Surveillance and Schmallenberg Virus Alasdair Cook MRCVS, AHVLA. Sheep Health & Welfare Conference Worcester, 21 st November 2012

Transcription

1 Surveillance and Schmallenberg Virus Alasdair Cook MRCVS, AHVLA Sheep Health & Welfare Conference Worcester, 21 st November 2012

2 AHVLA: Supporting a healthy and sustainable food and farming industry across Great Britain, and safeguarding society from animal related threats

3 Surveillance The systematic, ongoing or repeated measurement, collection, collation, analysis, interpretation and timely dissemination of animal health related data, essential for describing hazard occurrence and for the planning, implementation, and evaluation of risk mitigation measures Intelligence to inform decisions

4 Surveillance purposes AHVLA conducts animal health surveillance for Government in order to: Detect & control notifiable & statutory diseases Provide evidence for decision-making on animal disease Detect new or re-emerging threats to animal health Protect animal health & welfare Protect public health Provide evidence of freedom from disease Enable trade in livestock & livestock products

5 Surveillance methods Scanning (early-warning) surveillance: Voluntary reporting & interrogation of information, especially via submissions to AHVLA laboratories but increasingly through other sources of information Active surveillance: Formal surveys or other investigations commissioned by Government or others Scanning surveillance is a partnership between farmers, their private vets, AHVLA & Government Schmallenberg virus infection is an example of surveillance in action

6 Schmallenberg virus (SBV) SBV is an Orthobunyavirus Several members including Akabane virus also within this family and are known to cause congenital malformations in ruminants Short viraemia 2 5 days Followed by immunity Although SBV is related to Akabane and has shown similar effects, as it is a new disease we cannot be certain it will behave in the same manner

7 Diagnostic tests available Clinical sign and post mortem findings PCR detects virus RNA in tissues (brain) Histopathology typical microscopic appearance but slow and expensive Virus isolation Virus isolated in Germany and used for experimental inoculation of calves. Virus was detectable in blood for 2-5 days For surveillance our first aim was to establish whether SBV was present in any suspect herd or flock and our second aim was to determine whether any herds or flocks in an area had been affected

8 Antibody tests Antibody tests (serology): show evidence of previous infection through presence of antibodies in serum, milk or fetal fluid Infection may not be associated with clinical disease Antibodies are produced by the immune system after infection Antibody positive animals are probably immune to future infection Useful in surveys to show level of exposure In Netherlands, over 70% of cattle or sheep in affected herds or flocks were seropositive. This implies that many individuals were infected with SBV but did not have any evidence of disease Note that antibody tests cannot demonstrate when infection occurred

9 Sheep PCR testing by week Jan April /1 20/1 27/1 3/2 10/2 17/2 24/2 2/3 9/3 16/3 23/3 30/3 6/4 13/4 20/4 A few new infections must have occurred during the low midge activity season

10 Maps proved useful for understanding the distribution of SBV

11 Regions at risk of midge incursion 2011 Once SBV entered England, onward spread also possible by native midges

12 Counties where SBV confirmed in malformed fetuses

13 Counties where survey serology showed evidence of prior SBV infection in sheep

14 Acute SBV disease in cattle

15 GB Situation

16 Summary of present situation SBV has spread extensively in 2012 Currently, no evidence to suggest that the impact in flocks infected this season will be different to last season Most flocks will have little impact A few flocks may see more severe impact, depending on time of infection in relation to breeding Be aware of risk of problems at lambing if malformed lamb present Studies suggest that the majority of an infected flock will develop immunity even though only a few show clinical signs Testing is available from AHVLA, SURC and commercial labs Discuss your own circumstances with your vet, who can seek advice from AHVLA or SURC Whilst we understand more about SBV now, it is still a new disease and may surprise us.

17 Links HPA: Schmallenberg virus AZ/EmergingInfections/SchmallenbergVirus/ Defra: News: advice to pregnant women to avoid close contact with animals that are giving birth Defra: Animal diseases: Schmallenberg virus HSE: Information Sheet 23: Preventing or controlling ill health from animal contact at visitor attractions Welsh Government: w/disease/schmallenbergvirus/?lang=en

18 Acknowledgements Ian Davies Gavin Watkins Moyna Richey Adrian Colloff Gareth Hateley Falko Steinbach Helen Roberts Christine Middlemiss & many other colleagues across AHVLA, SURC/SAC, Defra & Welsh Government EBLEX National Sheep Association Sheep Vet Soc BCVA NFU & especially to all farmers and vets who have assisted us

19 Thanks + Questions