A Prior Usutu Virus Infection Can Protect Geese from Severe West Nile Disease

Abstract

Usutu virus (USUV) and West Nile virus (WNV) are closely related pathogens circulating between mosquitoes and birds, but also infecting mammals as dead-end hosts. Both viruses share the same susceptible hosts, vectors, and even distribution areas in Central Europe. The aim of the study was, therefore, to understand their amplification potential and interference upon a successive infection. Two-week old geese were initially infected with an USUV isolate from Germany and with a German WNV isolate17 days later. The geese were susceptible to the USUV and the WNV infections, as evidenced by specific flavivirus antibodies in all of the birds. Furthermore, in half of the USUV-inoculated geese, USUV genomes were detected in the blood and swab samples 2–4 days post-infection. Additionally, most of the examined organs contained USUV genomes and showed signs of encephalitis and ganglioneuritis. Interestingly, upon a sequential infection with WNV, the genome copy numbers in all of the examined samples were significantly lower and less frequent than after a WNV mono-infection. Similarly, the histopathological lesions were less severe. Therefore, it can be concluded that a previous USUV infection can protect birds from clinical disease in a subsequent WNV infection.

Epidemiology, surveillance and diagnosis of Usutu virus infection in the EU/EEA, 2012 to 2021

“…Experimental data indicate that previous exposure to USUV partially protects magpies against lethal challenge with WNV but does not prevent viraemia and possible direct transmission [52]. However, another study of experimental infection in geese showed that prior USUV infection protected the birds from clinical disease and led to significantly lower viraemia in a subsequent WNV infection [53]. In line with these results, field surveillance of migratory and resident birds in Germany identified WNV and USUV co-infection in six dead birds [54].…”