Evaluation of bioelectronics sensor compared to other diagnostic test in diagnosis of Johne's disease in goats

A bioelectronics sensor has been developed and it is evaluated for the diagnosis of paratuberculosis in goats. Initially hematite nanoparticles were prepared and using this nanoparticles as core, electrically active polyaniline coated magnetic (EAPM) nanoparticles are synthesized from aniline monomer (made electrically active by acid doping). These EAPM nanoparticles were fabricated with rabbit anti-goat IgG for the detection of goat antibodies on the capture pad. The protoplasmic antigen of Mycobacterium avium subspecies paratuberculosis (MAP) immobilized onto the capture pad will detect the antibody against MAP in the goat sera samples. This bound goat antibody will be detected by the anti-goat IgG previously bound to EAPM. Upon detection the EAPM nanoparticles bridges an electric circuit between the silver electrodes, flanking the capture membrane. The electrical conductance, caused by EAPM, was measured as direct charge transfer between the electrodes. Testing of the biosensor with known Johne's disease (JD) positive and negative serum samples gave significant difference in the electrical conductance value. Further the efficacy of this biosensor was compared with other serological tests like agar gel immunodiffusion (AGID) and absorbed ELISA using field sera. Out of 265 goat sera tested, positive results recorded were; AGID 36 (13.59%), bioelectronics sensor 49 (19.14%), and absorbed ELISA 51 (19.25%). This biosensor was also compared in live animals using intradermal Johnin test and nested PCR (detecting mycobacterial DNA in feces) in 65 animals. Of which, positive results recorded in animals were; Johnin test 21 (32%), biosensor 26 (40%) and fecal PCR detected mycobacterial DNA in 28 (43%) animals. Though the nanobioelectronics sensor was slightly less sensitive (not statistically significant) compared to absorbed ELISA and fecal nested PCR for mycobacterial DNA but it was simple to perform in field conditions and requires less time. The speed of detection and the equipment involved would support its application toward the various point-of-care opportunities aimed at control and management of Johne's disease in goats.