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Published Date: 2018-03-08 21:08:27
Subject: PRO/AH/EDR> Schmallenberg virus - Europe (05): Ireland, ovine, bovine
Archive Number: 20180308.5673917
SCHMALLENBERG VIRUS - EUROPE (05): IRELAND, OVINE, BOVINE
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Date: Wed 7 Mar 2018, 2:00 PM GMT
Source: Independent.ie - Farm Ireland [edited]
https://www.independent.ie/business/farming/sheep/schmallenberg-virus-appears-to-have-spread-further-north-in-ireland-in-2017-vet-labs-36679665.html


A high number of suspected Schmallenberg virus (SBV) cases in aborted lambs and calves were recorded by the Regional Veterinary Laboratories (RVL) network in the 1st week of this year [2018].

A number of suspect cases particularly in lamb foetuses submitted to Sligo and Athlone RVLs have birth deformities that are very suggestive of the effects of SBV infection of ewes during pregnancy, according to an RVL report.

It says while the polymerase chain reaction (PCR) results for these submissions are still pending to date, they appear to confirm observations by RVLs last autumn [2017] of animals showing antibodies to SBV present in previously unaffected areas north of the Dundalk-Galway line (Sligo, Cavan, Leitrim, and probably neighbouring counties).

Prior to this, all confirmed cases originated from the southern part of the country.

SBV infection causes only mild, unspecific clinical signs such as pyrexia, milk drop, anorexia, weight loss, and diarrhoea in adults.

In pregnant animals, it can cause abortions from the early stages of pregnancy and a range of congenital deformities that primarily affect the central nervous and musculoskeletal system and may be variable in severity.

Deformities commonly include arthrogryposis, (bent limbs, fixed joints) kyphosis, scoliosis, torticollis (twisted neck, spine), brachygnathia (short jaw), hydranencephaly [cerebral hemispheres absent to varying degrees and remaining cranial cavity is filled with cerebrospinal fluid], and cerebellar dysgenesis [abnormal development] that may occur or 'dummy' calves if infected at certain times during pregnancy.

Congenital deformities may occur due to other toxic and viral conditions, however, SBV should be suspected if there are multiple incidences in the same herd within a short time window and if deformities are similar to those described above.

[Byline: Ciaran Moran]

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[Since all earlier confirmed cases in Ireland "originated from the southern part of the country", it is suggestive that the virus has spread northwards by windborne infected vectors (primarily culicoid midges). Meteorological and climatic data, pertaining to the 2017 autumn months, may be helpful in analysing the spread pattern.

Sheep, due to their relatively short pregnancy (5 months, compared to 9 in cattle) will be the 1st to demonstrate deformed offspring following their exposure to the SBV during pregnancy, earlier than pregnant cows that have been simultaneously exposed. On the other hand, SBV has not been reported to cause clinical signs in infected sheep during their viraemic stage, while in susceptible adult bovines, transient febrile illness and milk drop were observed subsequent to their infection (see further details at https://www.agriculture.gov.ie/animalhealthwelfare/diseasecontrol/schmallenbergvirus/).

SBV is a member of the Simbu serogroup within the genus _Orthobunyavirus_ (family _Bunyaviridae_), which contains more than 170 viruses of different medical and veterinary relevance. Orthobunyaviruses are divided into 18 serogroups, and SBV belongs together with e.g. Akabane virus (AKAV), Aino virus(AINOV), Simbu virus, Douglas virus, and Sathuperi virus to the Simbu serogroup. These viruses are primarily transmitted by insect vectors (midges, mosquitoes). There is no direct transmission from animal to animal, other than maternal transmission from mother to offspring, in utero. There is no evidence to suggest that SBV is transmissible to humans; to date, people who have been in close contact with infected animals (such as animal workers, farmers, and veterinarians) have not reported any unusual illnesses. The disease is not officially notifiable.

Exposure to a similar virus -- Akabane virus (initially reported from Australia, Japan, and Israel during the 1960's/70's) induced strong immunity in the infected ruminant population which remained immune for several years following an episode of the disease. In fact, natural infection of young animals prior to their 1st pregnancy is rather advantageous, rendering them with natural immunity and preventing foetal infection/damage if/when exposed to the virus later during pregnancy. - Mod.AS

Maps of Ireland: http://smartraveller.gov.au/Countries/europe/northern/Pages/ireland.aspx#modal-country and http://healthmap.org/promed/p/39.]

See Also

Schmallenberg virus - Europe (04): UK (N. Ireland), ovine 20180224.5648493
Schmallenberg virus - Europe (03): UK (N. Ireland), ovine 20180210.5620283
Schmallenberg virus - Europe: UK (Scotland) bovine 20180105.5539887
2017
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Schmallenberg virus - Europe (06): Ireland (Midlands), bovine, susp. 20171216.5507986
Schmallenberg virus - Europe (05): UK (England, Wales, N. Ireland) ovine, bovine 20170610.509713
Schmallenberg virus - Europe (04): UK (England), ovine, increased incidence, RFI 20170301.4873070
Schmallenberg virus - Europe (03): UK (England, Wales), ovine, bovine 20170211.4831904
Schmallenberg virus - Europe (02): UK (England, Wales, Scotland) bovine 20170204.4814854
Schmallenberg virus - Europe: Ireland (CO, LS) bovine, reemergence 20170106.4747269
2016
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Schmallenberg virus - Europe (02): UK (England, Wales), reemergence susp 20161214.4698989
Schmallenberg virus - Europe: Netherlands, Belgium, reemergence 20161023.4578989
2013
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Schmallenberg virus - Europe (27): UK (Scotland) update 20130630.1800385
Schmallenberg virus - Europe (18): UK (Scotland) bovine, 1st clin case 20130420.1660025
Schmallenberg virus - Europe (16): UK (Scotland) update 20130328.1608058
2012
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Schmallenberg virus - Europe (70): UK (N Ireland) 1st case 20121102.1387033
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