1. Equine Viral Diseases INAG 120 – Equine Health Management September 19, 2011

2. What’s a Virus? VIRUS  Structure  Outer layer (envelope) is spiky  Protein coat  DNA/RNA Electron micrograph of a rotavirus. The one on the right has antibodies attached which prevent it from infecting cells © GrahamColm

3. What’s the difference between a virus and a bacterium? VIRUSBACTERIUM

4. More About Viruses VIRUS  VERY small  REPRODUCTION  Depend on host cells for reproduction  Attach to a cell and inject genes or are absorbed  Host cell mass-produces virus

5. Equine Viruses  Equine Herpes Virus (EHV)  Equine Encephalomyelites  Equine Influenza  Equine Infectious Anemia  West Nile Virus  Equine Viral Arteritis  Rabies

6. 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

7. 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

8. 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

9. 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

10. 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)

11. 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

12. 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)

13. 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

14. 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!

15. 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!

16. 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

17. 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!

18. 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

19. EEE

20. VEE – “Paddling”

21. 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

22. Equine Influenza  Symptoms:  Harsh, dry cough  Loss of appetite  Depression  Watery nasal discharge  Can lead to pneumonia!

23. Normal trachea  Image courtesy of Dr. Issel and Gluck Center

24. Trachea after cilia destroyed by flu  Image courtesy of Dr. Issel and Gluck Center

25. Equine Influenza  Treatment  Fresh air, rest  Avoid dust  Antibiotics to control secondary infection  Prevention:  Vaccination!  Most vaccines are effective against multiple strains

26. 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

27. 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

28. EIA – Ventral Edema

29. EIA – Symptoms

30. EIA  Subacute form is most common  Similar symptoms to acute, but not as severe  Death not as common  Chronic EIA:  Horses are unthrifty and lack stamina  May have acute or subacute attacks

31. EIA – Method of transmission  Blood from infected horses  Blood-sucking flies, mosquitoes  Needles  Surgical instruments  Dental floats  Bridle Bits

32. 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

33. 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!

34. 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.)

39. September 24, 2004

40. November 1, 2005

41. September 19, 2006

42. November 27, 2007

43. September 16, 2008

44. 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

45. 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!!!

46. 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!

47. 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