Comparative efficacy of diagnostic tests for paratuberculosis in goats

Abstract

Paratuberculosis (Johne’s disease) is a chronic debilitating infection of goats caused by Mycobacterium avium subsp paratuberculosis (MAP). Recently the organism was reported to be associated with enteric infection in humans and hence the disease is of public health importance. In the present study comparative efficacy of acid fast staining of faecal smear, single intradermal Johnin test and IS900 faecal PCR were investigated in two hundred goats for detection of MAP. Single intradermal Johnin test was carried out in two hundred goats. Faecal sample from all two hundred goats subjected to Ziehl-Neelsen acid fast staining and IS900 PCR for detection of MAP. Out of one hundred and fifty goats screened for paratuberculosis from University sheep and goat farm, Mannuthy, five animals (3.33 per cent) were found positive by acid fast staining, eight animals (5.3 per cent) were found positive by single intradermal Johnin test and thirty animals (20 per cent) were found positive by IS900 PCR. Out of fifty goats screened for paratuberculosis from field, one goat (2 per cent), three goats (6 per cent) and twelve animals (24 per cent) were found positive by Ziehl-Neelsen acid fast staining of faecal smear, single intradermal Johnin test and IS900 PCR respectively Results of present study from both farm and field indicate that amplification of the IS900 insertion element was the most specific and sensitive diagnostic method. The strategic use of PCR can provide a means for early identification of MAP infected goat, thus ensuring their elimination from an infected herd. Advantage of skin test is its ease of application and its low cost. Culling of CMI test positives could be a cost effective means of removing infected animals before they actually start faecal shedding. Ziehl-Neelsen staining had the lowest detection rate of the three tests under investigation and it proved unreliable in diagnosing Johne’s disease.