SHIC Issues a Call for Proposals for Improved Oral Fluids PCR Sensitivity

Recent unpublished, observational research indicates oral fluids (OF), when collected by rope as an aggregate sample, could be a good sample for rapid detection of African swine fever virus (ASFv). However this experimental data also suggests that there is potential for false negative testing results.  Therefore, the Swine Health Information Center (SHIC) is calling for proposals to develop methods to improve the detection of low levels of nucleic acid in OF through enhancements to sample pre-extraction treatment(s) or through improved extraction methodologies compatible with the high throughput testing currently done in NAHLN laboratories.

With thousands of OF samples coming into diagnostic labs each month, the value of this type of testing for swine disease monitoring is irrefutable. The objective of this SHIC-funded research is to address concerns about OF testing sensitivity. Then, with this knowledge, the potential for an official option for ASF testing beyond whole blood, which is the antemortem sample presently proposed by USDA for surveillance, opens. Due to the urgency of preparing for ASF and other foreign animal disease testing protocols, SHIC will favor proposals reflecting this immediate need.

In a negative cohort study, no false positives for ASFv were reported. Experimental, unpublished, observational work indicated that ASFv may be detected in OF prior to onset of clinical signs even if only a small proportion of animals are infected. However, as the viral load, as measured by PCR CT comparison, was much lower in OF than individual tissue samples, the study indicated false negatives do occur. This limits the potential use of swine OF as an official monitoring and surveillance tool in the event of an ASF outbreak in the US without further study and refinement.

OF samples are widely used in swine surveillance for porcine reproductive and respiratory syndrome virus (PRRSV), Influenza A virus in Swine (IAV-S), and Mycoplasma hyopneumoniae (MHP) nucleic acids on US farms and have shown the potential for use in foreign animal disease (FAD) surveillance, as well. To date, more than 27 pig pathogens have been shown to produce detectable levels of nucleic acid in OF.  The proposed research could lead to increased sensitivity of PCR testing for these domestic and foreign animal diseases.

SHIC is currently sponsoring OF sensitivity research in Vietnam related to ASF as well. Building on those projects, it is hoped the research related to this new request for proposals will result in methods sensitive enough to support OF PCR diagnostic validation.

The following detailed points are included in SHIC’s request for proposal.