Got blisters?

What to expect when blisters are reported to state and federal officials.

SVV Webinar for Veterinarians

Webinar #3 May 20, 2016: Reporting vesicles and lesions – what to expect. USDA and state animal health officials presented what practitioners and producers need to know about the state and federal governments’ roles and responsibilities in investigating cases of vesicular disease. The National Animal Health Laboratory Network and the Plum Island Animal Disease Center described the samples, testing and timeline needed to rule out Foot and Mouth Disease during an investigation.

Webinar #2 May 18, 2016 An update on current diagnostic tools – capabilities and work still to be done, focused on SHIC’s and universities’ funded research on Senecavirus A diagnostics. The genetic diversity of the virus in the U.S. and an update about the virus in South America, interpreting PCR values as they correlate to virus isolation, and the latest information about current and future serology tests were presented.

Webinar #1 May 16, 2016: Here’s what we know about the virus and how to manage it presented results of 2015-16 SHIC research investment as well as information regarding epidemiological investigations, virus transmission, sow and grow-finish shedding and a case example of a herd closure to eliminate the virus from the farm. This was funded by SHIC, the USDA-APHIS, USDA Ag Research Service, Universities of Minnesota and Iowa State. Sample collection and data management support was done by Swine Vet Center in St. Peter, Minnesota.

Seneca Valley Virus Summary

Etiology

  • Seneca Valley virus (SVV) is a small, non-enveloped picornavirus, unknown until 2002 when it was discovered incidentally as a cell culture contaminant.
  • Only a single species is classified in the genus Senecavirus. The family Picornaviridae also contains foot-and-mouth disease virus (FMDV) and swine vesicular disease virus (SVDV).

Cleaning and Disinfecting

  • The efficacy of most disinfectants against SVV is not clearly known.
  • Because vesicular diseases are clinically indistinguishable, disinfection protocols for FMDV should be followed even if SVV is suspected. This includes use of: sodium hydroxide, sodium carbonate, 0.2% citric acid, aldehydes, and oxidizing disinfectants including sodium hypochlorite.
  • Below are EPA-approved disinfectants USDA lists effective for FMD on page 30 http://www.aphis.usda.gov/animal_health/emergency_management/downloads/fad_epa_disinfect ants.pdf. Be sure to follow labeled directions.

Epidemiology

  • The survival of SVV in the environment has not been reported. Most cases of idiopathic vesicular disease, which is associated with SVV, seem to occur between spring and fall.
  • Neutralizing antibodies to SVV have been detected in small populations of swine, cattle, and wild mice in the United States. Specially, SVV has been reported in South Dakota, Iowa, Minnesota, North Carolina, New Jersey, Illinois, Louisiana, and California. The virus has also been reported in Australia, New Zealand, and Brazil.
  • There is no record of SVV causing symptomatic human disease. The virus has potent oncolytic abilities which are currently being explored in human cancer treatment research.

Transmission

  • The transmission route(s) for SVV are not well understood. Another picornavirus, FMDV, is known to spread readily by direct contact with infected individuals, fomites, or exposure to aerosolized virus, but it is unknown if these same modes of transmission also apply to SVV.

Infection in Swine/Pathogenesis

  • The pathogenicity of SVV in swine remains unclear. Experimental infections in swine have failed to produce signs of disease and SVV has been isolated from healthy pigs in the United States. However, the virus is linked to idiopathic vesicular disease and multiple cases of swine vesicular disease in the United States have been reported in which SVV was the only detected pathogen. SVV has also been linked to idiopathic vesicular disease during concurrent infection with porcine circovirus and porcine enterovirus.
  • SVV causes vesicular lesions in pigs that are clinically indistinguishable from foreign animal diseases such as FMD, SVD, vesicular stomatitis, and vesicular exanthema of swine virus. Lameness is commonly observed.
  • Gross lesions include multifocal, round, discrete erosive and/or ulcerative lesions on distal limbs, especially around the coronary bands. Crusting and sloughing of the hoof wall may also be observed. Similarly, fluid filled vesicles and multifocal chronic superficial and/or deep ulcers have been described in and around the oral mucosa, snout, and nares.

Diagnosis

  • SVV can be grown in human retinoblast (PER.C6® ) cells and human lung cancer cell monolayers (NCI-H1299a ), producing high virus titers. SVV replicates readily in certain human tumor cells with neuroendocrine properties that are most sensitive to killing by the virus, while leaving normal adult human cells relatively unscathed.
  • Electron microscopy, immunohistochemistry (IHC), reverse transcription polymerase chain reaction (RT-PCR), and quantitative real-time RT-PCR have been used in the study and diagnosis of SVV.
  • Monoclonal antibodies have been developed in an attempt to develop more rapid and sensitive immunoassays for diagnosis, leading to the creation of a successful competition enzyme linked immunosorbent assay (cELISA) for specific detection of anti-SVV antibodies.

Immunity

  • Serological studies have revealed the natural occurrence of neutralizing anti-SVV antibodies in swine, cattle, and mice, but rarely in humans. Both humans and mice have developed neutralizing antibodies after intravenous treatment with SVV-001.
  • No vaccines are currently available for SVV.
  • Swine SVV isolates are genetically similar to the prototype species, SVV-001.

Prevention and Control

  • Proven methods for prevention and control of SVV are lacking. Vaccination and stamping out have been used to control FMD, which is caused by a similar virus.
  • Common industry biosecurity practices should also be in place.
  • There is no national surveillance for SVV, although the state of California classifies SVV as a monitored condition.

Gaps in Preparedness

  • Continued research on the epidemiology of SVV and idiopathic vesicular disease is needed.
  • The development of more rapid, cost-effective diagnostic assays, combined with screening and monitoring of swine herds prior to the appearance of vesicular lesions, will be important in the future.

OVERVIEW

Seneca Valley virus (SVV) is a small, non-enveloped picornavirus, unknown until 2002 when it was discovered incidentally as a cell culture contaminant. Only a single species, Senecavirus A, is currently classified in the Senecavirus genus of the family Picornaviridae, although sporadic serologically similar isolates have been identified in porcine samples spanning almost three decades. Naturally occurring antibodies against the virus have been detected in swine, cattle, mice, and a single human sample, though the virus is not known to cause disease in humans. Pathogenicity in swine remains unclear. Outbreaks of idiopathic vesicular disease have been linked to SVV in the absence of other identified etiologic agents and also during concurrent infection with porcine circovirus and porcine enterovirus. In contrast, the virus has also been identified in healthy pigs, and experimental infection has failed to produce clinical signs thus far.

Swine SVV infection has occurred across the United States and Canada, and idiopathic vesicular disease has been reported globally from Europe to South America to Australia and New Zealand. Transmission of picornaviruses is generally very rapid and occurs in the cytoplasm of host cells. Clinical signs of SVV, when present, are indistinguishable from those of swine vesicular disease (SVD), vesicular stomatitis virus (VSV), vesicular exanthema of swine virus (VESV), and foot-and-mouth disease virus (FMDV), all more serious and economically devastating foreign animal diseases (FADs). Erosions, ulcerations, and vesicular lesions of the snout, oral mucosa, and distal limbs, especially around the coronary band, may be observed. Hoof sloughing and lameness can also occur, as well as more general symptoms of illness such as fever, lethargy, and anorexia.

Cultivation and purification of SVV can be performed in the laboratory using human retinoblast (PER.C6® ) cells and human lung cancer cell monolayers (NCI-H1299a ), yielding high virus titers. Replication of SVV occurs readily in certain human tumor cells with neuroendocrine properties that are most sensitive to killing by the virus, while leaving normal adult human cells relatively unscathed. Electron microscopy, immunohistochemistry (IHC), reverse transcription polymerase chain reaction (RT-PCR), and quantitative real-time RT-PCR have been used in the study and diagnosis of SVV. Monoclonal antibodies have been developed in an attempt to develop more rapid and sensitive immunoassays for diagnosis, leading to the creation of a successful competitive enzyme-linked immunosorbent assay (cELISA) for specific detection of anti-SVV antibodies.

Understanding the epidemiology of SVV and potential role of other species in virus transmission and origin, combined with continued development of rapid and specific diagnostics and elucidation of the link between viral infection and clinical disease in swine, will be crucial to our knowledge and ability to manage this newly discovered and little understood virus.

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AASV Swine Health Committee Considers SVV

Please download this PDF for some important information about the current incidence of Seneca Valley Virus (Senecavirus A). For perspective, keep in mind that in 2015 we’ve had confirmed SVV from only 20 – 30 cases from across the U.S. The incidence is low but it is much higher than the 2 or 3 sporadic cases per year that is our historical experience. The Swine Health Information Center is funding research and epi investigations to help us understand more about this virus and be better prepared and informed if we continue to see new cases.

Better preparedness with research and information is important but only one part of what we need. NPPC, NPB, AASV and SHIC have been working to draft plans for proposed industry responses to new or emerging diseases. One of the components of that response plan is a panel of producers and veterinarians to discuss and recommend to state animal health officials and USDA appropriate responses based on the information available about a new or emerging disease. In short, whether a new or emerging disease is local, regional or national and whether we have the knowledge and tools to rapidly and effectively respond. Unfortunately, SVV has shown up before that body could be formed.

In its absence, the AASV Swine Health Committee was asked if they would help inform responses by reviewing the available information and decide the scope and distribution of SVV already in the U.S. They also were asked to make recommendations about responses. That is what is attached.

There are two take home messages. First, they have defined the SVV incidence this summer as a “Type 3” status – national in scope with limited knowledge and tools. The details of a Type 3 status are in the AASV statement. That’s important to help put into context discussions about the effectiveness of local, specific responses like holding pigs from movement while waiting for them to stop shedding the virus.

The second is their repeated recommendation that pigs with illness or active SVV lesions should not be marketed until the lesions at least start to resolve. We can’t afford to have a packing plant shut down because of SVV being mistaken for FMD and stopping processing and commerce. At the same time, we can’t also become complacent and assume that active lesions are SVV, thus not alerting state or federal officials, whether on the farm or in the packing plant. Doing so puts pork producers, veterinarians and all of our industry at risk. Discussions are taking place with USDA and the packing companies about appropriate communications and responses about pigs that have had SVV, are healing, have had a FMD-negative test and are going to be presented to the market.

This isn’t “news”. It’s as it always has been. But there is heightened risk of complacency if we continue to find SVV after checking for FMD and that risk is unacceptable and avoidable.

This is an opportunity to underscore the message of careful observation and immediate reporting of clinical signs or out of ordinary events. The National Pork Board has multiple resources, including barn posters and other written and visual materials. They’d welcome sending you these materials to help with your effort.

Download the full document

Got Blisters?

What to expect when blisters are reported to state and federal officials.

SVV Webinar for Veterinarians

Webinar #3 May 20, 2016: Reporting vesicles and lesions – what to expect. USDA and state animal health officials presented what practitioners and producers need to know about the state and federal governments’ roles and responsibilities in investigating cases of vesicular disease. The National Animal Health Laboratory Network and the Plum Island Animal Disease Center described the samples, testing and timeline needed to rule out Foot and Mouth Disease during an investigation.

Webinar #2 May 18, 2016 An update on current diagnostic tools – capabilities and work still to be done, focused on SHIC’s and universities’ funded research on Senecavirus A diagnostics. The genetic diversity of the virus in the U.S. and an update about the virus in South America, interpreting PCR values as they correlate to virus isolation, and the latest information about current and future serology tests were presented.

Webinar #1 May 16, 2016: Here’s what we know about the virus and how to manage it presented results of 2015-16 SHIC research investment as well as information regarding epidemiological investigations, virus transmission, sow and grow-finish shedding and a case example of a herd closure to eliminate the virus from the farm. This was funded by SHIC, the USDA-APHIS, USDA Ag Research Service, Universities of Minnesota and Iowa State. Sample collection and data management support was done by Swine Vet Center in St. Peter, Minnesota.

Seneca Valley Virus Update

The incidence of Seneca Valley Virus (Senecavirus A) has increased in 2015 compared to historical incidence in other years.  SHIC is working with academics, researchers, USDA and others to help understand the scope of the cases and the role SVV has in causing clinical disease.