Development and Validation of Rapid, Sensitive and Inexpensive Protein G-based Point of Care Diagnostic Assay for Serodiagnosis of Paratuberculosis at Resource-Limited Areas

Paratuberculosis is caused by Mycobacterium avium subspecies paratuberculosis (MAP). It affects domestic cattle, ruminant livestock species with emerging zoonotic concerns and also causes human Crohn's disease. It is a chronic granulomatous enteritis and results in huge economic loss to domestic dairy cattle and ruminant industry. Further, there is mounting evidence on the zoonotic role of MAP in human Crohn's disease. MAP is not killed by pasteurization, therefore, milk and milk products are major sources of infection for humans. The disease affects cattle and small ruminant industries, thus impacting farmer's economy. Control of the disease is hampered by the lack of rapid and accurate diagnostic tests. Therefore, it is urgently needed to develop affordable as well as high performing diagnostic tools. So, the present study was aimed to develop a simple, inexpensive, rapid and robust point of care (POC) lateral flow diagnostic test kit for serodiagnosis of paratuberculosis infection in bovine cattle and in small ruminant livestock species. We developed a rapid, pen-side lateral flow antibody (Ab) diagnostic test kit for onsite screening of paratuberculosis. The rapid kit detects infection in 20 minutes and can be used directly by a farmer without the requirement of an expert or equipment. We evaluated 2, 502 samples using lateral flow assay (LFA) which included 243 reference sera and 2, 259 field samples. The results suggest that the sensitivity and the specificity of LFA were 91.01% and 98.94% respectively in comparison with the gold standard culture, polymerase chain reaction (PCR) and delayed-type hypersensitivity (DTH) methods. Thus, LFA aids to detect the MAP specific antibodies (Ab) in the collected samples at POC resource-limited areas and help the bovine and small ruminant livestock healthcare systems. This assay is well suited for the early diagnosis of MAP in less equipped laboratories and in resourcelimited POC settings suitable for the Indian environment.