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Disease Outbreak Alerts

Updates on current disease outbreaks are listed here as they occur and will include the date listed, disease name, location and current status. Specific premises will not be named but the general location by town, county and state will be listed. When locations, events or horses are at risk they will be listed. Updates will be posted as they are received.


Date Disease Location Status
May 01, 2015 Equine Herpes Viruses Marion County, OR Confirmed case(s): Quarantine
One Marion county horse has been hospitalized after testing positive for the neurological form of Equine Herpes Virus (EHV-1). The horse, which has been treated at Oregon State University’s College of Veterinary Medicine’s Large Animal Hospital, began showing acute neurologic signs on April 28 and was immediately referred to OSU. The positive EHV-1 diagnosis was made April 29. All horses at the Marion County property have been quarantined. The Oregon Department of Agriculture reports there is no indication at this time that the virus has spread to other horses beyond those being quarantined. Preliminary epidemiological investigations are underway. In all, there are 20 horses at the Marion County stable. The stable owner and all horse owners have been very cooperative and supportive of the disease control actions taken. The investigation shows that horses from the affected property have attended recent events held at the Linn County Fairgrounds in Albany on April 16-19, and the Oregon Equestrian Center in Eugene on April 25-26. While the risk to these horses appears to be low at this time, concerned horse owners are advised to contact their veterinarian.
April 23, 2015 Equine Herpes Viruses Maryland, MD Confirmed case(s): Quarantine
ANNAPOLIS, MD – A horse that was at the same breeding facility as a Montgomery County horse that was recently diagnosed with the mutant neurotropic form of Equine Herpes Virus (EHV-1) has tested positive for EHV-1. This second horse, which is still at the breeding facility, had no symptoms and was diagnosed as the result of lab tests. Both EHV-1 positive horses are under care by private veterinarians and are in strict isolation, according to protocol. The Montgomery County horse had been at the breeding facility for more than two weeks before returning home on Monday. While at the breeding facility and during her first day home, she exhibited no signs of illness. On Tuesday, the horse began showing mild respiratory and neurological signs and was seen by a private veterinarian, who reported the suspected neurological illness to the Maryland Department of Agriculture (MDA), as is required by law. Laboratory tests conducted by MDA confirmed the diagnosis. Following a Disease Investigation Protocol, MDA tested horses that were in close contact with the sick horse at the breeding facility. That investigation discovered the second positive horse. All horses that were exposed to the two positive horses are currently free of symptoms and are being monitored daily. All appear healthy. Both farms will remain under quarantine to ensure the virus is contained. As of today, MDA believes the virus is contained to these two farms and is not aware of any other EHV-1 cases in the state. MDA’s Animal Health Program continues to monitor the situation closely. Owners should contact their private veterinarians to arrange for EVH testing if a horse exhibits significant temperature elevations or neurologic signs. Veterinarians are required to report equine neurologic syndrome to MDA.
April 23, 2015 Equine Herpes Viruses Michigan, MI Outbreak Contained
EHV-1 Update for Friday, April 17, 2015: The number of EHV-1 positive horses in Michigan has remained at four. Two positive horses (1 was already euthanized) at the Livingston County quarantined index farm and two positive horses at a quarantined Saginaw County farm. There have been no new cases of EHV-1 since April 3,2015. In an effort to assist individual horse owners, whose horses are currently housed at the quarantined facilities, the Michigan Department of Agriculture and Rural Development (MDARD) has allowed three horses quarantined at the above Saginaw County premises to move to isolated locations, one each to Midland, St. Clair and Genesee Counties this week. The horses moved are not the EHV-1 positive horses mentioned above, but may have been exposed to EHV-1 positive horses. An isolated location has no other horses on the premises or within a quarter of a mile of the premises. The three isolated locations are also under quarantine. The reason for allowing horses to move from one premises to another while remaining under quarantine, is that horses continue to have fevers at the Saginaw facility, which restarts the 28 day count for horses that have no fevers or symptoms suggestive of EHV-1. Moving a horse to an isolated location allows that horse to be potentially removed from quarantine sooner than if it had stayed at the original farm. There are also an additional two premises that remain under quarantine, one in Ionia County and one in Saginaw County, where horses tested negative for EHV-1, but were exposed to the index horse and exhibited fevers and/or symptoms that can be seen with EHV-1. With the three additional secure location quarantines, there are now seven quarantines for EHV-1 in Michigan. All horses at quarantined facilities are under quarantine until all horses have either had no fevers and/or clinical signs exhibited that are consistent with EHV-1 for 21 consecutive days and have subsequently tested negative for EHV-1 or have had no fevers and/or clinical signs exhibited that are consistent with EHV-1 for 28 consecutive days.
April 16, 2015 Equine Herpes Viruses Montgomery County, MD Confirmed case(s): Quarantine
ANNAPOLIS, MD (April 15, 2015) – A horse stabled in Montgomery County has tested positive for the mutant neurotropic form of Equine Herpes Virus (EHV-1) and is being treated by a private veterinarian. The horse had been outside Montgomery County for breeding for more than two weeks before returning home on Monday. The horse began showing mild respiratory and neurological signs on Tuesday and was seen by a private veterinarian, who reported the suspected neurological illness to the Maryland Department of Agriculture (MDA), as is required by law. Laboratory tests conducted by MDA confirmed the diagnosis. The horse’s condition is improving. Other horses at the farm are now being tested as are horses that were in contact with the ill horse at the breeding facility. Those results will not be available until tomorrow. Both farms are presently under a 28-day investigational hold while MDA inspectors perform additional epidemiological and infectious disease testing. Stables near the one where the sick horse resides have been notified of the situation and owners cautioned to monitor horses at their premises carefully. MDA’s Animal Health Program is monitoring the situation closely. Owners should contact their private veterinarians to arrange for EVH testing if a horse exhibits significant temperature elevations or neurologic signs. Veterinarians are required to report equine neurologic syndrome to MDA.
April 06, 2015 Equine Herpes Viruses Michigan, United States Confirmed case(s): Quarantine
On March 19, MDARD was notified of a Livingston County horse testing positive for Equine Herpes Virus type 1 (EHV-1). Unfortunately, this horse had to be humanely euthanized. As of April 2, 2015, two additional Michigan horses have tested positive for EHV-1. Both horses developed fevers and are under veterinary care. One of these additional positive horses is from the same Livingston County stable in which the index horse resided. The second additional positive horse is at a separate stable in Saginaw County in which horses attended a March 7, 2015 event in Barry County also attended by the initial positive EHV horse. There are currently four facilities under quarantine, including the two facilities to which the EHV positive horses reside, that are monitoring horses for signs and symptoms of illness as they have had exposure to the index horse and a fever >101.5 Fahrenheit. MDARD continues to trace all contacts of infected horses to ensure no further disease transmission has occurred. Horse owners are encouraged to vaccinate their horses and to contact their veterinarian if a horse has a fever greater than 101.5.
November 25, 2014 Piroplasmosis Stanislaus County, CA No Status
On June 4, 2014, a 5 year old racing QH stallion was presented as an emergency to a private veterinary clinic for severe depression and urinating blood. At time of presentation the horse had a PCV of 10. The horse collapsed and subsequently died. The horse was confirmed positive for Equine Infectious Anemia and positive for Piroplasmosis (T. equi). The premises of origin has been placed under quarantine and 11 exposed horses will be tested for EIA and EP. Initial epidemiologic investigation indicates the positive horse competed in unsanctioned track racing. The California Department of Food and Agriculture continues to investigate.
November 07, 2014 Equine Herpes Viruses idaho, ID Confirmed case(s): Quarantine
The Idaho State Department of Agriculture (ISDA) is reporting that two horses in Bonneville County were euthanized after displaying neurological symptoms consistent with Equine Herpes Virus (EHV-1). Laboratory testing conducted on one of the horses, prior to its death, confirmed the horse to be positive for the neurologic strain of EHV-1.
May 21, 2014 Equine Herpes Viruses RioGrande County, CO No Status
EHV-1 case identified as part of EHM incident from May 14, 2014 in RioGrande County under quarantine and no further cases have been identified on this premises or others within Colorado at this time
May 16, 2014 Equine Herpes Viruses RioGrande County, CO No Status
EHV-1 (wild type) positive on euthanatized neurologic horse, diagnostic tests pending on febrile stablemate
May 14, 2014 Equine Herpes Viruses RioGrande County, CO Confirmed case(s): Quarantine
Horse euthanatized, Results of Diagnostic Tests Pending; this horse and its stable mates have history of travelling to several events within Colorado over the past several weeks. There was potential contact to other horses that attended the National High School Rodeo and Colorado Junior Rodeo events in Henderson, CO April 26-27, 2014; Eagle, CO May on 2-4, 2014 and Rocky Ford , CO May 10-11, 2014.