A Serosurvey of Flavivirus Infection in Horses and Birds in Slovakia

Abstract

In central Europe, at least three flaviviruses circulate among vectors and vertebrate hosts. West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne viruses maintained in the nature by enzootic cycle between mosquitoes and birds. Tick-borne encephalitis virus (TBEV) is a flavivirus causing annual human cases in Slovakia. The aim of this study is the prevalence assessment of flavivirus infections in horses (n = 145) and birds (n = 109) by enzyme-linked immunosorbent assay (ELISA) and confirmation by neutralization test (VNT). WNV antibodies have been detected in 11.7% of tested horses and 11.9% of tested birds and confirmed in 6.9% of horse and 9.2% of bird samples. None of the WNV seropositive or dubious horses had WNV IgM (ELISA), and none of the tested horses had USUV neutralizing antibodies. Autochthonous WNV infections have been confirmed in 16.7% of horses without international travelling history. Most of them were from western Slovakia with known endemic WNV transmission. An autochthonous WNV infection in a horse from highland area of Kremnické vrchy (central Slovakia) with unknown data of WNV circulation and without travelling history was detected. TBEV antibody was detected in 6.2% of horses and in 3.4% has been confirmed. In two horses, WNV and TBEV infection could not be distinguished. Confirmed WNV seropositive were eight raptors showing nonspecific signs or suffering from trauma, one white stork, and one house sparrow. The sparrow was caught in a locality in eastern Slovakia, where WNV RNA had been previously detected in sparrows. USUV neutralizing antibodies were present in pooled sample from four Eurasian great tits. Because of insufficient volume, TBEV VNT was not carried out in birds. Results further prove the endemicity of WNV and other vector-borne flaviviruses in natural and accidental hosts in Slovakia, giving better insight in flavivirus epidemiology in European countries in general.

Serological Evidence for Japanese Encephalitis and West Nile Virus Infections in Domestic Birds in Cambodia

“…Due to the cross-reactivity, retrospective seroprevalence studies for flaviviruses are challenging in regions where more than one of these viruses circulate. The HIA is characterized by a high crossreactivity which generally only allows a qualitative conclusion about the presence of flavivirus antibodies (48)(49)(50)(51). Our HIA analysis and the moderate correlation of HIA titers among all viruses also demonstrated a high cross-reactivity especially between the two DENV serotypes 2 and 3 (Spearman r = 0.8999).…”

Epidemiology of Usutu Virus: The European Scenario

“…USUV RNA was also found in bats ( Pipistrellus pipistrellus ) in Germany and Belgium [ 19 , 20 ]. Moreover, USUV antibodies were sporadically detected in horses [ 21 , 22 , 23 ], dogs [ 24 ], squirrels [ 25 ], wild boar, roe deer [ 26 ] and lizards [ 27 ] ( Figure 1 ), expanding the USUV host range ( Figure 1 ), however these species are considered incidental hosts.…”

In Vitro and In Vivo Models to Study the Zoonotic Mosquito-Borne Usutu Virus

“…Retrospective analyses have shown that the high mortality of blackbirds in Tuscany (Italy) in 1996 was also attributed to this virus [ 24 ]. In the following years, USUV circulation was identified in many countries in western, southern, and central Europe: United Kingdom (2001–2002) [ 25 ], Czech Republic (2005) [ 26 ], Hungary (2005) [ 27 ], Poland (2006) [ 28 ], Spain (2006) [ 29 ], Switzerland (2006) [ 30 ], Serbia (2009–2010) [ 31 ], Greece (2010) [ 32 ], Germany (2011) [ 33 ], Slovakia (2012–2014) [ 34 ], Belgium (2012) [ 35 ], France (2015) [ 36 ], and The Netherlands (2016) [ 6 ]. In many of these countries, USUV has managed to establish an endemic mosquito–bird life cycle and to co-circulate with WNV [ 37 ].…”