August 29, 2016
Washington State Diagnostic Lab Confirms 10 Equine WNV Cases
By Edited Press Release
The Washington Animal Disease Diagnostic Laboratory (WADDL) has confirmed 10 cases of West Nile fever in horses since Aug. 9.
The laboratory in Washington State University’s (WSU) College of Veterinary Medicine has tested 38 horses since Jan. 1. All 10 cases confirmed positive recently were in unvaccinated horses in Spokane, Lincoln, and Pend Oreille counties in Washington and Boundary County in northern Idaho. All 10 had neurologic disease that occurs with West Nile encephalitis characterized by inflammation of the central nervous system.
The cases are unrelated to the equine herpesvirus-1 case confirmed by WADDL in a hospitalized horse at WSU’s Veterinary Teaching Hospital. The EHV-1 horse has since been humanely euthanized.
August 19, 2016
CONTACT: Charlie Powell (509) 335-7073 (all hrs.) or [email protected]
WSU VETERINARIANS CONFIRM EQUINE HERPES CASE, TEACHING HOSPITAL REMAINS OPEN
PULLMAN, Wash.—The Washington State University College of Veterinary Medicine has confirmed a single horse with a rare neurologic form of Equine Herpes Virus (EHV-1).
Confirmation came late today and the horse has been in isolation in the Veterinary Teaching Hospital in Pullman, Wash., since its arrival yesterday at this time. The horse will be humanely euthanized today and its stall and surroundings will undergo terminal cleaning.
The horse in question is an 18 year-old quarterhorse mare from Newport, Wash., that has until it developed symptoms, been competing in rodeo events in the inland Pacific Northwest.
As required by law, WSU veterinarians have contacted the Washington Assistant State Veterinarian, Scott Haskell. His office and the Washington State Department of Agriculture (WSDA) will respond to the situation statewide.
The EHV-1 type was confirmed based upon clinical neurologic signs shown by the horse as well as testing by the Washington Animal Disease Diagnostic Laboratory (WADDL) in Pullman.
The virus is highly contagious and is spread via aerosolized secretions from infected coughing horses, by direct and indirect (fomite) contact with nasal secretions, and, in the case of EHV-1, contact with aborted fetuses, fetal fluids, and placentae associated with abortions. Disease can range from subclinical to the severe neurologic symptoms seen in the horse at WSU.
Horse owners are advised to contact their veterinarian to discuss vaccination and means for preventing EHV infections. The last outbreak affecting Washington horses came in May of 2011.
At this time and since the horse has been in constant isolation since arrival, the WSU Veterinary Teaching Hospital remains open to receiving equine patients as needed. Owners may want to call ahead to ensure the hospital is still open as this situation develops. The number is 509-335-0711.
WSDA and WSU will issue any additional status reports as information becomes available.
Notes from the Field: Fatal Infection Associated with Equine Exposure — King County, Washington, 2016
On March 17, 2016, Public Health—Seattle & King County in Washington was notified of two persons who received a diagnosis of Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) infections. S. zooepidemicus is a zoonotic pathogen that rarely causes human illness and is usually associated with consuming unpasteurized dairy products or with direct horse contact (1). In horses, S. zooepidemicus is a commensal bacterium that can cause respiratory, wound, and uterine infections (2). The health department investigated to determine the magnitude of the outbreak, identify risk factors, and offer recommendations.
Patient A, a previously healthy woman aged 37 years, operated a horse boarding and riding facility in King County, Washington. Patient A fed, groomed, and exercised the facility’s six horses and cleaned the stalls daily. During the week of February 21, 2016, patient A developed mild pharyngitis and cough. During the week of February 21, horse A developed mucopurulent ocular and nasal discharge and lethargy. On February 29, patient A began administering 10 days of sulfa-based antibiotics to horse A, which recovered without incident.
Patient B, a previously healthy woman aged 71 years and the mother of patient A, developed symptoms consistent with an upper respiratory infection during the week of February 21 while visiting patient A and living in the same household. On March 2, she developed vomiting and diarrhea. On March 3, she was found unconscious and transported to a hospital, where she died that day. Patient B had close contact (i.e., riding, petting, and walking) with horse A on at least February 25 and February 29.
Culture results of nasal swabs collected on March 10 from horse A and two other horses that appeared well were positive for S. zooepidemicus. Patient A did not report consumption of unpasteurized dairy products or exposure to other animals, apart from one healthy cat, during the preceding 2 months. A throat culture from patient A obtained March 10 and blood cultures from patient B grew S. zooepidemicus isolates indistinguishable by pulsed-field gel electrophoresis from isolates cultured from horse A and a second horse at the facility. S. zooepidemicus cultured from a third horse did not match other isolates.
The epidemiologic and laboratory evidence from this investigation linked a fatal S. zooepidemicus infection to close contact with an ill horse. Patient B might have been at increased risk for invasive disease by S. zooepidemicus because of her age and her possible antecedent upper respiratory infection. Because patient A specifically sought health care and a throat culture as a result of patient B’s death, determining whether the S. zooepidemicus infection preceded or followed her mild illness approximately 2 weeks earlier was not possible.
Although S. zooepidemicus is a rare zoonotic pathogen in humans, older persons might be at increased risk for a fatal outcome from this infection; in 32 reported cases, the median age was 61 years (range = <1 to 83 years) with 7 deaths (case-fatality rate = 22%) (1). Consistently practicing thorough hand washing with soap and water after contact with horses and other animals or areas where animals are housed is recommended (3). This outbreak highlights the need for more research regarding risk factors for zoonotic transmission and spectrum of human illness associated with S. zooepidemicus.