A virus precipitation method for concentration & detection of avian influenza viruses from environmental water resources & its possible application in outbreak investigations

Background & objectives

Avian influenza (AI) viruses have been a major cause of public health concern. Wild migratory birds and contaminated environmental sources such as waterbodies soiled with bird droppings play a significant role in the transmission of AI viruses. The objective of the present study was to develop a sensitive and user-friendly method for the concentration and detection of AI viruses from environmental water sources.

Methods

Municipal potable water, surface water from reservoirs and sea were spiked with low pathogenic AI viruses. To concentrate the viruses by precipitation, a combination of potassium aluminium sulphate with milk powder was used. Real-time reverse transcription-polymerase chain reaction was performed for virus detection, and the results were compared with a virus concentration method using erythrocytes. Drinking water specimens from poultry markets were also tested for the presence of AI viruses.

Results

A minimum of 10^1.0 EID₅₀(50% egg infectious dose)/ml spiked H5N1 and 10^1.7 EID₅₀/ml spiked H9N2 viruses were detected from spiked potable water; 10^1.0 and 10^2.0 EID₅₀/ml spiked H5N1 virus was detected from surface water and seawater samples, respectively. The present method was more sensitive than the erythrocyte-binding method as approximately 10-fold higher infectious virus titres were obtained. AI H9N2 viruses were detected and isolated from water from local poultry markets, using this method.

Interpretation & conclusions

Viability and recovery of the spiked viruses were not affected by precipitation. The present method may be suitable for the detection of AI viruses from different environmental water sources and can also be applied during outbreak investigations.

Two-Step Concentration of Complex Water Samples for the Detection of Viruses

The accurate detection and quantification of pathogenic viruses in water is essential to understand and reduce the risk of human infection. This paper describes a two-step method suitable for concentrating viruses in water and wastewater samples. The method involves a tangential flow ultrafiltration step that reduces the sample volume of 1–10 L to approximately 50 mL, followed by secondary precipitation using polyethylene glycol 6000, which reduces the volume to 1–4 mL. For method validation, water samples were spiked with different concentrations of enteric viruses, and viral recovery in the concentrates exceeded 10% in all experiments. The method is suitable for water samples with high and low salinity and turbidity, allowing an accurate comparison of viral titers in a diverse range of water types. Furthermore, the method has the potential to concentrate other pathogens, e.g., bacteria or protozoa. Hence, the use of this method can improve the holistic assessment of risks associated with wastewater-contaminated environments.