First detection of Bagaza virus in Common magpies (Pica pica), Portugal 2023

Abstract

Bagaza virus (BAGV) is a mosquito-borne flavivirus of the family Flaviviridae, genus Orthoflavivirus, Ntaya serocomplex. Like other viruses of the Ntaya and Japanese encephalitis serocomplexes, it is maintained in nature in transmission cycles involving viremic wild bird reservoirs and Culex spp. mosquitoes. The susceptibility of red-legged partridge, ring-necked pheasant, Himalayan monal and common wood pigeon is well known. Determining whether other species are susceptible to BAGV infection is fundamental to understanding the dynamics of disease transmission and maintenance. In September 2023, seven Eurasian magpies were found dead in a rural area in the Mértola district (southern Portugal) where a BAGV-positive cachectic red-legged partridge had been found two weeks earlier. BAGV had also been detected in several red-legged partridges in the same area in September 2021. Three of the magpies were tested for Bagaza virus, Usutu virus, West Nile virus, Avian influenza virus and Avian paramyxovirus serotype 1, and were positive for BAGV only. Sequencing data confirmed the specificity of the molecular detection. Our results indicate that BAGV is circulating in southern Portugal and confirm that Eurasian magpie is potential susceptible to BAGV infection. The inclusion of the abundant Eurasian magpie in the list of BAGV hosts raises awareness of the potential role of this species as as an amplifying host.

Keywords: Bagaza virus; Culex spp; Flaviviridae; Common magpies; Eurasian magpies; Ntaya serocomplex.

Figure 1

Phylogenetic analysis based on 35 partial nucleic acid sequences of Orthoflaviruses isolated in invertebrate and vertebrate species. The access number of the nucleotide sequences are given. The evolutionary history was inferred by using the Maximum Likelihood method and Kimura 2-parameter model. The tree with the highest log likelihood (− 1798.33) is shown. Initial tree(s) for the heuristic search were obtained automatically by applying Neighbor-Join and BioNJ algorithms to a matrix of pairwise distances estimated using the Maximum Composite Likelihood (MCL) approach, and then selecting the topology with superior log likelihood value. Only bootstrap values higher than 70 are shown. The evolutionary analyses were conducted in MEGA. The icons shown represent mosquitoes (Culex species), turkeys, Eurasian magpie, pheasant, red grouse and ducks.