Systematic Veterinary Virology

LABORATORY DIAGNOSIS

Virus isolation and identification

• Clinical materials: Samples from dead birds should consist of oro-nasal swabs, as well as samples collected from lung, kidneys, intestine (including contents), spleen, brain, liver and heart tissues. These may be collected separately or as a pool.
• Virus isolation: virus isolation is attempted by inoculating 9- to 11-day-old embryonating chicken eggs. Amnioallantoic fluid (AAF) is collected from all embryos dying after 24 hours postinoculation and tested for hemagglutination (HA) activity. If positive, the hemagglutination-inhibition (Hl) test is used with known NDV-positive serum to confirm the presence of NDV in the AAF. If NDV is found, it is characterized by inoculating 4- to 6-week-old chickens free of ND antibodies with the suspect AAF by swabbing the cloaca, instilling into the nares or conjuctival sac, or injecting into the thoracic air sac. If VVND virus is present, the inoculated chicks usually die in 3 to 7 days, revealing typical visceral lesions on postmortem examination. Neurotrophic  viruses will cause severe neurologic and respiratory signs in inoculated chickens but no visceral lesions. If no bird dies in 10 days, the APMV-1 is not considered to be the velogenic, viscerotropic type but is either a lentogenic or mesogenic.
• Nucleic acid identification methods: The virus can also be identified from clinical materials and AAF by RT-PCR (Reverse transcriptase Polymerase chain reaction) using primers for F gene.
• Nucleic acid probes
• ELISA techniques: Antigen capture and Antigen competitive ELISA techniques can also be used to identify APMV-1 from clinical materials and AAF.