ABSTRACT. Cross-protection between Haemophilus parasuis serovars 2 and 5 was examined in pigs using a bacterin based vaccine, and subsequently the safety and efficacy of a bivalent vaccine were evaluated. Upon intratracheal challenge of a serovar 2 or 5 strain, pigs immunized with a monovalent vaccine were protected against challenge with a homologous serovar strain, but not with a heterologous serovar strain. Immunization with a bivalent vaccine containing both serovars 2 and 5 bacterins conferred protection in pigs against lethal challenge with each of the serovar strains. A total of 86 pigs from two SPF herds were injected with the bivalent vaccine intramuscularly twice at a four-week interval. No adverse reactions following the vaccination were observed. On day 7 after the second vaccination, vaccinated and non-vaccinated control pigs from herd A were transferred to herd B, where Glasser's disease had broken out. Pigs in the control group developed clinical signs of the disease, and 6 of 8 (75%) pigs died until slaughter, in contrast with only 4 of 46 (9%) pigs in the vaccinated group. In herd C, where there was no outbreak of Glasser's disease, complement fixation antibody titer was raised only in the vaccinated group. A challenge experiment on days 20 and 79 after the second vaccination showed that only the vaccinated pigs were protected. From these findings, the safety and efficacy of the bivalent vaccine were confirmed under laboratory and field conditions.

Ten cases of bovine lymphohematopoietic neoplasms were investigated histologically, histochemically, and immunohistochemically, and were classified into eight histologic types on the basis of the origin and morphology of tumor cells. Case 1, a precursor B lymphoblastic leukemia, was positive for CD79a and terminal deoxynucleotidyl transferase. Case 2, a thymic B cell lymphoma, was also positive for these markers, but there were cytologic differences between the two cases. Cases 3-5 were diagnosed as pleomorphic B cell lymphomas, which were characterized by cytologic pleomorphism and expression of CD79a and CD5, and were etiologically associated with bovine leukosis virus (BLV). A case of diffuse large B cell lymphoma of the cerebrum (case 6) also showed a positive result for CD79a and CD5. However, the lymphoma was composed of a homogeneous population of large neoplastic cells, and was considered to be unrelated to BLV. The other B cell cases were categorized into immunoblastic (case 7) and lymphoplasmacytic (case 8) lymphomas, in which immunoglobulin-producing lymphoma cells were observed. In a cutaneous γδ T cell lymphoma (case 9), the neoplastic cells cytologically resembled those in case 6, but expressed CD3 and WC1. In case 10, an acute basophilic leukemia, some leukemia cells had intracytoplasmic granules that were metachromatic and tryptase positive but negative for naphthol AS-D chloroacetate esterase. Bovine lymphohematopoietic malignancies are classifiable into discrete histologic types according to immunophenotype. The classification is more scientific than the traditional one, the latter being based on the age of affected animals and/or the site of tumor formation.

ABSTRACT. A diagnosis of acute myeloid leukemia was made in a 10-month-old Holstein female calf. The leukemia was macroscopically characterized by great enlargement of the spleen and moderate enlargement of some lymph nodes. Histochemical and immunohistochemical examination disclosed the presence of neoplastic cells either containing metachromatic and tryptase-positive granules or expressing factor VIII-related antigen. The granules, which were positive for naphthol AS-D chloroacetate esterase and did not have particulate contents, were distinct from those of basophilic leukemia cells. This leukemia was thought to be derived from a common myeloid progenitor capable of giving rise to megakaryocyte-erythrocyte progenitors and granulocyte-monocyte progenitors with the ability to differentiate into mast cells.KEY WORDS: cattle, factor VIII-related antigen, myeloid leukemia, tryptase.

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