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Questions and Answers
What is the name of the avian disease that is also known as 'Big liver disease' and 'visceral leucosis'?
Lymphoid Leucosis
What percentage of birds are typically affected by tumor mortality in Lymphoid Leucosis?
1%–2% of birds
What is the name of the family of viruses that causes Lymphoid Leucosis?
Retroviridae
How many subgroups of the Avian Leukosis Virus have been classified?
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Which subgroup of the Avian Leukosis Virus is most prevalent and most frequently associated with Lymphoid Leucosis?
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What is the effect of subclinical infection on chicken flocks?
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What is the excess mortality per week that has been reported in commercial broiler-breeder flocks naturally infected with subgroup J avian leukosis virus?
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Which birds are susceptible to Lymphoid Leucosis?
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What is the characteristic of all field strains of avian leukosis virus?
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What is the significance of recombinant avian leukosis viruses isolated from field cases of myeloid leukosis in commercial layers?
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How do congenitally infected chickens transmit the virus to other birds?
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What is the mechanism of horizontal infection in chickens?
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Where does the replication of the ALSV occur?
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What is the characteristic of genetically resistant birds in a susceptible flock?
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What is the category of genetically susceptible birds in an infected flock?
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What is the significance of the category V+A+ in avian leukosis virus infection?
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Study Notes
Avian Leucosis Complex
- Avian leucosis complex occurs in four separate disease entities: Leucosis-sarcoma group (Lymphoid leukosis), Marek's Disease, Reticuloendotheliosis group (REV), and Lymphoproliferative agent of turkey.
Lymphoid Leucosis
- Also known as Big Liver Disease or Visceral Leucosis.
- Widely distributed worldwide in countries with developed industrial poultry breeding.
- Typically observed in birds at the age of 16 weeks and older.
- Accounts for 1%-2% of tumor mortality, with occasional losses of ≥20%.
- Subclinical infection can decrease egg production and quality.
- Can cause 1.5% excess mortality per week in commercial broiler-breeder flocks.
Causing Agent
- Caused by Alpharetrovirus genus of the family Retroviridae.
- Classified into 10 subgroups: A, B, C, D, E, F, G, H, I, and J.
- Subgroup A is most prevalent and frequently associated with Lymphoid Leukosis.
- Viruses are oncogenic, with differences in oncogenicity and replicative ability.
- Recombinant avian leukosis viruses can occur in field conditions, causing economic losses.
Transmission
- Transmission occurs vertically through egg albumin from one generation to another.
- Congenitally infected chickens fail to produce neutralizing antibodies and remain viremic for life.
- Horizontally infected chickens have a transient viremia followed by antibody production.
- Horizontal infection possible in chickens in the first few days after hatching, usually via contaminated vaccines.
Virus Replication
- Replication occurs in albumin-secreting glands of the oviduct.
- Four classes of avian leukosis virus infection are recognized in mature chickens:
- V-A-: No viremia, no antibody (birds in an infection-free flock and genetically resistant birds).
- V-A+: No viremia, with antibody.
- V+A+: With viremia, with antibody.
- V+A-: With viremia, no antibody (genetically susceptible birds in an infected flock).
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Description
Explore neoplastic diseases in animals, including lymphoid leucosis and Marek's disease. Learn about the different disease entities and their characteristics.
