SBV.  A FULL UPDATE

SCHMALLENBERG VIRUS,   Now shortened to SBV.

This is a completely new virus of the group Orthobunya Viruses, which have a known ability to mutate and exchange genetic material, leading to new strains being formed.

  It was first seen in the west of Germany in August 2011 as a disease of cattle which were generally off colour for 24 to 48 hours and had diarrhoea.  Milk yield dropped, sometimes substantially, but a full recovery was rapid. In retrospect, it is now being said that similar symptoms were seen in sheep and goats.

The full implication of SBV was not realised until October onwards, when some of the affected animals began to have deformed offspring, sometimes born prematurely,  the deformities often leading to dystokia.

The deformities vary, but in general it is thought that  calves infected in weeks 8 to 13 of pregnancy, and ewes and does infected between weeks 4 and 8 are born with vestigial brains, often replaced by hydrocephalus.  Offspring of dams infected in the middle third of pregnancy tend to  have deformed limbs and twisted necks, while those infected in later pregnancy tend to be born with stiff limbs. These are frequently born alive, but have difficulty in moving or sucking, and are often also affected with brain deformities which render them totally unable to cope with life.  There is anecdotal evidence from Holland and Germany that infected sheep flocks have had a higher than usual number of barren ewes, though no figures are available. Could this  suggest that infection very early in pregnancy will lead to early embryonic death?.

 Other members of the Orthobunya  virus group are known to be transmitted by the Culicoides genus of midge. SBV has now been found in C. Obsoletus and C Dewulfii midges caught in Belgium in September.  This does not yet PROVE that these midges are the vector insects for the disease, but it does make it a virtual certainty!!.  What is not known as yet is whether other species of biting insect might also be vectors.

 Since deformed offspring were first seen, disease has been confirmed by PCR on these animals on over 2000 premises, spread through  nearly all of Germany, Much of France, all of Holland and Belgium, Southern England, Luxembourg, and one so far isolated case  each in Northern Italy and Southern Spain.  Some of this spread is difficult to explain by likely vector spread, but could well be due to animal movements.

Read on for further information