The diagnostic performance of an antibody enzyme-linked immunosorbent assay using serum and colostrum to determine the disease status of a Jersey dairy herd infected with Mycobacterium avium subspecies paratuberculosis.

Colostrum may have the ability to improve the diagnostic accuracy of some tests when compared to serum for important livestock diseases because of the high concentrations of immunoglobulins present within this sample type. The ELISA for Johne's disease is one such test, as it suffers from low sensitivity when testing serum samples collected during the subclinical stage of infection. Blood and colostrum samples were collected from 34 Jersey dairy cows and tested for antibodies against Mycobacterium avium subspecies paratuberculosis (MAP) by ELISA. Fecal samples were also collected and tested by a high-throughput Johne's polymerase chain reaction (HT-J PCR) assay and fecal culture (FC), with the latter being used as the reference test. A receiver operating characteristic (ROC) analysis was performed, and the area under the curve (AUC) was calculated. The HT-J PCR and FC results were also compared. Of the 34 cows in this study, 4 had FC results consistent with MAP infection. The HT-J PCR did not identify any FC-positive cows. Using a 1:20 dilution and sample-to-positive (S/P) ratio cutoff threshold of 0.15, the relative sensitivity values of both serum (AUC 0. 56) and colostrum (AUC 0.63) were 0%. With lower sample dilutions, the relative sensitivity values of serum were 0% (1:2, AUC 0.62; 1:5, AUC 0.55); however, the relative sensitivity value of colostrum was 75% (95% confidence interval [CI]: 19-99%) at a dilution of 1:5, S/P ratio cutoff threshold of 0.15, and AUC of 0.73 (95% CI: 0.55-0.87). The testing of colostrum samples for MAP-specific antibodies by ELISA may provide improved identification of animals in the early stages of infection with MAP when compared with serum samples.

Erysipelothrix rhusiopathiae and Mycoplasma hyopneumoniae: the sensitivities of enzyme-linked immunosorbent assays for detecting vaccinated sows of unknown disease status using serum and colostrum, and the correlation of the results for sow serum, colostrum, and piglet serum.

Due to relatively high concentrations of immunoglobulins, colostrum has the potential to improve the sensitivity of diagnostic tests for diseases in pigs when compared with serum. It is possible that colostrum could improve the sensitivity of the antibody enzyme-linked immunosorbent assay (ELISA) compared with serum. Colostrum is also essential for piglets, providing protection against infections in the first few weeks and months of life. The sensitivity of 2 commercially available ELISAs, one for the detection of Erysipelothrix rhusiopathiae and the second for Mycoplasma hyopneumoniae antibodies, when used with sow colostrum in comparison with serum was investigated. The correlation of maternal E. rhusiopathiae- and M. hyopneumoniae-specific antibody levels with specific-antibody serum levels in the piglet was also determined. The sensitivity was defined as the proportion of vaccinated sows that were correctly identified as vaccinated at a given cutoff point. The true disease status of the sows with regard to the 2 infections was unknown. Blood and colostrum samples were collected from 20 sows, 10 primiparous and 10 multiparous, and blood samples were also collected from the piglets of each sow, 48-72 hr post-farrowing. The sensitivities of both ELISAs were significantly improved when using colostrum compared with serum. Sow serum and colostrum optical density (OD) values were significantly correlated. The mean sow OD values for serum for E. rhusiopathiae and M. hyopneumoniae and colostrum for E. rhusiopathiae were significantly correlated with piglet serum OD levels. If the improved sensitivity of colostrum can be demonstrated in infected animals, this will increase the ability of the test to identify infected animals using both individual and pooled colostrum. Testing serum and/or colostrum using ELISA can be useful predictors of piglet disease-specific OD values.

Comparison of serum, ear notches, and nasal and saliva swabs for Bovine viral diarrhea virus antigen detection in colostrum-fed persistently infected (PI) calves and non-PI calves.

The diagnosis of neonatal and young calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) by antigen-capture enzyme-linked immunosorbent assay (ACE) may be complicated by interference from colostrum-derived specific antibodies. Ten calves, with 3 calves identified as PI and 7 as non-PI were used in the current study. All non-PI calves were shown to be seropositive for BVDV-specific antibodies by antibody enzyme-linked immunosorbent assay (Ab-ELISA) on serum. Serum samples, ear notch samples, and nasal and saliva swabs were collected from each calf from birth until 12 weeks of age and tested by ELISA for BVDV-specific antigen and antibodies. Following colostrum ingestion, Ab-ELISA sample-to-positive (S/P) ratios rose by a mean of 0.95 (95% confidence interval [CI] = 0.64-1.25) and 1.72 (95% CI = 1.55-1.89) in seropositive, non-PI calves and in PI calves, respectively. The mean S/P ratios then declined to approximately 1.1 in non-PI calves and 0.5 in PI calves at between 60 and 80 days of age. In PI calves, testing for antigen in serum and nasal and saliva swabs was subject to interference by colostrum-derived antibodies in calves up to 3 weeks of age. Nasal swabs were less affected than serum and saliva swabs. Ear notches maintained positive ACE corrected optical densities at all sample times, despite a drop in the signal following the ingestion of colostrum.