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Center of Excellence for Emerging and Zoonotic Animal Diseases

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Kansas Biosciences Authority /National Pork Board Joint Call Funded Projects

 

Rapid detection and epidemiological surveillance of African Swine Fever using oral fluid

Kansas State University               PI: Alfonso Clavijo

Iowa State University                   Co-I: Jeffrey J. Zimmerman

Iowa State University                   Co-I: Luis G. Gimenez-Lirola

AAHL, Geelong, Australia            Co-I: David Williams

Kansas State University               Co-I: Raymond Rowland

Universidad Complutense de Madrid, Spain  Co-I: JM Sanchez-Vizcaino

07/01/2015 – 06/30/2016

 

Abstract:

This project is a continuation of previous NPB- and DHS-funded "oral fluid projects" assessing the feasibility of antibody detection in oral fluid and the direct detection of African Swine fever Virus (ASFV) in oral fluid by multiplex real-time quantitative polymerase chain reaction (mp RT-qPCR).  In the event of an ASFV outbreak in North America, the key to rapid detection and control is immediate access to accurate diagnostic tools and an efficient surveillance (sampling) strategy.  The major barrier to efficient surveillance is the complexity and cost of collecting and testing statistically appropriate numbers of samples.

Oral fluid-based diagnostics provide a possible solution to this problem by allowing for pen-based sampling.

  • Compared to serum, oral fluid sampling requires little labor, samples can be collected as frequently as necessary, and sampling is stress-free ("welfare-friendly") for both pigs and people.
  • Oral fluid samples are more sensitive than individual pig samples for detecting infections in populations because the "aggregrate" oral fluid sample contains "diagnostic contributions" from many of the animals in the pen sampled (Olsen et al., 2013).

Several PCR- and antibody-based diagnostic assays are currently available in commercial and public laboratories for the detection of ASFV using various diagnostic sample matrices, including oral fluid, serum, and feces.  Stimulated by the global spread of ASFV, additional assays are under development. 

The current standard for detection of ASFV is real time PCR (RT-PCR).  Previous DHS-supported research (#HSHQDC-11-X-00528 and #2010-ST-061-AG0002) showed that oral fluids are a suitable sample for a highly sensitive RT-PCR.  However, limiting the testing options to PCR is the diagnostic equivalent of "all eggs in one basket". 

Serum antibody detection has historically been used in combination with virus detection in ASFV surveillance and control programs in the Iberian Peninsula and Sardinia, particularly as a tool for the detection of ASFV carrier animals.  Research conducted by members of our research team confirmed that ASFV antibodies can also be detected in oral fluid (Mur et al., 2013).  More recently, NPB-supported research (#13-048) resulted in the development of a "dual" ASFV antibody ELISA (manuscript in preparation).  In brief, IgG antibodies were detected by 12 days post infection (DPI) in both serum and oral fluid specimens.  Evaluation of 200 serum and oral fluid samples submitted to the Iowa State University Veterinary Diagnostic Laboratory from U.S. swine herds (i.e., a known ASFV-negative population) showed specificities of 99.5% and 100% for serum and oral fluid samples, respectively.  Thus, the test detected ASFV antibodies in both oral fluid and serum samples and is highly specific for both specimen types.  Essentially, screening (oral fluid) and confirmatory (serum) testing may be done simultaneously using the same ELISA kit.