dr. peter merrill - schmallenberg syndrome and the precautionary principle: a case study in...
TRANSCRIPT
Peter L. Merrill, DVMDirector, Animal Imports
National Import Export Services
USDA APHIS Veterinary Services
NIAA ConferenceOmaha, NE April 1, 2014
Learning Objectives
Quick review of relevant Precautionary Principle issues, as well as APHIS’ missions
SBV: What, Who, Where, When, How
EU and US positions (past and current)
What’s at stake?
Salient PP Issues
KNYK, NKWYN, KWYDK, NKWYDK ‘Better safe than sorry’ ‘First, do no harm’ ‘The absence of evidence is not evidence of absence’ Proving the negative If an action or policy has a suspected risk of causing harm
to animal [public, environmental, etc.] health in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is NOT harmful falls on those taking an action
Problematic consensus regarding ‘suspected’, ‘risk’, ‘harm’, ‘science’
Zero-Risk Tolerance
Salient Missions: USDA/APHIS/VS/NIES
Protecting American agriculture while facilitating (safe) trade
Gaining, expanding, or retaining (safe) market access for animals and animal products/byproducts
Prevent the introduction of dangerous and costly pests and diseases (vs. mitigating/eradicating post-entry)
Domestic animal health and export status linked
What is Schmallenberg syndrome?
Disease caused by infection with Schmallenberg virus (SBV), named after region in North Rhine-Westphalia, Germany where virus was first isolated
Group V: enveloped, (-) sense, segmented, ssRNA
Family Bunyavirudae: Genus Orthobunyavirus: Simbuserogroup (e.g. Aino, Akabane, Shamonda viruses)
Closest relatives: Douglas/Sathuperi viruses
Causes a form of arthrogryposis-hydranencephalysyndrome (AHS)
Who is affected?
Ruminants (cattle, sheep, goats, bison, water buffalo, camels, llamas, alpacas, mouflon, roe/red/fallow deer. moose)…others?
Horses
Wild boar
Dogs?
Not presumed zoonotic
Farmers, regulators
Where did SBV come from, and where is it now? Origin uncertain/unknown; first Simbu virus in Europe
19 EU Member States (Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Hungary, Germany, Ireland, Italy, Latvia, Luxembourg, Netherlands, Poland, Slovenia, Spain, Sweden and United Kingdom)
3 other European countries (Switzerland, Norway, Croatia)
Many thousands of farms/holdings affected in Europe
NOT in North America
When did SBV appear? Probably Summer 2011 (first cases reported November) in The
Netherlands, Belgium and Germany
Continuous temporal distribution since 2011 has resulted in steady progression north and east
Sept 2011--Apr 2012
Sept 2012--Oct 2012
Nov 2012--Apr 2013
May 2012--Aug 2012
When did SBV appear?
SBV (2011-13) BTV(2003-13)
How is SBV transmitted? Biting midges (Culicoides spp.); other insects?
Transdermal; secretions?
Viral incubation/replication
Infective virus shed in bovine/ovine/caprinesemen
Trans-placental transmission to embryo/fetus
How is SBV transmitted? Wildlife reservoirs? Vector over-wintering Fomites Other pathways? Virulence factors; temporal evolution Material found to be positive by virus isolation (up to October
2013): Blood and semen from affected adults; and brain from infected
fetus
Material found PCR-positive (up to October 2013): Organs and blood of infected fetus, placenta, amniotic fluid,
meconium
Following an acute infection, SBV RNA can be detected up to several weeks in different tissues like semen, lymphatic organs (esp. mesenteric lymph nodes), and spleen
How is SBV detected? Clinical signs (not pathognomonic); abortions; stillbirths;
AHS
Viral culture: insect cells (KC); hamster cells (BHK), monkey kidney cells (VERO)
Serology: virus neutralization; serum neutralization,
IFA, ELISA
Molecular: RT-PCR (blood, not semen), rRT-PCR, EM
Samples for pathogen detection in acute infection: serum or EDTA blood samples when clinical signs are observed (fever, drop in milk yield, diarrhea).
Samples for pathogen detection in fetuses, abortions, stillbirths and malformed ruminants: brain (cerebrum and brainstem), amniotic fluid and placenta.
How is SBV neutralized*? Temperature: Infectivity lost (or significantly
reduced) at 50–60°C for at least 30 minutes.
Chemicals/Disinfectants: Susceptible to common disinfectants (1 % sodium hypochlorite, 2% glutaraldehyde, 70 % ethanol, formaldehyde)
Survival: Does not survive outside the host or vector for long periods
*extrapolated from other Orthobunyaviruses
How is disease* caused? Incubation period 1-4 days; viremia lasts for 1 -5 days
AB response; avg. seroconversion by 14-28 dpi
Morbidity/mortality*: up to 100%/<1% respectively in adults
In adult animals that are NOT pregnant: infection leads to variably transient/relatively brief clinical symptoms including:
inappetance
fever
diarrhea
loss in milk production
(up to 50% in dairy animals)
* More studied in cattle than sheep/goats
How is disease caused? In pregnant females, infection also leads to variable levels
of increased birth defects (species-dependent, but avg. ~4%?)
Critical gestational susceptibility: d. 40-150 (bovines);
d. 20-80 (S/G)
Abortions; stillbirths
Arthrogryposis/ Hydranencephaly
Brachygnathia inferior
Ankylosis; torticollis; scoliosis
Hypoplasia of the central nervous system
Porencephaly
Subcutaneous edema (calves)
How can SBV be prevented/treated? No treatment once infected/clinical Location in non-vector areas Re-synchronization of breeding season Vector-proofing breeding facilities Test/remove/culling Deliberate exposure (duration of immunity uncertain, or
whether cross-protective against new serotypes) Passive immunity via colostrum Killed vaccine commercially available; 2 doses 4 wks apart
(cattle); 1 dose S/G; cost variable but can be >$10/head; efficacy unknown
Passive immunity may interfere w/vaccine-stimulated ABs Genetic resistance?
European Approach (SBV)
Research (FLI, others)
EFSA reports
Impact Analysis
EC web portals
OIE Technical Fact Sheet
Intra-European Trade (SBV)
The European Commission (EC) has not applied any specified trade restrictions due to SBV;
Not a reportable condition; some individual Member States require donor testing and certifications (Intra-Community movement eligibility similar to US interstate requirements)
The EC does not consider that live animals, meat, milk or animal by-products to pose a risk of transmission
The EC considers restrictive trade measures for SBV taken by trading partners against exports of ruminants and their products are not justified
Similar to position for Aino/Akabane/BT (retrospectively)
OIE Technical Fact Sheet/EFSA correlations
EU Inventories and Statistics*
Bovines: ~115 million domestic head (2012)
Imports: none (from non-EU sources)
Exports: ~500,000/yr. (to non-EU countries)
S/G: (avg. annual 2007-11): ~90 million domestic sheep; ~13 million goats
~1.9 million sheep exports/yr. to non-EU countries (zero imports)
Economic values: well over $100 billion
Overall impacts from SBV losses unknown, but substantial
* Various sources
APHIS approach for SBV as an emerging disease
SBV technically meets criteria for FAD
APHIS considered (and considers) SBV as a significant emerging disease not known to be present in the United States
Canadian import requirements generally similar
Mexico import requirements: none?
Questions remain about the transmission risks associated with SBV; more research and information is considered necessary in order to determine an appropriate level of trade restrictions to prevent the introduction or spread of the disease
APHIS approach for SBV as an emerging disease
Pathways analysis
Culicoides vectors: C. obsoletus, C. dewulfi; others?
Case definition
Passive surveillance; AOS
APHIS fact sheets/outreach to industry
Laboratory collaborations
Scientific/trade information monitoring
Modified risk assessment through extensive literature review
Discussions with Canada and other trade partners/industry
Proactive import restrictions for ruminant germplasm
APHIS approach for SBV as an emerging disease
NIES Import Alerts: first in Mar. 2012
Applicable to EU and countries following EU legislation (exc. Iceland)
Only allowed bovine S/E collected prior to June 1, 2011
Oct. 2012-- additional criteria: Donors can be tested twice for SBV by a serum neutralization assay, with negative
results (using a 1:8 cutoff titer). The first SBV test must be performed within 30 days prior to collection, and the second between 28 and 60 days after collection. Tests must be performed at a laboratory approved by the country’s competent authority for animal health. Any serologically positive resident donors were re-tested negative by real-time RT-PCR or virus isolation within 4 days after additional collection(s) for export to the United States
May 2013-- further revision of that last sentence above: Until additional information is available, semen and embryos collected from bovines
that are seropositive for SBV are not eligible for importation to the United States
2014: Comprehensive Systematic Review (KNYK, etc)
O/C semen still not eligible for importation
Inventories and financial stats*: Ovines/Caprines
~77,000 sheep farms in the U.S
~138,000 goat farms in the U.S.
~5.5 million domestic sheep; ~2.5 million goats
<10,000 live sheep/goats imported/yr. (Can/Aus/NZ)
Avg. U.S. annual economic importance: live S/G imports value of ~$300,000 ; germplasm much less
U.S. exports of live S/G: ~$5 million
Domestic market value: ~$500 million sheep; goats?
*various sources
Inventories and financial stats*: Bovines
~750,000 beef cattle farms in the U.S.
~50,000 dairy cattle farms in the U.S.
US (2014): 87.7 million domestic head (lowest since 1951)
Imports: ~2 million/yr.
Exports: ~100,000/yr.
Avg. U.S. annual economic importance: live bovine/germplasm import value of ~$4 billion
U.S. exports of live bovines/germplasm: ~$300 million
Domestic market value: ~$50 billion beef; ~$45 billion dairy
* various sources
Industry and other perspectives Reported morbidity/mortality provided by EU farmers
differ widely from EFSA estimates and conclusions
Many S/G farms experience between 20-50% birth defects
Actual economic consequences can be catastrophic depending on many exposure factors
US ruminant producers have generally been supportive of APHIS’s position/approaches
US germplasm industry also generally supportive to date
European Commission has been highly critical of APHIS and other countries’ risk-aversion positions to date
‘Right’ vs. ‘wrong’ approaches?
Systematic Review results will help clarify the risk picture
Questions?