Oral fluid testing provides big diagnostic advantages

Most animal health specialists agree better on-farm infectious disease surveillance is needed for improved on-farm infectious disease control. When evaluated in the context of farm production data, enhanced surveillance could be the beginning of a new generation of highly effective herd management and disease control strategies leading to greater profitability.

Most experts also agree that on-farm collection of statistically appropriate numbers of blood or nasal swab specimens from individual pigs is too expensive and requires too much work to be done on a routine basis. The solution could be to switch to oral fluid diagnostic specimens.

Oral fluids are collected from pigs by hanging a length of rope in a pen for 20 to 60 minutes (see a video at vetmed.iastate.edu/vdpam/diseasetopics/oral-fluids). Oral fluids are absorbed as the pigs chew on the rope. The sample is extracted by inserting the bottom (wet) end of the rope into a plastic bag, squeezing the rope to release the fluid, and pouring the fluid into a tube for submission to the lab.

Oral fluids have significant diagnostic advantages:

  • They can be collected by a single person.
  • They can be collected as frequently as desired without stress to pigs or people.
  • They provide a higher probability of detection with fewer samples than serum or nasal swabs.

On the farm, we recommend “systematic spatial sampling.” This means collecting oral fluid samples uniformly across all buildings and spaces. When collected regularly, e.g., every two weeks, the results provide a clear story of the presence and circulation of infectious diseases on the farm.

A variety of antibody and polymerase chain reaction (PCR)-based tests are already available in most of the major swine diagnostic labs, including oral fluid antibody and PCR tests for porcine epidemic diarrhea virus and porcine reproductive and respiratory syndrome virus. The Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) introduced routine oral fluid testing in 2010. The growth in the number of tested samples indicates that swine producers and veterinarians like this approach. The ISU-VDL performed 10,329 tests on swine oral fluids in 2010, and anticipates around 120,000 samples in 2014.

This is still an area in development, but the research is gearing up, and new information on oral fluid-based testing and a wider variety of commercial oral fluid assays is coming. Thus, the latest International Pig Veterinary Society Congress (June 2014) had 64 abstracts with the words “oral fluid” describing research on a wide variety of bacterial and viral pathogens.

These developments present opportunities for health management. On-farm oral fluid surveillance data can be combined with farm production records to assist in identifying the circulation of specific pathogens, quantifying their effects on pig health and productivity, targeting interventions to the correct pathogen and population, and identifying when to intervene for the maximum effect.

At the regional level, oral fluid-based surveillance can make producer-driven area control programs more practical and affordable.

On the national level, surveillance-based oral fluids can facilitate the rapid collection of data for the detection and elimination of transboundary or foreign animal diseases.

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