Pathological and Molecular Characterization of Aspergillus niger Associated Aspergillosis in Indian Runner Ducklings

Abstract

An outbreak of aspergillosis in Indian Runner ducklings was investigated using pathological, microbiological and molecular approaches. The affected flock was reared on a harvested rice field with waterlogged areas, and nine-day-old ducklings developed dyspnoea, gasping and sudden mortality. Five moribund ducklings were examined. Necropsy revealed emaciation, ruffled feathers, turbid nasal exudation, severe pulmonary consolidation, multiple white-to-yellow caseous granulomatous nodules and cloudy, thickened air sacs. Histopathological examination of the lungs showed vascular congestion, bronchiolar oedema and necrotic nodular lesions surrounded by proliferating fibrous tissue, macrophages and giant cells. Grocott Gomori methenamine silver staining demonstrated fungal hyphae within necrotic foci. Lactophenol cotton blue examination of lung tissue triturate also demonstrated fungal hyphae, while culture on Sabouraud dextrose agar produced initially white colonies that subsequently developed dark pigmentation and a yellowish reverse appearance consistent with Aspergillus niger. DNA extracted from lung tissue was amplified using genus- and species-specific primers targeting the ITS1 region. A 307-bp product supported identification of A. niger, and Sanger sequencing of the AN1 isolate was submitted to NCBI under accession number MZ267248. Phylogenetic comparison with published GenBank sequences showed 95–100% identity. The combined pathological, cultural, PCR and sequence findings supported the diagnosis and species-level characterisation of A. niger-associated respiratory aspergillosis in Indian Runner ducklings.