Schmallenberg virus in Poland endemic or re-emerging? A six-year serosurvey

Serological prevalence of the Schmallenberg virus in domestic and wild hosts worldwide: a systematic review and meta-analysis

Schmallenberg virus (SBV) is an arthropod-borne virus that emerged recently in northwestern Europe in 2011 that affects domestic and wild ruminants and induces abortion, stillbirth, and newborns with congenital anomalies. Since its discovery, SBV has spread very rapidly to too many countries in the world. The overall serological investigation of SBV is needed to improve modeling predictions and assess the overall impact on ruminant animals, which helps to design interventions for control and prevention strategies. Thus, this study aimed to estimate the overall serological assay of SBV in both domestic and wild ruminants around the world. This systematic review was conducted as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. International databases were employed To search for relevant articles. The pooled prevalence with a 95% confidence interval was calculated with a random effects model. The Cochran's Q test, τ2, and I2 were used to assess the sources of heterogeneity. In the current meta-analysis, a total of 41 articles were included. The overall pooled proportion of SBV in domestic and wild ruminants was 49 and 26%, respectively. Substantial heterogeneity was observed in studies on domestic ruminants (I2 = 99.7%; p < 0.01) and studies on wild ruminants (I2 = 97.9%; p < 0.01). The pooled prevalence of SBV was significantly associated with publication time, detection techniques, and species of animals. According to the subgroup analysis, the highest pooled prevalence of SBV was reported in cattle (59%), followed by sheep (37%) and goat (18%). In addition to the subgroup analysis based on publication year, the pooled prevalence of SBV infection has become endemic since 2013 (49%) among domestic animals in the world. Of the diagnostic tests used, the highest anti-SBV antibodies (66%) were detected by a virus neutralization test. In this meta-analysis, the major wild animals that were infected by SBV were red deer, roe deer, fallow deer, mouflon, and wild boar. The highest sub-pooled prevalence of SBV was found in roe deer (46%), followed by fallow deer (30%), red deer (27%), mouflon (22%), and wild boar (11%). In general, the prevalence of SBV was high in cattle among domestic ruminants and in roe deer among wild animals. According to the current information provided by this meta-analysis, evidence-based risk management measures should be established to restrict SBV spread in both domestic and wild ruminants.

Bluetongue virus seroprevalence and risk factor analysis in cattle and water buffalo in southern Italy (Campania region)

Bluetongue is an arthropod-borne viral infection that is notifiable in several countries and causes significant economic losses and major concerns for ruminant trade. In this study, we investigated bluetongue 1seroprevalence in the Campania region, southern Italy, in cattle and buffalo populations, and assessed which factors were correlated with a high risk of exposure. The infection was widespread, as evidenced by the high individual (43.6%) and herd prevalence (85.4%). The highest prevalence was found in adult animals. Among the climatic factors analyzed, average temperature played a prominent role, being capable of affecting the probability of being positive for this infection. Surprisingly, exposure to Schmallenberg virus did not predispose animals to be positive for bluetongue virus, even though these infections share the same vector (Culicoides). Our data, consistent with those in the literature, suggest the transversal spread of bluetongue virus in the Mediterranean area, and indicate a limited co-exposure rate between Bluetongue and Schmallenberg viruses.

First evidence of schmallenberg virus infection in southern Italy

BACKGROUND

Schmallenberg virus (SBV) is a vector-borne pathogen that mainly affects ruminants. Schmallenberg disease has never been described in southern Italy, although this geographic area displays climatic features suitable for Culicoides biting midges, which transmit the pathogen. An observational study was carried out in the Campania region in 2020 to evaluate the seroprevalence in cattle and water buffalo as well as to identify the risk factors involved in the distribution of SBV.

RESULTS

Relatively high seroprevalences of 38.2% (cattle) and 43% (water buffalo) were found by using a commercial SBV ELISA, which is comparable to the prevalence obtained in other countries under post-epidemic conditions. A virus neutralization assay performed on positive samples showed high titers in a large percentage of animals which is assumed to indicate recent exposure. Bivariate analysis of several variables revealed some environmental factors associated with higher seroprevalence, such as mean annual temperature, distance from the coast, and altitude. Multivariate logistic regression confirmed the statistical association only for mean annual temperature, that was found to be the main factor responsible for the distribution of the virus in southern Italy. In addition, molecular diagnosis attempts were performed on serum samples and resulted in the detection of SBV RNA in two herds and six animals.

CONCLUSIONS

In this work we have demonstrated the circulation of SBV in southern Italy using both molecular and serological assays. This study emphasized the essential role of monitoring in preventing the re-emergence of vector-borne diseases in ruminants.

Emergence dynamics of adult Culicoides biting midges at two farms in south-east England

Background

Culicoides biting midges (Diptera: Ceratopogonidae) are biological vectors of livestock arboviruses that cause diseases with significant economic, social and welfare impacts. Within temperate regions, livestock movement during arbovirus outbreaks can be facilitated by declaring a ‘seasonal vector-free period’ (SVFP) during winter when adult Culicoides are not active. In this study we carry out long-term monitoring of Culicoides adult emergence from larval development habitats at two farms in the UK to validate current definitions of the SVFP and to provide novel bionomic data for known vector species.

Methods

Standard emergence traps were used to collect emerging adult Culicoides from dung heaps at two cattle farms in the south-east of England from June to November 2016 and March 2017 to May 2018. Culicoides were morphologically identified to species or complex level and count data were analysed using a simple population dynamic model for pre-adult Culicoides that included meteorological components.

Results

More than 96,000 Culicoides were identified from 267 emergence trapping events across 2 years, revealing clear evidence of bivoltinism from peaks of male populations of Culicoidesobsoletus emerging from dung heaps. This pattern was also reflected in the emergence of adult female Obsoletus complex populations, which dominated the collections (64.4% of total catch) and emerged throughout the adult active period. Adult male C. obsoletus were observed emerging earlier than females (protandry) and emergence of both sexes occurred throughout the year. Culicoides chiopterus and Culicoides scoticus were also identified in spring emergence collections, providing the first evidence for the overwintering of larvae in dung heaps for these species.

Conclusions

This study demonstrates continual and highly variable rates of emergence of Culicoides throughout the year. A lack of evidence for mass emergence in spring along with the ability to observe male generations highlights the need for complementary surveillance techniques in addition to light-trap data when investigating seasonality and phenology. Evidence was found of other vector species, C. chiopterus and C. scoticus, utilising cattle dung heaps as an overwintering habitat, further highlighting the importance of these habitats on farms.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05370-z.

Insights on Transmission, Spread, and Possible Endemization of Selected Arboviruses in Israel—Interim Results from Five-Year Surveillance

Outbreaks of arthropod-borne (arbo) viruses that infect livestock impact the health and welfare of domestic and wild animals are often responsible for significant economic losses in livestock production. Surveillance and early warning systems effectively predict the emergence and re-emergence of arboviral disease. This paper presents the interim results of five years monitoring the exposure of sentinel naïve heifers and Culicoides biting midges (Diptera; Ceratopogonidae) to bovine ephemeral fever virus (BEFV), Simbu serogroup viruses, bluetongue viruses (BTV), and epizootic hemorrhagic disease viruses (EHDV). The data were collected from 11 dairy farms situated within eight different geographical regions in Israel. The results indicate that cattle in Israel are affected by all four viruses from the early summer onward. The investigated viruses exhibit unique site-specific profiles in both ruminants and vectors. The potential of several vectors to transmit these viruses and lack of cross-protection to re-infection with multiple serotypes (BTV and EHDV) or species (Simbu serogroup viruses) highlights some likely mechanisms that may play a role in these viruses’ maintenance cycle and possible endemization in our region.