8/17/2017
Equine herpesvirus-1 & (EHV-4) ◦ Overview of current outbreak in cutting horses ◦ EHV facts ◦ EHV protection Mark Crisman, DVM, MS, DACVIM Equine Influenza Senior Veterinarian; ZOETIS Strangles Virginia-Maryland College of Veterinary Medicine Research update
Questions
9 herpesviruses infect equids(1-5 horse pathogens) Can cause significant upper Equine Herpes Myeloencephalopathy (EHM) respiratory tract disease (URTD) first reported in Norway 1966 EHV-1 and EHV-4 are ubiquitous in the world’s horse population Past 12 yrs, EHM more widespread (primarily EHV-1 but 4 has been linked) Can cause URTD without major predisposing factors EHV-1 & 4 co-evolved with horses over Circulate and transmitted year millions of years (carrier state) round Most often cause sub-clinical disease
Both have potential for causing . Antigenic diversity is limited widespread outbreaks of URTD . Viruses are antigenically stable Highest incidence of disease is in young . Minimal cross protection in horses horses under 3 years of age . Life long latency occurs in most Highest risk of infection between horses weaning and two years of age . Strong humoral and cellular immune response required in Spreads rapidly through susceptible both systemic and the horse populations respiratory mucosa . Virus is very susceptible to disinfectants
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Pathogenesis
Incubation period is 2-5 days after . Respiratory tract is the natural exposure entry point for EHV-1 and EHV- May shed virus for 14 days 4 virus, with the respiratory Peak viral shedding occurs during mucosal epithelium being the first few days after onset of nasal primary target for infection discharge and coincides with the . Viral infection can be acquired febrile faze by close physical contact with a Pathology of EHV URTD is focal, horse that is actively shedding cytolytic destruction and exfoliation the virus or with virus of the nasopharyngeal respiratory contaminated fomites epithelium . Viral aerosol transmission is Degree of viremia is key less than with EIV
EHV-1 pathogenesis (1).
Mononuclear leukocytes in Exposure occurs via respiratory route submandibular lymph node and sinus Virus replicates in nasopharyngeal epithelium
Mucosal erosions & viral shedding (4-7 days) 2. Spreads to lymph nodes, Ciliated Respiratory Virus infects leukocytes & endothelial cells & establishes epithelials viremia ensues with dissemination latency Infection of vascular endothelium- ischemia 3. Leukocyte- 1. Virus associated enters URT Viremia of naive host Nasal 4. Infection of vascular mucosa endothelia
Allen GP, Kydd JH, Slater JD, et al. Equid herpesvirus-1 (EHV-1) and equid herpesvirus-4 (EHV-4) infections.
EHV-1 pathogenesis (2).
EHV-1 and EHV-4 are
6. CNS vasculitis 70% genetically similar 5. Uterine vasculitis EHV-1 ◦ Upper respiratory ◦ Abortion ◦ Newborn Still Birth
4. Infection of vascular ◦ Neurological endothelia Mainly D752 point mutated EHV-1 strain EHV-4 Difference in pathogenic potential among naturally circulating strains? ◦ Mainly Upper Respiratory
Allen GP, Kydd JH, Slater JD, et al. Equid herpesvirus-1 (EHV-1) and equid herpesvirus-4 (EHV-4) infections.
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Respiratory Disease Prevalence Commonly affects younger horses – weaning to 2-3 years 75-80% of diagnosed respiratory Spread via inhalation & direct disease is due to EHV-1 and EHV-4 contact (ubiquitous in equine Greater than 90% of those cases are populations) due to EHV-4 Natural immunity is short lived (60 days) Uncommon in foals less than 3 months of age EHV-1 & 4 primary concern to horses- latent in lymph nodes of Most cases of URTD caused by EHV- respiratory tract (EHV1) and 4 occur between 4-12 months of trigeminal nerve ganglia (EHV4) age Once infected, they carry the EHV-4 URTD is more severe in virus for life yearlings that were not exposed at EHV 2 & 5 new players? an earlier age
24 month study EHV-1 761 samples submitted 11% . URTD due to EHV commonly referred to as “foal snots” ◦ fever, coughing or nasal EHV-4 . Yearling sales events have a discharge S. equi 38% significant incidence of URTD due 201/761 (26.4%) 23% to EHV-4 ◦ PCR positive for one . Older horses (2-3 yrs of age) in training, on the racing circuit or or more pathogens show barns URTD caused by EHV- EHV-4 (82 cases) EIV 1 and EHV-4 are common EIV (60 cases) 28% . Previously exposed horses older S. equi (49 cases) than 3 yrs of age continue to have periodic re-infection by EHV-1 EHV-1 (23 cases) and EHV-4 throughout their Voluntary Surveillance Program for Important Equine lifetime Infectious Respiratory Pathogens in the United States Nicola Pusterla, DVM, Diplomate ACVIM, et al. 2010 AAEP Proceedings
Most horses have seroconverted to Majority of viral transmission events EHV-4 by 2 years of age – less with usually results in URTD result in EHV-1 inapparent or mild clinical signs Post infection latency occurs for the life of the horse Seroconversion rate for EHV-1 and EHV- Reservoir for EHV-1 and EHV-4 is 4 exceed the incidence of clinically globally distributed latently observed disease infected horses – approximately 50% of population Stress causing the latent virus to Life cycle is dam to foal, latency in reactivate and shed is the main factor in affected foals, periodic reactivation disease outbreaks and viral shedding
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Latent virus is protected from Both EHV-1 and EHV-4 can be latent together and persist for recognition by the immune the life of the horse system even in the face of strong As many as 60% of horses acquired immunity recovering from a primary Reactivation of latency and viral respiratory disease can become shedding occurs with various latently infected with EHV-1 and episodes of stress or EHV-4 corticosteroid administration Reservoirs for latent EHV-1 and Latent virus that is reactivated EHV-4 are the trigeminal nerve can be shed without the horse ganglia and upper respiratory showing any clinical signs of lymph nodes disease
. Horses under stressful situations, transport, show…. Acute rhinitis and pharyngitis, and can . Horses in large groups, concurrent extend to the distal airways disease Clinical signs are highly variable and can range from inapparent disease to life threatening, primary viral pneumonia Bilateral nasal, clear serous discharge is most common signs of early infection Serous secretions carry high levels of infectious virus
Slide Dr. Julie Wilson
Occasional lower respiratory Serous nasal discharge will tract involvement progress to a mucoid nasal Clinical signs and viral discharge by the 2nd or 3rd day shedding greatest during first Mucoid nasal discharge changes few days of disease to mucopurulent nasal discharge Prognosis for full recovery is after day 5 after clinical onset good, usually by the end of two Pyrexia – as high as 41ºC, weeks, with very low mortality submandibular lymphadenopathy, Severe secondary bacterial conjunctivitis, lethargy and infection can complicate the anorexia, minimal coughing disease process
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Fever and/or cough . Secondary bacterial infection by Nasal discharge Strep zoo is common following Mild Limb edema URTD caused by EHV and can Poor appetite and depression progress to severe respiratory disease Abortion . EHV-4 replication is usually Poor anal / tail tone restricted to the URT and regional Inability to retract penis lymph nodes Ataxia . EHV-1 infection has the potential Bladder paresis for more serious clinical disease (respiratory, abortion, neonatal foal Fecal incontinence death, myeloencephalopathy, Muscle fasciculation pulmonary vasculotropic infection, Increased respiratory rate and ocular disease. ◦ (>14 b/min)
Dr. Julie Wilson- Slide
Diagnosis
Respiratory disease caused by EHV-1 or
EHV-4 can be indistinguishable from other Use a 25.4cm dacron swab to swab respiratory diseases based on clinical signs both nasal mucosal surfaces – keep moist and sealed in red top tube or Key to diagnosis is identifying presence of in transport media EHV-1 or EHV-4 in either nasopharyngeal Collect at least 7 mls of blood in red secretions or blood from infected horses top tube and keep chilled Best diagnostic results occur when Nasal swabs can be used for PCR nasopharyngeal samples are taken within 48 testing and blood for virus isolation of buffy coat hours of onset while horse is pyrexic and EHV-1 and EHV-4 can be nasal discharge is still serous distinguished from each other using diagnostic testing
EHV: Analysis Whole Blood & Swab Data from Dr. Steve Reed OSU
Viremia Nasal Shedding Temperature
FEVER
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Depends on severity of clinical signs
Goals are to decrease clinical signs of Prophylactic immunization, preventive infection, maintain hydration and feed health program, and good bio- intake, minimize secondary bacterial security measures Vaccination against EHV-1 and EHV-4 infections, and control or decrease level of is recommended by the Equine viremia Infectious Disease Advisory Board for Non-steroidal anti-inflammatories to all horses that are at risk for control pyrexia and inflammation acquiring infection Foals become sero-negative by 5-6 Antibiotics months of age Titer levels for EHV are not indicative of protection
Vaccination
. Vaccination does not prevent Vaccination and boosters should be infection – it decreases disease timed with periods of stress in mind incidence, severity of disease (weaning, transport, sales, training, and viral shedding relocation, shows) . It is recommended that horses Recommended vaccinations – 2 doses less than 3 years of age be IM 4 weeks apart starting at 3 months vaccinated with a product that of age, with booster doses every 6 contains both EHV-1 and EHV-4 months after 12 months of age for competitive horses (at risk) . Natural immunity is Broodmares at 5,7 & 9 months of approximately 60-90 days gestation . Goal of vaccination is to Latent carrier state is not prevented by decrease level of viremia vaccination
Characterization of immune responses in healthy foals when 1 a multivalent vaccine Frequent boosters for horses protocol was initiated at 90 or 180 days of age at risk is recommended E. G. Davis, N. M. Bello, A. J. Bryan, K. Hankins and M. Wilkerson because of short duration of Department of Clinical Sciences and 26 Diagnostic Medicine Pathobiology, College of Veterinary immunity due to vaccination Medicine, 37 Department of Statistics, Kansas State University, Manhattan, High vaccination coverage in Kansas 66506, herds can help slow or prevent Reasons for performing study: Protection from spread of infection due to herd infectious disease requires antigen specific immunity. In immunity foals, most vaccine protocols are delayed until 6 months Vaccination with a killed to avoid maternal antibody interference. Susceptibility vaccine during an outbreak to disease may exist prior to administration of may help reduce the spread of vaccination at 4-6 months of age. disease J Vet Immuno & Immunopath.
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Early Diagnosis- vital, know lab and proper Outbreaks of URTD caused by EHV samples (isolation, swabs for PCR) often spreads rapidly, and significant Prevention of further spread-disinfection, economic and equine welfare isolation, prevent aerosol & fomite consequences can occur transmission. Vaccination of horses at > risk? Priority during an outbreak is to In previously vaccinated horses- rapid anamnestic response may prevent spread of the virus from reduce spread. infected horses to other horses Management of clinical cases Isolation, quarantine and disinfection are key In environment- virus unlikely to survive > 21 Remove all clinically ill horses from days premise and move to an isolation facility if possible
Disease Outbreak Control
Flu/Rhino combos . Restrict movement of humans and other ◦ 30-33 Million Plaque Forming Units (PFU’s) animals on and around infected premises Prodigy . All horses that have been in physical ◦ 100 Million PFU’s contact or sharing facilities with ◦ No challenge data with EHM affected horses should be considered exposed to the virus Rhinomune . Monitor clinical signs of all horses on ◦ Modified Live premise ◦ EHM challenge data available . Use latex gloves, foot bathes and proper hygiene Pneumabort K . Disease outbreak can be considered ◦ 133 Million PFU’s clear 21 days after last positive viral ◦ EHM challenge data available diagnostic test ◦ Contains Army 183 and Ab4 strains of EHV-1
Both are D752 genotype
Presented at 2013 AAEP Convention in Nashville, Tennessee. Publication pending acceptance in a peer reviewed Journal
Objective – To determine if vaccination with a high antigenic mass vaccine (Pneumabort K + 1b) is able to reduce or prevent clinical in the face of a severe viral challenge with a neuropathogenic strain of EHV-1.
Materials/Methods - Twelve aged mares (20 years old) were randomized to either saline control or vaccination groups. Three intramuscular injections with a high antigen vaccine were administered at monthly intervals followed by inoculation with a neuropathogenic strain of EHV-1. Ataxia scores, rectal temperatures, and clinical Oklahoma State University - Lara Maxwell, Lyndi scores were determined. Gilliam, Todd Holbrook, Grant Rezabek, Richard Eberle, Timothy Snider, Dianne McFarlane
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Results - Control horses had more severe neurological signs, with Blinded study Evaluated for 21 days after five of six control horses versus one of six vaccinated horses Evaluated: challenge progressing to at least a two-grade change in ataxia (P 0.08). Mean Ataxia Vaccinates had statistically body temperature was lower during the biphasic fevers occurring on Viral shedding less: days 2 and 5 in vaccinates (P 0.1). The median clinical score was also 20% lower in vaccinates as compared with control horses (P Rectal Temperature ◦ Ataxia 0.3). Clinical scores ◦ Rectal Temperatures 8 Viremia ◦ Viral Shedding 6 Titer Levels ◦ Viremia
◦ Clinical Scores 4 Controls Vaccinates 2
0 Neurologic Avg Score
Conclusion - Immunization of horses with a high antigen vaccine, Pneumabort K®, significantly decreased viremia and appeared to decrease the severity of disease, as measured by several other disease parameters. Of particular interest, the severity of ataxia appeared to be lower in the vaccinated horses as compared to the saline controls although statistically significant differences were not observed. .
Influenza virus ◦ (A1 & A2) Influenza A evolved from ancestral avian Highly contagious precursor into different lineages infecting ◦ Horses inhale virus many species- including horses Particularly prevalent in young horses Birds are the natural reservoir of influenza A- ◦ Generally seen in horses 2 years of age and older pivotal role in emergence of new strains to Major concern in areas of high horse infect mammals population density Disease increases risk of secondary bacterial infection
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Infects & replicates in ciliated epithelial cells in upper & lower respiratory tract Rapid progression Results in de-ciliation of large areas w/in through the herd 4 to 6 days Attaches to Incubation period= 1 to 3 days epithelium via HA Fever, harsh dry cough= release of large spikes amounts of virus Destroys Serous…mucopurulent nasal discharge, epithelium and myalgia, inappetance, enlarged lnn. clumps cilia Regeneration requires 1 week for every day horse runs a fever
Image courtesy of Dr. Issel and Gluck Center Image courtesy of Dr. Issel and Gluck Center
Antigenic Shift Dependent on different immune Sudden change in mechanisms at both local and systemic HA level Recombines with another influenza Systemically- IgGa and IgGb responses Human & Avian associated w/ protection and likely depends Antigenic Drift on an INFγ mediated Th1 immune response Random mutation Mucosally- production of IgA critical and in HA and NA Limits long-term typically depends on Th2 immune response vaccine efficacy Horses…
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1986 – H3N8 virus diverged into American & Eurasian KY97 lineages (American dominant) 1990 – American lineage diverges into Kentucky & Florida KY99 sublineages (Florida dominant) CLADE 1 CLADE 2 KY01 Early 2000’s – Florida sublineage diverges into two homologous clades: 4,5,6 SA03 2002 -Clade 1 (predominantly North America) 5 -Clade 2 (predominantly Europe) 5 2003 2004 2004 NM03
2010 – OIE recommendation – Vaccines sold OH0 2006 2005 2006 internationally should have clade 1 & clade 2 EIV strains1 3 Genetic homology – Kentucky/97 (Fluvac Innovator 2006 2007 2007 2007 virus) has genetic homology with all 4 subsequent Florida sublineage isolates KY07 2007 Cross-reactivity against Richmond/07 – Kentucky/97 cross-reacts against clade 2 Richmond/07 virus RICH07
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Zoetis has a legacy of evaluating FLUVAC INNOVATOR for cross-reactivity against newly emerging equine influenza virus (EIV) isolates to help ensure that the vaccine remains immunologically current. OIE, the world organization for animal health, recommends that EIV vaccines for the international market contain a clade 1 and clade 2 virus of the Florida sublineage.1 OIE considers the Richmond/07 virus to be a contemporary representative of clade 2 EIV.1 Zoetis conducted a serologic study of horses vaccinated with FLUVAC INNOVATOR to determine if the vaccine cross-reacts against the Richmond/07 virus.
HI assays were performed using a non-ether method of stabilizing the Study Design: 2,3 test antigen, which yields a lower HI titer than ether treatment. 80 EIV seronegative horses Group 1 (n = 40): Vaccinated with West Nile Innovator EWT and Fluvac Innovator Percentage of horses with cross-reactive EHV-4/1 Day 28 serum samples: HI titers against Richmond/07 EIV strain Group 2 (n = 40): Sham vaccinated with 92.5% (37/40) Group 1 100.0% 92.5% saline (control group) horses had HI titers ≥ 80.0% 1:10 Vaccination schedule 1:10 HI titer is cross- 60.0% Vaccinated days 0 and 21 reactivity threshold Samples from the blinded Serologic methods study were analyzed by A 1:10 HI titer is 40.0% Serum samples obtained days 0, 21, 28, 42 University of Kentucky, equivalent to a 1:20 HI Gluck Equine Research 20.0% HI titers measured with non-ether technique titer for the ether- Center investigators treatment method 0.0% for cross-reactivity to Richmond/07 0.0% Fluvac Innovator Controls (n=40) (n=40)
Primary goals; (1) to reduce clinical signs, Previously vaccinated adult horse – annual (2) shorten convalescent period, (3) reduce (low risk) – semi annual (high risk) shedding Adult with unknown history – 3 doses – 2nd Ideally; provide long-term immunity, dose 4-6 weeks after first dose, 3rd dose 3-6 efficient memory response & cross months after second dose protection Foals – 3 doses – 1st dose at 6 months of age, Vaccine efficacy= clinical protection, 2nd dose 3-4 weeks after 1st dose, 3rd dose at absence of pyrexia, cough and discharge 10-12 months of age Virological protection= absence of virus in secretions
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Segregation of horses into smaller groups Do not use shared water Clean then disinfect stalls and sources, tack or equipment with a proper equipment disinfectant Isolate new horses for a minimum Have a plan in place in of 3 weeks before introduction case of an disease into the herd outbreak Clean then disinfect all shared buckets, tack or equipment Educate the horse owner Maintain all horses on a current on the importance of vaccination schedule good biosecurity
• Avirulent live S.equi vaccine (IN) • S.equi strain modified to remove HA capsule from cell wall • Removal of capsule ‘cripples’ ability of vaccine to cause/spread disease yet maintains ability to stimulate immune response • Recent improvement in genetic stability of vaccine by deletion of 2 genes responsible for capsule synthesis • This deletion provides means of differentiating vaccine from ‘wild’ S.equi strains by PCR • K State study; effectiveness of Per Os administration •AAEP 2014 • Pinnacle- 2012 ADE reports; 2.7/10,000
• A 15-month outbreak involving 62 clinical cases of strangles occurred on a large Standardbred breeding farm (average population of 1,400 horses). Sixteen asymptomatic horses were found to be PCR-positive for S. equi ssp equi. During the •History; outbreak, serologic samples from 48 clinically normal horses •Methods and Materials were found to be seropositive for S. equi ssp equi, confirming - 1400+ resident broodmare farm herd-wide exposure. After several clinical cases of strangles had - 2 years of clin path data and clinical been diagnosed, an intranasal S. equi ssp equi vaccine was outcomes while using abx’s, vaccination and biosecurity measures to control administered to clinically normal horses (n = 558) considered to “Strangles” epidemic on farm be at risk of exposure. Strangles complications included 7 fatalities (none in vaccinated horses) and 6 cases of purpura hemorrhagica (4 in vaccinated horses). • Midway through the outbreak, injectable, sustained release ceftiofur given as an initial dose followed by a second dose 4 days later was used exclusively for systemic antimicrobial treatment of clinically affected and PCR-positive horses. This
antimicrobial regimen coincided with a reduction in disease incidence and eventual resolution of the outbreak.
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Susceptible 2010 = 99.4% 2011 = 99.7% 30 2012 = 100%
25
20
15
Foalings 10 Reported Cases PCR +, no signs 2010 2011 2012 Clinical signs 5 Streptococcus N=14 N=10 equi subspecies N=72 5 1 equi 0 Streptococcus N=17 N=33 N=27 equi subspecies 3 7 6
zooepidemicus
11/12/12 to… 11/12/12 to… 12/24/12 10/22/12 to… 10/22/12 Staphylococcus N=12 N=10 N=48
aureus 3 9
3/5/12 to 3/11/12 3/5/12to 4/1/12 3/26/12to 5/13/12 5/7/12to 6/3/12 5/28/12to 7/15/12 7/9/12to 8/5/12 7/30/12to 2/10/13 2/4/13to 3/3/13 2/25/13to 4/14/13 4/8/13to 5/5/13 4/29/13to
1/23/12 to 1/29/12 1/23/12to 2/19/12 2/13/12to 4/22/12 4/16/12to 6/24/12 6/18/12to 8/26/12 8/20/12to 9/16/12 9/10/12to 10/7/12 10/1/12to 12/9/12 12/3/12to 1/20/13 1/14/13to 3/24/13 3/18/13to 5/26/13 5/20/13to 6/16/13 6/10/13to Week of Illness Onset Susceptible BP
Characterisation of immune responses in healthy foals when 1 a multivalent vaccine protocol was Results ◦ Outbreak brought under control initiated at 90 or 180 days of age along with ID of “carriers” and biosecurity measures E. G. Davis, N. M. Bello, A. J. Bryan, K. Hankins and M. Wilkerson ◦ DO NOT recommend IN Pinnacle in Department of Clinical Sciences and 26 Diagnostic Medicine the face of a Strangles problem on Pathobiology, College of Veterinary a farm Medicine, 37 Department of Statistics, Kansas State University, Manhattan, Kansas 66506, Timeline Reasons for performing study: Protection from ◦ Submission to EVE: March ‘15 infectious disease requires antigen specific immunity. In foals, most vaccine protocols are delayed until 6 months to avoid maternal antibody interference. Susceptibility to disease may exist prior to administration of vaccination at 4-6 months of age. J Vet Immuno & Immunopath. 78
Questions?
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