1. Newcastle Disease (ND)
- Causative Agent: Newcastle Disease Virus (NDV)
- Family: Paramyxoviridae
- Genus: Orthoavulavirus
Transmission
- Direct contact with infected birds or secretions (droppings, nasal discharge).
- Aerosol and contaminated feed, water, or equipment.
Replication Cycle
- Virus attaches via hemagglutinin-neuraminidase (HN) to host cell receptors.
- Fusion, replication in cytoplasm, assembly, and release by budding.
Pathogenesis
- Tropism for respiratory, gastrointestinal, and nervous systems.
- Varying virulence (lentogenic, mesogenic, velogenic strains).
Clinical Signs
- Respiratory distress (coughing, nasal discharge).
- Neurological signs (torticollis, paralysis).
- Drop in egg production and diarrhea.
Control
- Live and inactivated vaccines.
- Biosecurity and movement control.
2. Infectious Bronchitis (IB)
- Causative Agent: Infectious Bronchitis Virus (IBV)
- Family: Coronaviridae
- Genus: Gammacoronavirus
Transmission
- Aerosolized respiratory secretions.
- Indirect via contaminated surfaces.
Replication Cycle
- Virus binds to receptors using spike protein (S).
- Replicates in the cytoplasm and buds through the endoplasmic reticulum.
Pathogenesis
- Targets respiratory, renal, and reproductive systems.
- Damage to ciliated epithelium and secondary bacterial infections.
Clinical Signs
- Sneezing, coughing, nasal discharge.
- Nephritis (wet droppings).
- Poor-quality eggs and production drop.
Control
- Live attenuated and inactivated vaccines.
- Biosecurity and proper ventilation.
3. Marek’s Disease (MD)
- Causative Agent: Marek’s Disease Virus (MDV)
- Family: Herpesviridae
- Genus: Mardivirus
Transmission
- Inhalation of infected feather dander or dust.
Replication Cycle
- Initial replication in respiratory epithelium.
- Latency in lymphocytes; productive replication in feather follicles.
Pathogenesis
- Lymphoid tumor formation, peripheral nerve infiltration, immunosuppression.
Clinical Signs
- Paralysis, weight loss, visceral tumors.
- Grey eye (ocular form).
Control
- Vaccination (HVT, bivalent vaccines).
- Biosecurity and hygiene.
4. Avian Influenza (AI)
- Causative Agent: Avian Influenza Virus (AIV)
- Family: Orthomyxoviridae
- Genus: Alphainfluenzavirus
Transmission
- Direct contact with infected birds, secretions, or excretions.
- Indirect via contaminated water, equipment, or wild birds.
Replication Cycle
- Attachment via hemagglutinin (HA), fusion, replication in the nucleus, release via neuraminidase (NA).
Pathogenesis
- LPAI: Mild respiratory disease.
- HPAI: Systemic infection with high mortality.
Clinical Signs
- Sudden death, cyanosis, edema.
- Hemorrhages on legs and internal organs.
Control
- Vaccination in endemic regions.
- Movement restrictions and biosecurity.
5. Infectious Bursal Disease (IBD)
- Causative Agent: Infectious Bursal Disease Virus (IBDV)
- Family: Birnaviridae
- Genus: Avibirnavirus
Transmission
- Fecal-oral route; highly stable in the environment.
Replication Cycle
- Replicates in bursa-associated lymphoid tissue.
Pathogenesis
- Targets immature B lymphocytes in the bursa, causing immunosuppression.
Clinical Signs
- Vent pecking, dehydration, whitish diarrhea.
- Secondary infections due to immunosuppression.
Control
- Live attenuated and inactivated vaccines.
- Hygiene and biosecurity.
6. Fowl Pox
- Causative Agent: Fowlpox Virus
- Family: Poxviridae
- Genus: Avipoxvirus
Transmission:
- Mechanical (bites of mosquitoes or other insects).
- Direct contact with infected birds.
Replication Cycle:
- Cytoplasmic replication; forms characteristic inclusion bodies.
Pathogenesis:
- Localized or systemic infection.
- Skin and mucosal lesions.
Clinical Signs
- Cutaneous nodules, diphtheritic plaques in mucosa.
Control
- Vaccination (wing-web puncture method).
- Mosquito control and biosecurity.
7. Infectious Laryngotracheitis (ILT)
- Causative Agent: Gallid herpesvirus 1
- Family: Herpesviridae
- Genus: Iltovirus
Transmission
- Aerosolized respiratory secretions.
Replication Cycle
- Replicates in the nucleus of epithelial cells.
Pathogenesis
- Tracheal inflammation and pseudomembrane formation.
Clinical Signs
- Severe respiratory distress, gasping.
- Blood-stained mucus and high mortality in severe cases.
Control
- Live attenuated vaccines.
- Strict biosecurity.
8. Chicken Anemia Virus (CAV)
- Causative Agent: Chicken Anemia Virus
- Family: Circoviridae
- Genus: Gyrovirus
Transmission
- Vertical (hen to chick via eggs).
- Horizontal (feces or respiratory secretions).
Replication Cycle
- Targets hemocytoblasts in the bone marrow and thymus.
Pathogenesis
- Anemia, lymphoid depletion, immunosuppression.
Clinical Signs
- Pale combs, anemia, secondary infections.
Control
- Vaccination of breeder flocks.
- Hygiene and biosecurity.
By controlling these diseases through vaccination, biosecurity, and hygiene practices, poultry farmers can minimize losses and maintain healthy flocks. Let me know if you’d like further details on any specific disease.