Schmallenberg Virus Infection Research Articles

DNA vaccination regimes against Schmallenberg virus infection in IFNAR−/− mice suggest two targets for immunization

Schmallenberg virus (SBV) is an RNA virus of the Bunyaviridae family, genus Orthobunyavirus that infects wild and livestock species of ruminants. While inactivated and attenuated vaccines have been shown to prevent SBV infection, little is known about their mode of immunity; specifically, which components of the virus are responsible for inducing immunological responses in the host.As previous DNA vaccination experiments on other bunyaviruses have found that glycoproteins, as well as modified (i.e. ubiquitinated) nucleoproteins (N) can confer immunity against virulent viral challenge, constructs encoding for fragments of SBV glycoproteins GN and GC, as well as ubiquitinated and non-ubiquitinated N were cloned in mammalian expression vectors, and vaccinated intramuscularly in IFNAR−/− mice. Upon viral challenge with virulent SBV, disease progression was monitored. Both the ubiquitinated and non-ubiquitinated nucleoprotein candidates elicited high titers of antibodies against SBV, but only the non-ubiquitinated candidate induced statistically significant protection of the vaccinated mice from viral challenge. Another construct encoding for a putative ectodomain of glycoprotein GC (segment aa. 678–947) also reduced the SBV-viremia in mice after SBV challenge. When compared to other experimental groups, both the nucleoprotein and GC-ectodomain vaccinated groups displayed significantly reduced viremia, as well as exhibiting no clinical signs of SBV infection.These results show that both the nucleoprotein and the putative GC-ectodomain can serve as protective immunological targets against SBV infection, highlighting that viral glycoproteins, as well as nucleoproteins are potent targets in vaccination strategies against bunyaviruses.

The N-terminal domain of Schmallenberg virus envelope protein Gc is highly immunogenic and can provide protection from infection

Schmallenberg virus (SBV) is transmitted by insect vectors, and therefore vaccination is one of the most important tools of disease control. In our study, novel subunit vaccines on the basis of an amino-terminal domain of SBV Gc of 234 amino acids (“Gc Amino”) first were tested and selected using a lethal small animal challenge model and then the best performing formulations also were tested in cattle. We could show that neither E. coli expressed nor the reduced form of “Gc Amino” protected from SBV infection. In contrast, both, immunization with “Gc Amino”-encoding DNA plasmids and “Gc-amino” expressed in a mammalian system, conferred protection in up to 66% of the animals. Interestingly, the best performance was achieved with a multivalent antigen containing the covalently linked Gc domains of both, SBV and the related Akabane virus. All vaccinated cattle and mice were fully protected against SBV challenge infection. Furthermore, in the absence of antibodies against the viral N-protein, differentiation between vaccinated and field-infected animals allows an SBV marker vaccination concept. Moreover, the presented vaccine design also could be tested for other members of the Simbu serogroup and might allow the inclusion of additional immunogenic domains.

Generation and characterization of a potentially applicable Vero cell line constitutively expressing the Schmallenberg virus nucleocapsid protein.

Schmallenberg virus (SBV) is a Culicoides-transmitted orthobunyavirus that poses a threat to susceptible livestock species such as cattle, sheep and goats. The nucleocapsid (N) protein of SBV is an ideal diagnostic antigen for the detection of viral infection. In this study, a stable Vero cell line, Vero-EGFP-SBV-N, constitutively expressing the SBV-N protein was established using a lentivirus system combined with puromycin selection. This cell line spontaneously emitted green fluorescent signals distributed throughout the cytoplasm, in which the expression of SBV-N fusion protein was confirmed by western blot analysis. The expression of SBV-N protein in Vero-EGFP-SBV-N cells was stable for more than fifty passages without puromycin pressure. The SBV-N fusion protein contained both an N-terminal enhanced green fluorescent protein (EGFP) tag and a C-terminal hexa-histidine (6×His) tag, by which the N protein was successfully purified using Ni-NTA affinity chromatography. The cell line was further demonstrated to be reactive with SBV antisera and an anti-SBV monoclonal antibody in indirect immunofluorescence assays. Taken together, our results demonstrate that the Vero-EGFP-SBV-N cell line has potential for application in the serological diagnosis of SBV infection.

Post-epidemic Schmallenberg virus circulation: parallel bovine serological and Culicoides virological surveillance studies in Ireland.

BackgroundSchmallenberg virus (SBV) emerged in northern-Europe in 2011 resulting in an epidemic of ruminant abortions and congenital malformations throughout the continent. In the years following the epidemic there have been reports of SBV overwintering and continued circulation in several European countries. When the population-level of immunity declines in exposed regions, re-introduction of SBV could result in further outbreaks of Schmallenberg disease. The aims of this study were to determine the SBV seroprevalence in previously exposed Irish dairy herds in 2014 and to investigate if SBV continued to circulate in these herds in the three years (2013–2015) following the Irish Schmallenberg epidemic.Whole-herd SBV serosurveillance was conducted in 26 herds before (spring) and following the 2014 vector-season (winter), and following the 2015 vector-season (winter). In spring 2014, 5,531 blood samples were collected from 4,070 cows and 1,461 heifers. In winter 2014, 2,483 blood samples were collected from 1,550 youngstock (8–10 months old) and a subsample (n = 933; 288 cows, 645 heifers) of the seronegative animals identified in the spring. Youngstock were resampled in winter 2015. Culicoides spp. were collected in 10 herds during the 2014 vector-season and analysed for SBV; a total of 138 pools (3,048 Culicoides) from 6 SBV vector species were tested for SBV RNA using real-time PCR.ResultsIn spring 2014, animal-level seroprevalence was 62.5 % (cows = 84.7 %; heifers = 0.6 %). Within-herd seroprevalence ranged widely from 8.5 %–84.1 % in the 26 herds. In winter 2014, 22 animals (0.9 %; 10 cows, 5 heifers, 7 youngstock) originating in 17 herds (range 1–4 animals/herd) tested seropositive. In winter 2015 all youngstock, including the 7 seropositive animals in winter 2014, tested seronegative suggesting their initial positive result was due to persistence of maternal antibodies. All of the Culicoides pools examined tested negative for SBV-RNA.ConclusionsSBV appears to have recirculated at a very low level in these herds during 2013 and 2014, while there was no evidence of SBV infection in naïve youngstock during 2015. A large population of naïve animals was identified and may be at risk of infection in future years should SBV re-emerge and recirculate as it has done in continental Europe.

Schmallenberg Virus Infection Diagnosis: Results of a German Proficiency Trial.

Since Schmallenberg virus (SBV), an orthobunyavirus of the Simbu serogroup, was detected in Central Europe in 2011 for the first time, numerous diagnostic test systems for genome or antibody detection have been established. Therefore, a laboratory proficiency trial with 28 veterinary laboratories was initiated to allow performance evaluations of the different veterinary diagnostic laboratories and the performance of the used assays. A panel of selected sera and bovine semen samples for the analysis by real-time PCR and an additional set of serum samples for serological analysis were provided. All participants were asked to investigate the samples with the test systems routinely used in their laboratory. While SBV-genome was reliably detected in serum samples, the sensitivity in semen samples seems to depend on the application of the recommended optimized nucleic acid extraction method (TRIzol® LS Reagent-based, Hoffmann etal., 2013, Vet. Microbiol., 167, 289). SBV-antibody-positive samples and sera negative for antibodies against Simbu serogroup viruses were in most cases correctly classified by the participants with the used commercial ELISA kits. However, a serum of the panel which contained antibodies against Akabane and Aino viruses, which are closely related to SBV, was repeatedly tested positive by two of four used ELISA kits. However, an excellent diagnostic sensitivity and specificity was achieved using a serum neutralization test. In conclusion, the here described German SBV proficiency test demonstrated that the available test systems allowed reliable SBV diagnostics in standard veterinary laboratories when recommended and approved assays are used.

A case–control study to estimate the effects of acute clinical infection with the Schmallenberg virus on milk yield, fertility and veterinary costs in Swiss dairy herds

Schmallenberg virus (SBV) was first detected in Switzerland in July 2012 and many Swiss dairy farmers reported acute clinical signs in dairy cattle during the spread of the virus until December 2012. The objectives of the present study were to investigate the effects of an acute infection with SBV on milk yield, fertility and veterinary costs in dairy farms with clinical signs of SBV infection (case farms), and to compare those farms to a matched control group of dairy farms in which cattle did not show clinical signs of SBV infection.Herd size was significantly (p<0.001) larger in case farms (33 cows, n=77) than in control farms (25 cows, n=84). Within case herds, 14.8% (median) of the cows showed acute clinical signs. Managers from case farms indicated to have observed a higher abortion rate during the year with SBV (6.5%) than in the previous year (3.7%). Analysis of fertility parameters based on veterinary bills and data from the breeding associations showed no significant differences between case and control farms. The general veterinary costs per cow from July to December 2012 were significantly higher (p=0.02) in case (CHF 19.80; EUR 16.50) than in control farms (CHF 15.90; EUR 13.25). No differences in milk yield were found between groups, but there was a significant decrease in milk production in case farms in the second half year in 2012 compared to the same period in 2011 (p<0.001) and 2013 (p=0.009). The average daily milk yield per cow (both groups together) was +0.73kg higher (p=0.03) in the second half year 2011 and +0.52kg (p=0.12) in the second half year 2013 compared to the same half year 2012. Fifty-seven percent of the cows with acute clinical signs (n=461) were treated by a veterinarian.The average calculated loss after SBV infection for a standardized farm was CHF 1606 (EUR 1338), which can be considered as low at the national level, but the losses were subject to great fluctuations between farms, so that individual farms could have very high losses (>CHF 10,000, EUR 8333).

Serological screening for Schmallenberg virus in exotic and indigenous cattle in Nigeria

Schmallenberg virus (SBV), a recently emerged Orthobunyavirus, is associated with abortions, stillbirths and congenital malformations in ruminants. Considering that Culicoides species which transmit this disease have previously been identified in Nigeria as vectors of bluetongue, another livestock disease that causes abortions, it is speculated that SBV also circulates in the Nigerian ruminant population. We therefore conducted a pilot study to investigate the occurrence of anti-SBV antibodies in a limited population of cross-breed, exotic and indigenous cattle in Nigeria. Serum samples obtained from 60 Friesian-White Fulani (FWF), 7 Jersey and 53 indigenous cattle were screened for SBV antibodies using a commercial indirect ELISA kit that detects antibodies against recombinant SBV nucleoprotein in ruminant sera. An overall seropositivity of 29.2% (35/120) was obtained with antibodies being detectable in 23.3% FWF (14/60), 42.9% Jerseys (3/7) and 34.0% (18/53) indigenous cattle. All indigenous breeds of cattle tested had seropositive animals: White Fulani (13/38, 34.2%), Sokoto Gudali (2/8, 25.0%), Red Bororo (1/5, 20.0%) and Bunaji (2/2, 100.0%). The detection of antibody-positive animals among unvaccinated cattle provides evidence of possible SBV infection in Nigeria. However, there is also the probability of cross-reactivity with other Simbu serogroup viruses, especially considering that some of these viruses have previously been reported in Nigeria. Further studies to confirm these preliminary findings using serum neutralisation assay, viral isolation or detection of SBV RNA from ruminants or Culicoides are necessary.Keywords: Abortions, Antibodies, Cattle, Congenital malformations, Nigeria, Schmallenberg virus

Epizootiology of the Schmallenberg virus in Poland

The Schmallenberg virus (SBV), as a new for Europe Ortobuniaviridae genus member, emerged in Poland in 2012, spreading rapidly across the country. Serological monitoring revealed a continuous increase of seropositivity among farm ruminants; moreover, the virus was detected in the insect vector, i.e. biting midges in different regions. The sylvatic cycle of SBV infections cannot be ruled out due to the detection of SBV antibodies in 24% of free living ruminants. Breeding losses related to SBV infection are difficult to estimate because of the lack of regulations for mandatory notifications. Furthermore specific symptoms associated with congenital malformations in newborns are observed only in a small percentage of intrauterine infections. Due to the current restrictions or bans on the export of animals resulting from SBV infection significant economic losses are recorded. The emergence of a new, never previously detected in Europe arbovirus raises a number of questions about its manner of transmission, vector ecology, the possibility of its spread and prevention as well as control of the diseases.

Circulation of Schmallenberg virus in Turkey, 2013

Schmallenberg virus (SBV) infection emerged in European domestic and wild ruminants in 2011. There is very limited information about the characterization of SBV isolates and the epidemiology of its infections in the rest of world, except for in European countries. We investigated the circulation of SBV in cattle herds in Central Anatolia, Turkey, in 2013. A total of 180 whole-blood samples were analyzed using real-time RT-PCR. The presence of SBV RNA was detected in 6 (3.3%) samples. For phylogenetic analysis and confirmation of real-time RT-PCR results, the S gene segment was amplified, sequenced, and compared to other segments. In addition, SBV-specific antibodies were detected in 87 (24.1%) of 360 sera using a virus neutralization test. In the S gene sequence analysis of four randomly selected samples, 98%-99% nucleotide identity was observed between our strains and SBVs isolated in European countries between 2011 and 2013. The results of this study indicate that SBV was in Turkey in 2013. Furthermore, the sequencing results suggest that it could be the same virus that is in European countries.

The impact of infection with Schmallenberg virus on weaning rate in Irish sheep flocks

Schmallenberg virus (SBV) disease emerged in Europe in 2011, with the virus initially identified in Germany, and the first confirmed case of SBV infection in Ireland diagnosed in a dairy calf in October 2012. SBV was subsequently confirmed by RT-PCR in 49 cattle herds and 39 sheep flocks. While these studies provide a good representation of the spatial distribution of SBV in Ireland, they do not quantify the impact of SBV on productivity. The objectives of this study were to assess the impact of SBV on weaning rate in Irish sheep flocks, based on data reported by Irish sheep farmers, and to evaluate weaning rate in sheep flocks as an indicator to be used in emerging disease surveillance systems. A questionnaire on productivity and management practices in sheep flocks was developed to gather data from sheep farmers. Valid responses from 267 sheep farmers were received. Negative binomial regression indicated that flocks with a confirmed SBV diagnosis had a weaning rate 0.9 times that of flocks free of SBV. The 10% reduction in weaning rates as a result of SBV is a justifiable concern for farmers and should be considered in formulating flock breeding policy. This study shows the value of a production database as an indicator of an emerging disease and the economic impact of that disease in Irish sheep flocks.

Exposure to Schmallenberg virus in Irish sheep in 2013

MALFORMED fetuses attributable to Schmallenberg virus (SBV) were found in 49 cattle herds and 30 sheep flocks exclusively in the southern and eastern parts of Ireland (Barrett, D., More, S....

Persistence of the protective immunity and kinetics of the isotype specific antibody response against the viral nucleocapsid protein after experimental Schmallenberg virus infection of sheep.

Schmallenberg virus (SBV) is an Orthobunyavirus that induces abortion, stillbirths and congenital malformations in ruminants. SBV infection induces a long lasting seroconversion under natural conditions. The persistence of the protective immunity and the isotype specific antibody response upon SBV infection of sheep has however not been studied in detail. Five sheep were kept in BSL3 facilities for more than 16 months and subjected to repeated SBV infections. Blood was regularly sampled and organs were collected at euthanasia. The presence of SBV RNA in serum and organs was measured with quantitative real-time PCR. The appearance and persistence of neutralizing and SBV nucleoprotein (N) isotype specific antibodies was determined with virus neutralization tests (VNT) and ELISAs. The primo SBV infection protected ewes against clinical signs, viraemia and virus replication in organs upon challenge infections more than 15 months later. Production of neutralizing SBV specific antibodies was first detected around 6 days post primo-inoculation with VNT and correlated with the appearance of SBV-N specific IgM antibodies. These IgM antibodies remained present for 2 weeks. SBV-N specific IgG antibodies were first detected between 10 and 21 dpi and reached a plateau at 28 dpi. This plateau remained consistently high and no significant decrease in titre was found over a period of more than 1 year. Similar results were found for the neutralising antibody response. In conclusion, the SBV specific IgM response probably eliminates SBV from the blood and the protective immunity induced by SBV infection protects sheep against reinfection for at least 16 months.

Schmallenberg virus in Germany 2011-2014: searching for the vectors.

Following the emergence of Schmallenberg virus (SBV) in 2011, 21,397 culicoid biting midges (Diptera: Ceratopogonidae) from targeted and non-targeted sampling activities carried out during the summer months of 2011 to 2013 and in late 2014 in various regions in Germany were analyzed for the virus by real-time RT-PCR. While no SBV was found in biting midges collected during 2011 and 2013, 2 out of 334 pools including 20 and 22 non-engorged females of the Obsoletus complex sampled in 2012 tested positive for the SBV S-segment with Ct values of 42.46 and 35.45. In addition, 673 black flies (Diptera: Simuliidae) captured during the same studies were screened for the presence of SBV and proved negative. In late autumn 2014, biting midges were collected again in a limited study in eastern Germany after some cases of SBV infection had occurred in a quarantine station for cattle. Due to the unfavorable seasonal weather conditions, only few specimens were caught, and these were also negative for SBV. The German experience suggests that biting midge collections launched only after an outbreak and are not locally targeted may be ineffective as to virus detection. It rather might be advisable to collect biting midges at sentinel farms on a permanent basis so to have material available to be examined in the case of a disease outbreak.

Experimental Infection of Sheep at 45 and 60 Days of Gestation with Schmallenberg Virus Readily Led to Placental Colonization without Causing Congenital Malformations.

BackgroundMain impact of Schmallenberg virus (SBV) on livestock consists in reproductive disorders, with teratogenic effects, abortions and stillbirths. SBV pathogenesis and viral placental crossing remain currently poorly understood. Therefore, we implemented an experimental infection of ewes, inoculated with SBV at 45 or 60 days of gestation (dg).Methodology“Mourerous” breed ewes were randomly separated in three groups: eight and nine ewes were subcutaneously inoculated with 1 ml of SBV infectious serum at 45 and 60 dg, respectively (G45 and G60). Six other ewes were inoculated subcutaneously with sterile phosphate buffer saline as control group. All SBV inoculated ewes showed RNAemia consistent with previously published studies, they seroconverted and no clinical sign was reported. Lambs were born at term via caesarian-section, and right after birth they were blood sampled and clinically examined. Then both lambs and ewes were euthanatized and necropsied.Principal Findings/SignificanceNo lambs showed any malformation suggestive of SBV infection and none of them had RNAemia or anti-SBV antibodies prior to colostrum uptake. Positive SBV RNA detection in organs was rare in both G45 and G60 lambs (2/11 and 1/10, respectively). Nevertheless most of the lambs in G45 (9/11) and G60 (9/10) had at least one extraembryonic structure SBV positive by RTqPCR. The number of positive extraembryonic structures was significantly higher in G60 lambs. Time of inoculation (45 or 60 dg) had no impact on the placental colonization success rate but affected the frequency of detecting the virus in the offspring extraembryonic structures by the time of lambing. SBV readily colonized the placenta when ewes were infected at 45 or 60 dg but infection of the fetuses was limited and did not lead to congenital malformations.

Virus-induced congenital malformations in cattle.

Diagnosing the cause of bovine congenital malformations (BCMs) is challenging for bovine veterinary practitioners and laboratory diagnosticians as many known as well as a large number of not-yet reported syndromes exist. Foetal infection with certain viruses, including bovine virus diarrhea virus (BVDV), Schmallenberg virus (SBV), blue tongue virus (BTV), Akabane virus (AKAV), or Aino virus (AV), is associated with a range of congenital malformations. It is tempting for veterinary practitioners to diagnose such infections based only on the morphology of the defective offspring. However, diagnosing a virus as a cause of BCMs usually requires laboratory examination and even in such cases, interpretation of findings may be challenging due to lack of experience regarding genetic defects causing similar lesions, even in cases where virus or congenital antibodies are present. Intrauterine infection of the foetus during the susceptible periods of development, i.e. around gestation days 60–180, by BVDV, SBV, BTV, AKAV and AV may cause malformations in the central nervous system, especially in the brain. Brain lesions typically consist of hydranencephaly, porencephaly, hydrocephalus and cerebellar hypoplasia, which in case of SBV, AKAV and AV infections may be associated by malformation of the axial and appendicular skeleton, e.g. arthrogryposis multiplex congenita. Doming of the calvarium is present in some, but not all, cases. None of these lesions are pathognomonic so diagnosing a viral cause based on gross lesions is uncertain. Several genetic defects share morphology with virus induced congenital malformations, so expert advice should be sought when BCMs are encountered.Electronic supplementary materialThe online version of this article (doi:10.1186/s13028-015-0145-8) contains supplementary material, which is available to authorized users.

Schmallenberg virus activity in cattle in Switzerland in 2013

SCHMALLENBERG virus (SBV), a novel Orthobunyavirus , was detected for the first time in November 2011 in Germany in blood samples originating from cattle suffering from acute clinical signs such...

Schmallenberg virus infection in South American camelids: Field and experimental investigations

During the first epizootic wave of the novel, teratogenic Schmallenberg virus (SBV, Orthobunyavirus) in ruminants in Northern Europe, serological evidence of a previous SBV-infection demonstrated that South American camelids (SAC) are also susceptible to SBV. However, their potential role in SBV spread remains unknown. To investigate the prevalence and course of SBV-infection in SAC, a German field study and an animal trial with three llamas and three alpacas were conducted.From September 2012 to December 2013, 313 of 502 SAC (62.35%) were found SBV seropositive, but negative for SBV-RNA. The estimated between-district (94.23% of 52) and median within-district (71.43%) and herd (73.13%) SBV seroprevalence in German SAC was similar to the seroprevalence reported in cattle herds and sheep flocks at the time. An age of >1 year was found a statistically significant risk factor for SBV-infection, which could be explained by the spatio-temporal spread of SBV in Germany during the study period. No clinical signs or an increase of abortion and congenital malformation associated with SBV-infection in SAC were reported by the study participants.Similar to SBV-infected ruminants, SBV-RNAemia in experimentally SBV-infected SAC was detected for a short time between days 3 and 7 after infection (dpi), and seroconversion occurred between 9 and 21 dpi.Despite the similar virological and serological results, the lack of clinical signs and congenital malformation associated with SBV-infection suggests that SBV causes subclinical infection in SAC. However, their role as reservoirs in the spread of SBV has to be further investigated.

Exposure of Asian Elephants and Other Exotic Ungulates to Schmallenberg Virus.

Schmallenberg virus (SBV) is an emerging Orthobunyavirus, first described in 2011 in cattle in Germany and subsequently spread throughout Europe, affecting mainly ruminant livestock through the induction of foetal malformations. To gain a better understanding of the spectrum of susceptible species and to assess the value of current SBV serological assays, screening of serum samples from exotic artiodactyls and perissodactyls collected at the Living Collections from the Zoological Society of London (Whipsnade and London Zoos) and Chester Zoo was carried out. There was compelling evidence of SBV infection in both zoological collections. The competitive ELISA has proved to be applicable for the detection of SBV in exotic Bovidae, Cervidae, Suidae, Giraffidae and most notably in endangered Asian elephants (Elephas maximus), but unreliable for the screening of Camelidae, for which the plaque reduction neutralisation test was considered the assay of choice.

Schmallenberg disease in sheep or goats: Past, present and future

Schmallenberg disease has emerged in North-Western Europe in 2011 and has since spread widely, even across the European borders. It has the potency to infect many, mainly ruminant, species, but seems to lack zoonotic potential. Horizontal transmission occurs through various Culicoides biting midges and subsequent trans-placental transmission causes teratogenic effects. In some small ruminants, clinical signs, including fever, decreased milk production and diarrhea occur during the viraemic phase, but infection is mostly asymptomatic. However, fetal Schmallenberg virus infection in naïve ewes and goats can result in stillborn offspring, showing a congenital arthrogryposis-hydranencephaly syndrome. The economic impact of infection depends on the number of malformed lambs, but is generally limited. There is debate on whether Schmallenberg virus has newly emerged or is re-emerging, since it is likely one of the ancestors of Shamonda virus, both Orthobunyaviruses belonging to the species Sathuperi virus within the Simbu serogroup viruses. Depending on the vector-borne transmission and the serologic status, future outbreaks of Schmallenberg disease induced congenital disease are expected.

Productive and reproductive performances of dairy cattle herds in Treviso province, Italy (2009-2012): an assessment of the potential impact of Schmallenberg virus epidemic.

BackgroundSchmallenberg virus (SBV) has spread across Europe since mid-2011, causing unspecific and transitory symptoms in ruminants and congenital malformations in their offspring. Evidence for the impact of SBV on cattle (re)productive performance is limited. Using a comprehensive data set from a SBV-affected province in North-East Italy, this study aimed at assessing the potential impact of SBV emergence on 11 productive and reproductive performance indicators of dairy cattle herds, accounting for weather conditions and other herd-level factors that could also influence these indicators.ResultsA total of 127 farms with an average of 71 cows per farm (range 29–496) were monitored monthly from January 2009 to June 2012. Mixed-effects linear models for longitudinal data were used to assess the average variation in herds’ performance indicators over semesters (Jan-Jun 2009, Jul-Dec 2009, Jan-Jun 2010, Jul-Dec 2010, Jan-Jun 2011, Jul-Dec 2011, Jan-Jun 2012) and trimesters therein. Taking the second semester of 2011 as reference, significant decreases in the average lactation length (−6 days, on average) and calving-to-conception interval (−4 days, on average) were observed relative to the same semesters of the years 2010 and 2009, respectively. Similarly, during the last trimester of 2011, which is most likely to cover the SBV infection period in the study area, there was an average decrease of −4 days (lactation length) and −7 days (calving-to-conception interval) compared to the same trimesters of the years 2010 and 2009, respectively. However, the observed decreases actually represent a positive outcome that is not as such imputable to SBV emergence, but rather reflects other beneficial changes in farm management. None of the other indicators showed significant variations, confirming the relatively mild expression of SBV infection in cattle.ConclusionsAlthough the emergence of SBV might have significantly affected the (re)productive performance of some individual farms, we concluded that overall at the province level there were no significant variations attributable to SBV, at least not in a way that would lead to negative effects on farm profitability.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-015-0527-1) contains supplementary material, which is available to authorized users.