Use of Competition ELISA for Monitoring of West Nile Virus Infections in Horses in Germany

Abstract

West Nile virus (WNV) is a mosquito-borne viral pathogen of global importance and is considered to be the most widespread flavivirus in the World. Horses, as dead-end hosts, can be infected by bridge mosquito vectors and undergo either subclinical infections or develop severe neurological diseases. The aim of this study was to detect WNV specific antibodies in horses in Germany as an indicator for an endemic circulation of WNV. Sera from more than 5,000 horses (primarily fallen stock animals) were collected in eight different federal states of Germany from 2010 to 2012. Sera were screened by a competitive ELISA and positive reactions were verified by an indirect IgM ELISA and/or by virus neutralization tests (VNT) for WNV and Tick-borne encephalitis virus (TBEV) in order to exclude cross-reacting antibody reactions. In essence WNV specific antibodies could not be detected in any of the horse sera. Not surprisingly, a small number of sera contained antibodies against TBEV. It is noteworthy that equine sera were often collected from horse carcasses and therefore were of poor quality. Nonetheless, these sera were still suitable for WNV ELISA testing, i.e., they did not produce a high background reaction which is a frequently observed phenomenon. According to these data there is no evidence for indigenous WNV infections in horses in Germany at present.

West Nile Virus Epidemic in Germany Triggered by Epizootic Emergence, 2019

“…However, low WNV activity is also observed in the neighboring countries of Germany (France, Austria, and Czech Republic). Therefore, over the last decade, different monitoring programs were implemented in Germany to screen for WNV RNA and antibodies in birds, horses, mosquitoes and chicken eggs [8][9][10][11][12]. In 2018, an epizootic emergence of WNV was observed in Germany for the first time [13].…”

First Detection of Co-circulation of West Nile and Usutu Viruses in Equids in the South-west of Tunisia

“…But, they are unable to generate a level of viraemia high enough to infect new mosquitoes. Hence, they are considered 'dead-end' hosts (Ziegler et al, 2013). For USUV infection, horses do not show also a strong immune response (not induce high antibody titres) (Savini et al, 2011).…”

West Nile Virus Antibody Prevalence in Horses of Ukraine

“…False positive ELISA results caused by TBE cross-reactive antibodies had been observed in earlier serological studies looking at horses from Germany and Austria [26,27,28] which impede the interpretation of the ELISA results. However, no TBEV-NT positive horse serum was found among the Ukrainian horse sera.…”

“…As the WNV ELISA used also detects cross-reacting antibodies induced by other flaviviruses, e.g. TBEV [26,27,28], all sera negative in the WNV NT were also screened using a TBEV NT as well as a Japanese encephalitis virus (JEV) NT, all with negative outcomes (data not shown). The reason for ELISA reactivity of the seven sera (positive WNV ELISA, but negative in all conducted NTs, Table 3) is unclear at present.…”