Oral fluid collection in wild boar: a field protocol

Traditional wildlife sampling methods have limitations in providing a well-distributed, timely and accurate disease surveillance in wildlife. We developed a field protocol for collecting wild boar (Sus scrofa) oral fluid samples for non-invasive active disease surveillance using environmental ropes. We deployed ropes in field settings and tested the rope-sampled oral fluids for antibodies against Mycobacterium bovis and closely related members of the Mycobacterium tuberculosis complex (MTC). Oral fluid samples were collected from three wild boar populations in Spain with endemic tuberculosis across two seasons with contrasting natural food availability. Additionally, we studied the effect of placing the ropes close to aggregation points and of impregnating the ropes with corn powder. The results suggested that installing environmental ropes in summer, close to feeders or aggregation points, and baited with corn powder significantly increases the proportion of bitten ropes. No significant differences were observed in the effectiveness of ropes for oral fluid sampling across the three study sites. The average rate of antibody detection by ELISA was 38% (range 34 to 45%) of the bitten ropes. This method appears to be both precise and sensitive in detecting antibodies against MTC in oral fluid samples collected from environmental ropes, making it a potentially valuable tool for early detection and monitoring of MTC circulation. This noninvasive sampling method can easily be adapted for other relevant diseases of wild suids including African swine fever. Therefore, environmental ropes represent an effective, inexpensive, flexible, environmentally friendly, and noninvasive alternative for active wildlife disease surveillance.