Histopathologic lesions in conventional pigs experimentally infected with Haemophilus parasuis serovar 5.

OBJECTIVE: In the present study various tissues of pigs were investigated for the presence of histopathologic lesions after an experimental infection with Haemophilus (H.) parasuis serovar 5. MATERIAL AND METHODS: Conventional pigs (n = 36) were divided into a control group B (n = 9) and a challenge group A (n = 27), which was infected intratracheally. Pigs that did not die prior to study termination were euthanized on day 14 post inoculation. Postmortem samples of the lung, heart, liver, kidney, spleen, left tarsal joint capsule and brain were collected. RESULTS: All but one pig with detectable histopathologic lesions (n = 11) showed typical macroscopic changes. Histopathologic examination of all tissue samples identified pyelitis (n = 10), synovitis (n = 7) and meningitis (n = 7) and all those animals were euthanized prior to study termination. No histopathologic lesions were found in pigs of the control group. The correlations between pyelitis and meningitis, pyelitis and synovitis and synovitis and meningitis were significant (p < 0.001). No significant correlation could be observed between the histopathologic and the clinical examination of the joints. The investigation of samples from the joints by PCR was not significantly correlated with the observed synovitis. The clinical observation of neurologic signs was significantly correlated with meningitis (p = 0.03). A significant correlation (p < 0.001) could be detected between meningitis and the detection of H. parasuis by PCR in brain samples. CONCLUSIONS: H. parasuis constantly causes clinical signs and pathologic lesions as soon as it infects the brain while it can infect the joints without causing histopathologic lesions. Pigs with histopathologic lesions do not always show typical clinical signs. Only few studies described the finding of kidney lesions in pigs with Glässer's disease and this is the first study to describe a pyelitis in pigs experimentally infected with H. parasuis. The observed pyelitis mainly occurred in acute cases.

Histophilus somni-induced infections in cattle from southern Brazil.

The sudden death of three calves, one diarrheic calf, and one aborted fetus from four farms in southern Brazil was investigated. Two Histophilus somni-associated syndromes were identified: systemic histophilosis (n = 4) and abortion (n = 1). The principal pathological findings included vasculitis, meningoencephalitis with thrombosis, necrotizing myocarditis, renal infarctions, hepatic abscesses, and bronchopneumonia. PCR assays were used to amplify specific amplicons of the ovine herpesvirus 2, bovine herpesvirus 1 and -5, Listeria monocytogenes, H. somni, and pestivirus; bovine group A rotavirus (BoRV-A) and bovine coronavirus (BCoV) were investigated in calves with diarrhea. H. somni DNA was amplified in tissues from all calves and the brain of the aborted fetus with pathological alterations consistent with histophilosis. All other PCR assays were negative; BoRV-A and BCoV were not identified. These findings confirm the participation of H. somni in the pathological alterations observed in this study and represent the first description of histophilosis in cattle from Brazil.

Histopathological evaluation of disseminated intravascular coagulation in Haemophilus somnus infection in cattle.

The frequency and distribution of fibrin thrombi (microthrombi) in the main organs of spontaneously infected cattle were investigated to evaluate disseminated intravascular coagulation (DIC) in Haemophilus somnus infection. This infection is well known as infectious thrombo-embolic meningo-encephalitis (ITEME) and is characterized histopathologically by formation of thrombi, necrosis of blood vessels and neutrophil infiltration. The precise pathogenic mechanism of this disease has not yet been fully elucidated. The liver, spleen, kidney, lung, heart and brain of 11 cattle showing thromboembolic meningo-encephalitis were examined histopathologically and special attention was paid to fibrin thrombi. PTAH staining showed a high frequency of fibrin thrombi in the small vessels and capillaries in more than 3 organs and all the cases were regarded as falling within the histopathological criterion of DIC. The results of the present study indicate that the pathogenesis of the infection is closely related to the DIC.

[Sleeper syndrome in beef cattle; meningoencephalitis caused by Haemophilus somnus]. / 'Sleeper syndroom' bij vleesstieren; meningoencephalitis veroorzaakt door Haemophilus somnus.

Central nervous system disturbances, among which somnolence was a particularly marked feature, were observed in a herd of four-month-old beef cattle. Laboratory studies showed that the clinical picture was due to meningo-encephalitis, from which Haemophilus somnus was isolated. Other animals of this herd showed a serological response with regard to the micro-organism. The importance of further studies on the incidence of this infection in the Netherlands is stressed.

Isolation of Haemophilus somnus antigens and their use as vaccines for prevention of bovine thromboembolic meningoencephalitis.

Antigens extracted from Haemophilus somnus were examined for their suitability as vaccines for prevention of thromboembolic meningoencephalitis and as antigens in immunologic tests for detection of susceptible cattle. Saline extraction of whole H somnus cells produced an outer membrane complex (OMC) that contained 2 major antigens when tested against antiserum to intact cells by immunoelectrophoresis. Anion exchange chromatography was used to separate an anionic antigen (AA) from the more cationic antigen (CA). According to chemical analysis and polyacrylamide gel electrophoresis, both AA and CA were complex mixtures--probably, outer membrane fragments. Enzyme-linked immunosorbent assays were used to measure serum levels of immunoglobulin (Ig) G and IgM against AA and CA in cattle vaccinated with whole cells, OMC, CA, or AA. Protection of vaccinated cattle was assessed after IV challenge exposure to H somnus. Moderate IgG and IgM responses occurred when cattle were given 2 vaccinal doses of 0.1 mg or 1.0 mg of whole cells, OMC, or AA. Two of 10 cattle given 2 vaccinal doses (1.0 mg) of OMC died after IV challenge exposure, whereas 8 of the 10 controls died, indicating significant protection (P less than 0.05). All of the 10 cattle given 2 vaccinal doses (1.0 mg) of AA were protected from IV challenge exposure, whereas 5 controls died (P less than 0.05). Two vaccinal doses of either 0.1 mg or 1.0 mg of CA produced high IgG and IgM responses. However, 3 of 10 cattle given 2 vaccinal doses (1.0 mg) of CA died after IV challenge exposure, as did 3 of the 10 controls, indicating that CA was not protective.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphologic features, structure, and adherence to bovine turbinate cells of three haemophilus somnus variants.

Three colony variants (translucent, small opaque, and large opaque) of Haemophilus somnus recovered during infection studies of chicken embryos were examined using electron microscopy. Ruthenium red-strained H somnus preparations revealed no capsule in any variants. Pili were not seen on phosphotungstate-negative stained preparations. The translucent variant was thin-walled and had an irregular, pleomorphic rod shape. The small opaque variant had a thicker cell wall and an even rod shape. The large opaque variant had the thickest, most rigid wall of the 3, with uniform rod morphologic features. When each of the 3 variants was allowed to contact bovine epithelial turbinate cells, the translucent and small opaque were significantly (P less than 0.01) more adherent than was the large opaque variant.

Model infection of the chicken embryo with Haemophilus somnus.

Infectious thromboembolic meningoencephalitis of cattle which is caused by Haemophilus somnus has been difficult to study due, in part, to lack of model infection in a laboratory animal. Model infection was induced in 12-day-old chicken embryos after IV injection of H somnus. Death with typical lesions (hemorrhage, degeneration of brain, congestion of venules with leukocytes and meningitis) was seen in the chicken embryo between 2 and 6 days after injection of organisms. Bacteria could be demonstrated in lesions, using Warthin-Starry silver strain. Three stable colonial variants of H somnus were cultured from dead embryos. They appeared as small translucent (ST), small opaque (SO), and large opaque (LO). Lethal dose50 values of ST was 4.4 x 10(4); for SO, 3.6 x 10(4); and for LO, 8 x 10(6). Statistical analysis indicated that ST and SO were significantly more lethal (P less than 0.001) than LO.

Host humoral factors in natural resistance to Haemophilus somnus.

Natural serum bactericidal activity against Haemophilus somnus in various age groups of cattle was investigated. The level of antibacterial reactivity correlated with the agglutinating titer and age of the given animal. This activity was complement dependent, but the concentration of bactericidal antibody appeared to be the limiting factor in sera which had reduced killing capacity. Immunized animals developed high serum concentrations of bactericidal activity. The results of this study indicated that bactericidal antibodies may be important in host defense from H somnus infection and that immunization can enhance this resistance by stimulating high serum concentrations of bactericidal activity.