A longitudinal study of factors influencing the result of a Mycobacterium avium ssp. paratuberculosis antibody ELISA in milk of dairy cows

Abstract

The influence of milk yield and milk composition on the diagnosis of Mycobacterium avium ssp. paratuberculosis (MAP) by milk ELISA in the context of the total IgG secretion patterns in milk throughout lactation and serum concentrations were investigated. A 2-yr trial was performed in which 1,410 dairy cows were sampled monthly and MAP milk ELISA status and milk yield and composition were determined. Data were analyzed by mixed model analysis. Milk yield was found to significantly influence ELISA results expressed as sample-to-positive (S/P) ratios. For each 5-kg increase in milk, the S/P ratio has to be multiplied by 0.89; therefore, high milk yield can change the MAP milk ELISA outcome of a cow in early infection from positive to negative. Parity influenced ELISA outcome significantly, indicating that cows with a parity >1 are more likely to be identified by milk testing. Also, herd was an important predictor, showing that herd prevalence influences the milk ELISA strongly. Other factors influencing the S/P ratios were protein concentration, somatic cell count, and days in milk. The IgG concentration and mass excreted per day were determined longitudinally in a subset of 41 cows of which samples and data of a complete lactation were available. Again, the IgG concentration in milk was mainly influenced by milk yield. The total IgG mass secreted per day in milk was found to be relatively constant, with a mean of 8.70 ± 5.38 g despite an increasing IgG concentration in serum at the same time. The variation of IgG concentration in milk can be mainly attributed to dilution through changes in milk yield. This supports the assumption that concentrations of MAP-specific antibodies are influenced by changes in milk yield similarly. In conclusion, we confirmed that antibody concentrations, and therefore MAP ELISA outcome, were influenced by milk yield, herd, and parity. To enhance performance, milk ELISA tests should either be performed in early or late lactation, when milk yield is low. From a management perspective, sampling should be done during early lactation before cows are bred again. Based on the slow progressive infection dynamics, only first-parity cows should be preferentially tested at the end of their first lactation to avoid false-negative results.

Bulk tank milk antibody ELISA as a biosecurity tool for detecting dairy herds with past exposure to Mycoplasma bovis

“…Given that cows in the seasonal-and split-calving study herds calved over several weeks, it is not surprising that the model-based mean BTM ELISA ODC% was significantly higher at 5 to 8 wk compared with ≥13 wk after the commencement of the calving period in these herds ( Figure 2). The subsequent decline in the model-based mean BTM ELISA ODC% from 5 to 8 wk onward is also consistent with studies that have demonstrated that total individual milk IgG concentrations decrease as the number of days in lactation increase (Liu et al, 2009;Eisenberg et al, 2015). Therefore, the relationship between time after the commencement of the calving period and BTM ELISA ODC% may be attributable not just to the temporal relationship to calving but also to individual cow milk production factors.…”

Early detection of Mycobacterium avium subsp. paratuberculosis infection in cattle with multiplex-bead based immunoassays

“…Previous studies investigating factors that influence the outcome of MAP ELISA in milk have suggested the role of a number of factors including milk yield (concentration of MAP-specific antibodies, mainly related to days in milk, DIM), herd (prevalence of JD), and parity (related to number of lactation) were mainly attributed [ 30 , 31 ]. In our investigation, days in milk (DIM) and lactation numbers were considered for animals in each group, and the results show no significant difference for DIM and lactation number between groups ( Table 1 ).…”

Association of paratuberculosis sero-status with milk production and somatic cell counts across 5 lactations, using multilevel mixed models, in dairy cows

“…During early stages of infection, a cellular immune response is produced, whereas antibody production develops in later stages of infection, which translates to different test accuracy in different stages of infection (Stabel et al, 2014;Laurin et al, 2015Laurin et al, , 2017. Although serum ELISA specificity is considered to be greater than 97%, sensitivity can vary from 15 to 75% depending on the stage of the disease (Timms et al, 2011;Mitchell et al, 2015) and also on milk yield, lactation, herd prevalence, DIM, milk protein, and SCC (Eisenberg et al, 2015).…”