Feasibility and performances of oral fluid and blood samples associated with commercial ELISA for PRRS antibodies detection in group housed sows

PRRSV leads to huge economic losses for the swine industry worldwide. Availability of simple, easy-to-use and accurate collection methods and laboratory tests are crucial for efficient PRRS diagnosis and monitoring. Blood sampling is currently the most frequently used method in the field for these purposes. A welfare friendly collection method, namely oral fluid (OF), has recently gained interest in the field as an alternative technique to blood sample. However, the feasibility and the diagnostic performances of this technique for PRRS antibodies detection have not yet been assessed for group housed sows and compared to those of blood sampling. Thus, the aim of this study was to assessand compare the feasibility and the diagnostic performances of 1/OF collection at the animal level associated with a commercial ELISA and 2/blood samples coupled with a serum-ELISA to detect PRRSV antibodies in group housed sows.

The study was carried out in 35 French breeding herds infected (32 herds) or non-infected (3 herds) by PRRSV. In every herd at least 30 gestating group housed sows and 3 pens were sampled at random. OF and blood were collected from each sow. OF and blood sampling times were recorded. OF and serum samples were analysed by commercial ELISA specific to each specimen (PRRS OF and PRRS X3, IDEXX, Eragny sur Oise, France). A Bayesian approach was used to estimate the sensitivity and specificity of each ELISA method without gold standard.

A total of 1598 sows were sampled. On average, individual OF sample took 2 minutes 57 seconds (sd=2min 55s) per sow (one investigator) while blood sample took 1min 16s (sd=1min 03s) (two investigators required). The sows chewed the OF sampling device during on average 1min 36s (sd=1min 06s). Aggressive behaviours of group housed sows towards the investigators were observed during blood sampling in 37% of the herds whereas OF collection was peaceful in every herds. Although ELISA used on individual OF showed on average the same level of sensitivity (Se) than serum-ELISA (mean Se=95%), it lacked specificity (Sp) when compared to serum-ELISA (mean OF-ELISA Sp=84% and mean serum-ELISA Sp=94%).

OF sampling appears to be a more welfare friendly technique than blood sampling in group housed sows and is a promising tool for increasing the efficiency and cost effectiveness of PRRS infection surveillance in swine herds once the performances of the lab tests will be improved.

Disclosure of Interest: None Declared.