Pathogenicity of West Nile Virus Lineage 1 to German Poultry

Abstract

West Nile virus (WNV) is a mosquito-borne virus that originates from Africa and at present causes neurological disease in birds, horses, and humans all around the globe. As West Nile fever is an important zoonosis, the role of free-ranging domestic poultry as a source of infection for humans should be evaluated. This study examined the pathogenicity of an Italian WNV lineage 1 strain for domestic poultry (chickens, ducks, and geese) held in Germany. All three species were subcutaneously injected with WNV, and the most susceptible species was also inoculated via mosquito bite. All species developed various degrees of viremia, viral shedding (oropharyngeal and cloacal), virus accumulation, and pathomorphological lesions. Geese were most susceptible, displaying the highest viremia levels. The tested waterfowl, geese, and especially ducks proved to be ideal sentinel species for WNV due to their high antibody levels and relatively low blood viral loads. None of the three poultry species can function as a reservoir/amplifying host for WNV, as their viremia levels most likely do not suffice to infect feeding mosquitoes. Due to the recent appearance of WNV in Germany, future pathogenicity studies should also include local virus strains.

Pathogenesis of West Nile Virus Lineage 2 in Domestic Geese after Experimental Infection

“…Moreover, we focused on farm birds, aiming to clarify the role of these animals in the spread of WNV over the time course of the disease. A similar study had already been performed with geese, albeit the birds were infected with a WNV lineage 1 isolate from Italy [28]. At the time of implementation, WNV had not been detected in Germany and it was suspected that WNV lineage 1 strains would be introduced into the country from the south [28].…”

“…The highest and longest-lasting viremia as well as virus excretion was detected in geese. Yet it was concluded that all three domestic species most likely do not act as a virus reservoir for the transmission of WNV lineage 1 via mosquitoes [28]. At that time, it was assumed that WNV would come to Germany from the south, and therefore in the form of WNV lineage 1 rather than 2 [28].…”

“…Yet it was concluded that all three domestic species most likely do not act as a virus reservoir for the transmission of WNV lineage 1 via mosquitoes [28]. At that time, it was assumed that WNV would come to Germany from the south, and therefore in the form of WNV lineage 1 rather than 2 [28]. Differences in the pathogenicity of European WNV lineage 2 compared to lineage 1 strains have been described in a small number of experimental studies [29][30][31].…”

“…For the accurate tracking of the virus not only in blood or swab material but also in specific tissues at different time points post-infection (pi), three geese were euthanized and analyzed at interim time points (3, 6, 10, and 14 dpi). Days 3 and 6 pi were chosen because these coincided with the highest viral loads in the blood and swab samples in preceding experiments reported in the literature [27,28,32]. Day 10 was chosen due to the expected mounting of the humoral response.…”

“…Day 10 was chosen due to the expected mounting of the humoral response. Additionally, day 14 was chosen as geese infected with WNV lineage 1 in Italy showed clinical signs in the third week after infection [28]. Day 21 was selected for the detection of overall serological response.…”