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Schmallenberg virus

Between 2012 and 2014, infections with Schmallenberg virus (SBV) in Germany were detected in cattle, sheep and goats from 2504 holdings, in the subsequent years only sporadic cases were reported. Furthermore, the virus has been detected in numerous European countries since its first occurrence in late 2011.

In November 2011, the Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health (FLI) first detected a virus of the genus Orthobunyavirus in cattle in Germany. Comparative analyses of the genetic material revealed that the virus belongs to the Simbu serogroup (other members of this group are e.g. Sathuperi, Shamonda, Aino and Akabane viruses). The virus could be isolated, cultivated and replicated. Based on the geographic origin of the sample, the virus was designated Schmallenberg virus (SBV). Further investigations revealed that it belongs to the species Sathuperi virus and that it is no reassortant (novel virus generated by the exchange of genetic material of two or more viruses). The origin of Schmallenberg virus remains unclear.

The FLI developed a specific detection method (real-time RT-PCR) which was made available to the diagnostic agencies of the federal states and other European institutions, but also worldwide. In addition, licensed test systems for antibody detection exist. 

Simbu viruses are distributed in Australia, Asia and Africa and, as a rule, cause mild clinical symptoms which can lead to problems such as a reduction in milk yield, fever etc. persisting for several days. If pregnant animals are infected however, temporarily delayed, significant congenital damages, premature births and reproductive disorders may occur. The malformations are the consequence of infection at an early stage of pregnancy. The virus can be found in the blood of infected adult animals for a relatively short time. Once infected, animals develop immunity against the virus which protects them from re-infection. The duration of immunity is unknown. 

According to the current state of knowledge infection with SBV in sheep is more efficient than in cattle. In sheep, Schmallenberg virus mainly has been found in the brain of malformed lambs.

Simbu viruses mainly are transmitted by biting midges (blood-sucking mosquitoes). Biting midges infected with Schmallenberg virus have been detected in several European countries.

These viruses which are relevant in ruminants (cattle, sheep, goat) represent no risk for humans. They are no zoonotic pathogens. Due to the relationship of Schmallenberg virus with Sathuperi, Shamonda, Aino  and Akabane virus a human health risk is unlikely (also see risk assessment of the European Center for Disease Prevention and Control). Furthermore, investigations of the Robert Koch-Institute in persons who had close contact with infected animals, particularly sheep, did not provide any evidence of human infections (also see information of the Robert Koch-Institute).

Schmallenberg virus

In Germany animals from a total of 2504 holdings have been tested positive for Schmallenberg virus (SBV) since the beginning of 2012. The cases occurred in 1478 cattle holdings, 973 sheep holdings and 53 goat holdings. Affected federal states are North Rhine-Westphalia (295 cattle, 276 sheep, 14 goat holdings), Lower Saxony (235 cattle, 147 sheep, 6 goat holdings), Hesse (125 cattle, 142 sheep holdings, 11 goat holdings), Schleswig-Holstein (115 cattle, 110 sheep holdings, 1 goat holding), Rhineland-Palatinate (1 Bison holding, 52 cattle, 40 sheep, 5 goat holdings), Baden-Wuerttemberg (70 cattle, 40 sheep, 7 goat holdings), Brandenburg (26 cattle, 25 sheep holdings), Thuringia (35 cattle, 53 sheep, 2 goat holdings), Saxony-Anhalt (19 cattle, 23 sheep, 3 goat holdings), Hamburg (3 cattle, 6 sheep holdings), Bavaria (466 cattle, 48 sheep holdings, 1 goat holding), Saxony (18 cattle holdings, 44 sheep holdings), Mecklenburg-Western Pomerania (17 cattle, 14 sheep holdings, 1 goat holding), Saarland (1 cattle holding, 4 sheep holdings, 2 goat holdings) and Berlin (1 sheep holding).

Infections with Schmallenberg Virus have been detected in a row of european countries so far.

Table: Confirmed case number on the stocks concerned in Germany; last updated March 24, 2014, 9.00 h; source: TSN
Federal stateCattleSheepGoatTotal
Schleswig-Holstein1151101226
Hamburg369
Lower Saxony2351476388
North Rhine-Westphalia29527614585
Hesse12514211278
Rhineland-Palatinate53 (davon 1 Bison)40598
Baden-Wuerttemberg70407117
Bavaria466487515
Saarland1427
Berlin11
Brandenburg262551
Mecklenburg-Western Pomerania1714132
Saxony184462
Saxony-Anhalt1923345
Thuringia3553290
Total1478957

53

2504

In November 2011, the Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health (FLI) first detected a virus of the genus Orthobunyavirus in cattle in Germany. Comparative analyses of the genetic material led to the assumption that the virus belongs to the Simbu serogroup (like e.g. Sathuperi, Shamonda, Aino, and Akabane viruses). The virus could be isolated, cultivated and replicated. Based on the geographic origin of the sample, the virus was named ‛Schmallenberg virus’ (SBV). Further investigations showed that it belongs to the species Sathuperi virus and is no reassortant (a new virus that has developed by exchange of genetic material from two or more viruses). The origin of Schmallenberg virus is still unknown.

The FLI developed a detection method (real-time RT-PCR) that has been made available to institutions in Belgium, France, England, the Netherlands, Italy, and Switzerland. Meanwhile, a test system for antibody detection is also available. Different research groups have developed prototypes for inactivated vaccines, none of which has however been granted marketing authorization yet.

Simbu viruses are widely distributed in Australia, Asia, and Africa and, as a rule, initially cause very mild clinical symptoms which can lead to a loss in milk production, fever etc that may persist for a few days. If pregnant animals are infected, however, temporarily delayed, sometimes considerable congenital damages, premature births and reproductive disorders may occur. The malformations are a long-term consequence of infection at an early stage of pregnancy. The virus is detectable in the blood of infected adult animals for a relatively short period of time only. Once infected, the animals develop immunoprotection which prevents repeated infection based on the current state of knowledge. So far, it is unknown how long this immunoprotection lasts.

According to the current state of knowledge, infection with SBV is more efficient in sheep than in cattle. In sheep, Schmallenberg virus so far has mainly been detected in the brain of malformed lambs.

Simbu viruses are mainly transmitted by biting midges. Biting midges infected with Schmallenberg virus have so far been detected in Belgium, Denmark, Germany, Italy, and Norway.

These viruses which are relevant in cattle do not represent a risk for humans. They are no zoonotic agents. Due to the relationship of ‛Schmallenberg virus’ with Sathuperi, Shamonda, Aino, and Akabane virus, a risk for humans is not to be expected (also see risk assessment of the European Center for Disease Prevention and Control). A study of the Robert Koch-Institute showed no evidence for infections of people with close contact to infected animals, especially sheep (also see information of the Robert Koch-Institute).

Publications

Wernike K., Hoffmann B., Conraths F. J., Beer M. Schmallenberg Virus Recurrence, Germany, 2014. Emerg Infect Dis. 2015 Jul.

DOI: 10.3201/eid2107.150180


Wernike K, Nikolin VM, Hechinger S, Hoffmann B, Beer M. Inactivated Schmallenberg virus prototype vaccines. Vaccine. 2013 May

DOI: 10.1016/j.vaccine.2013.05.062 [Epub ahead of print]


Goller KV, Höper D, Schirrmeier H, Mettenleiter TC, Beer M. 

Schmallenberg virus as possible ancestor of Shamonda virus. Emerg Infect Dis. 2012 Oct.

DOI: 10.3201/eid1810.120835


Hoffmann B, Scheuch M, Höper D, Jungblut R, Holsteg M, Schirrmeier H, et al. Novel orthobunyavirus in cattle, Europe, 2011. Emerg Infect Dis. 2012 Mar.

DOI: 10.3201/eid1803.111905