Schmallenberg virus infection of ruminants: challenges and opportunities for veterinarians

Figures & data

Figure 1 European countries having reported cases of SBV infection in cattle, sheep, or goat herds or having detected antibodies in serum or milk between summer 2011 and late autumn 2014 presented as a cumulative list (A) and [img], [img], [img], [img], [img], [img] colored on a map of Europe (B).

Notes: *Countries having reported SBV re-emergence in 2012. ^#Countries having reported novel SBV episode in 2014.
Abbreviation: SBV, Schmallenberg virus.

Table 1 Mammalian species susceptible to SBV and classified following possible way(s) of identification of viral infection for each of them

Species	Clinical signs	Direct pathogen detection (SBV genome)	Indirect pathogen detection (anti-SBV antibodies)
Alpaca		x	x
Buffalo		x	x
Bison		x	x
Camelid			x
Cattle	x (A and N)	x	x
Chamois			x
Dog		x	x
Elk			x
Fallow deer			x
Goat	x (rare)	x	x
Horse			x
Mouflon			x
Muntjac			x
Red deer			x
Roe deer			x
Sheep	x (N)	x	x
Sika deer			x
Wild boar			x

Note: The 19 tested SBV-seropositive zoo species are not presented in this table.

Abbreviations: SBV, Schmallenberg virus; A, adult animals; N, neonates.

Figure 2 Schmallenberg virus infection in stillborn lambs presenting arthrogryposis, scoliosis, and torticollis (A), brachygnathia inferior (B), and cerebellar/cerebral hypoplasia (C).

Figure 3 Bluetongue virus serotype 8 infection in stillborn lambs presenting arthrogryposis (A), brachygnathia superior and anophthalmia (B), and cerebellar hypoplasia (C).

Figure 4 Diagnosis of SBV infection by observation of clinical signs in adult animals and aborted fetuses, stillborns, or newborns, and by performing most commonly used laboratory ways of diagnosis.

Note: ELISA and VNT allows to detect anti-SBV antibodies and are thus considered as indirect tools of diagnosis, while RT-PCR allows direct diagnosis because of detection of SBV genome in biological samples.
Abbreviations: SBV, Schmallenberg virus; ELISA, enzyme-linked immunosorbent assay; VNT, virus neutralization test; RT-PCR, real-time polymerase chain reaction.

Table 2 Comparison between BTV-8 and SBV

	BTV-8	SBV
Virus classification (family, genus)	Reoviridae, Orbivirus^Citation64	Bunyaviridae, Orthobunyavirus^Citation5
Viral genome	Double-stranded RNA virus	Negative-sense single-stranded RNA virus
Time of first detection	August 2006^Citation64	August 2011^Citation5
Places of first detection	Germany – the Netherlands – Belgium^Citation64	Germany – the Netherlands – Belgium^Citation5
Number of European affected countries at the end of the epidemic	Nine (Belgium, Czech Republic, Denmark, France, Germany, Luxemburg, the Netherlands, Switzerland, UK)^Citation64	27 (Figure 1)^Citation14
Transmission routes	Vector transmission^Citation64 Transplacental transmission^Citation66 Venereal transmission^Citation69,Citation70 Placentophagia^Citation66	Vector transmission^Citation6 Transplacental transmission^Citation42 Venereal transmission^Citation4,Citation33
Vectors	Insects: Culicoides spp.^Citation64	Insects: Culicoides spp.^Citation6
Susceptible species	Domestic ruminants (cattle, sheep, goat) Wild ruminants (eg, deer, elk) Carnivores species^Citation71,Citation72	Domestic ruminants (cattle, sheep, goat) Wild ruminants (eg, buffalo, deer, elk) Other mammalian species (eg, dog, horse, wild boar)
Clinical signs	Adult animals^Citation67  Nasal discharge  Excessive salivation  Subcutaneous edema (particularly on the head)  Ulceration of the oral mucosa  Cyanosis of the tongue  Abortions Aborted fetuses and newborns (essentially in sheep)^Citation67  Neurological deficits (“dummy” lamb)  Brachygnathia superior  Hydranencephaly  Hydrocephalus  Porencephaly, cerebellum and/or cerebrum aplasia, or hypoplasia	Adult animals (mainly in cattle and sheep)^Citation15  Hyperthermia  Inappetence  Diarrhea  Drop in milk production  Abortions Aborted fetuses and newborns (mainly in cattle and sheep)^Citation40  Arthrogryposis  Scoliosis, lordosis, torticollis  Brachygnathia inferior  Hydranencephaly, cerebellum and/or cerebrum aplasia, or hypoplasia
Duration of viremia	Until 5–14 days postinfection (experimental)^Citation65	Until 2–5 days postinfection (experimental)^Citation5
Common laboratory diagnosis	Observation of clinical signs Direct (BTV genome): RT-PCR Indirect (anti-BTV antibodies): ELISA and VNT	Observation of clinical signs Direct (SBV genome): RT-PCR Indirect (anti-SBV antibodies): ELISA and VNT
Prevention	Vaccination^Citation65	Vaccination^Citation58
Impact on ruminant health and productivity	Important^Citation67	Low or limited^Citation42

Abbreviations: BTV-8, bluetongue virus serotype 8; SBV, Schmallenberg virus; RT-PCR, real-time polymerase chain reaction; ELISA, enzyme-linked immunosorbent assay; VNT, virus neutralization test.

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