
In broilers, roaster and
broiler breeders viral arthritis (reovirus infection) may cause lameness or
ruptured tendons. Ruptured tendons are usually caused by rapid growth and
large body size (heavy weight) and there is usually thickening of the
tendon above the hock.
If growing birds are lame,
and there is no evidence of infection or rickets, cut into the proximal
tibia and look for necrosis caused by osteomyelitis or dyschondroplasia and
split the spine at T4 to look for spondylolisthesis (kinky-back), a plug of
cartilage impinging on the cord or consider Marek's disease.
Necrotic dermatitis is caused
either by staph. or clostridium infection and is associated with
immunosuppression (usually by CAV or IBD). Scabby-hip is usually from
overcrowding, poor litter conditions, poor feathering or scratches.
Dermatitis or granulation in the neck may be a vaccine reaction, or
10. Disturbances of the nervous
system may cause incoordination, staggering, paralysis, walking backwards
(with wings flapping for balance), tremors, stargazing, and other odd
In case of lameness,
paralysis, or incoordination, examine the sciatic nerves, spinal cord, and
brain. Histologic examination will be required for diagnosis.
ND may produce CNS
disturbances in pigeons as well as nervous, respiratory, intestinal and
reproductive lesions in chickens, pheasants, turkeys, and wild and cage birds
of all ages.
Range paralysis is a form of
Marek's disease affecting the peripheral and central nervous system causing
lameness, incoordination and paralysis. Marek's can also cause
botulism-like paralysis and transient paralysis.
Vitamin E deficiency (avian
encephalomalacia) causes soft, dark areas of hemorrhage in the cerebellum
which may be visible grossly. B vitamin deficiency (thiamine and other) may
also cause nervous signs.
Avian encephalomyelitis (AE)
(epidemic tremor) affects birds up to 3-4 weeks old from non-immune
Arsenilic acid and other feed
additives and toxins (botulism, lead) may cause CNS disturbances, while
others like the ionophores and coffee weed seeds (Cassia) cause nerve or
muscle damage. Bacterial infection (pasteurella, pseudomonas, salmonella,
staph. etc.) and fungi (aspergillus, etc.) also cause meningoencephalitis,
occasionally in outbreak proportions.
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