In vivo virology
Procedure for the isolation and detection of viruses from avian species using embryonated eggs
This protocol details the procedure to isolate the causative virus in embryonated eggs to allow for diagnosis of viral disease in avian species. Embryonated eggs are inoculated with the supernatant from the centrifugation of homogenised sample material suspended in antibiotic solution. Statutory testing on samples received in the National and International Reference Laboratory APHA are routinely inoculated into the allantoic cavity of 9-11 Specific Pathogen Free embryonated fowl eggs. The effect on the embryos is examined and presence of a haemagglutinating virus in the allantoic fluids is detected using haemagglutination testing. Samples with positive haemagglutination may be typed to determine the haemagglutinating agent. Note that the absence of isolated virus cannot rule out current viral infection.
Sources
WOAH Manual of Diagnostic Tests and Vaccines for Terrestrial Animals
Protocols
The Intravenous Pathogenicity Test for avian influenza
This protocol details the intravenous pathogenicity test (IVPI) used to determine whether an avian influenza virus is highly pathogenic by observing clinical signs in infected birds over a 10-day period. The birds are examined and scored 0 (normal) to 3 (dead) dependent on severity of clinical signs, the intravenous pathogenicity test index (IVPI) can then be calculated from these scores. This test is normally only performed on H5 and H7 isolates which have been determined as LPAI by conventional sequencing or on index cases of an outbreak. In the UK, IVPI can only be performed by trained staff who hold a HO license.
Sources
WOAH Manual of Standards for Diagnostic Tests and Vaccine
Protocols
The Intracerebral Pathogenicity Index Test for Avian Orthoavulavirus Type 1
This protocol details the Intracerebral Pathogenicity Index Test (ICPI) used to determine the pathogenicity of a viral isolate by observing clinical signs in infected birds over an 8-day period. It involves determining the mean death time in day-old chicks. Avian paramyxovirus type 1 (APMV-1) is defined by WOAH as an infection of birds caused by a virus of AOAV-1 serotype 1 that has an ICPI in day-old chicks of 0.7 or greater. ICPI is not routinely performed on all AMPV-1 isolates due to the severity of procedure and is only usually carried out on APMV-1 isolates which are determined as low virulence by conventional sequencing or on index cases of an outbreak. In the UK, ICPI can only be performed by trained staff who hold a HO license.
Sources
Council Directive 1992: 92/66/EEC 6
WOAH Manual of Standards for Diagnostic Tests and Vaccines