Histophilus somni: actualización de la patogenicidad en vacuno / Histophilus somni: Pathogenecity in cattle. An update

Histophilus somni (H. somni) is a Gram-negative bacterium currently classified as a member of the Haemophilus-Actinobacillus-Pasteurella group. Clinical syndromes associated with H. somni infection involve thromboembolic meningoencephalitis, pneumonia and disease of the reproductive tract in cattle. Animals can be carriers of non-pathogenic variants of the organism, mainly in the genital mucosa. The causes of these differences in virulence between strains are not defined. Several determinants of virulence of the pathogen are proposed. However, many of these factors cannot be clearly related to clinical disease. H. somni avoids killing by phagocytic cells. Thus, it is able to evade the immune response by intracellular survival in the infected host. The bovine adaptive immune response against H. somni is not completely characterized. IgG2 antibodies are thought to be protective. However, the major antigen determinants of the bacterium are still unknown. Studies with H. somni bacterins have inconsistent results, especially because the factors involved in pathogenesis and immune response remain unclear(AU)

Histophilus somni (H. somni) es una bacteria Gram negativa actualmente clasificada como un miembro del grupo Haemophilus-Actinobacillus-Pasteurella (HAP). Los síndromes clínicos en el ganado bovino asociados con la infección por H. somni incluyen meningoencefalitis tromboembólica, neumonía y enfermedad del tracto reproductivo. Los animales pueden ser portadores de variantes no patogénicas del microorganismo, principalmente en la mucosa genital. Las causas de las diferencias en la virulencia entre cepas no están definidas. Se propusieron varios determinantes de la virulencia del patógeno. Sin embargo, muchos de estos factores no pueden relacionarse claramente con la enfermedad clínica. H. somni elude la destrucción por parte de las células fagocíticas. De este modo, es capaz de evadir la respuesta inmunitaria a través de la superviviencia en forma intracelular en el huésped infectado. La respuesta inmune adaptativa del bovino contra H. somni no está caracterizada completamente. Se estima que los anticuerpos IgG2 son protectores. Sin embargo, los principales determinantes antigénicos de la bacteria se desconocen. Los estudios con las bacterinas de H. somni han tenido resultados inconsistentes, especialmente debido a que los factores involucrados en la patogénesis y en la respuesta inmunitaria permanecen sin esclarecer(AU)

Effect of a vaccine product containing type III secreted proteins on the probability of Escherichia coli O157:H7 fecal shedding and mucosal colonization in feedlot cattle.

Preharvest intervention strategies to reduce Escherichia coli O157:H7 in cattle have been sought as a means to reduce human foodborne illness. A blinded clinical trial was conducted to test the effect of a vaccine product on the probability that feedlot steers, under conditions of natural exposure, shed E. coli O157:H7 in feces, are colonized by this organism in the terminal rectum, or develop a humoral response to the respective antigens. Steers (n = 288) were assigned randomly to 36 pens (eight head per pen), and pens were randomized to vaccination treatment in a balanced fashion within six dietary treatments of an unrelated nutrition study. Treatments included vaccination or placebo (three doses at 3-week intervals). Fecal samples for culture (n = 1,410) were collected from the rectum of each steer on pretreatment day 0 and posttreatment days 14, 28, 42, and 56. Terminal rectum mucosal (TRM) cells were aseptically collected for culture at harvest (day 57 posttreatment) by scraping the mucosa 3.0 to 5.5 cm proximal to the rectoanal junction. E. coli O157:H7 was isolated and identified with selective enrichment, immunomagnetic separation, and PCR confirmation. Vaccinated cattle were 98.3% less likely to be colonized by E. coli O157:H7 in TRM cells (odds ratio = 0.014, P < 0.0001). Diet was also associated with the probability of cattle being colonized (P = 0.04). Vaccinated cattle demonstrated significant humoral responses to Tir and O157 lipopolysaccharide. These results provide evidence that this vaccine product reduces E. coli O157:H7 colonization of the terminal rectum of feedlot beef cattle under conditions of natural exposure, a first step in its evaluation as an effective intervention for food and environmental safety.

Isotype-specific antibody responses against Escherichia coli O157:H7 locus of enterocyte effacement proteins in adult beef cattle following experimental infection.

Escherichia coli O157:H7 is an important food-borne pathogen and cause of hemorrhagic colitis and hemolytic uremic syndrome in humans. Cattle are an important reservoir of E. coli O157:H7, in which the organism colonizes the intestinal tract and is shed in the feces. Vaccination of cattle has significant potential as a pre-harvest intervention strategy for E. coli O157:H7; however, basic information about the bovine immune responses to important bacterial colonization factors resulting from infection has not been reported. The serum and fecal IgG and IgA antibody responses of adult cattle to E. coli O157:H7 intimin, translocated intimin receptor (Tir), E. coli-secreted proteins (Esp)A, EspB and O157 lipopolysaccharide (LPS) in response to infection were determined. All animals were seropositive for all five antigens prior to inoculation, with antibody titers to EspB and O157 LPS significantly higher (P<0.05) than those to Tir, intimin and EspA. After inoculation, the cattle became colonized and developed significant increases in their serum antibody titers to intimin, Tir, EspB, EspA and O157 LPS (P<0.05); however, by 42 days post-inoculation the titers to all except EspB were on the decline. In contrast, pre- and post-inoculation fecal IgG and IgA antibodies to these same antigens were not detected (<1:5). These results indicate that cattle respond serologically to E. coli O157:H7 type III secreted proteins, intimin and O157 LPS during the course of infection and the response is correlated with the extent of fecal shedding.

Primary infection, latency, and reactivation of bovine herpesvirus type 5 in the bovine nervous system.

Bovine herpesvirus type 5 (BHV-5) infection in calves causes meningoencephalitis, a fatal disease highly prevalent in South America. To study the pathogenesis of BHV-5 infection in cattle, 12 calves (group 1: acute infection) and 11 calves (group 2: latent infection) were intranasally inoculated with an Argentinean BHV-5 isolate at 10(8) and 10(4.7) tissue culture infective doses, respectively; six calves (control group) were mock infected. At 3 months postinoculation, all of the calves in group 2 and three calves in group 3 were given dexamethasone to reactivate the virus. The animals were euthanatized between days 6 and 17 postinoculation (group 1) and between days 6 and 16 postreactivation (group 2). Seventy-five percent and 91% of animals in groups 1 and 2, respectively, excreted BHV-5 in nasal and ocular discharges. Following dexamethasone administration, 45% of calves shed virus in both types of secretions. Spontaneous virus reactivation and shedding was observed in one calf. Neurologic signs consisting of circling, teeth grinding, ptyalism, jaw chomping, tongue protrusion, and apathy were observed in two animals in group 1 and, during the reactivation period, in four animals in group 2. Macroscopic findings consisted of softening of the cerebral tissue, meningeal hemorrhages and swelling, and edema and hemorrhages of prescapular, retropharyngeal and submandibular lymph nodes. Histologic lesions consisted of meningitis, mononuclear perivascular cuffing, neuronophagia, satellitosis, gliosis, hemorrhage, and necrosis and edema. Lesions in anterior cerebral cortex, medulla, and pons were consistently seen in all the animals of group 1. In the acutely infected animals, lesions in the diencephalon appeared at day 10 postinoculation, whereas in the latently infected calves these lesions were observed as early as at day 6 postreactivation. Latently infected animals developed lesions simultaneously in anterior cortex, medulla, pons, and diencephalon, showing a remarkable difference from the acutely infected group. Trigeminal ganglionitis appeared relatively early in animals of both groups (day 7 postinoculation in group 1 and day 8 postreactivation in group 2).

[Comparative temperature measurement by thermoprobes and infrared pyrometry in the rewarming of frozen kidneys using short wave generators]. / Vergleichende Temperaturmessungen durch Thermosonden und Infrarot-Pyrometrie bei der Wiedererwärmung eingefrorener Nieren mittels Kurzwellen-generatoren).

Mini pigs' kidneys were frozen to -20 degrees C after initial hypothermic perfusion and cryopreparation with dimethyl sulphoxide. They were subsequently thawed out with short-wave radiation. During this procedure continuous temperature measurement is only possible using infra-red pyrometry without physical contact. After completion of short-wave irradiation at ca. 4 degrees C the surface and internal temperatures are measured with thermoelements. In comparison with measurement by thermoprobes, infra-red pyrometry proves to be quite practicable, with certain limitations. If a homogeneous distribution of temperature in the organ is assumed; the internal temperature could be calculated from the surface temperature. Also, continuous observation of temperature changes ist possible.

[Ultrasonic Doppler methods of blood flow studies of the arterial circulation from the aorta up to the kidney parenchyma in animals]. / Untersuchungen des Strömungsverhaltens des Blutes in der arteriellen Strombahn Ausgehend von der Aorta bis zum Nierenparenchym mit dem Ultraschall-Doppler-Verfahren im Tierversuch.

The Doppler method of ultrasonography was used in experimental investigations to examine the circulator behaviour at various points in the arterial system in the retroperitoneum as fast as the kidney in animals with normal circulation. This enabled reproducible Doppler curves to be determined. It remains to be seen to what extent characteristic curve patterns exist for e.g. partial or subtotal vascular occlusion. For the future it will be especially important to determine the flow curves in the cortical region of the renal parenchyma as an area of small and very small vessels, for this can give us important information on the circulation of blood in the individual segments of the kidney.

[Behavior of the renal perfusion resistance during automatic organ preservation]. / Untersuchungen zum Verhalten des renalen Strömungswiderstandes während der maschinellen Organkonservierung.

It is reported on experimental investigations in the preservation of mini pig kidneys. At first the behaviour during the initial hypothermic gravitation perfusion is examined. From the relation of perfusate outflow to the perfusate inflow the perfusion quotient PQ is calculated. It is a measure for the volume storage developing during the perfusion (tissue oedema?) and significantly correlates with the warm dead time. The behaviour of the renal current resistance during the following machine permanent perfusion was examined with the help of KABI-albumin-solution and Collins-solution with 5% dextran M 40, and Collins-solution with 5% dextran M 75. Here was shown that the increase of the current resistance correlates with the preservation time depending on the PQ of the initial perfusion. The result is a typical behaviour for the individual solutions. We are of the opinion that the judgement of the behaviour of the kidneys during the machine perfusion must be seen in connection with the initial perfusion.

[Temperature measurements and course in a kidney preservation unit]. / Temperaturmessungen und -verläufe in einer Nierenkonservierungseinrichtung.

It is reported on two models of organ containers in which the course of the temperature was measured and registered on different conditions. The principle of construction used allowed the resignation of a special isolation. The results show that behaviour and course of the temperature in the organ containers meet all requirements.

[Experimental coronary stenoses and occlusions]. / Experimentelle Erzeugung von Koronargefässstenosen und -verschlüssen.

A constrictor for experimentally inducing stenoses and obstructions of the coronary artery is described. Smallness, good adaptability to every vascular diameter, atraumatic insertion, and slow swelling are its advantages. Within 12 months a coronary artery could be constricted by two thirds. In one third of the cases the lumen was narrowed by more than 75 per cent. Just 50 per cent of the cases showed chronic infarction after coronary obstruction, the other half developed differently marked myocardiac fibrosis. At high-degree narrowing of the arteries, 75 per cent of the cases showed disseminated myocardiac fibrosis. The occlusion of the vessel is caused by constrictor, by fibroplastic alteration of the vascular wall, and by thrombosis. Different degrees of myocardiac ischemia are sequelae of different development of collaterals. The constrictor may be used for studies on the development of collaterals as well as on therapeutic measures in chronic ischemia of the myocardium.

[Dye-marking and hydrogen clearance in demonstrating acute ischemic myocardial areas]. / Farbstoffmarkierung und Wasserstoffclearance zum Nachweis akut-ischämischer Myokardbezirke.

After acute myocardial infarction (produced by ligation in the dog), the authors marked the borders of infarction with disulphine blue or methylene blue and determined, by means of hydrogen clearance, the blood supply in the centre and at the margin of infarction as well as at different distances from the latter. At the margin of infarction, the value for blood flow amounted to almost 17% of the value measured prior to ligation. Only at a distance of 1 cm. from the visible margin of infarction, 50 to 80% of the initial value were obtained. The extension of the area of infarction beyond the marked visible margin must be considered in surgical interventions.