Detection of Japanese Encephalitis Virus in bone marrow of healthy young wild birds collected in 1997–2000 in Central Italy

Abstract

Japanese Encephalitis Virus (JEV) is a flavivirus responsible for an important zoonotic, vector-borne disease included in the OIE list. JEV is endemic in a large area of Asia. In Italy, JEV has been found in dead birds collected in 1997-2000 and in a pool of Culex pipiens mosquitoes collected in 2010. Viral ecology in the inter-epidemic periods is not known. The aim of this study was to investigate JEV in FFPE archival samples of healthy birds collected in 1997-2000 in Tuscany (Italy) in the same area and a few months after collection of birds resulted infected by JEV. Different samples from 37 young birds and 83 adults were available. Immunohistochemistry detected JEV antigen only in bone marrow samples from 12 young healthy birds. Positive cells were morphologically referable to monocyte-macrophages lineage and were positive for anti-CD11b in serial sections. Real-time PCR detected JEV RNA in four of these samples. These results suggest that healthy birds can harbour JEV in bone marrow cells, while no other organs resulted infected. The role of healthy birds in JEV ecology should be better investigated. Surveillance programmes should include sampling of the most appropriate target organs.

Emerging Threats to Animals in the United Kingdom by Arthropod-Borne Diseases

“…tritaeniorhynchus, a species found in south east Europe (59). A number of recent reports have presented evidence for JEV in Europe (60,61). However, these results are based on detection of partial genomic sequences not a complete genome, and live virus has not been isolated and as such there is some controversy over whether these are genuine cases of infection.…”

Review of Emerging Japanese Encephalitis Virus: New Aspects and Concepts about Entry into the Brain and Inter-Cellular Spreading

“…The tropical regions have been declared endemic, whereas regions with subtropical and temperate climate recorded epidemic events. Recently, a first autochthonous human case outside Australasia has been reported in Angola, Africa [10], and JEV has also been detected in birds in Italy, Europe [11]. However, various transmission chains and cycles have been described (Figure 2).…”

“…Ducks may spread JEV over shorter distances, but also across seas, as shown in Japan and Korea [12,13,14,15]. Interestingly, JEV has been found in the bone marrow of birds in Italy [11], probably due to long distance bird migration from Asia to Europe. However, little is known about migration routes of these birds.…”

Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe?

“…However, among these exotic flaviviruses, JEV presented the highest propensity to spread, with transmission evidenced westward to Nepal and Pakistan, as well as eastward in western Pacific regions in the 1990s (Eastern-most territories in Indonesia, Papua New Guinea and Australia in 1995 and 1998), subsequent to changes in human activities (deforestation, irrigation, expansion of pig breeding) [165]. Intriguingly, JEV genome fragments have been recently identified in birds and mosquitoes collected in Italy [166,167]. JEV actively circulates in rice paddies, rural and semi-urban areas, amplified by Ardeid birds (herons and egrets) and pigs as natural maintenance reservoirs and Culex tritaeniorhynchus or other mosquito species mainly from the Culex genus as vectors (reviewed in [20]).…”