Sensitivity of Quails (Coturnix coturnix), Siskins (Carduelis spinus), and Frogs (Rana ridibunda) to West Nile Virus.

The level of viremia and features of the course of experimental infection caused by West Nile virus were studied in two species of migratory birds, siskins Сarduelis spinus and quails Coturnix coturnix, and in one species of amphibians, frogs Rana ridibunda. In quails, the virus caused a fatal disease; histological analysis revealed pathological changes in the heart, kidneys, liver, and brain stem. In siskins and frogs, virus antigen was detected in cloacal smears despite the absence of clinical manifestations, the level of viremia was sufficient to infect insect vectors during bloodsucking. These findings suggest that siskins and frogs can be potential reservoirs of West Nile virus and play a role in its circulation.

Influence of Biological Model on the Formation of the Pathogenic Properties of the West Nile Virus Isolate.

Various biological models are used to isolate West Nile virus, but their role as a selection factor that facilitates selection of isolates with certain properties is usually not evaluated. We compared pathogenic properties of three strains of the West Nile virus obtained from one sample of virus-containing material using different models: WNV Volgograd 900m/18 (on the model of suckling mice), WNV Volgograd 900a/18 (on C6/36 cells) and WNV Volgograd 900v/18 (on Vero cells). WNV Volgograd 900m/18 strain demonstrated virulent (LD50 5×103±0.005×104 PFU, p≤0.05) and neuroinvasive properties, induced viremia and pathomorphological changes in the liver, lymph nodes, and brain of nonlinear white mice. WNV Volgograd 900v/18 strain had similar characteristics except for neuroinvasiveness. WNV Volgograd 900a/18 variant demonstrated minimum virulence (LD50 5×104±0.005×104 PFU, p≤0.05), did not cause neurological symptoms, and was not isolated from the blood of infected animals.