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  • Author or Editor: Martin J. Van Der Maaten x
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SUMMARY

A nested polymerase chain reaction (pcr) test was developed to examine infection with the bovine lentivirus, bovine immunodeficiency-like virus (biv), in cattle. Primers were designed to amplify 2 separate regions of the pol and env segments of the biv genome. Two calves were experimentally infected with an isolate derived from the original strain of biv, R29, or with a recent field isolate, FL491. Serial blood samples were collected and examined by virus isolation, protein immunoblot, and nested pcr. The nested pcr test detected biv infection by 3 days after inoculation, earlier than the other 2 methods, and continued to identify infected cattle 9 to 15.5 months after inoculation, even when results from virus isolation and serology became negative. Nested pcr also detected multiple-size env products in samples obtained later in the infection from the calf that received FL491, giving evidence that viral quasispecies were selected during in vivo replication of the virus. Results indicated that the nested pcr test is more sensitive than virus isolation or serology for the detection of biv infection in cattle.

Free access
in American Journal of Veterinary Research

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

SUMMARY

Leukocytosis (34,600 wbc/μl of blood) was detected in an apparently healthy 7-day-old Holstein heifer. Analysis of blood samples obtained over the next 41 days revealed chronic progressive neutrophilia, which peaked at > 85% neutrophils and exceeded 100,000 wbc/μl. In vitro assessment of isolated blood neutrophils obtained from the heifer at 38 and 45 days of age revealed selected functional abnormalities. Endocytosis of immunoglobulin-opsonized Staphylococcus aureus and killing of this test organism by the calf’s neutrophils were significantly diminished, as were phagocytosis-associated superoxide generation, chemiluminescence activity, and myeloperoxidase-catalyzed iodination. Diminished H2O2 elaboration by the calf’s neutrophils was evident during ingestion of opsonized zymosan or on exposure to phorbol myristate acetate. Extracellular release (secretion) of elastase during ingestion of zymosan was also diminished, although total cell content of elastase was normal, compared with that of neutrophils from age-matched calves, and granular or other morphologic abnormalities of the calf’s neutrophils were not evident by ultrastructural examination. Abnormalities of random migration were inconsistently detected, and normal or high degree of antibody-dependent cytotoxicity or natural killing by the calf’s neutrophils was observed. Similar in vitro assessment of neutrophils obtained from the calf’s dam revealed no functional abnormalities. The calf died at 48 days of age, with persistent fever and chronic diarrhea, despite administration of antibiotics. Histologic examination at necropsy revealed large numbers of intravascular neutrophils in most tissues, including massive neutrophil sequestration in spleen. However, a striking lack of extravascular neutrophils was evident in inflamed submucosa adjacent to intestinal ulcers heavily contaminated with enteric microorganisms. Bone marrow examination revealed diffuse myeloid hyperplasia, but no other abnormalities.

The clinical and pathologic features in this calf were similar to those in previously reported human patients or Irish Setters with genetic deficiency of the CD11/CD18 leukocyte glycoprotein complex, thus prompting further postmortem evaluations. Results of immunoblot analyses of the neutrophil lysates of the heifer calf (isolated and stored prior to death) documented severe deficiency of Mac-1 (CD11b/CD18). Results of immunofluorescent analyses indicated substantially diminished (intermediate) amounts ofthe Mac-1 β subunit (CD18) on blood neutrophils of the calf's dam and sire and on neutrophils of 8 of 15 paternal half-siblings; findings were consistent with an autosomal recessive trait in the proband's kindred. Findings also indicate that genetic abnormalities of CD11/CD18 proteins may underlie the molecular pathogenesis of disease in this calf as well as other previously described examples of the granulocytopathy syndrome in Holstein cattle.

Free access
in American Journal of Veterinary Research