Attempts to produce granulomatous colitis in Boxer dogs with a mycoplasma.

Four of six Boxer dogs with granulomatous colitis had mycoplasmas in the colon and three in the draining lymph node as well. One isolate identical with Mycoplasma strain HRC-689 was inoculated into the colon of five Boxer dogs at eight weeks of age; four controls were inoculated with medium. Animals were killed at two week intervals and examined. The mycoplasma strain produced changes of the colon characterized by lymphocytic infiltration of mucosa, lymphocytic submucosal perivasculitis, and enlargement of colonic lymphoid nodules but granulomatous colitis did not occur. The experimental dogs developed antibodies, and dogs from a kennel with a high prevalence of colitis cases had high antibody titers against strain HRC-689.     

Changes in anti-erythrocyte membrane antibody level of dogs experimentally infected with Babesia gibsoni.

To account for the conflict between the excessive destruction of erythrocytes and the number of parasitized erythrocytes in dogs infected with Babesia gibsoni, we examined the correlation between anti-erythrocyte membrane antibody level (AEMAL) and the number of erythrocytes (RBC count) in dogs with experimentally induced babesiosis using hematological examination and an enzyme linked immunosorbent assay (ELISA). In the infected dogs without splenectomy, more prominent reduction in RBC count accompanied with the elevated AEMAL was presented than anticipated from parasitemia until the 21st day. Furthermore, autoagglutinated erythrocytes and spherocytes were demonstrated in blood films. These results suggest that a humoral immunologic mechanism may be involved in a decrease in RBC count in dogs infected with B. gibsoni.     

Erythrocyte response to Trypanosoma brucei in experimentally infected dogs.

Trypanosoma brucei infection produced an acute and fatal disease in Nigerian mongrel dogs due to a rapidly developing anaemia. Infected dogs responded with increased reticulocytosis, which was not sustained with chronicity. In comparison the response to artificially-induced haemolytic anaemia was progressive, marked and sustained. The anaemia of T. brucei infection of dogs was either normocytic normochromic in acute infection or microcytic normochromic in chronic infection. Artificially-induced haemolytic anaemia was either macrocytic normochromic or normocytic normochromic. The erythropoietic potential of plasma in vivo in mice increased in T. brucei-infected dogs except at the terminal parasitaemia. The anaemia in Trypanosoma brucei-infected dogs is therefore initially responsive but becomes poorly involved with chronicity.     

Cardiopulmonary responses to experimentally induced gastric dilatation in isoflurane-anesthetized dogs.

Gastric dilatation was experimentally induced in 6 anesthetized dogs maintained with constant-dose isoflurane in oxygen. An intragastric balloon was used to distend the stomach with a constant 30 mm of Hg pressure for 3.5 hours. The PaCO2 was maintained between 35 and 45 mm of Hg, using intermittent positive-pressure ventilation. Cardiopulmonary measurements prior to stomach distension (baseline) were compared with measurements taken during 0.1, 0.5, 1.0, 1.5, 2.5, and 3.5 hours of stomach distension by analyzing the change from baseline in a randomized-block analysis with each dog as a block. After distending the stomach, cardiac index increased (P less than 0.01) from 1.5 to 3.5 hours. Stroke volume did not change, thus the increase in the cardiac index was attributable to an increase in heart rate. During inflation, increases were observed in systemic arterial, pulmonary arterial, and right atrial pressure. Respiratory frequency was unchanged; however, to maintain PaCO2 constant, it was necessary to progressively increase peak airway pressure. Although PaO2 tended to decrease during gastric dilation, the dogs were never hypoxemic. These results indicate that when our methods are used to maintain a constant anesthetic dose of isoflurane in oxygen, an observed increase in cardiovascular performance is expected. This differs from other studies in anesthetized dogs that have shown reduction in cardiovascular performance following gastric dilatation.     

Doxycycline clearance of experimentally induced chronic Ehrlichia canis infection in dogs

BACKGROUND: Ineffective clearance of Ehrlichia canis after doxycycline administration has been reported despite the fact that the recommended treatment for canine ehrlichiosis is doxycycline. The effectiveness of doxycycline in clearing E canis infection from the blood and tissues of dogs requires additional evaluation. HYPOTHESIS: Doxycycline (5 mg/kg PO q12h), administered for 4 weeks, will eliminate E canis infection from the blood and tissues of experimentally infected dogs. ANIMALS: Fifteen Walker hound-mixed breed dogs were inoculated subcutaneously with E canis-infected canine histiocytic cells 4 months before doxycycline treatment. METHODS: Four dogs were treated with doxycycline (5 mg/kg PO q12h for 3 weeks), 5 dogs were treated with doxycycline at the same dosage for 4 weeks, and 5 control dogs were not treated. Dexamethasone (0.4 mg/kg i.v.) was given after treatment to precipitate recrudescence of any remaining E canis organisms. Platelet counts, anti-E canis immunofluorescent antibodies, and polymerase chain reaction (PCR) detection of E canis deoxyribonucleic acid (DNA) in blood and tissues were evaluated. RESULTS: E canis DNA was not detected in the blood and tissues of doxycycline-treated dogs after treatment. Platelet counts were within reference intervals, and E canis antibodies decreased. Spontaneous clearance of E canis infection occurred in 2 of 5 control dogs. Three control dogs had E canis DNA detected in blood and tissues, platelet counts remained low or within the reference interval, and E canis antibodies remained high. CONCLUSIONS AND CLINICAL IMPORTANCE: As administered in this study, doxycycline cleared E canis from the blood and tissues of experimentally infected dogs.     

Lymphoscintigraphy in healthy dogs and dogs with experimentally created thoracic duct abnormalities.

Lymphoscintigraphic evaluation of the thoracic duct (TD) was performed in 10 healthy and 12 dogs with experimentally created TD abnormalities (6 dogs with TD lacerations and 6 dogs with cranial vena ligations). Complete imaging took 4 hours and caused no adverse effects or complications. Lymphoscintigraphy of healthy dogs failed to image the TD; however, background activity in the abdomen and thorax, and radioactivity in the kidneys, bladder, liver, and heart were noticed. Lacerations and transections of the TD were experimentally created in 6 dogs to ascertain whether TD rupture could be detected with lymphoscintigraphy. Lymphoscintigraphy was performed within 48 hours of creating the TD defect. There was no significant difference in the scintigraphic pattern of healthy dogs and those with experimentally created TD defects. Ligation of the cranial vena cava was performed in 6 dogs; 3 dogs developed chylothorax. In those 3 dogs, diffuse radioactivity was imaged in the thorax and was compatible with thoracic lymphangiectasia. In one of these dogs, linear activity consistent with the TD and localized regions of radioactivity cranial to the heart (compatible with the mediastinal lymph nodes) were noticed. Lymphoscintigraphic findings in these dogs correlated with lymphangiographic findings.     

Changes in activities of enzymes related to malate-aspartate shuttle in leukocytes from dogs given a herb supplement.

Changes in activities of enzymes related to the malate-aspartate shuttle were measured in leukocytes (WBC) from dogs given food supplemented with 2 mg/kg of herb powder, Echevaria glauca, every day for 4 weeks. There were no significant differences in plasma concentrations of glucose, immunoreactive insulin, free fatty acids and triglyceride between dogs given food with or without the herb supplementation. Activities of malate dehydrogenase (MDH) and aspartate aminotransferase (AST) in the malate-aspartate shuttle increased remarkably in mitochondria of WBC from dogs fed the herb supplementation. It is suggested that Echevaria glauca herb supplementation might activate NADH shuttle systems and mitochondrial energy metabolism in dogs.     

Tolerance of a rice-based oral rehydration solution given to normal calves

The objective of the study was to test the tolerance of a rice-based oral rehydration formula when fed to calves. Six healthy Holstein calves, 1 week of age, were fed the formula instead of milk replacer for 3 days. Pre- and posttreatment results of clinical examination and laboratory parameters were compared. Vital signs, attitude, appetite, clinical hydration status, urine specific gravity, and most routine serum biochemistry test results did not vary and remained within the normal range. Five of the 6 calves developed diarrhea when fed the rice-based formula, which was accompanied by a reduction in fecal pH and presence of reducing sugars in the feces. This effect was reversed when calves were returned to the milk replacer diet at the end of the study. Diarrhea was accompanied by increased water consumption, which allowed the calves to maintain normal hydration status. These results suggest that calves are unable to properly digest the rice-derived carbohydrate, and this type of formula is not recommended for oral rehydration of calves.     

Resistance of neonatal calves given colostrum diet to oral challenge with a septicemia-producing Escherichia coli.

Twenty Holstein-Friesian male calves were obtained within 4 hours after bith (colostrum deprived) and allotted to 1 of 4 groups, each given a different feeding: colostrum, milk replacer, polyvinylpyrrolidone (PVP), and saline solution (0.85% NaCl). Each calf was fed 2 L of the respective diets every 12 hours. Rectal temperatures were recorded and blood samples were collected immediately before each feeding. At approximately 27 hours of age, all calves were inoculated orally with 1.5 X 10(10) viable organisms of a septicemia-producing Escherichia coli serotype O26: K60:NM. Within 8 hours, all calves had diarrhea. Coli-septicemia (E coli cultured from liver, spleen, and cardiac blood) was present in 1 of the 5 calves fed colostrum, in 5 or the 5 calves fed milk replacer, in 5 of the 5 calves fed PVP, and in 4 of the 5 calves fed saline solution. At necropsy of the calves (12 to 48 hours after oral inoculation), the same organism was isolated by cultural technique from small intestines of 19 of the 20 calves. Serum immunoglobulin G concentrations increased (P less than 0.01) in calves fed the colostrum diet in sharp contrast to the agammaglobulinemia occurring in calves fed the milk replacer, PVP, or saline solution. Results indicate that colostrum fed to the calf soon after birth provides protection from colisepticemia, but does not prevent the diarrhea of colibacillosis.     

Hematopathology in dogs experimentally infected with a Swedish granulocytic Ehrlichia species

Seven, adult, female beagles were inoculated with a Swedish granulocytic Ehrlichia organism closely related to Ehrlichia equi and E. phagocytophila. Blood and bone marrow changes were evaluated throughout the acute phase of infection. All dogs developed moderate to severe thrombocytopenia during the parasitemic period. The mean platelet volume and platelet distribution width increased, and large platelets were seen on blood smears when platelet numbers were low. In bone marrow, absolute numbers of megakaryocytes and immature megakaryocytes were increased. These results suggested the thrombocytopenia was caused by increased platelet destruction. The dogs also developed mild, normocytic, normochromic anemia, with simultaneous decreases in serum iron concentration and total iron-binding capacity that resembled the anemia of inflammation. In bone marrow, there was a slight increase in immature erythroid cells and no erythroid hypoplasia; iron stores were normal to increased. Myeloid hyperplasia was seen in all infected dogs, despite neutropenia in peripheral blood. Lymphopenia occurred early in the parasitemic period, but lymphocytes responded strongly and numbers increased above baseline levels by the end of parasitemia. Blast-transformed lymphocytes (5% to 20%) were seen in peripheral blood for a few days. Experimentally-induced canine granulocytic ehrlichiosis caused cytopenias of short duration, coincident with the appearance of ehrlichial inclusions in neutrophils.     

Antimicrobial resistance in Staphylococcus spp., Escherichia coli and Enterococcus spp. in dogs given antibiotics for chronic dermatological disorders, compared with non-treated control dogs

The aim of this study was to evaluate antimicrobial resistance in canine staphylococci, Escherichia coli and enterococci, which were isolated from 22 dogs with pyoderma and a history of previous antibiotic treatment, compared to bacterial isolates from 56 non-treated control dogs. Two isolates of each bacterial species per dog were investigated, if detected. Staphylococcal isolates from dogs with pyoderma (35 isolates) were more resistant to sulphatrimethoprim than the isolates from controls (56 isolates) (57% vs. 25%, p < 0.004). Multiresistance in staphylococci was also more common in dogs with pyoderma (29% vs. 9%, p = 0.02). A similar trend among isolates of E. coli was detected (24 and 74 isolates from treated and control dogs, respectively), but the differences were not significant. Resistance for macrolide-lincosamides was approximately 20% among staphylococci in both groups. Resistance to ampicillin among enterococci was 4%-7%. The age of the dogs might have an impact on resistance: multiresistance among staphylococcal isolates from younger dogs (< or = 5 years) was more common than in older dogs (26 years) (24%, vs. 0%, 63 and 27 isolates, respectively, p = 0.02). Staphylococci in younger dogs were more resistant to tetracycline (48% vs. 11%, p < 0.001) and sulphatrimethoprim (48% vs. 15%, p < 0.01) than those in older dogs. In contrast, the isolates of E. coli from older dogs tended to be more resistant, although a significant difference was detected only in resistance to tetracycline (13% vs. 2% of 40 and 50 isolates respecthely, p = 0.04)). The results of this small study indicate that resistance in canine staphylococci in the capital area of Finland is comparable with many other countries in Europe. Resistance in indicator bacteria, E. coli and enterococci, was low.     

Treatment of reperfusion injury in dogs with experimentally induced gastric dilatation-volvulus.

In dogs, gastric dilatation-volvulus (GDV) is characterized by cardiogenic shock, with resulting hypoperfusion. Treatment goals include reperfusion of transiently ischemic tissues, which indicates that reperfusion injury may be a factor in the physiopathogenesis of GDV. Recently, we obtained data that indicate that reperfusion injury may be involved in experimentally induced GDV. Using this GDV model, we evaluated mortality in 24 dogs of 4 equal groups, treated with deferoxamine (an iron chelator), dimethylsulfoxide (a free radical scavenger), a combination of the 2 drugs, or isotonic saline solution. All 6 dogs that were given deferoxamine survived; however, 3 dogs of the dimethylsulfoxide-treated group, 2 dogs of the combination-treated group, and 4 dogs of the saline-treated group died. Results of the study indicate that mortality associated with experimentally induced GDV is reduced by appropriate and timely pharmacologic intervention to prevent or attenuate reperfusion injury, and that deferoxamine may be more effective than dimethylsulfoxide.     

Characterization of the renal response to protein ingestion in dogs with experimentally induced renal failure.

Effects of a protein meal (2.7 g of casein/kg of body weight) on glomerular filtration rate (GFR) and renal plasma flow (RPF) were assessed in dogs after 15/16 nephrectomy (n = 10), and were compared with observations in dogs with intact kidneys (n = 5). Increase in GFR and RPF was observed in both groups of dogs between 1.5 and 8 hours after protein ingestion. A maximal value for GFR was observed between 4 and 5 hours after protein ingestion in dogs of both groups. Enhancement of urinary protein excretion was evident in partially nephrectomized dogs after protein ingestion (P less than 0.05), a result that was confirmed by 24-hour total urine collection from partially nephrectomized dogs fed a balanced ration. A qualitatively similar vasodilatory response was observed in partially nephrectomized dogs and in dogs with intact kidneys, and the mean maximal increase of GFR and RPF expressed as a percentage of baseline values in the latter dogs (47.0 +/- 8.1 and 43.6 +/- 10.3%, respectively) exceeded that observed in partially nephrectomized dogs (20.8 +/- 2.2 and 22.7 +/- 6.3%, respectively; P less than 0.01). The incremental response of the kidneys to protein ingestion was directly related to the degree of renal function, as reflected in the linear regression relationship between the incremental increase in GFR and the baseline value for GFR (P less than 0.01, R2 = 0.721).     

Use of breath hydrogen testing to detect experimentally induced disaccharide malabsorption in healthy adult dogs.

OBJECTIVE: To develop a noninvasive method to detect disaccharide malabsorption in dogs by measuring hydrogen concentration ([H2]) in exhaled breath before and after experimentally induced disaccharide malabsorption. ANIMALS: 8 healthy mixed-breed dogs. PROCEDURE: [H2] was measured every 30 minutes for 8 hours after administration of disaccharide solutions (lactose, 0.5 g/kg of body weight; lactose, 1.0 g/kg; sucrose, 2.0 g/kg; maltose, 1.5 g/kg; and lactose [0.5 g/kg] and sucrose [2.0 g/kg]) to determine reference ranges of [H2] for each solution, which were compared with [H2] in dogs with experimentally induced disaccharide malabsorption. To induce disaccharide malabsorption, dogs were given a mild overdose of lactose (1.5 g/kg) or a disaccharidase inhibitor. In the latter experiment, acarbose (10 mg/kg, PO) was given with the combination of lactose (0.5 g/kg) and sucrose (2 g/kg), and with maltose (1.5 g/kg). RESULTS: Overdosing with lactose resulted in [H2] persistently outside the reference range for lactose in 5 of 8 dogs. Acarbose administration resulted in [H2] persistently outside the reference range in 7 of 8 dogs that received a combination of sucrose and lactose but did not consistently affect [H2] after administration of maltose. CONCLUSIONS: Disaccharide malabsorption resulted in [H2] outside the reference ranges in most of the adult dogs studied, suggesting that the technique may be useful in detecting naturally occurring disaccharidase deficiency.     

Immunopathology of Bartonella vinsonii (berkhoffii) in experimentally infected dogs.

Following natural infection with Bartonella, dogs and humans develop comparable disease manifestations including endocarditis, peliosis hepatis, and granulomatous disease. As the immunologic response to infection in these hosts has not been clearly established, data presented here was derived from the experimental infection of six specific pathogen free (SPF) beagles with a known pathogenic strain of Bartonella. Six dogs were inoculated intravenously with 10(9)cfu of B. vinsonii ssp. berkhoffii and six control dogs were injected intravenously with an equivalent volume of sterile saline. Despite production of substantial levels of specific antibody, blood culture and molecular analyses indicated that Bartonella established chronic infection in these dogs. Flow cytometric analysis of monocytes indicated impaired bacterial phagocytosis during chronic Bartonella infection. There was also a sustained decrease in the percentage of CD8+ lymphocytes in the peripheral blood. Moreover, modulation of adhesion molecule expression (downregulation of L-selectin, VLA-4, and LFA-1) on CD8+ lymphocytes suggested quantitative and qualitative impairment of this cell subset in Bartonella-infected dogs. When compared with control dogs, flow cytometric analysis of lymph node (LN) cells from B. vinsonii infected dogs revealed an expanded population of CD4+ T cells with an apparent na?ve phenotype (CD45RA+/CD62L+/CD49D(dim)). However, fewer B cells from infected dogs expressed cell-surface MHC II, implicating impaired antigen presentation to helper T cells within LN. Taken together, results from this study indicate that B. vinsonii establishes chronic infection in dogs which may result in immune suppression characterized by defects in monocytic phagocytosis, an impaired subset of CD8+ T lymphocytes, and impaired antigen presentation within LN.     

Local and systemic immune responses to Echinococcus granulosus in experimentally infected dogs

Local and systemic immune responses were studied in six dogs experimentally infected with the dog/sheep tapeworm Echinococcus granulosus. All dogs developed similar IgG antibody response to parasite antigens. In contrast, IgE and IgA responses differed widely. No relationship between IgA responses and parasite burden at the end of the infection were observed. Further, clear differences in the anti-parasite IgA response in serum as compared with specific IgA forming cells in mesenteric lymph nodes were observed within the same dog. An inverse association of anti-parasite IgE and parasite load seemed to be present, with the strongest IgE response in the one dog that had no worms in the intestine at the end of the experiment. No differences were observed in the numbers of intestinal mast cells and goblet cells among all infected dogs. However, the dog with no detectable parasite load had a marked reduction of detected mast cells in the submuscular and muscular layer of the mucosa. Our data give new insight into the immune response of dogs during E. granulosus infection and provide information that may be useful for the rational design of vaccines for the control of hydatid disease.