ARS | Publication request: The effects of pooling, swab type and transport conditions on avian influenza virus and Newcastle disease virus detection

Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: August 15, 2012
Publication Date: N/A

Technical Abstract: A crucial aspect of achieving high diagnostic test accuracy is sample collection and transport. In order to optimize avian influenza virus (AIV) detection in poultry we have evaluated swab pooling, different swab material types, and transport conditions. Swab pooling was evaluated with Newcastle disease virus (avian paramyxovirus-1 (APMV-1)) in addition to AIV. Parameters for each method which is currently used were compared with potential improvements that are expected to be practical both economically and logistically. Swab pooling is used to save time and money when multiple animals are tested from the same flock or premise. Currently pools of 5 are common for poultry testing however 11 total swabs (2-3 pools) are required to meet the statistical recommendations of the National Poultry Improvement Plan, therefore it would be more efficient for the commercial industry to pool all swabs from the same flock. However, pooling 11 swabs does have cost and logistical disadvantages for the diagnostic lab (pros and cons will be discussed). Detection of virus by rRT-PCR, virus isolation, and for AIV, commercial antigen detection immunoassays were compared with pools of 5 or 11 swabs, or a single swab (oro-pharyngeal and cloacal). Swabs were collected from chickens experimentally exposed to A/chicken/VA/SEP-67/2002 H7N2 LPAIV or the Roakin strain of APMV-1. Virus detection by all methods with 1, 5 or 11 swab pools for either AIV or APMV-1 was similar. A second parameter that was evaluated was swab material type. Currently plastic shafted swabs with a wound nylon tip are most common in the U.S.; however, some new swabs types, nylon flocked and urethane foam, are expected to have superior capture and release characteristics, thus improving virus detection. Importantly they cost the same as nylon wound swabs. Using oropharyngeal and cloacal swabs collected from chickens experimentally exposed to H7N2 LPAIV, we found that flocked swabs were significantly better (P<0.05) to wound nylon swabs and that foam swabs were also better for virus recovery, particularly with cloacal swabs. Finally, we compared: 1) collecting a sample and leaving the swab in the vial during transport with; and 2) collecting the samples, expressing the swab contents into the vial and then removing the swab prior to transport. This work was just completed; therefore, the results are still pending.