Detection of Influenza A virus in porcine oral fluid samples

Porcine oral fluids have been used for the detection of Porcine reproductive and respiratory syndrome virus and Porcine circovirus-2. The objective of the present study was to determine whether Influenza A virus (FLUAV) is present in porcine oral fluids at detectable levels and to validate a standard FLUAV molecular diagnostic test for porcine oral fluids. Pen-based oral fluid samples were collected on 3, 4, 5, and 6 days postinfection (DPI) from 4 groups of 6 pigs each that were inoculated intratracheally with A/Swine/Iowa/00239/2004 H1N1 and from 2 untreated or mock-inoculated groups of 6 pigs each that served as negative controls. Individual nasal swabs were also collected from these 36 pigs on 3 and 7 DPI. All oral fluid samples were examined for the presence of FLUAV by matrix gene real-time reverse transcription polymerase chain reaction (real-time RT-PCR) and virus isolation. Nasal swabs were tested initially by virus isolation followed by retest of negative samples with real-time RT-PCR. No oral fluid sample from virus-inoculated pigs was positive by virus isolation, but 15 of 16 positive (94%) oral fluids were positive by real-time RT-PCR. In contrast, virus was isolated from 32 of 48 (67%) nasal swabs collected from virus-inoculated pigs. In addition, 382 of 910 porcine oral fluids collected from pigs in the field between August 1, 2009, and January 31, 2010, were positive by real-time RT-PCR. The results of the present study indicate that pen-based oral fluids provide an easy, effective, and safe collection method for the detection of FLUAV with rapid testing methods such as real-time RT-PCR.