Proof of principle: Non-invasive sampling for early detection of foot-and-mouth disease virus infection in wild boar using a rope-in-a-bait sampling technique

In this study we describe the use of a rope-in-a-bait sampling method (“pSWAB”: pathogen sampling wild animals with baits) for non-invasive saliva sampling aimed at the detection of foot-and-mouth disease (FMD) viral genome in wild boar. The pSWABs are produced in the form of a standardized product by embedding a 10 cm long cotton rope in a cereal-based bait matrix. To assess the general suitability of this novel sampling technique an animal experiment was conducted to detect FMD viral genome in saliva of infected wild boar. Two juvenile animals were inoculated in the bulb of the heel with a recent wild boar FMD virus isolate and kept together with three noninoculated wild boar of the same age. Over a period of 29 days, the animals were sampled by using five pSWABs per day in addition to the collection of blood and conventional saliva swabs taken every three to four days. Viral RNA in pSWABs was identified already 24 h after infection during the incubation period and until 23 dpi. Comparison of the results of pSWAB sampling with those of conventional saliva swabs or serum samples showed satisfactory sensitivity. These experimental data demonstrate the suitability of non-invasive sampling of wild boar by using pSWABs as a sensitive, cheap and feasible sample collection technique independent of hunting activities. In addition, the use of non-invasive sampling in an appropriate surveillance strategy is discussed.