The Risk of False-Positive Serological Results for Paratuberculosis in Mycobacterium bovis-Infected Cattle

Abstract

Both bovine tuberculosis (BTB) and paratuberculosis (paraTB) continue to cause significant economic losses in cattle breeding; in addition, their etiological agents have zoonotic potential. Although the diagnostics of both diseases are still being improved, problems still remain, such as the potential for cross-reactivity to the antigens used in tests. The aim of the present study was to confirm whether animals known to harbor Mycobacterium bovis antibodies are at increased risk of yielding positive results in paraTB serotesting and, additionally, to verify the accuracy of three commonly used methods for confirming M. bovis infection: ELISA, the tuberculin skin test (TST), and the presence of gross lesions. Material was collected from 98 dairy cattle suspected of BTB due to TST-positive results. During postmortem examination, gross lesions were assessed visually. Blood, lymph nodes, and TB-suspected organs were collected. Serum was obtained from the collected blood and tested serologically for TB and paraTB. The tissues underwent standard microbiological testing for M. tuberculosis complex. Among the 98 TST-positive individuals, tuberculous gross lesions were detected in 57 (58.1%), MTBC were isolated in 83 (84.7%), and the ELISA test was positive for 21 (21.4%). None of the lesions characteristic for paraTB were detected. The chance of obtaining a positive TB result by ELISA was seven times higher using the ELISA-paraTB method; hence, there is a significant risk of obtaining false-positive serological results for paraTB in M. bovis-infected cattle. However, the hypothesis that infection of M. bovis or prior TST performance may have boosted the host immune response and therefore increased the sensitivity of the paraTB-ELISA cannot be excluded.

Mycobacterium avium Subspecies paratuberculosis in Asymptomatic Zoo Herbivores in Poland

“…As tuberculosis has previously been confirmed in Polish zoos [ 36 , 37 ], it should be noted that MAP-positive animals can complicate the diagnosis of tuberculosis, due to cross-reactions [ 38 , 39 , 40 ].…”

Evaluation of the diagnostic accuracy of the serological test for paratuberculosis in cattle according to tuberculosis status

“…31 Monitoring the humoral immune response by bPTB-ELISA provides faster results and is a cheaper alternative to other diagnostic tools to detect infected animals. 8,10 However, different studies have questioned the usefulness of the technique due to its limited accuracy, 10,12,15,32,33 which should be considered when designing a bPTB control programme. 1,7 Different studies showed that the SE and SP values of the bPTB-ELISA ranged between 7% and 94% and 40% and 100%, respectively, 8,12 depending on the test, the sample used in the reference test (faeces or intestinal tissues), age or clinical stage of infection, 8,11 interference with other mycobacteria [14][15][16] or the time elapsed between the test and the SIT test.…”

“…1,7 Different studies showed that the SE and SP values of the bPTB-ELISA ranged between 7% and 94% and 40% and 100%, respectively, 8,12 depending on the test, the sample used in the reference test (faeces or intestinal tissues), age or clinical stage of infection, 8,11 interference with other mycobacteria [14][15][16] or the time elapsed between the test and the SIT test. 13,17,32,33 In the present study, microbiological culture of intestinal tissue (ileocaecal lymph nodes and ileocaecal valve, respectively) was used as a reference test, in contrast to most studies using faecal samples. However, tissue culture is more sensitive than faecal culture, allows detection of animals in the early stages of infection, is a postmortem technique to confirm the diagnosis of positive animals 11 and is also used to validate rapid diagnostic tests.…”

“…However, different studies have questioned the usefulness of the technique due to its limited accuracy, 10,12,15,32,33 which should be considered when designing a bPTB control programme 1,7 . Different studies showed that the SE and SP values of the bPTB‐ELISA ranged between 7% and 94% and 40% and 100%, respectively, 8,12 depending on the test, the sample used in the reference test (faeces or intestinal tissues), age or clinical stage of infection, 8,11 interference with other mycobacteria 14‐16 or the time elapsed between the test and the SIT test 13,17,32,33 . In the present study, microbiological culture of intestinal tissue (ileocaecal lymph nodes and ileocaecal valve, respectively) was used as a reference test, in contrast to most studies using faecal samples.…”

Development of a monoclonal antibodies-based interferon-gamma enzyme-linked immunosorbent assay (ELISA) for rapid and accurate diagnosis of bovine tuberculosis

“…Also, the test is labor intensive and time-consuming. Consequently, many investigators have attempted to develop alternative methods [16][17][18][19][20][21].…”