Assessment of predisposing effect of Chicken Anaemia Virus (CAV) in Gangrenous Dermatitis (GD) outbreaks in commercial layer chicken

Abstract

Gangrenous dermatitis (GD) is an economically important disease in commercial layer chicken and its severity have increased for the past few years despite effective farm management system and suitable antibiotic treatments. This study was designed to explore the immunosuppressive role of Chicken Anaemia Virus (CAV) in gangrenous dermatitis outbreaks in Namakkal region of Tamil Nadu, India. Thirty commercial white leghorn layer flocks were investigated in and around Namakkal District of Tamil Nadu State, India. Detailed farm history was collected. Serum and blood samples were collected to screen the antibody titer and haemogram, respectively. Heart blood, liver samples from dead birds and cutaneous swabs from ailing and dead carcasses were taken to identify the bacterial etiology. Detailed necropsy was conducted and the gross lesions were recorded. Thymus, bone marrow, liver and muscle were collected for screening of CAV by Polymerase chain reaction and histopathological studies. The sera samples showed 100 per cent positivity for CAV and the blood profile showed anaemic picture. The GD affected birds showed anaemia, severe serosanguinous, haemorrhagic and gangrenous lesions in wings, suncutaneous tissue and interdigital space of toes. Necropsy revealed severe gangrene, extravasation of serosanguinous fluid from the skin, hypoplasia of thymus and paleness of bone marrow. Microscopic examination showed hypoplasia / atrophy of thymus and replacement of erythropoietic tissue of bone marrow with fat cells. Cultural examination exhibited the presence of Closrtidium perfringens, Staphylococcus aureus and E. coli. The significance of the study was that CAV is the major culprit in GD outbreaks in poultry which invites the diverse etiological agents by its immunosuppressive action.