Visceral leishmaniasis in the German shepherd dog. II. Pathology

Three German shepherd dogs were inoculated with Leishmania chagasi and three with Leishmania donovani and the infection was followed for 82 days. All infected dogs developed splenomegaly and lymphadenomegaly. In lymph nodes there was a reduction in lymphocyte population in paracortical areas, extensive proliferation of macrophages in paracortical areas and medullary cords, follicular hyperplasia, and increased numbers of plasma cells. The spleen had decreased numbers of lymphocytes in periarteriolar lymphoid sheaths, proliferation of macrophages in these regions, follicular hyperplasia, and enlargement of the red pulp with clusters of macrophages and plasma cells. The morphology of the tonsil was similar to the lymph nodes. Clusters of macrophages, often containing Leishmania spp, were present in liver, bone marrow, lung, and the intestines. The morphologic changes in lymph nodes and spleen were suggestive of a suppressed cell-mediated immunity and an active humoral immunity. The German shepherd dog may be a useful laboratory model for the study of immunopathologic changes in visceral leishmaniasis.     

Mortality and recovery of runt white sturgeon (Acipenser transmontanus) in a commercial farm in California, USA

We investigated the effect of raising runt white sturgeon (Acipenser transmontanus) separately from dominant fish during the initial stages of grow-out in a commercial farm. Runt fish are poor-growers, have underdeveloped muscle mass, swim slowly and are more-frequently found at the top of the water column. The objective of the study was to describe the mortality and recovery rates (and their determinants) of white-sturgeon runts after separating them from dominant fish. Runt white sturgeon were stocked into twelve 2 m × 2 m rectangular tanks and graded periodically during a follow-up of 46–102 days. Overall mortality rates ranged from 0.3 to 7 dead fish per 1000 sturgeon-days at risk and overall recovery rates from 3.9 to 13.5 recovered fish per 1000 sturgeon-days at risk. Period-specific mortality and recovery rates increased over time. The period-specific mortality rates for all three periods were significantly higher for tanks of runts originating from grow-out tanks with high mortality (p-values: first period = 0.06; second period = 0.09; third period = 0.03), but were similar for tanks of runts of high- and low-mean initial weight. The period-specific recovery rates were significantly higher in runts originating from high-mortality grow-out tanks only for the third period (p = 0.05) but not the first and second periods (p-values = 0.33 and 0.25, respectively). Recovery rates were significantly higher in the higher-mean-weight runts tanks for the first and third period but not for the second (p-values: first period = 0.02; second period = 0.65; third period = 0.06). We concluded that the proportion of runts that recover during a 46–89 day period is substantial (16–58%); therefore, it might be worthwhile growing such fish separately in a fish farm for about three months. Financial analysis showed that this practice was profitable, if the value of white sturgeon fish for the farm exceeded $2.05 per kg.     

Histologic features of the healing of bone graft donor sites in dogs

Healing of cancellous bone graft donor sites in the proximal tibial metaphysis of 12 healthy adult dogs was studied histologically. Cancellous bone was curetted from the metaphysis of the proximal end of the tibia, via a 1-cm diameter circular opening in the medial cortex. A hematoma and fibrovascular tissue filled the bone defect at 2 weeks. At 4 and 8 weeks, endosteal callus, composed initially of cartilage and woven bone and later of lamellar bone, filled the marrow cavity. At 12 weeks, the normal structural arrangement of lamellar bone and hematopoietic marrow was reestablished in the marrow cavity. The medial cortex defect was filled only with lamellar trabecular bone. It was concluded that, in adult dogs, a second cancellous bone graft could be collected from the proximal portion of the tibial metaphysis 12 weeks or more after an initial collection.     

The Effects of Growth Factor on Testicular Germ Cell Apoptosis in the Stallion

Apoptosis is necessary for both initiation and control of spermatogenesis; however, an increase in apoptosis can lead to subfertility/infertility in stallions, causing substantial financial loss in the equine industry. The ability of stem cell factor (SCF), leukemia-inhibiting factor (LIF), granulocyte–macrophage colony-stimulating factor (GM-CSF), and estradiol (E₂), alone or in combination, to prevent apoptosis of germ cells in short-term equine testicular cultures was examined. Testicular tissue was sectioned into approximately 2-mm cubes and placed in media-filled culture chambers. Concentrations of SCF (100 ng/mL), LIF (10 ng/mL), GM-CSF (5 ng/mL), and E₂ (10⁻⁹ mol/l) were added alone or in combination to each well. After 6 hours in culture, the tissue was fixed and immunohistochemically (terminal deoxynucleotidyl transferase-mediated nick-end labeling; TUNEL) stained for apoptosis detection. Apoptotic cells per 100 Sertoli cell nuclei within seminiferous tubules were counted until the 500^th Sertoli cell nuclei was reached. This counting procedure was used for each slide. An analysis of variance (ANOVA) with a Tukey's test was used to compare apoptotic rates. In comparison with the control, GM-CSF alone lowered apoptosis by 34.77%. GM-CSF–treated tissue combined with SCF and LIF as well as GM-CSF combined with SCF, LIF, and E₂ reduced apoptosis when compared with the control (37.45% and 44.40%, respectively) or other treatment combinations. GM-CSF alone reduced apoptosis; results suggest possible synergy for the combinations of SCF and LIF with GM-CSF and for E₂ with SCF, LIF, and GM-CSF.     

The Prediction of Parturition Date in Canine Pregnancy

In bitches, the length of gestation is highly variable when measured from the day of mating, thus prediction of parturition may be greatly inaccurate when determined from this point. The ability to precisely predict the duration of pregnancy is of practical importance for managing parturition or planning caesarean section and this review analyses the methods that can be used to accurately forecast the day of parturition. At the time of breeding, determination of the luteinizing hormone surge and the initial rise in progesterone provide reliable information on gestational length of the bitch, but when pregnancy is ascertained, ultrasonography is the most useful tool to predict the delivery day. In fact, by ultrasonographic measurements of the extra-foetal and foetal structures an accurate prediction can be made both in early and late pregnancy.     

Resumption of postpartum luteal function of primiparous, suckled beef cows exposed continuously to bull urine

The objective of this experiment was to determine if continuous exposure to bull urine alters resumption of ovarian cycling activity of primiparous, suckled beef cows. We tested the hypotheses that interval from urine exposure to resumption of luteal activity and proportions of cows that resume luteal activity by the end of the urine-exposure period do not differ between cows exposed to mature bull urine or steer urine. Thirty-eight Angus (A) x Hereford (H) cows, 4 mature A x H bulls and four 10-mo-old A x H steers, were used in this study. Cows were stratified by calving date, cow BW, calf BW, calf sex, dystocia score, and BCS; fitted with a controlled urine delivery device 2 wk before the start of treatments; and assigned randomly to be exposed continuously (24 h/d) to bull urine (n = 19) or steer urine (n = 19) beginning 40 d after calving. Urine was collected from bulls and steers every third day of the experiment. Blood samples were collected from cows starting on d 0 and every third day thereafter until the end of the exposure period (approximately 64 d). Likewise, controlled urine delivery devices were filled and refilled on the same schedule. Neither interval from urine exposure to resumption of luteal activity nor proportions of cows that resumed luteal activity during the urine-exposure period differed between cows exposed to bull urine or steer urine. We concluded that continuous exposure to mature bull urine does not affect resumption of luteal activity of primiparous, suckled beef cows.     

Fall panicum (Panicum dichotomiflorum) hepatotoxicosis in horses and sheep

BACKGROUND: Fourteen horses at a boarding stable in Virginia were diagnosed with hepatic disease and locally grown hay was implicated as the cause. HYPOTHESIS: Panicum dichotomiflorum, the predominant grass species in the hay, is hepatotoxic to horses. ANIMALS: Naturally occurring cases were adult horses of various breeds. Two healthy adult horses and 2 healthy adult sheep were used in feeding trials. METHODS: Blood and liver specimens collected from affected animals during the outbreak were analyzed. Some of the affected animals were treated supportively; the main intervention was hay withdrawal. Feeding trials were not blinded and no treatments were provided. Blood and liver specimens were collected and analyzed throughout the trials. RESULTS: Five affected animals were euthanized, whereas the others recovered. One research horse was euthanized for postmortem examination, and the other research animals recovered after hay withdrawal. All affected animals had evidence of hepatic disease with abnormally high aspartate aminotransferase (AST), sorbitol dehydrogenase (SDH), gamma glutamyl transferase (GGT), and alkaline phosphatase (ALP) activity. Evaluation of liver biopsy specimens disclosed mild lymphocytic and histiocytic inflammation, mild vacuolar change (hydropic degeneration), prominently clumped chromatin, and necrosis of individual hepatocytes. CONCLUSIONS AND CLINICAL IMPORTANCE: Severe hepatotoxicosis developed rapidly after Panicum hay exposure. Patchy hepatocyte necrosis was observed, implicating apoptosis as the mechanism of hepatotoxicosis. Absence of fibrosis in the research animals indicates that immediate withdrawal of Panicum hay should allow all but severely affected animals to recover from acute exposure.     

Bovine NK cells acquire cytotoxic activity and produce IFN-gamma after stimulation by Mycobacterium bovis BCG- or Babesia bovis-exposed splenic dendritic cells

Early interactions of innate immune cell populations, such as dendritic cells (DC) and natural killer (NK) cells, can affect the ability of the acquired immune response to control infection of intracellular microorganisms. In this study, we investigated the activation of bovine NK cells by CD13(+) splenic DC stimulated with either Mycobacterium bovis BCG or Babesia bovis merozoites. Splenic DC were used either immediately after selection (cytokine(-)) or after exposure to GM-CSF, IL-4 and Flt3L for 72 h (cytokine(+)). Phenotypic analyses showed up-regulation of MHCII, CD80 and CD86 on cytokine(+) DC when compared to cytokine(-) DC. Purified NK cells (CD335(+)CD3(-)CD2(+/-)CD8alpha(+/-)) were co-cultured with microbial-exposed cytokine(-) DC or cytokine(+) DC in either transwell or cell-to-cell format and NK cell IFN-gamma production and cytotoxicity were assessed. NK cell IFN-gamma production was dependent on cell-to-cell contact. Microbial-stimulated cytokine(+) DC induced significantly more IFN-gamma production from NK cells than cytokine(-) cells. In contrast, cytotoxicity and perforin up-regulation were more pronounced in NK cells cultured with cytokine(-) DC than cytokine(+) DC. Therefore, activation of bovine NK cells by microbial-stimulated CD13(+) splenic DC is influenced by the maturation state of the DC suggesting different roles for the splenic DC during disease-induced maturation.     

Acute myeloid leukemia with multilineage dysplasia in an alpaca

An 18-year-old female alpaca was presented to the Colorado State University Veterinary Teaching Hospital for chronic ill thrift over a 1-year period. Six weeks previously, an infected left mandibular cheek tooth was removed by oral extraction. On physical examination the patient was cachectic, lethargic, and weak. Abnormalities on the CBC included neutropenia, thrombocytosis, and severe nonregenerative, macrocytic, hypochromic anemia. Dysplastic nucleated erythrocytes and micromegakaryocytes were observed on the peripheral blood smear. Neutrophils, bands, and metamyelocytes appeared markedly toxic. Numerous blasts containing variable numbers of fine azurophilic granules were also observed. Based on their morphology, the cells were interpreted to be progranulocytes and myeloblasts, and a presumptive diagnosis of acute myeloid leukemia (AML) was made. The blast cells accounted for 60% of the nucleated cell population on bone marrow aspirates, further supporting a diagnosis of AML with multilineage dysplasia. Post mortem examination showed infiltration of the neoplastic cells into spleen, liver, kidney, and lymph nodes. Based on histologic findings, the morphologic diagnoses were disseminated myeloid neoplasia, chronic regionally extensive tooth root abscess, and membranous glomerulonephritis. The neoplastic cells were CD172a-positive on flow cytometry, chloroacetate esterase-positive by cytochemistry, and myeloperoxidase-positive by immunohistochemistry, confirming myeloid origin. To our knowledge, this is the first case of AML with multilineage dysplasia in an alpaca, with only one other case of myelodysplasia described previously in this species.