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  • Author or Editor: Judith R. Stabel x
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Abstract

Objective—To compare cytokine secretion patterns of peripheral blood mononuclear cells (PBMC) from healthy cows and cows subclinically and clinically infected with Mycobacterium paratuberculosis.

Animals—5 noninfected cows, 6 cows with subclinical paratuberculosis, and 4 cows with clinical paratuberculosis.

Procedure—PBMC were isolated, and concentrations or activities of secreted interleukin (IL)-1, IL-2, IL- 6, tumor necrosis factor (TNF), and interferon−γ (IFN-γ) were measured after in vitro stimulation of cells with concanavalin A (ConA), lipopolysaccharide (LPS), or a whole-cell sonicate of M paratuberculosis (MpS). Proliferative responses of PBMC were also determined after stimulation with ConA, phytohemagglutinin, pokeweed mitogen (PWM), or MpS.

Results—After stimulation with ConA, cells from subclinically infected cows secreted significantly more, and cells from clinically infected cows secreted significantly less, IFN-γ, compared with cells from control cows. Cells from cows with subclinical paratuberculosis produced significantly more TNF and IFN-γ in response to MpS than cells from the other 2 groups. Stimulation of PBMC from subclinically infected cows with ConA or MpS resulted in significantly higher proliferative responses, compared with cells from control and clinically infected cows. In contrast, clinically infected cows had significantly higher proliferative responses to PWM than cells from the other 2 groups.

Conclusions and Clinical Relevance—A decrease in T-cell responses to mitogens or MpS was observed in cows clinically infected with M paratuberculosis, compared with subclinically infected cows, suggesting that activated T cells may delay the progression of paratuberculosis. (Am J Vet Res 2000;61:754–760)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To estimate the risk of subclinical Mycobacterium avium subsp paratuberculosis (MAP) infection in cows that ingested MAP DNA–positive raw colostrum as calves, compared with risk in cows that ingested MAP DNA–negative raw colostrum as calves.

Animals—205 calves born in 12 commercial dairy herds.

Procedures—Each calf was separated from its dam within 30 to 60 minutes after birth and fed raw colostrum. For each calf, samples of the colostrum fed were collected and tested for the presence of MAP DNA by use of a nested PCR assay for the target gene ISMAP02. Calves fed colostrum positive or negative for MAP DNA were classified into exposed (n = 69) and unexposed (136) groups, respectively. Each calf was tested for MAP infection at 30, 42, and 54 months of age by use of a serum ELISA and bacterial culture of feces. Weibull hazard regression models were used to evaluate the association between exposure to MAP DNA–positive colostrum and time to testing positive for MAP infection.

Results—Hazard of MAP infection was not different between groups (exposed vs unexposed) when serum ELISA, bacterial culture of feces, or both diagnostic tests (parallel interpretation) were positive.

Conclusions and Clinical Relevance—Heifer calves fed MAP DNA–positive colostrum were at no greater risk of MAP infection, compared with heifer calves fed MAP DNA–negative colostrum. This result contradicts findings from other studies and should be interpreted with caution.

Full access
in American Journal of Veterinary Research