Extent of Mycobacterium bovis infection in dairy cattle herds subject to partial culling as determined by an interferon-gamma assay

The interferon-gamma (IFN-gamma) assay is employed as a complementary diagnostic test for bovine tuberculosis (BTB) in many countries. To simplify this assay, we established a 96-well plate format using the ESAT-6 and CFP-10 antigens and then employed it to determine the extent of Mycobacterium (M.) bovis infection in dairy herds with a history of BTB outbreaks in a country where only selective culling is practiced. The sensitivity and specificity of this IFN-gamma assay were 85.9% and 100%, respectively, based on comparison with the conventional single intradermal tuberculin test (SIDT). The IFN-gamma assay was also positive in 30.4% and 36.8% of SIDT-negative animals from herds with recent and remote BTB outbreaks, respectively. Of 14 SIDT-negative, IFN-gamma positive cattle, five (35.7%) were culture positive and an additional six were positive based on a polymerase chain reaction-based test for M. bovis. Therefore, the IFN-gamma assay has the potential to serve as a specific and sensitive test for M. bovis infection in dairy cattle. Further, the results indicated that a substantial portion of SIDT-negative animals in herds with previous BTB outbreaks were actually infected with M. bovis. Accordingly, the present selective-culling strategy may require modifications to include this more sensitive assay.

A Case of Atypical Cutaneous Tuberculid in an Immunocompromised Patient / 대한피부과학회지

Cutaneous tuberculids are relatively rare hypersensitivity reactions to Mycobacterium tuberculosis, characterized by erythematous eruption on the skin of a tuberculosis patient. Papulonecrotic tuberculid, lichen scrofulosorum, erythema induratum and nodular tuberculid were originally included in tuberculids. However, some cases are difficult to classify into the subtypes because of their broad spectrum of cutaneous manifestations and various histopathologies. This is particularly true in immunocompromised patients. We report a case of atypical cutaneous tuberculid in an immunocompromised patient in whom mycobacterical DNA was not demonstrated by PCR. However, the diagnosis of latent tuberculous infection was supported by IFN-gamma assay (QuantiFERON(R)-TB Gold test) and tuberculous lymphadenitis was diagnosed. The skin lesions responded dramatically to anti-tuberculous therapy, and there has been no evidence of recurrence.

Comparison of tuberculin skin test with Interferon-gamma assay for the diagnosis of bovine tuberculosis in Korean cattle / 대한수의학회지

Bovine tuberculosis (bTB), caused primarily by Mycobacterium bovis, continues to exert an economic loss, even in countries with active control measures, and is one of zoonotic diseases enable to be transmitted to human. The control and eradication of bTB are mainly based on a test and slaughter policy and/or abattoir surveillance. Various factors including limitation of diagnostic tests have been considered as major constraints to eradication. Single intradermal test (SIT) is the official diagnostic test. New diagnostic methods are needed to be developed, because of limitations of the test. In the present study SIT was compared with single intradermal comparative cervical test (SICCT) and interferon (IFN)-gamma assay. There was very low correlation between SIT and SICCT. However, high correlation was shown between SIT and IFN-gamma assay while no correlation was observed between SICCT and IFN-gamma assay. Therefore, our results suggest the possibility of replacement of SIT with IFN-gamma assay for the diagnosis of bovine tuberculosis.