Poultry Diseases (Common Symptoms, Postmortem Findings and Transmission)

SPECIFIC DISEASES OF POULTRY

Diseases caused by viruses and Chlamydia

Avian influenza (Fowl plague, highly pathogenic avian influenza (HPAI))

Avian influenza is a viral disease of several avian species in various parts of the world. The disease can range from asymptomatic and mild to hyperacute and fatal. Avian influenza occurs infrequently in humans. It is seen as an occupational hazard, primarily to those associated with varied activities in the poultry industry; employees in abattoirs, vaccinators, laboratory staff and other personnel. In most cases the clinical picture is that of conjunctivitis with rare systemic reactions. Avian influenza is re portable disease in many countries. It has to be confirmed by virus isolation.

Transmission: Secretions from infected birds, by wild birds and contaminated feed, equipment and

people. Seabirds and migratory waterfowl comprise the main reservoir for avian influenza virus.

Antemortem findings:

1. The incubation period varies from a few hours to about seven days.

2. The morbidity and mortality rates can reach 100 % in cases of highly pathogenic strain of the

viruses.

3. Marked depression, loss of appetite and watery diarrhea

4. Coughing, sneezing, rales, excessive Lacrimation

5. Drop in egg production in layers

6. The conjunctiva is congested and swollen, and occasionally hemorrhagic.

7. Swollen combs with cyanotic tips and hemorrhagic surface

8. Edematous wattles and edema around the eyes, head and neck

9. Ruffled feathers and dark red skin

10. Diffuse hemorrhages between the hocks and feet

11. Blood in the cloaca

12. Some birds may recover, even after being severely affected.

Postmortem findings:

1. Birds that die with the peracute form of AI may show no significant gross lesions

2. Dehydration

3. In highly pathogenic influenza virus, fibrinous exudates are found in air sacs, oviduct, peritoneum

and pericardial sacs.

Mild to moderate infection

4. Inflammation of conjunctivae, trachea and air sacs

5. Pronounced congestion of the musculature

6. Ovarian regression in laying birds

7. Edema of the head with congestion, hemorrhages and cyanosis of the combs, wattles and

sinuses

8. Vesicles and ulceration of the comb

9. Petechial and ecchymosed hemorrhages in abdominal fat, various serosal and mucosal surfaces,

heart, gizzards, proventriculus and small intestine (ecchymosed : The passage of blood from

ruptured blood vessels into subcutaneous tissue, marked by a purple discoloration of the skin…

petechial A small purplish spot on a body surface, such as the skin or a mucous membrane,

caused by a minute hemorrhage and often seen in typhus )

10. The feet often appear edematous with hemorrhages. Red discoloration of the shanks is also

noted.

Newcastle Disease (NCD)

Velogenic Viscerotropic Newcastle disease (VVND) or Asiatic Newcastle disease (AND). 

NCD is in its chronic form an infection of domestic fowl with symptoms such as rejection of food, listlessness, abnormal breathing, discharge from eyes and greenish diarrhea. Mortality in chicken is 50 –80 %, but in adults much lower due to available vaccination. VVND is an acute, fatal infection of birds of all ages with predominant hemorrhagic lesions of the gastrointestinal tract, severe depression, and death

prior to clinical manifestations. This disease is caused by the most virulent strain of the Newcastle disease virus. The virus of VVND is very resistant and remains viable at extreme pH and temperature

ranges, and may remain viable in the bone marrow of poultry carcasses for weeks.

Transmission: 

Transmission is by direct contact, fomites, and by aerosols through coughing, gasping and respiratory fluids. The virus has a wind borne potential for spread creating quite a challenge for control and prevention. Faces and insect and rodent vectors are also involved in the transmission.

Antemortem findings:

1. The incubation period varies from 2 – 15 days.

2. Depression and loss of appetite

3. Sudden death

4. Edema of the head. Swelling of the lower eyelid, often accompanied by conjunctivitis.

5. Dark ring around the eye (black eye)

6. Excessive fluids from the respiratory tract

7. Paralysed wings and twisting of the head and neck (torticollis)

Postmortem findings:

Acute form

1. Peracute deaths will often show no discernible lesions in some of the first birds dying in an

outbreak.

2. The esophagus shows hemorrhage and erosions.

3. Edema of the head and neck

4. The mucosa of the trachea is frequently hemorrhagic.

5. Hemorrhages are throughout the gastrointestinal tract with a tendency to ulcerate and become

necrotic as the disease progresses.

6. In the intestine there is generally an inflammatory response and marked involvement of the

caecal tonsils and Peyer's patches.

7. The mucosal lining of the proventriculus is a frequent site of hemorrhage, especially at the

junction between the esophagus and proventriculus.

8. Edematous or hemorrhagic ovaries

9. In hens that have survived the disease, there is a tendency to lay misshapen eggs or develop

egg yolk peritonitis.

Chronic form

10. Catarrhal inflammation of the respiratory system

11. Edema in surrounding connective tissue

Infectious bronchitis (IB)

Infectious bronchitis is an acute, highly contagious viral disease of chickens, manifested by respiratory signs, renal disease and a significant drop in egg production.

Transmission: 

Airborne transmission in the direction of prevailing wind. The spread of infection is rapid in a flock. Some birds become carriers and shedders of the virus through secretions and discharges for many months after the infection. IB virus persists in contaminated chicken houses for approximately four

weeks.

Antemortem findings:

1. Indifference and depression

2. Sneezing, gasping and coughing

3. Nasal discharge

4. Abnormal respiratory sounds (rales)

5. Weakness and huddling near the light source

6. Reduced egg production in laying birds. Low egg quality and soft egg shells are noted.

7. Mortality due to kidney disease caused by the nephrotropic strain of the IB virus.

8. Inflammation of the air sacs may be a complication of IB.

Postmortem findings:

1. Serous, catarrhal and caseous exudates in the upper respiratory tract including nasal passages,

trachea, sinuses and bronchi

2. Cloudy air sacs

3. Abdominal air sacs may contain yellow caseous exudates.

4. Occasionally swollen and pale kidneys containing urolith deposits (uric acid crystals)

5. Yolk material or fully formed egg in the abdominal cavity in layer hens

6. Small cystic oviducts

Laryngotracheitis (LT)

LT is an acute viral disease of chicken characterized by difficult breathing, gasping and coughing up of bloody exudates.

Transmission:

Virus entry in LT is via the respiratory route and the intraocular route. Oral infection may also occur. The transmission from acutely infected birds is more common than from recovered or vaccinated birds. The latter may shed the virus for a prolonged period of time. Mechanical transmission via fomites is another possibility.

Antemortem findings:

1. Incubation 6 – 12 days following natural exposure

2. High morbidity and moderate mortality (10 – 20 %)

3. Difficult breathing and coughing

4. Loud gasping or wheezing sounds

5. In mild form of LT, lacrimation, nasal discharge, swelling of conjunctivae and sinuses and reduced

egg production.

Most chicken usually recover in 10 –14 days and up to 4 weeks in severe cases.

Fowl Pox (FP, Pox, Avian Pox)

Fowl Pox is a viral disease of chicken, turkeys and other birds distinguished by cutaneous lesions on the head, neck, legs and feet. It has a worldwide distribution and affects birds of all age groups, except the recently hatched.

Transmission: 

The virus is present in lesions and in desquamated scabs. It is resistant to environmental factors and persists in the environment for many months. It usually infects birds through minor abrasions. Mechanical transmission occurs by cannibalism. Some mosquitoes can transmit the virus from infected to uninfected birds. The virus can be also transmitted by injury to the skin.

Antemortem findings: 

Two forms of lesions are recognized; - the cutaneous (dry form) and the

diphtheria (wet form)

Cutaneous form

1. Low mortality

2. Lack of flock vigour and weight loss

3. A mild to moderate loss in egg production

4. Scabby lesions on the head, neck and unfeathered parts of the skin

Diphtheria form

5. Mortality low to moderate

6. Difficult breathing

7. Nasal and ocular discharge

Postmortem findings: 

The following stages of the pox lesions papules, vesicles and pustules may be observed.

Cutaneous lesions

1. Papules are light colored nodules.

2. Vesicles and pustules are raised and commonly yellow.

Diphtheria lesions

3. Buff to yellow plaques on mucous membranes in the mouth, esophagus and upper respiratory

tract

4. Occlusion of trachea, and death due to asphyxiation

Histopathology shows characteristic intracytoplasmic inclusion bodies (Bollinger bodies) in the infected epithelium.

Avian leucosis complex occurs in four separate disease entities:

1. Leucosis-sarcoma group (Lymphoid leucosis)

2. Marek's disease (MD)

3. Reticuloendotheliosis group (REV)

4. Lymphoproliferative agent of turkey

Transmission:

 L/S virus is transmitted by egg in vertical transmission and by shedders in horizontal transmission (chicken to chicken). Tumor lesions may or may not develop. Developed tumors can be differentiated by the bird's age on necropsy, histology and impression smears. In horizontal transmission, chicken which contract the virus after hatching develop antibodies; some will remain shedders, some will develop tumors and die, and others will overcome the infection. Infection from flock to flock is unlikely as the virus does not survive a long time in the environment. In many chickens the virus may be also in a latent state.

(A) Lymphoid leucosis (big liver disease, visceral lymphomatosis)

This disease is being studied because of its economic significance, and also as an experimental model

of cancer. Lymphoid leucosis is a B cell tumor which starts in the bursa and, before sexual maturity, may spread to other organs. Mature birds are more affected than young birds. Male birds are also affected in lesser numbers than female due to the earlier regression of bursa in male birds.

Antemortem findings:

1. The disease occurs in 14 – 30 weeks old birds.

2. Pale, shriveled comb and loss of appetite

3. Dehydration and emaciation

4. Diarrhea, green scant faces

5. Enlarged liver, bursa of Fabricius and kidneys

6. Distended abdomen due to enlarged liver

7. Reduced egg production

Postmortem findings:

1. Grey tumor lesions in the liver , spleen and bursa

(B) Marek's Disease (Polyneuritis, Fowl paralysis, Neurolymphomatosis gallinarum)

Marek's disease is caused by the herpes virus (DNA).

Transmission: 

It is spread by airborne infection involving follicle cells called chicken dander.

Transmission of the virus is horizontal. At room temperature the virus of Marek's disease remains viable

Marek's disease is commonly associated with coccidiosis in the field. This is probably due to lack of

immunity against coccidiosis in birds affected with Marek's.

There are 6 types of Marek's disease.

1. Peracute in 3–5 weeks old chicks; manifested with sudden death

2. Anemia in 3–6 weeks old chicken

3. Classical Marek's disease (range paralysis) showing paralysis of two wings and legs due to

peripheral nerve involvement. The nerves are 2–3 times their normal size. Central nerve

involvement may also occur.

4. Acute Marek's disease occurs mainly in 6–12 weeks old birds. It is manifested with tumors in the

liver, spleen, kidneys, brain, spinal cord and dorsal root ganglia and with sudden death. The

heart, lungs, gonads and muscles may also be involved.

5. Skin leucosis. Noted in broiler chicken on postmortem examination in abattoirs as enlargement of

feather follicles and associated lymphoid infiltrations

6. Transient paralysis in 12–18 weeks old pullets become paralyzed and may recover with 24 hours

if moved to a quiet place.

Postmortem findings:

1. Skin neoplasia

2. Enlarged spleen

3. Diffuse proliferation of white pulp

Ornithosis (Psittacosis, Avian chlamydiosis)

Ornithosis is an acute or chronic disease of turkeys, ducks, chicken, pheasants and pigeons. It is caused by Chlamydia psittaci. In psittacoses birds such as parrots, parakeets, cockatoos, macaws etc. and humans, this disease are called psittacosis.

Transmission: 

Wild carrier birds and cage birds transmit Chlamydia to their nestling which may survive and become carriers. Carrier birds shed Chlamydia in their secretions and excretions. Chlamydia present in faecal dust may be inhaled or ingested. Pigeons are suspected of being dissemination of infection.

Antemortem findings:

1. Mild cases may be unobserved or show mild respiratory signs and diarrhea

In turkeys

2. Depression and weakness

3. Reduced weight

4. Nasal discharge

5. Green yellow diarrhea

6. Watery diarrhea in ducks, geese

In pigeons

7. Unilateral or bilateral conjunctivitis

8. Depression and loss of appetite

9. Abnormal respiratory sounds (rales) and watery diarrhea

Postmortem findings:

1. Inflammation of the lungs, air sacs, liver, heart, spleen, kidneys and peritoneum

In turkeys

2. Wasting

3. Vascular congestion

4. Fibrinous inflammation of pericardium, air sacs, lungs

5. Congestion of the lungs and an enlarged congested spleen

In pigeons

6. Swollen eyelids and conjunctivitis

Dr.khaled fujairah municipality 15

Differential diagnosis of bird flu

7. In cage birds enlarged spleen and liver, inflammation of the air sacs and pericardium and

intestinal congestion.

Diseases caused by bacteria

Salmonellosis

Salmonellosis is responsible for significant losses to the poultry industry. Salmonella infections in this include pullorum disease, fowl typhoid, Arizona infection and paratyphoid. Pullorum disease

occurs in chicken and turkeys and is caused by Salmonella pullorum. The greatest losses are in chicken less than 4 weeks old.

Antemortem findings (in young chicks):

1. Anorexia

2. Diarrhea

3. Pasting of vent

4. Stunted, unthrifty

5. Poor feathering

6. Pale shrunken comb and wattles

Postmortem findings:

1. Multiple grey nodules in the heart, lungs, liver, spleen, peritoneum, the gizzard, intestine and

pancreas of a poult

2. Abnormal ovary showing discolored follicles in an adult bird

3. Rarely peritonitis, ascites or oviduct impaction

4. Swelling of the tibiotarsal joint

Paratyphoid infection

Paratyphoid infection is an acute and chronic infection of poultry and mammals. Ten to twelve species of Salmonella are associated with most outbreaks in poults. The most commonly involved is S.typhimurium in birds less than one month old.

Antemortem findings:

1. Drooping wings

2. Shivering and huddling near a heat source

3. Muscular in coordination and trembling

Postmortem findings:

1. Nodular lesions in the pancreas

2. Button type lesion in the intestine

3. Enteritis

4. Dehydration

5. Unabsorbed yolk material and omphalitis

6. Less frequent are joint infections

7. Blindness

8. Swollen eyelids

Tuberculosis

Tuberculosis is a chronic granulomatous disease of poultry caused by Mycobacterium avium. It is usually found in older chicken which are kept beyond the laying season. Other poultry are also affected.

Antemortem findings:

1. Depressed and progressive loss of weight leading to emaciation

2. Pale skin of the face, wattles and comb

3. Dull, ruffled feathers

4. Diarrhea

5. Unilateral lameness

Postmortem findings:

1. Irregular grayish yellow or grayish white nodules of different sizes in the liver, spleen, and

intestine

2. In advanced cases, TB nodules are found in the bone marrow.

3. Lesions are rarely found in the heart, ovaries, testes and skin.

4. TB lesions on organ surfaces are easy enucleated from the surrounding tissue. Mineralization is

not present in the lesions.

“Air sac disease” and Chronic Respiratory Disease (CRD)

The term “Air sac disease” usually refers to a respiratory syndrome characterized by airsacculitis, per

hepatitis and pericarditis in broiler chickens between 4 – 8 weeks of age. Pneumonia is also frequently present. Primary factors associated with the etiology of air sac disease are poor air quality and dust, associated with either viral or mycoplasmal agents. E. coli is usually a secondary invader.

Chronic respiratory disease (CRD) refers to respiratory infection of the upper respiratory tract of chicken caused by Mycoplasma gallisepticum. This agent affects turkeys more severely and causes infectious sinusitis.

Postmortem findings: 

Postmortem examination of affected chicken reveals inflammation of trachea and frothy exudates in the air sacs. With presence of secondary invaders, inflamed air sacs have an opaque appearance in the early stages of infection. In the later stages air sacs are thickened and caseous yellow exudates is usually present. Yellow fibrinous deposits on the pericardium (pericarditis) and liver (per hepatitis) are also observed.

Parasitic diseases

Diseases caused by protozoa

Trichomoniasis, Canker, frounce

Introduction:

Trichomonas gallinae is a protozoan parasite of pigeons & doves (canker), raptor (frounce), turkeys & chickens. It has variable pathogenicity. Morbidity is high & mortality varies but may be high.

Transmission is via oral secretions in feed & water, & crop milk.

Post mortem lesions

1- Yellow plaques & raised cheesy masses in mouth, pharynx, esophagus, crop & preventriculus.

2- Reptors may have liver lesions.

Histomoniasis (Enterohepatitis or Blackhead)

Histomoniasis is a protozoa disease of turkeys, chicken and game birds. It often occurs in turkeys run

with or after chicken. It is caused by Histomonas meleagridis which is transmitted in the ova of caecal worms (Heterakis gallinarum) and by earth worms. Well developed hepatic and caecal lesions are pathognomonic for histomoniasis.

Antemortem findings:

1. In young turkeys, mortality and morbidity may reach 100 %.

2. Indifference and loss of appetite

3. Depression, drooping wings and closed eyes

4. Cyanotic (black) head

5. Yellow sulphur colored faces

6. Blood in faces

7. Emaciation in older birds

Postmortem findings:

1. The ceca are characterized with a thickened wall, ulcerated mucosa and caseous exudates.

2. If the caecal wall becomes perforated, inflammation of the peritoneum is observed.

3. The liver lesions consist of circular yellow necrotic tissue surrounded with white rings.

Coccidiosis

Coccidiosis is a major disease problem in commercial poultry and the most common cause of enteritis. It is caused by various species of the protozoan genus Eimeria. At least nine species have been described in chicken. The most important of these are E. acervulina, E. brunetti, E. maxima, E. necatrix and E. tenella.

The identification of different species of coccidia is based on the distribution of the lesion in the intestine, gross and microscopic appearance, and the size and shape of oocysts. Coccidia are species specific which means that coccidia in chicken will not be found in turkeys and vice versa.

Whether the coccidia actually cause illness or death of the bird depends on the species, dose, and

location of parasitic reproduction and immune status of the bird.

Birds affected with Marek's disease and IBD are more susceptible to coccidiosis.

If parasitic reproduction occurs in the epithelium of the intestine, disease follows and if it occurs

sub endothelially, the birds usually bleed to death in acute cases. With ingested oocysts moving to the intestinal lining, the life cycle of coccidia begins. Intestinal cells are damaged and in 4 – 8 days, depending on the species, oocysts are shed in the faces. Within 12 – 30 hours in a moist environment and in a temperature of 20 – 30°C, the oocysts sporulate and become infective. Birds raised on the range will have more outbreaks of this condition in the spring and summer compared to birds raised in total confinement of barnyards. In the latter, outbreaks can occur at any time. Coccidiosis causes severe losses in intensive broiler production and in layers; it causes a drop in egg production. This is in spite of great discoveries of many different coccidiostats. Even when the disease is controlled, medication expenses run very high.

1. Ruffled feathers

2. Anemia and dehydration

3. Retracted head and neck

4. Bloody diarrhea

5. Weight loss

Findings in poults include:

6. Listlessness and droopiness

I. Chicken coccidiosis

(A) E. acervulina

E. acervulina is found in the duodenum and upper jejunum. It is frequent in growing birds and broilers and causes duodenal coccidiosis.

Postmortem findings:

1. Whitish transverse lesions which may coalesce.

2. Parasite location in tissue section is epithelial.

(B) E. brunetti

E. brunetti is found in the lower small intestine, rectum and proximal part of ceca.

Postmortem findings:

1. Fibrinous inflammation of the intestine (fibrinous enteritis) with bloody mucous exudates

2. Whitish blood streaked faces

(C) E. maxima

E. maxima is found in the middle part of the small intestine and less frequently, throughout the intestine

Postmortem findings:

1. Hemorrhagic enteritis showing a thickened wall and petechial hemorrhage

2. Large oocysts on microscopy

(D) E. tenella

E. tenella is found in the ceca. It causes caecal coccidiosis.

Postmortem findings:

1. Hemorrhage in the ceca

2. In later stages core, of clotted blood and thickened whitish mucosa

3. In young birds, bloody diarrhea

(E) E. necatrix

E. necatrix is found in the middle part of the intestine near the yolk sac diverticulum. In severe cases, this coccidium is observed throughout the intestine and ceca. It causes acute mortality and weight loss in laying birds.

Postmortem findings: Intestinal distention, mucous blood filled exudates and white spots noted on the

serosa Coccidiosis. Hemorrhage in the ceca characteristic of E. tenella infection. Intestinal distention, mucous blood filled exudates and white spots noted on the serosa with E. necatrix infection.

II. Coccidiosis in turkeys

Three species of coccidia in turkeys are considered pathogens. These include E. meleagrimitis, E.

adenoeides and E. gallopavonis.

(A) E. meleagrimitis

E. meleagrimitis is found in small intestine. It is the most pathogenic for turkeys.

Antemortem and postmortem findings:

1. Dehydrated birds showing the breast skin adhering to underlying muscles

2. Severe inflammation in duodenum and upper jejunum

3. The upper part of intestine contain excessive fluid and the lower part contain a greenish mucus

(B) E. adenoeides

E. adenoeides is found in the lower small intestine, ceca and large intestine.

Postmortem findings:

1. Severe inflammation of intestinal mucosa and swollen and edematous intestinal wall

2. Fluid faces with mucus and small amount of blood

(C) E. gallopavonis

E. gallopavonis is found in the lower one-third of small intestine, large intestine and ceca.

Postmortem findings:

1. Necrotic enteritis associated with creamy white exudates

2. Thickened and damaged intestinal wall devoid of food