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Diagnosis, epidemiology and pathogenicity of chicken astrovirus - OD0347

Infectious diseases affecting the digestive tract of commercial poultry cause animal health and welfare problems and considerable economic losses to poultry producers. Although death rates can be high, more typically enteric diseases affect the value of the flock by depressing growth rate. Enteritis in poultry is associated with a variety of viruses, the most common being known as "rotaviruses", "astroviruses" and "enterovirus-like viruses (ELV)". Although the detailed composition of rotaviruses and astroviruses are known, comparatively little is known about ELVs except that they are small round viruses. Earlier work in our laboratory identified 4 different ELV types in chickens, named ELV 1, ELV 2, ELV 3 and ELV 4. Experimental evidence indicated that ELVs 1, 3 and 4 were capable of causing growth retardation in
chickens. Investigation of samples from UK flocks that were experiencing severe growth depression problems in 2004-05 indicated the presence of at least one and frequently all 3 of these ELV types. In addition, investigation has shown that ELV 3 can be detected in eggs that fail to hatch and that it may be causing hatchability and growth problems for the
newly-hatched chick. However, the exact extent of the disease problems caused by these ELVs to the UK and global chicken industry remains unknown due to the lack of convenient diagnostic tests. A major reason for this lack is that, so far, it has not been possible to grow these ELVs in cultured cells, and this also explains why details of ELV composition including knowledge of its genetic information or genome have not yet been determined. Research investigations performed elsewhere have recently identified 2 types of chicken astrovirus, named type 1 (CAstV-1) and type 2 (CAstV-2), and we have recently shown that these correspond to ELV 1 and ELV 4 respectively. In very recent work in our laboratory, novel molecular methods have been applied to isolate and identify a small part of the genome of ELV 3. On
the basis of this genetic information, known as "nucleotide sequence", this ELV was characterised as a novel chicken astrovirus, which we have named chicken astrovirus type 3 (CAstV-3). Knowledge of some of the nucleotide sequence of CAstV-3 has created the possibility of developing a new type of diagnostic test, based on the detection of virus nucleic acid, which is sensitive, specific and convenient. The main aims of this project are to develop such a test for CAstV-3, and to apply this test to determine the occurrence of this virus in flocks with hatchability, enteritis and growth
depression problems. A second type of diagnostic test will also be developed and applied. This test will detect antibodies to the virus, which are produced by chickens in their blood (serum) in response to virus infections. In this project antibody-detecting diagnostic tests will be developed and applied to determine the prevalence of CAstV-1, 2 and 3 infections in broiler flocks (used for meat) and in their parent (breeder) flocks. Application of diagnostic tests for detecting virus and virus-specific antibody will allow us to determine how widespread infections are and to assess the importance of CAstV-3 infections in causing disease problems. Additional experiments will be undertaken to determine whether older chickens are less severely affected by CAstV-3 infection than young chicken and to determine whether antibody transferred via the egg to the young chick from the parent hen can protect against disease. This knowledge combined with that relating to the prevalence of infection will help to indicate whether methods for controlling disease caused by chicken astroviruses in general and CAstV-3 in particular are likely to be feasible. More specifically, the knowledge gained will be useful in deciding whether vaccination of parent flocks is likely to protect against disease
problems relating to growth depression in broilers and impaired hatchability.
Project Documents
• EVID4 - Final project report : OD0347 Final Report   (258k)
Time-Scale and Cost
From: 2006

To: 2009

Cost: £78,021
Contractor / Funded Organisations
BBSRC Central Office
Animal Health              
Avian Diseases              
Chicken Astrovirus              
Plants and Animals              
Fields of Study
Animal Health