Summary (300 words)
Flaviviruses West Nile (WNV), Usutu (USUV) and Bagaza (BAGV) virus and
avian malaria parasites are vector borne pathogens that circulate
naturally between avian and mosquito hosts. WNV and USUV and potentially
also BAGV constitute zoonoses. Temporal and spatial co-circulation and
co-infection with Plasmodium spp., and West Nile virus has been
documented in birds and mosquito vectors, and fatally USUV infected
passerines coinfected with Plasmodium spp. had more severe
lesions. Also, WNV, USUV and BAGV have been found to co-circulate. Yet
little is known about the interaction of BAGV and malaria parasites
during consecutive or co-infections of avian hosts.
Here we report mortality of free-living red-legged partridges in a
hunting estate in Southern Spain due to coinfection with BAGV andPlasmodium spp. The outbreak occurred in the area where BAGV
first emerged in Europe in 2010 and where co-circulation of BAGV, USUV
and WNV was confirmed in 2011 and 2013.
Partridges were found dead in early October 2019. Birds had mottled
locally pale pectoral muscles, enlarged, congestive greenish-black
tinged livers and enlarged kidneys. Microscopically congestion and
predominantly mononuclear inflammatory infiltrates were evident andPlasmodium phanerozoites were present in the liver, spleen,
kidneys, muscle and skin. Molecular testing and sequencing detectedPlasmodium spp. and BAGV in different tissues of the partridges,
and immunohistochemistry confirmed the presence and co-localization of
both pathogens in the liver and spleen. Although Plasmodium spp.
are known to be highly prevalent in red-legged partridges, this is the
first account of mortality caused by co-infection with BAGV andPlasmodium sp. Due to the importance of the red-legged partridge
in the ecosystem of the Iberian Peninsula and as driver of regional
economy such mortalities are of concern. Also, they may reflect climate
change related changes in host, vector and pathogen ecology and
interactions that could emerge similarly in other pathogens.
Keywords: Flavivirus; avian malaria; co-localization; avian
host.