Field study on the utility of fluid obtained from testicles as a sample for detecting antibodies to selected swine pathogens

Processing fluid is a promising alternative to blood for monitoring porcine diseases, although certain aspects of its routine use remain unclear. This study evaluated serum from females and males, along with corresponding testicular only processing fluid, for antibodies against Actionbacillus pleuropneumonie, hepatitis E virus, porcine epidemic diarrhea virus, influenza A virus, Erysipetothrix rhusiopathie and Mycoplasma hyopneumoniae, using commercial ELISAs (ID Screen APP, Hepatitis E, PEDV, Influenza A from ID Vet, France; Civtest suis SE/MR from Hipra, Spain; and Mycoplasma hyopneumoniae from Idexx, USA). Differences in the proportion of positive results across sample types were analysed to assess the utility of testis-derived processing fluid for litter-level health monitoring. ROC analysis was used to establish optimal cut-offs for processing fluid, followed by evaluation of diagnostic performance using both manufacturer-recommended and ROC-derived thresholds. A pooling simulation was also performed. Results indicate that processing fluid collected exclusively from testes can detect antibodies against selected pathogens effectively. Some ELISA kits validated for serum may be applicable to processing fluid, provided that appropriate cut-off values are determined for this sample type. However, pooling processing fluid samples may reduce sensitivity and increase the risk of false-negative results. These findings highlight the potential of testis-derived processing fluid for large-scale serological surveillance while underscoring the need for test-specific validation.