INVESTIGATION ON FOWL ADENOVIRUS (GROUP 1) CIRCULATING IN BANGLADESH AND MOLECULAR CHARACTERIZATION OF SPECIFIC SEROTYPES ASSOCIATED WITH INCLUSION BODY HEPATITIS

Abstract

Fowl adenoviruses (FAdVs) cause numerous diseases resulting in economic losses to the poultry industry worldwide. Several FAdV serotypes cause inclusion body hepatitis in chicken. Although FAdV infection was suspected, there was no confirmatory report from Bangladesh. The study was conducted to investigate the FAdV infection and specific antibodies in chicken. A total of 50 samples, each composed of liver and spleen, were collected from different chickens of Gazipur, Dinajpur and Panchagarh district. Three suspected organ samples derived from liver were also inoculated in to SPF embryonated chicken eggs for viral propagation. Each location is belonging to A, B and C poultry zones of Bangladesh, respectively. Viruses were detected by real-time PCR and conventional PCR. Blood samples (n=303) were collected at beginning and after recovery from infection and tested by indirect ELISA. Sequencing of PCR products were done for phylogenetic analysis. The indirect ELISA serological technique was employed which detects antibodies to Group 1 FAdVs and does not differentiate specific serotypes. Specific serotypes were detected through real time PCR and sequencing data analysis. All the flocks exhibited clinical symptoms of anorexia, drowsiness, ruffled feathers, reduced body weight, lack of uniformity and high mortality. Enlarged friable liver with yellow to tan color mottled with focal soft area, fluid in pericardial sac, swollen and hemorrhagic kidneys, enlarged congested spleen and hemorrhagic pancreas were found on postmortem examination. FAdVs were detected in 9 flocks (90%) out of 10 flocks except commercial layer flock from Dinajpur. Three serotypes namely serotype 8b in 7flocks (70%), serotype 11 in 2 flocks (20%) and serotype 5 in 1 flock (10%) were detected. The antibody titer increases significantly (p<0.05) after recovery from the infection. Phylogenetic analysis revealed that the Bangladeshi FAdVs have close identity with viruses from Asia, Europe, South and North America. These results implied that FAdVs have been introduced to Bangladesh multiple times. In this situation vaccination against detected particular serotypes associated with IBH (Inclusion Body Hepatitis) and upholding comprehensive biosecurity measures are crucial for the prevention and control of the disease.