Serologic evidence for Schmallenberg virus circulation at high altitude, Central Portugal, 2015-2016

Abstract

A few years after the initial 2011 large scale Schmallenberg virus (SBV) epidemic that affected Europe, a subsequent decrease in new SBV infections was observed presumably associated with natural substitution of previously exposed animals. In the present work, a 2-year prospective serosurvey was performed to evaluate SBV circulation in a population of sheep living at high altitude in the central region of Portugal and with restricted movement. Blood from a representative sample of 168 autochthonous sheep was collected in 2015 and again in 2016, and tested for the presence of anti-SBV IgG by ELISA. Of the 2015 sample collection, seven animals tested positive for anti-SBV IgG, corresponding to a seroprevalence of 4.2% while of the 2016 sample collection, 10 presented SBV antibodies, showing a seroprevalence of 6.0% (p = 0.619). Results show that SBV is endemic in sheep of central Portugal, even in herds at high altitude locations. When comparing anti-SBV seroprevalences of 2015/2016 found in this study, to one detected in 2014 in the same region, a steep decrease could be observed (p < 0.001). This is in accordance with what has been documented in Western European countries, where a decrease in the number of SBV-infected sheep has been found, a fact which may pose a new threat for SBV re-emergence.

Epidemiological surveillance of Schmallenberg virus in small ruminants in southern Spain

“…While it has been shown that the probability of C. imicola occurrence is very limited at altitudes >900 m (Conte et al., 2003), we nevertheless detected seropositivity in flocks above 1,000 masl in non‐transhumant farms. Consistent with our results, SBV exposure was detected in domestic and wild ruminant species in areas of the Iberian Peninsula above 2,000 m altitude (Esteves et al., 2018; Fernández‐Aguilar et al., 2014). These findings indicate that other Culicoides species such as those belonging to Culicoides obsoletus group (Meigen, 1818), [ C. obsoletus and Culicoides scoticus (Downes & Kettle, 1952)], Culicoides pulicularis group (Linnaeus, 1758) [ C. pulicularis and Culicoides lupicaris (Downes & Kettle, 1952)] and others (Alarcón‐Elbal, 2015; Pérez et al., 2012), may also play a role in SBV transmission in the study area, as has been suggested for other Spanish regions (Pagès et al, 2018).…”

“…While it has been shown that the probability of C. imicola occurrence is very limited at altitudes >900 m (Conte et al, 2003), we nevertheless detected seropositivity in flocks above 1,000 masl in non-transhumant farms. Consistent with our results, SBV exposure was detected in domestic and wild ruminant species in areas of the Iberian Peninsula above 2,000 m altitude (Esteves et al, 2018;Fernández-Aguilar et al, 2014 -Elbal, 2015;Pérez et al, 2012), may also play a role in SBV transmission in the study area, as has been suggested for other Spanish regions (Pagès et al, 2018).…”

“…Serological surveys of small ruminants at the end of the first epidemic period (2011–2013) revealed high within‐flock immunity levels in affected countries (Table S1). Subsequent serosurvey studies have shown a decreasing trend in SBV circulation in ruminant livestock populations in Europe (Delooz et al., 2017; Esteves et al., 2018; Stokes et al., 2016; Veldhuis et al., 2017; Wernike et al., 2015, 2018), which could favour SBV re‐emergence in favourable epidemiological scenarios (Larska, 2018; Lievaart‐Peterson et al., 2015; Poskin et al., 2016; Stavrou et al., 2017; Wernike & Beer, 2020). In this connection, the re‐emergence of SBV in 2016 in different European countries was associated with an increase in the number of naïve ruminants (Delooz et al., 2017; Larska, 2018).…”

Occurrence and Distribution of Fasciolosis in a Cohort of Ovine Livestock Restricted to a Mountain Plateau in Central Portugal

“…Sera collection was performed in a previous study [17] preserved at −80 • C. The sampling scheme consisted of sera from a sheep cohort (n = 92), initially collected in January/February 2015, and again in January/February 2016 from the same animals (in a total of 184 sera samples = 92 paired). As herd size averages 40 animals, a total of four animals (~10% of herd size) aging 6 months and older, was randomly selected from 23 herds of Serra da Estrela sheep, located on 21 parishes of 4 municipalities of the region (Carregal do Sal, Celorico da Beira, Gouveia, and Seia).…”

A 2-Year Longitudinal Seroepidemiological Evaluation of Toxoplasma gondii Antibodies in a Cohort of Autochthonous Sheep from Central Portugal

“…Sera collected from a previous study was used [14]. Briefly, blood from 168 "Serra da Estrela" breed sheep was collected in January/February 2015, and again in January/February 2016 from the same animals (168 paired samples, for a total of 336).…”