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Current Concerns  >  2012  >  No 9, 1 March 2012  >  Answers of the Friedrich-Löffler-Institute to questions concerning the Schmallenberg virus [printversion]

Answers of the Friedrich-Löffler-Institute to questions concerning the Schmallenberg virus

State of affairs 13 January 2012

What is the Schmallenberg virus and where does it come from?

The Schmallenberg virus is an orthobunya virus which is closely related to the so called Simbu-serogroup. This group for example includes the Akabane-, the Shamonda- and the Aino-virus. The closest genetic similarity was found to the Shamonda-virus. These viruses are known from Africa, Asia and Australia. It is the first detection of viruses of this group in Europe. It is not clear so far how this virus got to Europe.

Which animals are affected?

So far cattle, sheep and goats are affected.

Can wild ruminants (roe deers, red and fallow deers, muofflons) also become infected?

It can be taken for granted that infections also are possible in wild ruminants. But it is not yet understood what effects an infection will have in wild animals.
Hunters should pay attention to malformed fawns and calves mostly in regions where the virus was detected in cattle, sheep or goats. Malformed young animals should be reported to the responsible authorities or brought to an examination.

Why are the descendants damaged and how is the disease timeflow? Does the infection take place in a certain stadium of pregnancy (like the Akabane-virus in sheep probably between day 28 and 36 (56) and in cattle probably between day 75 and 110 (150)), the virus can infect the fetus and lead to serious damages.

Alongside abortion and mummified fetuses especially premature birth or stillbirth and the birth of malformed and weak lambs is typical. Such serious effects could also occur in calves.

The most frequent malformations are serious arthrogryposis (joint stiffness, tendon shortening), torticollis (strongly overstretched neck) and hydranencephaly (missing of brain structures and replacement through cerebrospinal fluid, hydrocephalus). The central nervous system can show most grievous deformations. Collectively the clinical picture is similar to that of infections with the Akabane virus. The malformations induced through viruses of the Simbu-serogroup are called “arthrogryposis-hydranencephaly-syndrom (AHS)”.

How is the virus transferred?

The transmission of the Schmallenberg virus probably happens like in the other viruses of the Simbu-serogroup by insects (biting midges and mosquitoes).

How can receptive animals be protected?

At the moment the protection of receptive animals from biting midges /mosquitoes is the only possibility which comes into question for a reduction of cases in the next season. For now a vaccine is not available.

Is a vaccine developed?

The development of a vaccine initially will probably concentrate on an inactivated vaccine (inactivated virus with adjuvants). For the development of a prototype several months are required. After that harmlessness and effectiveness of the vaccine have to be examined especially in pregnant animals before it can be approved and used. How long this process will take can not be estimated yet.

The FLI is involved in the development of such a prototype.

Are once infected animals protected of further infections?

We can proceed from the assumption that infected animals build an immune protection. So far in infected animals neutralizing antibodies against the virus could be detected. How long this immunity persists is not yet known.

If an infected mother suffers a stillbirth will the next young also be damaged?

At the present state of knowledge the malformations caused by the Schmallenberg-virus are only expected in the youngs of infected, not immune mothers. An infected mother develops antibodies whereby no negative effects on the fetus should be possible during a new infection. But it is not known how long the natural immunity of once infected animals persists.

Could other animals (horses, pigs, dogs etc.) be infected?

At the present time no statement is possible to this. It is known from the Akabane-viruses that they can infect pigs. In horses and dogs there were found antibodies as well, but the animals don’t show any clinical symptoms.

Corresponding examinations shall be carried out with the Schmallenberg virus.

Can the Schmallenberg virus infect humans?

Viruses similar to Akabane virus which already occurred in cattle represent no risk to humans. They are no zoonotic agents. According to present state of knowledge because of the relationship of the Schmallenberg-virus with the Shamonda, Aion- and Akabane-viruses a risk for humans has not to been assumed. (see the risk assessment of the European Centre for Disease Prevention and Control: http://ecdc.europa.eu/eu/publications/Publications/Forms/ECDC_Dispform.aspe?ID=795.

Which kind of danger comes from milk-, meat and game products?

According to the present state of knowledge there is no danger.

Who is responsible for the examinations of the animal?

Responsible for the examinations are the veterinarian laboratories of the federal states. The FLI clarifies suspected cases in so far not affected regions and in newly affected animal species.

Which kind of ancillary samples is most suitable for an examination?

For the detection of pathogens during the acute infection of adult animals serum probes or anticoagulated blood are suitable. They have to be taken during the acute clinical phase (fever, decline of milk, diarrhea).

The detection of pathogens in fetuses, aborted fetuses, stillbirths and malformed lambs and calves (AHS) is made mainly from brain probes. Splenic and blood probes should be examined if possible. The probe material should include at least cerebrum, cerebellum, spleen and blood.

Is there an antibody-test?

At the moment there is no antibody-test suitable for large scale use. At present time the FLI uses an indirect immunofluorescence test and a serum neutralization test. Because of this only restricted numbers of probes can be examined. An ELISA-Test (Enzyme linked Immunosorbent Assay) suitable for large scale use is under development.

Source: Das Magazin für Schaf- und Ziegenhalter (www.schafzucht-online.de, www.fli.bund.de)

(Translation Current Concerns)