West Nile Virus in Slovenia

Abstract

<jats:p>West Nile virus (WNV) is a flavivirus transmitted by mosquitoes. Birds are the reservoir for the virus; humans, horses and other mammals are dead-end hosts. Infections caused by WNV in humans can vary from asymptomatic infections to West Nile fever (WNF) or West Nile neuroinvasive disease (WNND). In 1995, a serosurvey was performed in Slovenia on forest workers, and WNV specific IgG antibodies were confirmed in 6.8% of the screened samples, indicating that WNV is circulating in Slovenia. No human disease cases were detected in Slovenia until 2013, when the first case of WNV infection was confirmed in a retrospective study in a 79-year old man with meningitis. In 2018, three patients with WNND were confirmed by laboratory tests, with detection of IgM antibodies in the cerebrospinal fluid of the patients. In one of the patients, WNV RNA was detected in the urine sample. In 2017, 2018 and 2019, a mosquito study was performed in Slovenia. Mosquitoes were sampled on 14 control locations and 35 additional locations in 2019. No WNV was detected in mosquitoes in 2017 and 2019, but we confirmed the virus in a pool of Culex sp. mosquitoes in 2018. The virus was successfully isolated, and complete genome sequence was acquired. The whole genome of the WNV was also sequenced from the patient’s urine sample. The whole genome sequences of the WNV virus detected in Slovenian patient and mosquito indicate the virus most likely spread from the north, because of the geographic proximity and because the sequences cluster with the Austrian and Hungarian sequences. A sentinel study was performed on dog sera samples, and we were able to confirm IgG antibodies in 1.8% and 4.3% of the samples in 2017 and 2018, respectively. Though Slovenia is not a highly endemic country for WNV, we have established that the virus circulates in Slovenia.</jats:p>

Emerging Trends in the Epidemiology of West Nile and Usutu Virus Infections in Southern Europe

“…The first case was confirmed in 2013 in a patient with meningitis. Thereafter, in 2018, three cases of WNND were confirmed by detection of IgM antibodies in the CSF samples (99). In 2009, 481/1912 (25.2%) clinically healthy horses were positive for WNV IgG antibodies (100).…”

Detection of Antibodies Against Tick-Borne Encephalitis Virus and Other Flaviviruses in a Zoological Collection in Slovenia

“…mosquitos was found to be positive by RT-PCR in 2018, but negative in 2017 and 2019. A sentinel study on dog sera samples confirmed WNV antibodies by an indirect immunofluorescence study in 1.8 and 4.3% of samples collected in 2017 and 2018, respectively ( 23 ).…”

A Sentinel Serological Study in Selected Zoo Animals to Assess Early Detection of West Nile and Usutu Virus Circulation in Slovenia

“…On the other hand, birds that become infected may develop symptoms arising from the infection. The first positive active cases of WNV in people in Slovenia were detected in 2018 in three patients with IgM antibodies in the cerebrospinal fluid of the patients [ 2 ]. In animals, the first active cases of WNV in Slovenia were detected in a hooded crow ( Corvus cornix ) and a horse in the Ljubljana region in 2018 [ 3 ].…”

“…In the same year, the first cases of USUV in Slovenia were detected in a common blackbird ( Turdus merula ) and a song thrush ( Turdus philomelos ) [ 4 ]. Based on the successful virus isolation and complete genome sequencing, connection between positive human cases and WNV found in mosquitos has been made [ 2 ]. Additionally, the whole genome sequence indicates that virus most likely spread from the north because of the geographic proximity as well as the sequence cluster with the Austrian and Hungarian sequences [ 2 ].…”

“…Based on the successful virus isolation and complete genome sequencing, connection between positive human cases and WNV found in mosquitos has been made [ 2 ]. Additionally, the whole genome sequence indicates that virus most likely spread from the north because of the geographic proximity as well as the sequence cluster with the Austrian and Hungarian sequences [ 2 ]. Captive and free-ranging animals have been used quite often as sentinels to monitor arbovirus infections in the past decades [ 5 , 6 ].…”