Morphological and Biochemical Characteristics of Avian Faecal Droppings and Their Impact on Survival of Avian Influenza Virus

Environmental specimens such as faecal droppings are considered important for the detection of avian influenza viruses (AIV). In view of lower rates of AIV isolation from avian faecal droppings, characterization of droppings is imperative to elucidate contributing factors. However, there are no reports on morphological and biochemical characteristics of droppings. The objective of the present study was the characterization of droppings from different avian species and their impact on the AIV detection and isolation. A total of 373 droppings belonging to 61 avian species from 22 families of apparently healthy wild migratory, resident, domestic birds and poultry were studied during five winter migratory bird seasons between 2007 to 2012 and 2016–2017. The colour, morphology and size of the droppings varied from species-to-species. These data could be useful for the identification of avian species. Droppings from 67% of the avian species showed acidic pH (4.5–6.5); nine species showed neutral pH (7.0), and 11 species showed alkaline pH (7.5). The infectious titers of AIV in droppings with acidic pH were significantly lower (p < 0.05) than those of the droppings with neutral and alkaline pH. However, acidic pH did not hamper AIV detection by real-time RT-PCR. In order to avoid the impact of acidic pH, collecting fresh droppings into viral transport medium (pH 7.0–7.5) would help improve the rate of AIV isolation.