Usability of a gamma interferon release assay in the diagnosis of naturally infected pigs with Mycobacterium avium subspecies hominissuis

Abstract

In the current study, the results of an intradermal tuberculin test and a gamma interferon (IFN-γ) release assay were compared. IFN-γ release assay is based on the detection of IFN-γ production after in vitro stimulation with Mycobacterium avium subsp. avium-specific antigen for the discrimination of pigs naturally infected with M. avium subsp. hominissuis. Fiftyfive clinically healthy pigs were used in the study. Three of these were proven by culture and real-time quantitative polymerase chain reaction methods to be infected with M. avium subsp. hominissuis (2 animals) and Mycobacterium xenopi (1 animal). No animals were positive by the tuberculin test. Both M. avium subsp. hominissuis-positive pigs were evaluated as positive by the IFN-γ release assay. Bacteriologically negative and M. xenopi-positive pigs were unresponsive in the IFN-γ release assay, indicating the specificity of the method. The results suggest that the IFN-γ release assay has a higher sensitivity than the tuberculin test and that the assay can be used for diagnosis of M. avium infections in live, naturally infected pigs.

Mycobacteriosis in Pigs – An Underrated Threat

“…Joint research of Norwegian and Serbian researchers has found that the use of bovine and aviary tuberculin increases the detection sensitivity to mycobacteria, including members of MAC. A reaction to both types of tuberculin is common although only MAH was detected [53,56].…”

“…Intradermal tuberculin test and gamma interferon tests are the only methods that can be used for live animals. Unfortunately, the use of tuberculin skin test in the majority of EU countries has not been mandatory for many years, while the use of gamma interferon test in swine production is only used mostly for research purposes [56]. Although imperfect, the tuberculin test is a cheap method that has signifi cantly contributed to the eradication of tuberculosis in cattle and consequently in humans [65].…”

“…At rare occasions, the results are obtained by using tuberculin skin reaction and gamma interferon probe [8,[53][54][55][56]. The morphological signs of MAC infections are not always macroscopically visible, although granulomas are formed in the tissues as a response to the presence of mycobacteria [54] (Figure 1).…”

Evaluation of a MPB70-ELISA to differentiate Mycobacterium bovis from M. avium-sensitized swine

“…Conversely, other mycobacteria, such as members of the Mycobacterium avium complex (MAC), lead to a granulomatous lymphadenitis (GL)in head and mesenteric lymph nodes that, despite its economic importance due to the condemnation of carcasses (Faldyna et al 2012), present a lower public health risk, often restricted to immunocompromised people.…”

“…Although serological assays have been developed with promising results (Boadella et al 2011, Wisselink et al 2010, as well as an Interferon-gamma release assay (Faldyna et al 2012), they are mainly focused on the diagnosis of lymphadenitis, which is determined by MAC. To our knowledge, there are no studies addressing the diagnosis of M. bovis infections in swine and/or designed to discriminate between infections determined by M. bovis or MAC.…”