The Single Intradermal Cervical Comparative Test Interferes with Johne’s Disease ELISA Diagnostics

Abstract

Enzyme-linked immunosorbent assays (ELISA) of milk and serum samples are a routinely used method of screening herds for Mycobacterium avium subspecies paratuberculosis (MAP). Infection with MAP causes granulomatous enteritis of ruminants known as Johne’s disease (JD). The sensitivity (Se) and specificity (Sp) of MAP ELISAs leads to difficulties in the identification of both infected and infectious animals. Interference with MAP ELISA Se and Sp has been reported in MAP seronegative cows following administration of purified protein derivative (PPD) as part of intradermal testing for bovine tuberculosis (bTB). The aim of this study is to examine the impact of the single intradermal cervical comparative test (SICCT) for bTB, on both serum and milk MAP ELISA tests, in a herd containing both seropositive and seronegative cows pre-SICCT. A secondary objective is to provide appropriate timing of JD ELISA tests in relation to the SICCT. A herd of 139 cows were serum and milk sampled pre- and post-SICCT administration. Prior to SICCT, 6% of the herd tested seropositive for MAP using milk ELISA, with 8% positive on serum. ID Screen Paratuberculosis Indirect Screening Test (ID Vet) was used to screen the herd. Within 14 days of PPD administration, a significant increase in the prevalence of seropositive cows was recorded. Identical prevalence’s were recorded with both test matrices (39%). ELISA values remained significantly higher until day 43 post-SICCT in milk (P = 0.850), and day 71 in serum (P = 0.602). If the “new” positives detected post-bTB testing are deemed false positives due to generation of cross-reacting antibodies by administration of PPD, milk would appear a more suitable sample for JD ELISA testing within 2 months of SICCT. In summary, sampling for JD utilizing milk ELISA should be avoided in the 43-day period following PPD administration, with serum ELISA sampling avoided for an additional 28 days.

Association between results of diagnostic tests for bovine tuberculosis and Johne's disease in cattle

“…Yet, when the individual results from the SIT or IGRA were analysed, a lack of association with JD positivity was observed, in contrast with previous studies 13 15 40 50 54. This could indicate that JD reactors were therefore not infected with M bovis , and therefore positivity in the JD-ELISA would not be due to cross-reactivity in M bovis- infected animals.…”

Is TB Testing Associated With Increased Blood Interferon-Gamma Levels?

“…Additionally, Kennedy et al ( 23 ) have hypothesized that Irish cows may be less susceptible than international counterparts to developing clinical signs (progressive emaciation and diarrhea) of JD. Reasons suggested for this include low average herd size (75 cows), a predominantly grass-based diet, and the comprehensive bTB testing regime conducted in Ireland ( 23 , 24 ). In terms of investigating this further, we sought to examine the impact of administration of avian and bovine PPD, as part of the required annual SICCT test, on in vivo levels of plasma IFN-γ.…”

Interplay of primary bovine lymphocytes and Mycobacterium avium subsp. paratuberculosis shows distinctly different proteome changes and immune pathways in host-pathogen interaction

“…The same is true for cows: while they are often in contact with MAP, resulting in high frequencies of seropositive animals – approximately 20% and at least 3–5% in several countries (Boelaert et al, 2000; Nielsen and Toft, 2009) – Johne’s disease incidence is very rare. For example, a total of 232 clinical cases of Johne’s disease were reported in Ireland from 1995 to 2002 (Kennedy et al, 2014), yielding an average annual rate of approximately 0.0005%, given a cattle population of six million (Maher et al, 2008). A study examining environmental samples from 362 dairy farms located in all 10 provinces of Canada for detection of MAP by culture revealed true prevalence estimates of 66% for farms in Western Canada, 54% in Ontario, 24% in Québec, and 47% in Atlantic Canada (Corbett et al, 2018).…”