Three Different Routes of Inoculation for Experimental Infection with Schmallenberg Virus in Sheep

Abstract

Schmallenberg virus (SBV) is an emerging Orthobunyavirus affecting European domestic ruminants. In this study, three groups of ewes (n = 3) were inoculated with 1 ml of an SBV infectious serum, via the subcutaneous (SC), intradermal (ID) or intranasal (IN) route. The ewes were monitored for 10 days and no clinical signs were reported. IN inoculation failed to generate any detectable RNAemia. SC and ID inoculation induced typical SBV RNAemia and seroconversion upon day 6 post-inoculation in 3/3 and 2/3 sheep, respectively. In all the animals that showed RNAemia, the viral genome could be detected in spleen and mesenteric lymph nodes. Both the SC and ID routes seem suitable to properly reproduce field conditions, as comparable observations were reported regarding RNAemia, seroconversion and viral genome detection in organs.

Monitoring of Schmallenberg virus in Spanish wild artiodactyls, 2006–2015

“…To the best of our knowledge, this is the first time SBV RNA has been detected in these species. The low frequency of SBV RNA-positive animals is consistent with the short duration of viraemia detected in domestic ruminants [ 22 ,43, 41 ]. The presence of SBV RNA-positive animals confirms the circulation of the virus during the years 2011 and 2015.…”

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

“…As meconium is an end-product of the amniotic fluid being swallowed by the fetus during gestation time, it is likely that SBV detection in the meconium could reflect the former transient presence of the virus in the amniotic fluid. Fecal shedding was reported following SBV experimental infection in heifers [ 46 ] and ewes [ 47 ]. Hence positive SBV RNA detection in meconium might be the in utero version of the previously reported positive detection in the feces of adult animals.…”

Reliable and Standardized Animal Models to Study the Pathogenesis of Bluetongue and Schmallenberg Viruses in Ruminant Natural Host Species with Special Emphasis on Placental Crossing

“…In several recent studies [14] clinical signs reported in BTV infected animals were of a lesser extent than those reported from the field [14,17,27,28,32,33,34]. As modified live vaccines gain their attenuation through serial cell passages, the first and most obvious hypothesis to explain the mild severity of bluetongue disease in the experiment is the use of culture grown virus.…”

“…Several authors including us [17] used mixed routes to overcome the respective disadvantages of each approach (Table 1; [34,54]). In a study of our group, we compared intranasal, intradermal and subcutaneous routes for experimental infections of ewes with SBV [28]. Intradermal is an interesting yet underused route: indeed most haematophagous arthropods do not pass the skin and their mouthparts only allow them to feed intradermally.…”

“…We investigated the intranasal route to test whether or not a potential direct SBV contamination between sheep could be achieved [28]. Regarding BTV several authors reported unexpected and inconclusive direct horizontal transmission with different serotypes (BTV8, BTV1, and BTV26 at least) [58,59,60,61].…”