Equine Herpes Virus Species Specific Three Subfamilies: alpha, beta, gamma 9 documented strains, but only 5 affect domestic horses EHV-1 ( ) Subtype 1 Rhinopneumonitis (respiratory form) Abortion Birth of weak foals Peracute vasculitis Neurological
EHV-1… EHV-1 is common throughout the world Can be sudden and deadly High temperature “Fulminating” respiratory disease May see all 5 of the syndromes at once Horses of all ages are affected Mares 3-9 months pregnant most susceptible Abortion storm virus first identified in the 1940s
EHV-1… Viral incubation for 2-10 days: Fever (102 - 107º F for 1-7 days) Malaise, depression, anorexia Congestion and serous discharge from the nostrils Swollen lymph nodes Mild incoordination to severe ataxia, paresis and paralysis Loss of bladder tone, tail tone, skin sensation in hind limbs
EHV-1 Treatment and prognosis: Supportive nursing If horse remains standing, prognosis is good NSAID’s to control malaise and fever Encourages eating Fluid therapy if dehydrated Antibiotics to prevent secondary bacterial infection (especially if respiratory disease) Corticosteroids to reduce nerve inflammation
Equine Herpes Virus EHV-2 and EHV-5 Gamma Family “Ubiquitous” but rarely causes disease Found in nearly 100% of healthy foals Can cause problems in the following diseases: Conjunctivitis in young foals May act as a forerunner infection that leads to Rhodococcal (through immune suppression)
Equine Herpes Virus EHV-3 Venereal Disease Equine Coital Exanthema Rare but important ($$) Doesn’t cause death Self-limiting Characteristic lesions on genitalia of stallions and mares
Equine Herpes Virus EHV-4 Respiratory infection only (“Rhino”) Non-fatal Severe, widespread outbreaks in young horses Foals 3 years old in training Not a problem in older horses (develop immunity)
EHV-1 Outbreaks: USA & UK # outbreaks caused by Five-year interval # Outbreaks Wild-typeMutant 1970-1975101 1976-1980303 1981-1985422 1986-1990615 1991-1995514 1996-2000624 2001-200532230
EHV in Ohio University of Findlay, January 12, 2003: 138 horses quarantined at the English riding facility 35-40 horses showed obvious neurological signs 12 horses died Within 5-6 days of first horse showing symptoms, 80-90% of horses had fevers Strain confirmed as EHV-1 Respiratory and neurological symptoms Not sure where the strain came from All horses were current on vaccinations!
EHV in Maryland Montgomery County, March 2004: 12 horses exhibit signs of neurologic illness 5 horses died Farm houses mostly polo ponies Strain confirmed as EHV-type 1 Confirmed after multiple tests on July 8 Not sure where the strain came from Hindlimb ataxia, inability to stand, coma All horses were current on vaccinations!
EHV in Maryland Howard County, Columbia Horse Center March/April 2005 – June 2005 Facility strictly quarantined 4? horses euthanized Pimlico, Eastern Shore, January 2 – March 2006 EHV-1 detected in one barn 4 Barns quarantined (but not quickly enough) EHV-1 spreads to training farm on the Shore, leading to the euthansia of 2 horses. Pimlico closes on January 23 rd (reopens February 8 th ) Pennsylvania and Kentucky Tracks not accepting horses from Maryland or allowing horses to race in Maryland EHV shows up at Laurel Park, January 25 th EHV-1 at Marion DuPont Scott Equine Medical Center February 2007 – March 29, 2007
Equine Encephalomyelitis Arthropod-borne viruses that cause Central Nervous System dysfunction and moderate to high mortality Western (20-30% fatal) Eastern (70-90% fatal) Venezuelan (50- 75% fatal) Transmitted by mosquitoes! Not horse-horse or horse-human Zoonotic Diseases!
Equine Encephalomyelitis Clinical Signs: Generally occur 5 days after infection Death may occur within 2-3 days Ataxia, wandering, impaired vision, reduced reflexes, circling, inability to swallow, drooling, fever Paralysis usually followed by death
Equine Encephalomyelitis Diagnosis: Laboratory tests on blood samples or necropsy tissues Treatment: Successful for mildly affected animals Supportive nursing care Control: Vaccination one month prior to mosquito season
Equine Influenza Symptoms: Harsh, dry cough Loss of appetite Depression Watery nasal discharge Can lead to pneumonia!
Normal trachea Image courtesy of Dr. Issel and Gluck Center
Trachea after cilia destroyed by flu Image courtesy of Dr. Issel and Gluck Center
Equine Influenza Treatment Fresh air, rest Avoid dust Antibiotics to control secondary infection Prevention: Vaccination! Most vaccines are effective against multiple strains
Equine Infectious Anemia “Swamp Fever” Horses are the only known natural host! No treatment available to eliminate EIA from an infected horse Horses surviving EIA can relapse and/or pass it on to other horses Lifetime Quarantine Euthanasia 2006: Appeared in Ireland
EIA Clinical Signs Sudden onset of high fever of 104º - 108º Severe depression Depressed appetite Weight Loss Weak/incoordination Jaundice Ventral edema Rapid destruction of red blood cells
EIA - Diagnosis COGGINS TEST Dr. Leroy Coggins of Cornell University Only 10 cc of blood is needed for the test Results can be available in 48 hours Most states require a negative Coggins test for transported horses Most shows require negative Coggins test for participants Some states require negative Coggins for sales
West Nile Virus Vector-borne virus first in this hemisphere in 1999 Humans, horses, and birds are incidental hosts Many horses infected with WNV do not become ill Approximately 33% die Zoonotic Diseases!
WNV Control: Mosquito Control! Eliminate standing water Mosquitoes can breed in as little as an inch of water Vaccination –95% control rate WNV Antibody for horses already infected (from Novartis Animal Vaccines, Inc.)
Equine Viral Artereitis Acute upper respiratory infection caused by a herpes virus Similar to influenza and rhino Fever (102-106º) Nasal discharge All age groups susceptible Can cause abortion (approximately 50%) Edema of the limbs Increased respiratory rate Skin rash
EVA Most common in Saddlebreds and Standardbreds Most animals recover without treatment Vet may prescribe antibiotics to prevent secondary infection Transmission: Inhalation of droplets from infected horses STD!!!
Rabies Neruotropic Rhabdovirus Saliva of infected animal horse Travels up the NERVES to the brain Reproduces in the brain Sheds virus through the salivary glands BLOOD TEST WON’T DIAGNOSE DISEASE!!! Saliva test? Zoonotic Diseases!
Rabies Symptoms: Neurological disorder, choking, weakness, staggering, unprovoked excitement Behavioral changes are most common May take 2-6 weeks or even 3 months to show symptoms after infection NO EFFECTIVE TREATMENT!! Prevention = annual vaccination Problem in horses in the Mid-Atlantic Raccoon strain is predominant here