Isolation & Identification of FAV-4 Tianjin Strain and Pathogenicity to Chicks

Abstract

The Hydropericardium-hepatitis Syndrome (HHS) caused by Fowl adenovirus 4 (FAV-4) is a new epidemic disease in recent years and firstly reported in Tianjin, 2016. The isolation, identification and pathogenicity of FAV-4 Tianjin strain were studied in the paper for providing the theoretical basis to the law of occurrence, development and termination. The virus was isolated and identified from dead & sick birds on a chicken farm in Tianjin by chicken embryo inoculation with tissue homogenate supernatant, PCR and sequencing experiment with viral allantoic fluid; And the pathogenicity was proceeded by inoculating the isolate into 100 one-day-old chicks, which divided into group A, B, C (experimental group) and group D (control), the symptoms, mortality and morphological changes were observed daily, meanwhile the virus was detected by PCR to be sure the same as inoculating strain. The results show that the isolate was 665bp in electrophoresis, had homology of 98.3%-97.3% with FAV-4 by sequencing analysis and finally named as FAV-4 TJ1607 strain in GenBank; They also show in Pathogenicity research that the symptoms were appeared on the 3nd day, death on the 4th day and the peak of death on the 5th day and end of the 8th day in group A and B; The mortality was 64% in group A and 72% in group B; Hepatic edema & congestion, large amounts of basophilic intranuclear inclusions, hydropericardium, parechymal myocarditis and pulmonary edema were observed obviously on the 4th day in group A and B; ALL above changes were the same in group C just appeared 3 days later except death trend and mortality for 32%; And FAV-4 TJ1607 was detected in all experimental groups. The measures of prevention and treatment will be recommended in poultry industry accordance with the HHS disease model.