SOME STRAINS OF SEROTYPE-4 FOWL ADENOVIRUSES CAUSE INCLUSION-BODY HEPATITIS AND HYDROPERICARDIUM SYNDROME IN CHICKENS

Fowl adenoviruses were isolated and characterized from severe cases of hydropericardium syndrome in Ecuador and Pakistan. All were neutraliz ed by antibodies against serotypes 4 and 11. Cross-neutralization test s and restriction enzyme analysis strengthen the classification as ser otype 4 strains. The restriction endonucleases used allowed the differ entiation among field isolates and reference strains. All field isolat es tested induced high embryo mortality. One-day-old specific pathogen free (SPF) chicks were infected with 10(5) plaque-forming units by na tural routes to reproduce the disease with plaque purified virus. Wher eas no mortality was seen with the reference strain, the mortality wit h the field isolates was 100%. A reduced mortality occurred with a low er infectious dose. Field isolate K1013 from Ecuador was also highly p athogenic for 1- to 3-week-old SPF chicks after intramuscular inoculat ion. The main pathological sign's were swollen livers, severe hydroper icardium and nephritis, reflecting the field situation and underlining the role of FAV4 strains in the aetiology of infectious hydropericard ium.