Management of an infectious disease yard outbreak BEVA East Anglia Regional Meeting Tuesday 16th April 2013 Philip Ivens MA VetMB CertEM (Int.Med.) DipECEIM MRCVS European Specialist in Equine Internal Medicine Outbreak toolbox Information Prevention Communication HBLB Codes of Practice ACVIM Consensus Statement Control the outbreak Diagnostic tests Taking advice Livery Yard – Unique challenges • Diverse and individual owners • Conflicting interests and economic status • Key for message to be clear and simple • Key for multi-vet yards to work together • Yard owner/manager central to this. Outline • Disease situation – local and national/international • Differentials Diagnoses • Clinical Signs • Diagnostic Tests • Biosecurity and vaccination Disease Situation Locally • Local knowledge/experience – internal practice communication/team work. • Communication between practices • Local laboratories Disease Situation Nationally • National Laboratories – e.g. AHT. • DEFRA/AHT/BEVA Equine Quarterly Disease Surveillance Reports - http://www.aht.org.uk/cmsdisplay/disease_surveillance.html • Influenza Alert System - Merial • Strangles mapping – future? Strangles Outbreaks • Text alerts for vets when equine flu diagnosed at the AHT – – – – – Raise awareness of equine influenza in the UK Increased surveillance Increase number of horse vaccinated Improved health and welfare of UK horses Reduce the risk of an outbreak in the UK • Sign up at www.merial.co.uk or today! • 10 confirmed outbreaks in 2010 • 11confirmed outbreaks in 2011 • 9 confirmed outbreaks in 2012 • 30 outbreaks in 23 counties • All clade 2 Disease Situation Internationally Endemic DDx Viruses: • EIV – Influenza • EHV1,4 – Herpes • ERV – Rhinovirus • Adenovirus Bacteria: • Streptococci • • • • S. equi subsp equi S. equi subsp zooepdemicus S. dysgalactiae subsp equisimilis S. pneumoniae Non-infectious: • RAO/IAD • Smoke inhalation Exotic DDx Viruses: • EVA • Hendra Virus • AHS • (Parainfluenza-3) Bacterial: • Glanders Clinical Signs – Any help??? • Fever • Nasal Discharge – mucoid→mucopurlent • Submandibular Lymph Nodes Enlargement • Cough • Conjunctivitis, anorexia, depression Clinical Signs Table Fever Influenza Nasal Discharge SMLN Cough +++ 2-4dys Serous initially ++ +++ Paroxysmal ++ Biphasic 8-10dys Serous initially ++ + ERV ++ Serous initially ++ + EVA ++ Serous initially ++ ++ Strangles +++ Purulent +++ + Strep zoo ++ Purulent ++ + EHV1,4 Diagnostic tests • Which animals, which samples, which tests? End-point analysis of amplification product • Interpretation? Diagnostic Tests • Strangles – most common and general principles • EHV-1,4 • Equine Influenza Strangles - Culture • Gold standard for diagnosis? • Nasopharyngeal swabs, abscess or (GP lavage) • β-haemolytic, Group C Gram positive cocci • Does NOT ferment lactose, sorbitol, ribose. • Need sufficient live bacteria for a positive - FRAGILE PCR • Detects nucleic acid (bacterial DNA) • Exponential (enzyme catalysed) amplification of target DNA sequences • Very sensitive in ideal conditions • Sensitivity reduced in clinical samples • Rapid (hours) and specific • Potentially quantative End-point analysis of amplification product Interpreting Strangles PCR results PCR positive PCR negative Culture positive ? ? Culture negative ? ? Interpreting Strangles PCR results PCR positive PCR negative Culture positive Infected Infected Culture negative ? ? Interpreting Strangles PCR results Culture positive Culture negative PCR positive PCR negative Infected Infected Infected Not infected? Gronbaek et al, 2006 (Equine Vet J 38: 59-63) Strangles clinical signs No clinical signs of strangles Sensitivity Nasal swabs Culture = 18% PCR = 45% Abscesses Culture = 20% PCR = 80% Gronbaek et al, 2006 (Equine Vet J 38: 59-63) Strangles ELISA • A antigen • ≤0.2 0.D. - negative • 0.3-0.4 0.D. – inconclusive • ≥0.5 0.D. - positive • B antigen • C antigen • ≤0.2 0.D. - negative • 0.3-0.4 0.D. – inconclusive • ≥0.5 0.D. - positive • ≤0.5 0.D. – negative • 0.6-0.9 0.D. – inconclusive • ≥1.0 O.D. - positive • Inconclusive results need a second sample after 14 d to determine if rising or falling titre. The Strangles Serology Using two S. equi proteins (A and C): Sensitivity 93.3% Specificity 88.0% Protein A (>0.5 is +ve) Protein C (>0.5 is +ve) Blank 0.0 1.2 0.1 0.0 0.1 0.0 -ve 0.0 0.7 0.0 0.0 0.2 0.0 +ve 1 2.7 0.5 0.0 1.4 0.5 0.0 +ve 2 2.0 0.3 0.0 1.5 0.1 0.0 0.3 0.8 0.1 0.0 0.4 0.0 1.0 0.8 0.0 0.1 0.5 0.1 0.2 0.0 0.0 0.1 0.2 0.0 1.4 0.0 0.0 0.8 0.0 0.0 ELISA interpretation • Antibodies can take up to 14 days to rise and stay high for at least 6mths - ?use in acute outbreak • Paired serology requires re-testing of sample 2 vs sample 1 • Inter-assay variation • Result and re-test ±0.3 • Valid comparison ONLY between samples tested as pairs i.e. A to A, B to B and C to C Equine Herpes Virus 1 and 4 • NPS – Tissue culture or PCR • Tracheal Wash – Viral Antigen – IF • Serology • Compliment Fixation – short lived • Virus Neutralisation – long lived DIAGNOSTIC TEST Immunofluorescenc e (IF) RAPID TEST? Yes SAMPLE REQUIRED COMMENTS AirwayDiagnostic swabs or frozen Useful EHV Testinitial screening test; highly sections; fresh blood samples (for viremia) Polymerase chain reaction (PCR) Yes Virus isolation No Histopathology No Hematology Yes Serology No specific; false negatives occur; blood samples may be transiently IF positive Airway swabs or lavages; Highly specific test; can blood; frozen or fixed differentiate between different tissue samples EHVs; qPCR allows estimation of virus load and presumptive differentiation of lytic and latent infection; D/N752 qPCR used to identify viruses with neuropathogenic potential; good sensitivity; false negatives occur Airway swabs and lavages; “Gold standard” for diagnosis; fresh blood, fetal and time-consuming; highly specific; placental tissue samples false negatives occur Fixed tissue samples Definitive diagnosis of abortion and EHM, especially if used with ISH Whole blood in EDTA May provide nonspecific evidence of virus infection Serum (clotted blood Highly specific test, although CF samples); take two and VN tests do not differentiate samples 10-14 days apart EHV-1 from EHV-4, but EHV-1 IgG to demonstrate rising ELISA is type specific (allows antibody titers differentiation); provides indirect Equine Influenza • NPS – virus culture, ELISA nucleoprotein, PCR/IF direct Ag – ACUTE PHASE – NEW CASES • Serology – Ab’s - Haemagglutination inhibition (HI) • > 4x increase in Ab titre between convalescent and 14dy sample - significant • Subclinical infections do not show 4x increase • Single radial haemolysis (SRH) – detects 2x ↑ Abs Economics • Strangles • Influenza • Culture - £16.50 • Ag - qPCR or ELISA £25.00 • qPCR - £20.50 combined £30.50 • Serology HI - £15.50, SRH- £36.00 • Serology - £27.50 all three £50.75 • EHV1,4 • Tissue culture - £33.00 • Respiratory Viral serology screen: • £38.75 • plus equi £59.00 • NPS Screen – EHV-1,4, Strep • PCR - £45.00 equi, zoo PCR plus Flu ELISA or • Serology – CF £20.50 qPCR - £100.00- White top Nasopharyngeal Swab • Up to level medial canthus and ensure horse swallows. • High surface area, absorbent swab required. Transport media • Charcoal • Saline • AHT • Green – Bacteriology plus PCR • Pink – Influenza NOT bacteria • White – Virology NOT bacteria Transport Media – Top tip • Contains antibiotic – need to be frozen • Once sample has been taken put back in plastic sleeve and keep in cool dark place in your car • Cut off and place directly in media and post. Equine Influenza Surveillance Scheme • FREE to join – FREE diagnostic testing NPS & sera • Kits include submission form and swabs/transport media. • Epidemiological information gathered fed back into OIE. • www.equiflunet.org.uk or e-mail [email protected] • Informs OIE of current virus strains and feeds into vaccine recommendations. Outline • Disease situation – local and national • Differentials Diagnoses • Clinical Signs • Diagnostic Tests • Biosecurity Biosecurity Biosecurity Principles • Isolation – separate building/field – 10-25m (strangles) 25-50m (EHV) >200m (EIV) • Separate water supply • Separate equipment. • Restrict personnel access and NO pets • Preferable isolation personnel only • Dispose of bedding, uneaten food and water • Protective clothing/hand hygiene • Disinfect when finished – General purpose disinfectants Biosecurity – differences or not • Droplet transmission vs airborne transmission. • Both EIV and EHV are enveloped viruses and susceptible to common disinfectants cf to Salmonella • Strangles very susceptible to disinfectants • Foot dip or not?????? Release from Biosecurity EHV Option 1: • Isolate 21 days • Daily temps – no NSAIDs Option 2: • Isolate 28 days • Daily temps – no NSAIDs • NPS qPCR • No new cases then lift quarantine • -ve quarantine lifted Release from Biosecurity Strangles • How long to isolate? • What animals to sample? • What samples to take Control - Strangles • Segregate clinical cases and contacts – designate as ‘dirty’. • Stop movements. • Take rectal temperatures q12hrs to detect and promptly segregate new cases. • Very high hygiene standards. • Screen convalescing cases and their healthy contacts. • Aim to move horses from the ‘dirty’ to the ‘clean’ areas. Isolation groups • Red Clinical signs/+ve diagnostics • Amber In contacts – measure temperatures • Green No contact and no clinical signs HBLB Code of Practice. • 3 NPS should be taken at 5-7 days interval or 1 GPL • No animal in ‘dirty’ (red) area should be released from isolation until three negative swabs have been obtained. http://www.hblb.org.uk/document.php?id=43 Screening for carriers • 3 NPS – culture only will be +ve on one swab ≈ 66% • 3 NPS culture and PCR will be +ve on one swab ≈ 90% • 1 GPL ≡ 3NP • Serology screen and the GPL +ves When to start screening for carriers Treatment of GP Carriers • Topical gelatine benzyl penicillin G mix. 2g of gelatin and 40 mls sterile water. Heat to dissolve and cool to 45-50ºC. 10mls sterile water in 10 Mega (2 vials) crystapen. Cool. Heat to desired fluidity. Infuse into pouch and keep head elevated for 5 minutes. • Memory-helical polyp retrieval baskets – remove chondroids. • Surgical hyovertebrotomy/modified Whitehouse/laser surgery. Chondroid removal Yard Biosecurity Poster Vaccination Equilis StrepE • One licensed product in Europe, different to USA vaccine • MSD Equilis® StrepE. • Given into the lip mucosa. • Mild lip abscessation. • Reduces clinical signs and reduces morbidity. Equilis® StrepE • Launched in 2005 • 150,000 vaccines sold world-wide • Taken off the market in Europe in 2006, relaunched in 2011 • Manufacturing problem and not because of adverse reactions • Duration of immunity only 3 months • Will respond to booster up to 6 months in face of an outbreak. • Protection – Good but not perfect • 50% of vaccinated horses protected against abscess formation • Another 25% have reduced severity of clinical signs Adverse Drug Reactions (ADRs) • 150,000 vaccines administered • 84 ADRs in animals and 14 in humans • 0.123% - classified by EMEA as uncommon • Better than perceived • A few high profile cases skew public perception of the risk of ADRs • Two cases of head abscesses caused by vaccine strain Equilis® Strep Summary • Unfair veterinary and horse owner expectation • ADRs less than perceived by public in the U.K. • The global experience is that in certain situations this is a very helpful tool to help control strangles • It is not the golden bullet to eradicate strangles • Must be employed at herd level in tandem with traditional control techniques EHV Vaccination • Two killed vaccines available in UK • Equip EHV1,4 in activated EHV1,4 • Equilis Resequin – influenza and inactivated EHV1,4 • Europe – Pneumobort K inactivated EHV-1 – higher Ag load Take Home Messages • Communication and team work very important • Know the current disease state locally and nationally • Be critical of your laboratory tests and optimise them • Biosecurity key in preventing spread of disease Acknowledgements • Josh Slater – The Royal Veterinary College • Animal Health Trust – Andrew Waller and Richard Newton • MSD