The diagnosis of enzootic bovine leukosis

This paper reviews the clinical and virological diagnostic procedures for enzootic bovine leukosis (EBL). The clinical diagnosis must be always confirmed by a specific laboratory test for Bovine Leukaemia Virus (BLV). Many virological tests were proposed. The sensitivity of all the diagnostic methods is sufficient to do an early detection of a BLV infection on an individual base. Advantages of the highly sensitive methods like RIA and ELISA appear when the samples to be tested have naturally very low antibody titers (individual milk, bulk milk, pooled sera).     

Cytogenetic study of bovine leukosis

Nine dairy cows aged four to eleven years were subjected to examination by chromosomal analysis. These cows had been found, by haematological examination, to suffer from leucosis. The study also covered one ten-day-old calf - heifer. The test group included two dam-daughter pairs. The animals belonged to the Black-Pied Lowland breed. The blood was sampled from vena jugularis and the karyotypes were processed and evaluated by the method after Moorhead et al. (1960), modified by Lojda et al. (1974). A list was kept for each animal. The tested animals were included in classes by the percentages of the chromosome aberrations: class I - two animals (up to 10% of aberrations), class II - seven animals (from 10% to 20% of aberrations), class III - one animal (above 20% of aberrations). Hyposomy was found in all cases, polysomy and hyperploidy in four cases. Structural aberrations were observed in nine cases, breaks being the most frequent anomalies (7 cases). Breaks on sexual chromosomes were observed in five cases, including the dam-daughter pairs; centric fusion occurred in one case and mixed aberrations in two cases.     

Enzootic bovine leukosis virus in Brazil

Summary A sero-epidemiological survey for antibodies to the glycoprotein of enzootic bovine leukosis virus showed that the infection is widely disseminated in the State of Rio de Janeiro, Brazil. Sera from 1,290 females and 154 males from 12 dairy herds were tested by the agar gel precipitin test. Seven hundred and one females (54.3%) and 68 males (44.2%) were found to have specific antibodies. These antibodies were demonstrated in all 7 age groups tested. The older age groups contained the highest percentage of reactors. The results are briefly discussed in relation to management practices and environmental conditions.

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El Virus De La Leucosis Bovina Enzootica En Brasil

Resumen Una encuesta suero-epidemiológica por anticuerpos contra la glicoproteina del virus de la leucosis bovina enzootica mostró que la infección está ampliamente diseminada en el Estado de Rio de Janeiro, Brasil. Sueros de 1290 hembras y 154 machos pertenecientes a 12 rebaños lecheros fueron examinados en la prueba de precipitación en agar. Se encontró que 701 hembras (54.3 por ciento) y 68 machos (44.2 por ciento) poseían anticuerpos específicos. Estos anticuerpos fueron demonstrados en todos los siete grupos de edad examinados. Los grupos de mas edad contenian un porcentaje mayor de reactores. Los resultados son discutidos brevemente en relación a las prácticas de manejo y a las condiciones ambientales locales.

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Virus De La Leucose Bovine Enzootique Au Bresil

Résumé Une enquête séro-épidémiologique pour la détection de la présence de la glycoproteine du virus de la leucose enzootique bovine a montré que cette affection est largement disséminée dans l'Etat de Rio de Janeiro, au Brésil. Des échantillons de sérum provenant de 1290 femelles et 154 mâles appartenant à 12 troupeaux laitiers ont été étudiés par précipitation en gélose—701 femelles (54,3 p. 100) et 68 mâles (44,2 p. 100) ont été reconnus comme possédant des anticorps spécifiques. Ces anticorps ont été mis en évidence dans la totalité des 7 groupes d'âges étudiés. Les groupes d'âges plus élevés contenaient le plus haut pourcentage d'animaux positifs. Les résultats sont brièvement discutés, dans leur relation avec les pratiques de l'élevage et les conditions de l'environnement.

     

Tissue culture studies in bovine leukosis

By examining cover slips stained at regular intervals the development of primary lymph node tissue cultures from 2 cases of juvenile bovine leukosis and 2 “normal” foetuses was studied. Secondly, comparisons were made between cell lines prepared from 23 bovines — “normal” animals and foetuses, cases of adult leukosis, juvenile leukosis and skin leukosis — with respect to susceptibility to infection with interferon sensitive viruses (VSV and PRV) and/or growth rate in the presence of sera from “normal” and leukotic animals.Nuclear budding, nuclear fragmentation, lymphocyte adsorption and giant cell formation were observed — though to a much greater extent in cultures prepared from the leukosis animals — in all 4 cases studied. No indications of different susceptibility for the test virus infections appeared between cell lines prepared from “normal” and leukotic animals. The growth rate of the cell lines seemed similar irrespective of the kind of serum used.     

Enzootic bovine leukosis virus in Brazil

A sero-epidemiological survey for antibodies to the glycoprotein of enzootic bovine leukosis virus showed that the infection is widely disseminated in the State of Rio de Janeiro, Brazil. Sero from 1,290 females and 154 males from 12 dairy herds were tested by the agar gel precipitin test. Seven hundred and one females (54.3%) and 68 males (44.2%) were found to have specific antibodies. These antibodies were demonstrated in all 7 age groups tested. The older age groups contained the highest percentage of reactors. The results are briefly discussed in relation to management practices and environmental conditions.     

The eradication experience of enzootic bovine leukosis from Lithuania

Before 1985 the situation regarding enzootic bovine leukosis (EBL) in Lithuanian cattle was described only haphazardly. In 1986 serological investigations were initiated together with an eradication programme. The EBL bovine leukosis virus (BLV) situation was monitored by the Institute of Immunology Vilnius University, national and regional veterinary laboratories. Starting in 1986 all EBL-positive cattle were separated from negative cattle into BLV-infected and BLV-free herds. To create the latter, calves were fed pasteurized milk. The seroprevalence in 1990 was 7.29%, but it steadily declined to 0.32% in 2006.     

Spontaneous regression of bovine cutaneous leukosis

Biopsies of skin from a 2-year-old heifer with spontaneously regressing dermal leukosis were examined. The heifer was not infected with bovine leukemia virus and was negative for tumor-associated antigens of enzootic bovine lymphosarcoma. By hematological standards for bovine leukemia, the heifer was positive at about 60 days post-occurrence of the disease (POD). At 53 days POD, lymphoblastic neoplastic cells in the dermis reacted with anti-T lymphocyte monoclonal antibody by the avidin biotin peroxidase complex method. The cells had intracytoplasmic clustered dense bodies under electron microscopy. From 53 to 83 days POD, figures of the transepithelial elimination (TE) against neoplastic cells and perivascular infiltration of small lymphocytes were in the dermis. Small lymphocytes reacted with anti-T lymphocyte monoclonal antibody. At necropsy there were no neoplastic lesions; there were flat lymph node-like tissues in the subcutis. Many germinal centers were seen in the lymphatic organs. Blood lymphocytes at 46 days POD were stimulated by phytohemagglutinin-P and concanavalin A. Sera, taken until 75 days POD and at necropsy, showed an inhibitory effect on mitogen-induced blastogenesis of normal bovine lymphocytes. These results suggested the existence of a spontaneous regressive mechanism against neoplastic lesions by TE and tumor immunity.     

Chemotherapy and immunotherapy of bovine leukosis

To prevent the progression of the disease, we treated leukemic or preleukemic cows with (1) adriamycin (ADM) entrapped in liposomes conjugated with monoclonal antibody, c143, against tumor-associated antigens (TAA) of bovine leukemic cells and (2) an immunotherapy using an immunopotentiator consisting of the cell wall skeleton of Nocardia rubra (N-CWS). Five leukemic or preleukemic cows with TAA-positive peripheral blood lymphocytes (PBL) received four injections of ADM alone (0.4 mg/kg body weight) or c143-conjugated liposomes containing the same dose of ADM (L-ADM-c143) through the jugular vein at about 4-day intervals. In three animals treated with L-ADM-c143, the TAA-positive cells gradually decreased with treatment and finally two animals became TAA-negative during a 6-week period and a 14-week period after treatment, respectively. About 6 weeks later, however, TAA-positive cells gradually increased. In the control, two animals treated with ADM alone showed no decrease of TAA-positive cells. Five TAA-positive animals with enlarged subcutaneous lymphatic nodules, each nodule estimated to be from 1 to 4 cm3 in size, were treated by injection of N-CWS into the tumors. Complete regression of tumor was observed in seven out of ten tumors treated in five animals. Decrease of TAA-positive cells was also observed in PBL for all five treated animals. In one animal, the TAA-positive cells remained low for at least 280 days after treatment. This study documents that ADM treatment and intralesionally administered N-CWS are effective in the treatment of bovine leukosis.