DISEASES AFFECTING POULTRY

By Penjani Nzima

THE cold season willsoon be a thing of the past here in Zambia and that automatically marks theentrance of the warm to hot season.

As the year 2023 is slowly but surely movingtowards the end, the temperatures are also beginning to rise much more when wehit October the hottest month here in this country.

The hot season comes along with its ownchallenges just like the cold season had to the poultry farmers. These farmersmust be on the look out for the common diseases that may affect their flockduring this time of the year.

And According to Sherebiah Kangwa NewcastleDisease (NCD) and Infectiousbronchitis (IB) are some of the common poultry diseases.

NCD is in its chronic form an infection of domestic fowl withsymptoms such as rejection of food, listlessness, abnormal breathing, dischargefrom eyes and greenish diarrhoea.

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-bornepotential for spread creating quite a challenge for control and prevention.Faeces 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. Haemorrhages 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 haemorrhage, especially     at the junction between the oesophagus and proventriculus.
8. Edematous or     haemorrhagic 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.

Birds with VVND or NCD should not be admitted to the abattoir. Ifdisease is suspected laboratory confirmation should be obtained. If confirmed,carcass is condemned and premises with equipment should bedisinfected.

In case that laboratory confirmation is not possible, suspectedcarcasses should be also condemned. In some countries compensationis paid for condemned birds.

INFECTIOUS BRONCHITIS (IB)

INFECTIOUS bronchitis is an acute, highly contagious viral diseaseof chickens, manifested by respiratory signs, renal disease and a significantdrop in egg production.

Transmission 

Airborne transmission in the direction of prevailing wind. Thespread of infection is rapid in a flock. Some birds become carriers andshedders of the virus through secretions and discharges for many months afterthe infection. IB virus persists in contaminated chicken houses forapproximately 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 exudate in the upper respiratory tract including     nasal passages, trachea, sinuses and bronchi.
2. Cloudy air     sacs.
3. Abdominal air     sacs may contain yellow caseous exudate.
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.

Affected birds are treated as suspects on antemortem inspection. Acarcass showing acute signs of clinical disease accompanied with emaciationis condemned. A carcass in good flesh and without systemic changesis approved. The affected parts are condemned.

FAO

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