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  • Author or Editor: M. E. Kehrli Jr. x
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SUMMARY

The role of interleukin 1 (il-1) as an inflammatory mediator during mastitis and the therapeutic effect of recombinant human il-1 receptor antagonist (il-1ra) for bovine mastitis was studied. Cows were intramammarily infused with lipopolysaccharide (25 μg) in 1 mammary gland. Half the cows also received infusions of 5 mg of il-1ra into the same mammary gland just prior to endotoxin infusion and 4, 8, and 12 hours later. After endotoxin infusion, tumor necrosis factor and high il-1 bioactivity were detected in whey from infused glands. Vascular permeability changes and neutrophil accumulation in milk paralleled the appearance of cytokines. A systemic reaction, characterized by pyrexia and an increase in blood cortisol concentration, also were observed. Milk yield was inhibited and milk composition was altered in infused and noninfused glands. The increase in il-1 bioactivity in milk after endotoxin infusion was almost completely prevented in glands receiving il-lra. However, il-lra had no effect on local inflammation, systemic reaction, or impairment in productive performance. These results indicate that il-1 does not mediate its effect within the milk compartment, and suggest either that il-1 is not critical to the mastitic response or that intramammary infusion of il-1ra does not place the antagonist where il-1 interacts with its receptor.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To define causes of increased susceptibility to coliform mastitis after parturition.

Animals

12 healthy Holstein cows assigned to 2 groups. Group-1 cows (n = 6) had calved between 6 and 10 days earlier. Group-2 cows (n = 6) were in midlactation.

Procedure

Cows from each group were paired and challenge exposed with Escherichia coli in 1 mammary gland. Mastitis severity was determined by bacterial concentration in milk, pyrexia, and milk production. Measures of host defense were neutrophil chemotaxis, adhesion molecule expression, leukocyte recruitment, and cytokine production.

Results

After challenge exposure, group-1 cows had more rapid E coli growth, higher peak bacterial concentration, and higher fever. Leukocyte recruitment was poor in 1 group-1 cow that had peracute mastitis. In contrast, leukocyte recruitment in 5 other group-1 cows began sooner than that in group-2 cows. In these group-1 cows, prechallenge-exposure milk somatic cell counts (SCC) were significantly lower than those in group-2 cows. Pre-challenge-exposure SCC were correlated to stimulated CD18 expression (R2 = 0.79), and both measures correlated inversely with bacterial growth rate (R2 = -0.75). Values for tumor necrosis factor α, interleukin 1, and interleukin 8 in group-1 cows after challenge exposure were greater than or equal to those in group-2 cows.

Conclusions

Weak leukocyte recruitment to the mammary gland is associated with increased severity of coliform mastitis. Impaired production of cytokines measured is not a cause of increased susceptibility to coliform mastitis in early lactation.

Clinical Relevance

Low milk SCC after calving may increase susceptibility to severe coliform mastitis. (Am J Vet Res 1996;57:1569–1575)

Free access
in American Journal of Veterinary Research

Summary:

In Holstein cattle, an inherited disease has been recognized recently in which leukocytes lack surface glycoproteins termed β2 integrins, which are important in cell adhesion processes. This disease is the homologue of leukocyte adhesion deficiency in human beings and has been termed bovine leukocyte adhesion deficiency. The molecular basis of this disease is failure to produce normal CD18. The gene encoding bovine CD18 and its abnormal mutation have been sequenced, allowing specific diagnosis of the condition by DNA amplification by polymerase chain reaction followed by specific endonuclease digestion. This test was applied to formalin-fixed archival tissues from 18 cattle that had been admitted to the veterinary medical teaching hospital between 1975 and 1991 and that had had persistent and severe neutrophilia. Blood samples were collected from 2 additional cattle, and leukocytes from these samples also were tested. Fourteen cattle were confirmed to have been homozygous for the bovine leukocyte adhesion deficiency gene. Cattle with this condition had ranged in age from 2 weeks to 8 months at admission. They typically had had chronic bacterial infections that had failed to respond to or had recurred after conventional treatment. Consistent findings in these cattle included signs of bronchopneumonia, gingivitis, periodontitis, and peripheral lymphadenopathy. Severe neutrophilia, usually without a left shift, was a hallmark of the disease; consistent clinical biochemical findings included hypoalbuminemia, hyperglobulinemia, and hypoglycemia. This disease is important because it mimics common calfhood diseases such as pneumonia and diarrhea, but is ultimately consistently fatal before adulthood.

Free access
in Journal of the American Veterinary Medical Association

Objective—

To determine microscopic features and involvement of viruses in teat-end lesions (TEL) of dairy cows during winter.

Sample Population—

Teats with TEL on lactating Holstein cows and from udders of carcasses.

Procedure—

Tissues obtained from TEL of 10 teats from 7 cows on 2 research farms during the winter of 1994 to 1995 and 13 teats with TEL excised from udders of carcasses at an abattoir during February 1995 were submitted for virus isolation. During the winter of 1995 to 1996, an increased prevalence of TEL was observed in a research herd. After a decrease in ambient temperature, TEL were identified, and a full-thickness section of epidermis was removed from skin surrounding teat orifices. Tissues were examined by use of light and electron transmission microscopy.

Results—

Viruses were not isolated from TEL tissues. Lesions ranged from mild elevations of the epidermis to thickened oval regions that encircled the teat orifice. The most severe lesions were dark and had thick crusts. Histologically, TEL were composed of thickened regions of epidermis most notably caused by hyperplasia of cells within the stratum spinosum. Excess production of keratinocytes was also evident, and the keratinocyte layer often contained bacteria. Ultrastructurally, squamous cells contained large amounts of keratin, but virions were not detected. Evidence of a viral etiologic agent for TEL was not detected.

Clinical Implications—

Development of TEL may be associated with decreases in ambient temperature. Numerous bacteria were evident in the keratin of TEL. Lesions and associated bacteria may predispose cows to mastitis. (J Am Vet Med Assoc 1998;213:862-865)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To analyze surface antigen expression and functional responses of leukocytes from calves heterozygous and homozygous for bovine leukocyte adhesion deficiency (BLAD).

Animals

8 clinically normal calves, 4 calves heterozygous for BLAD, and 4 calves homozygous for BLAD.

Procedure

Surface antigen expression was examined by flow cytometric analysis of leukocytes stained with monoclonal antibodies. Neutrophil function analyses included phagocytosis and killing of Candida albicans and measurement of respiratory burst activity using cytochrome c and dihydrorhodamine 123 assays. Differential leukocyte counts also were performed.

Results

Leukocytes from heterozygous calves were similar to those of clinically normal calves with respect to surface antigen expression, C albicans phagocytosis and killing, and respiratory burst activity. In contrast, neutrophils from calves homozygous for BLAD had significantly reduced phagocytic and yeast-killing capacity but had higher respiratory burst activity than cells from clinically normal or heterozygous calves. Homozygous calves also had extreme neutrophilia and significantly more immature neutrophils.

Conclusions

The heterozygous BLAD genotype does not cause detectable functional differences in leukocytes, compared with those of clinically normal calves. In contrast, leukocytes from homozygous calves seem to upregulate alternative host defense capabilities (eg, respiratory burst activity) to partially compensate for the lack of typical adherence-dependent host defense functions. (Am J Vet Res 1999;60:1255–1261)

Free access
in American Journal of Veterinary Research