Procoagulant activity of bovine neutrophils incubated with conditioned media or extracellular vesicles from Histophilus somni stimulated bovine brain endothelial cells.

Histophilus somni is a Gram negative coccobacillus that causes respiratory, reproductive and central nervous system disease in cattle. The hallmark of H. somni infection is diffuse vasculitis and intravascular thrombosis that can lead to an acute central nervous system disease known as thrombotic meningoencephalitis (TME). Because neutrophils are major players in the pathophysiology of septic meningitis, we sought to determine their role in H. somni-induced fibrin clot formation in vitro. Bovine brain endothelial cells (TBBE cells) were exposed to H. somni cells at a 1:25 ratio, respectively. Conditioned media (CM) were collected after a 6 h incubation at 37 °C with 5% CO2, and then incubated with bovine peripheral blood polymorphonuclear neutrophils (PMNs). Following incubation, fibrin clot formation and tissue factor activity were assessed by a re-calcified plasma clotting assay. We found greater tissue factor activity in cell lysates and CM from H. somni-stimulated TBBE cells than unstimulated control TBBE cells. In addition, PMNs exposed to CM or extracellular vesicles from H. somni-stimulated TBBE cells expressed von Willenbrand factor, exhibited increased fibrin clot formation, and displayed greater tissue factor activity than PMNs exposed to CM or extracellular vesicles from unstimulated control TBBE cells. These results suggest that bovine PMNs might acquire extracellular vesicles from endothelial cells that leads to thrombus formation in bovine brain microvasculature and contribute to the process that characterizes TME.

Histophilus somni-associated syndromes in sheep from Southern Brazil

Abstract Histophilus somni is a Gram-negative bacterium that is associated with a disease complex (termed histophilosis) that can produce several clinical syndromes predominantly in cattle, but also in sheep. Histophilosis is well described in North America, Canada, and in some European countries. In Brazil, histophilosis has been described in cattle with respiratory, reproductive, and systemic disease, with only one case described in sheep. This report describes the occurrence of Histophilus somni-associated disease in sheep from Southern Brazil. Eight sheep with different clinical manifestations from five farms were investigated by a combination of pathological and molecular diagnostic methods to identify additional cases of histophilosis in sheep from Brazil. The principal pathological lesions were thrombotic meningoencephalitis, fibrinous bronchopneumonia, pulmonary abscesses, and necrotizing myocarditis. The main clinical syndromes associated with H. somni were thrombotic meningoencephalitis (n = 4), septicemia (n = 4), bronchopneumonia (n = 4), and myocarditis (n = 3). H. somni DNA was amplified from multiple tissues of all sheep with clinical syndromes of histophilosis; sequencing confirmed the PCR results. Further, PCR assays to detect Pasteurella multocida and Mannheimia haemolytica were negative. These findings confirmed the participation of H. somni in the clinical syndromes investigated during this study, and adds to the previous report of histophilosis in sheep from Brazil.

Histophilus somni-associated syndromes in sheep from Southern Brazil.

Histophilus somni is a Gram-negative bacterium that is associated with a disease complex (termed histophilosis) that can produce several clinical syndromes predominantly in cattle, but also in sheep. Histophilosis is well described in North America, Canada, and in some European countries. In Brazil, histophilosis has been described in cattle with respiratory, reproductive, and systemic disease, with only one case described in sheep. This report describes the occurrence of Histophilus somni-associated disease in sheep from Southern Brazil. Eight sheep with different clinical manifestations from five farms were investigated by a combination of pathological and molecular diagnostic methods to identify additional cases of histophilosis in sheep from Brazil. The principal pathological lesions were thrombotic meningoencephalitis, fibrinous bronchopneumonia, pulmonary abscesses, and necrotizing myocarditis. The main clinical syndromes associated with H. somni were thrombotic meningoencephalitis (n=4), septicemia (n=4), bronchopneumonia (n=4), and myocarditis (n=3). H. somni DNA was amplified from multiple tissues of all sheep with clinical syndromes of histophilosis; sequencing confirmed the PCR results. Further, PCR assays to detect Pasteurella multocida and Mannheimia haemolytica were negative. These findings confirmed the participation of H. somni in the clinical syndromes investigated during this study, and adds to the previous report of histophilosis in sheep from Brazil.

Histophilus somni-induced thrombotic meningoencephalitis in cattle from northern Paraná, Brazil / Meningoencefalite trombótica-induzida por Histophilus somni em bovinos da região norte do Paraná

Thrombotic meningoencephalitis (TME) is a fatal neurological disease of cattle, predominantly from North America, that is caused by Histophilus somni with sporadic descriptions from other countries. This manuscript describes the occurrence of spontaneous TME in cattle from northern Paraná, Brazil. Most cattle had acute neurological manifestations characteristic of brain dysfunction. Hematological and cerebrospinal fluid analyses were not suggestive of bacterial infections of the brain. Histopathology revealed meningoencephalitis with vasculitis and thrombosis of small vessels that contained discrete neutrophilic and/or lymphocytic infiltrates admixed with fibrin at the brainstem, cerebral cortex, and trigeminal nerve ganglion of all animals. All tissues from the central nervous system used during this study were previously characterized as negative for rabies virus by the direct immunofluorescence assay. PCR and RT-PCR assays investigated the participation of infectious agents associated with bovine neurological disease by targeting specific genes of H. somni, Listeria monocytogenes, bovine herpesvirus -1 and -5, bovine viral diarrhea virus, and ovine herpesvirus-2. PCR and subsequent sequencing resulted in partial fragments of the 16S rRNA gene of H. somni from brain sections of all animals with histopathological diagnosis of TME; all other PCR/RT-PCR assays were negative. These findings confirmed the participation of H. somni in the neuropathological disease observed in these animals, extend the geographical distribution of this disease, and support previous findings of H. somni from Brazil.(AU)

Meningoencefalite trombótica (Thrombotic meningoencephalitis- TME) é uma doença neurológica fatal de bovinos ocasionada por Histophilus somni. A infecção tem sido descrita predominantemente na América do Norte e de forma esporádica em outros países. O objetivo deste estudo é relatar a ocorrência de TME em bovinos da região norte do estado do Paraná, Brasil. A maioria dos animais apresentaram sinais clínicos neurológicos característicos de disfunção cerebral aguda. Análises hematológicas e do fluido cerebrospinal não foram sugestivas de infecção bacteriana do cérebro. A histopatologia revelou meningoencefalite com vasculite e trombose de pequenos vasos com discreto infiltrado neutrofílico e/ou linfocítico mesclada com fibrina no tronco e córtex cerebral e no gânglio do nervo trigêmio de todos os animais. As amostras de sistema nervoso central incluídas nesse estudo foram previamente caracterizadas como negativas para raiva por meio de técnica de imunofluorescência direta. A participação de agentes infecciosos associados à doença neurológica em bovinos foi avaliada por técnicas moleculares como PCR e RT-PCR para amplificação parcial de genes de H. somni, Listeria monocytogenes, herpesvírus bovino 1 e 5, vírus da diarreia viral bovina e herpesvírus ovino 2. As seções do cérebro de todos os animais com diagnóstico histopatológico de TME foram positivas em PCR para a detecção do gene 16S rRNA de H. somni. O sequenciamento dos produtos amplificados confirmou a presença de DNA de H. somni nos fragmentos de cérebro avaliados. As reações de PCR/RT-PCR para todos os outros micro-organismos avaliados resultaram negativas. Os resultados desse estudo confirmaram a participação do H. somni nos episódios de doença neurológica observada nos animais avaliados, amplia a distribuição geográfica da TME e ratifica estudos prévios realizados no Brasil que demonstraram a presença de H. somni em outras formas de manifestação clínica das infecções por essa bactéria.(AU)