Oklahoma Has First Equine VSV Case
A premise in Washington County, Oklahoma, has a confirmed case of vesicular stomatitis virus (VSV) in a horse.

Oklahoma has its first confirmed case of vesicular stomatitis virus (VSV) in a Washington County horse. USDA APHIS

On July 7, 2020, the National Veterinary Services Laboratories in Ames, Iowa, confirmed a finding of vesicular stomatitis virus (VSV) infection (Indiana serotype) on an equine premises in Washington County, Oklahoma. 

One horse on the premises has met confirmed case definition with compatible clinical signs and a positive complement fixation test (CFT) titer of 1:40 or greater. This is the 2020 VSV Index Case for Oklahoma. 

Index Premises (Oklahoma): The index premises in Oklahoma is a small equine premises located in Washington County. There are two horses present, only one of which is showing clinical signs of VSV (muzzle and tongue lesions), which were first noted around June 24, 2020. There are no other susceptible species present on the premises and there have been no recent animal movements. 

Known competent vectors for transmission of VSV include black flies, sand flies and biting midges (Culicoides spp.). The epidemiological investigation on this VSV-positive premises indicates that incursion of VSV-infected insect vectors is the likely source of infection on the premises. 

Biosecurity measures and vector mitigation have been instituted to reduce the within-herd spread of the virus. The animals are being monitored and the premises will remain under state quarantine until 14 days from the onset of lesions in the last affected animal on the premises. 

Additionally, since the last situation report (7/2/2020), there have been 14 new VSV-affected premises identified (10 confirmed positive, 4 suspect) in 2 states. 

Updates are as follows: 

Kansas (9 new confirmed positive, 4 new suspect premises) 

  • Butler County – 4 new confirmed positive (1 cattle, 3 equine), 1 new suspect equine premises 
  • Cowley County – 1 new confirmed positive cattle, 2 new suspect premises (1 cattle, 1 equine) 
  • Greenwood County – 1 new confirmed positive, 1 new suspect premises (all equine) 
  • Montgomery County (New Infected County) – 1 confirmed positive equine premises • Sedgwick County – 2 new confirmed positive equine premises 
  • The following previously VSV-infected or suspect premises have been released from quarantine: 13 in Butler County, 1 in Cowley County, and 3 in Sedgwick County. 

Nebraska (1 new confirmed positive premises)

  • Buffalo County – 1 new confirmed positive equine premises

Summary of the Outbreak

The 2020 VSV outbreak began on April 13, 2020, when the National Veterinary Services Laboratories (NVSL) in Ames, Iowa, confirmed the first VSV-positive premises in Dona Ana County, New Mexico. 

Arizona, Texas, Kansas, Nebraska and Oklahoma subsequently broke with VSV cases, which were confirmed by NVSL on April 22, 2020 (Cochise County, Arizona), April 23, 2020 (Starr County, Texas), June 16, 2020 (Butler County, Kansas), June 24, 2020 (Buffalo County, Nebraska), and July 7, 2020 (Washington County, Oklahoma). 

Since the start of the outbreak, 122 VSV-affected premises have been identified (92 confirmed positive, 30 suspect). One hundred fifteen (115) of these premises had only equine species clinically affected and 7 premises had clinically affected cattle (McMullen, Starr, and Zapata Counties, Texas; Butler and Cowley Counties, Kansas). 

Arizona has identified 19 affected premises (18 confirmed positive, 1 suspect) in 7 counties (Apache, Cochise, Gila, Maricopa, Pima, Pinal, and Santa Cruz Counties). 

Kansas has identified 74 affected premises (48 confirmed positive, 26 suspect) in 7 counties (Butler, Cowley, Greenwood, Marion, Montgomery, Sedgwick, and Sumner Counties). 

Nebraska has identified 2 affected premises in 1 county (Buffalo County). New Mexico has identified 16 affected premises (13 confirmed positive, 3 suspect) in 6 counties (Bernalillo, De Baca, Dona Ana, Eddy, Grant and Sierra Counties). 

Oklahoma has identified 1 affected premises (1 confirmed positive) in 1 county (Washington County). 

Texas has identified 10 affected premises (10 confirmed positive, 0 suspect) in 6 counties (El Paso, Hudspeth, Kerr, McMullen, Starr, and Zapata Counties). 

There have been a total of 68 previously VSV-infected or suspect premises that have completed the quarantine period and been released. To date, all VSV-quarantined premises have been released in New Mexico (since June 4, 2020) and Texas (since June 8, 2020). Fifty-four (54) premises remain under VSV quarantine in Arizona, Kansas, Nebraska and Oklahoma. 

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