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Table 2 Overview of experimental and field studies with Schmallenberg virus in domestic ruminants contributing to our understanding of the efficacy of transplacental crossing, the capacity to induce congenital malformations, and the relationship between clinical and pathological malformations observed at birth in offspring and the moment of gestation at which the dam became infected

From: Schmallenberg virus: a systematic international literature review (2011-2019) from an Irish perspective

Study type Virus strain Species No. studied Inoculation route Stage of gestation (day) at infection Stage progeny examined Major Outcome Reference
Exp. Field
+   FLI inoculuma Cattle 24 Sub-cutaneous 60-150 6 weeks PI Preliminary data; indications for efficient placental crossing but limited capacity to induce malformations Schmallenberg virus: Final Report EU, 2014c
+   FLI inoculuma Cattle 11 Sub-cutaneous 105-120 10-28 DPI Preliminary data; indications for efficient placental crossing but limited capacity to induce malformations Schmallenberg virus: Final Report EU, 2014c
  + Field Cattle 71 Vector-mediated 13-162 At birth Evidence of transplacental SBV infection only found in 13% of calves at birth; only 1 calf with malformations [69]
+   Field Cattle 36 Sub-cutaneous 60-150 10-35 DPI SBV genome was detectable in at least one organ system of 18 out of 35 foetuses, but limited capacity to induce malformations [225]
+   FLI inoculuma Sheep 21 Sub-cutaneous 38-45 7 DPI Preliminary data; indications of transplacental crossing in 64% of foetuses at 7 DPI; no malformations observed Schmallenberg virus: Final Report EU, 2014c
+   FLI inoculuma Sheep 28 Sub-cutaneous 45-60 At birth Evidence of transplacental SBV infection only found in 14% of lambs at birth; no congenital malformations observed [119]
+   FLI inoculuma Sheep 17 Sub-cutaneous 45-60 At birth Evidence of transplacental SBV infection; no congenital malformations observed; Placenta of 5 ewes contained infectious SBV at birth [168]
+   FLI inoculuma Goats 10 Sub-cutaneous 28-42 14-25 DPI Preliminary data; several haemorrhagic and small foetuses observed after SBV infection Schmallenberg virus: Final Report EU, 2014c
  + Field C/S/G 13 Vector-mediated 32-81 NS 13 cows with early foetal death after SBV infection [98]
  1. Table adapted from De Regge et al. (2017) [226]. Exp Experiment, NS Not specified, C Cattle, S Sheep, G Goats, DPI Days post inoculation
  2. aInoculum consisting of bovine serum collected 3 days post SBV infection, prepared and distributed by Friedrich Loeffler Institute
  3. bSchmallenberg virus, March 2014, Technical and scientific studies, Final Report for the European Union Commission implementing Decision of 27 June 2012: available online at library.wur.nl/WebQuery/wurpubs/fulltext/310772