Those reports resulted in the start of a remarkably rapid series of developments in oral fluid-based tests in human diagnostics, … but there was little spillover to veterinary medicine until February 2005, when Iowa State University veterinarians found themselves frustrated with collecting individual pig samples (primarily serum or tonsil scraping samples) for monitoring porcine reproductive and respiratory syndrome virus (PRRSV). Looking for an easier and better alternative, the first oral fluid sample was collected by hanging a rope in a pen of PRRSV-infected pigs housed in the Livestock Infectious Disease Isolation Facility at ISU. Why rope? “PRRSV colonizes the tonsils, so collecting an oral fluid sample using a length of rope seemed to be our best option,” Zimmerman says.
Collaborating with ISU Professor Dr. En-min Zhou (now Professor and Dean College of Veterinary Medicine Northwest A&F University in Shaanxi, China) and ISU Professor Dr. Kyoung-Jin Yoon, the first oral fluid samples were tested using technology available in their laboratories and shown to contain detectable levels of PRRSV (RT-PCR) and anti-PRRSV antibody.
“Pen-based oral fluids provide both higher herd-level sensitivity (the probability that an infected population will test positive) and higher herd-level specificity (the probability that an uninfected population will test negative) than individual pig samples. Compared to individual pig samples, far fewer oral fluids are needed to meet or exceed a targeted detection threshold,” Zimmerman said. “Oral fluids are better for producers, veterinarians, and pigs because they are easier and faster to collect than individual pig samples (nasal swabs or blood). Plus, it is fun to watch the pigs.”
Seeing the potential of the approach, the National Pork Board awarded funds for a proposal entitled “An improved method for PRRSV surveillance and monitoring (#05-146) to Drs. Zimmerman and Zhou in June of 2005. This allowed the group to develop and standardize the oral fluid collection methods and begin the process of optimizing nucleic acid and antibody tests for oral fluids. By November of 2005, graduate student Dr. John Prickett (currently a veterinarian with Carthage Veterinary Service, Ltd) was able to start presenting the results of testing samples collected from animals under either experimental or field conditions at national and international scientific meetings. Over the next 5 years the team spent their time researching, presenting, collecting, testing, and creating assays.
Dr. Prickett observed that “in the beginning there were 2 camps regarding the concept. Part of the crowd was very enthusiastic and shared our vision for future applications of the concept after complete validation. This group of swine veterinarians and researchers started collecting oral fluid samples themselves thereby contributing to the developing body of work. The other camp, most of which had a lifetime of serum diagnostics under their belts, expressed that they had always used serum and always would.”
Starting in February 2010, the ISU Veterinary Diagnostic Laboratory began to offer oral fluid testing on a routine basis and 10,000 oral fluid samples were tested the first year. In 2014, the Chilean government’s Servicio Agricola y Gandero (Agriculture and Livestock Service) officially approved the use of oral fluids in their National PRRSV elimination program. Currently, the World Animal Health Organization’s OIE Terrestrial Manual 2015 lists oral fluids as a diagnostic specimen in two chapters (PRRS virus and Influenza virus). With the number of oral fluid tests at ISU’s Diagnostic Lab reaching 175,000 in 2015 and new diagnostic assays using oral fluids appearing rapidly, it is clear that a concept that originated some 100 years ago has globally transformed livestock diagnostic medicine and will continue to serve as an important tool in improving swine health and productivity in Iowa and elsewhere.
Rodger Main, ISU Professor and Director of Veterinary Diagnostic Lab Operations, recognized that “Dr. Zimmerman et al.’s initial discovery and subsequent diagnostic methods development work evaluating the fitness of swine oral fluids as a diagnostic specimen has created a notable step-wise improvement and transformative change in swine diagnostic medicine. Oral fluids have quickly become the ante-mortem sample type of choice for an ever increasing number of systemic, respiratory, and enteric disease surveillance-based diagnostic applications in growing pigs and replacement breeding stock. While progress to date has been significant both locally in the US and now rapidly gaining adoption across the world; it feels like we are extremely early-on in the translational discovery and development phase, when compared the eventual potential that this user-friendly and broadly applicable ante-mortem diagnostic specimen has to offer.”
Dr. Jeffrey Zimmerman and his group are focused on 3 areas going forward: 1. Continued test development, especially for emergency or exotic diseases, 2. Statistically-valid approaches to oral fluid-based surveillance in the field, and 3. Development of an integrated and comprehensive plan to react quickly and effectively to an outbreak of an emergency or exotic disease in Iowa or the U.S.
For Further Questions Contact: Dr. Jeffrey Zimmerman (515-294-1073, jjzimm@iastate.edu); Dr. Rodger Main (515-294-6945, rmain@iastate.edu)
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