Pneumonia associated with Haemophilus somnus in a calf

Histophilus somni disease conditions with simultaneous infections by ovine gammaherpesvirus 2 in cattle herds from Southern Brazil

This report investigated the cause of cattle mortality in two farms in Southern Brazil. The tissues of one animal from each farm (animals #1 and #2) respectively were used in pathological and molecular investigations to determine the possible cause of death. The principal pathological findings observed in animal #1 were pulmonary, myocardial, and encephalitic hemorrhages with vasculitis, and lymphoplasmacytic interstitial pneumonia with proliferative vascular lesions (PVL). The main pathological findings observed in animal #2 were purulent bronchopneumonia, hemorrhagic myocarditis, and lymphoplasmacytic interstitial pneumonia with PVL. An immunohistochemical assay detected intralesional antigens of a malignant catarrhal fever virus (MCFV) from multiple tissues of animal #2 while PCR confirmed that the MCFV amplified was ovine gammaherpesvirus 2 (OvGHV2), genus Macavirus, subfamily Gammaherpesvirinae; OvGHV2 was also amplified from multiple tissues of animal #1. Furthermore, PCR assays amplified Histophilus somni DNA from multiple fragments of both animals. However, the nucleic acids of Mannheimia haemolytica, Pasteurella multocida, Mycoplasma bovis, bovine respiratory syncytial virus, bovine alphaherpesvirus virus 1 and 5, bovine coronavirus, and bovine parainfluenza virus 3 were not amplified from any of the tissues analyzed, suggesting that these pathogens did not participate in the development of the lesions herein described. These findings demonstrated that both animals were concomitantly infected by H. somni and OvGHV2 and developed the septicemic and encephalitic manifestations of H. somni. Furthermore, the interstitial pneumonia observed in cow #2 was more likely associated with infection by OvGHV2.

Adaptive sampling during sequencing reveals the origins of the bovine reproductive tract microbiome across reproductive stages and sexes

Cattle enterprises are one of the major livestock production systems globally and are forecasted to have stable growth in the next decade. To facilitate sustainable live weight production, optimal reproductive performance is essential. Microbial colonisation in the reproductive tract has been demonstrated as one of the factors contributing to bovine reproductive performance. Studies also implied that reproductive metagenomes are different at each stage of the estrous cycle. This study applied Oxford Nanopore Technologies’ adaptive long-read sequencing to profile the bovine reproductive microbiome collected from tropical cattle in northern Queensland, Australia. The microbiome samples were collected from cattle of different sexes, reproductive status and locations to provide a comprehensive view of the bovine reproductive microbiome in northern Australian cattle. Ascomycota, Firmicutes and Proteobacteria were abundant phyla identified in the bovine reproductive metagenomes of Australian cattle regardless of sexes, reproductive status and location. The species level taxonomical investigation suggested that gastrointestinal metagenome and the surrounding environment were potentially the origins of the bovine reproductive metagenome. Functional profiles further affirmed this implication, revealing that the reproductive metagenomes of the prepubertal and postpartum animals were dominated by microorganisms that catabolise dietary polysaccharides as an energy substrate while that of the pregnant animals had the function of harvesting energy from aromatic compounds. Bovine reproductive metagenome investigations can be employed to trace the origins of abnormal metagenomes, which is beneficial for disease prevention and control. Additionally, our results demonstrated different reproductive metagenome diversities between cattle from two different locations. The variation in diversity within one location can serve as the indicator of abnormal reproductive metagenome, but between locations inferences cannot be made. We suggest establishing localised metagenomic indices that can be used to infer abnormal reproductive metagenomes which contribute to abortion or sub-fertility.

Bovine respiratory disease in Brasil: a short review

The bovine respiratory disease (BRD) complex is a multifactorial and multietiological disease entity described in all geographic regions of Brazil. This brief review discusses aspects related to epidemiology, etiologic agents, clinical and pathological manifestations, and challenges in the diagnosis of BRD in Brazil. The main infectious disease agents associated with respiratory outbreaks in cattle from Brazil are bovine alphaherpesvirus type 1, bovine viral diarrhea virus, bovine respiratory syncytial virus, and Mycoplasma bovis. Ovine gammaherpesvirus-2 and HoBi-like pestivirus have been associated with the development of pneumonia in adult cattle and calves, respectively in Brazil, and should be considered as possible causes of BRD. Additionally, studies using epidemiological data, histopathological and molecular associations with morbidity and mortality should be carried out in Brazil, to demonstrate the real impacts of BRD on livestock.

Histophilus somni-induced thrombotic meningoencephalitis in cattle from northern Paraná, Brazil

Thrombotic meningoencephalitis (TME) is a fatal neurological disease of cattle, predominantly from North America, that is caused by Histophilus somniwith 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.

Association of Histophilus somni with spontaneous abortions in dairy cattle herds from Brazil

This study investigated the participation of infectious agents in spontaneous abortions and reproductive problems at eight dairy cattle herds from three geographical regions of Brazil. Fourteen aborted fetuses and the organ sections of one cow with history of repeated abortions were received for pathological evaluations and molecular diagnostics. PCR/RT-PCR assays targeted specific genes of abortifacient agents of cattle: bovine viral diarrhea virus (BVDV), bovine herpesvirus 1 (BoHV-1), Listeria monocytogenes, Neospora caninum, Leptospira spp., Brucella abortus, and Histophilus somni. Six fetuses were adequate for pathological investigations; one of these did not demonstrate remarkable pathological alterations. Significant histopathological findings included vasculitis, hemorrhage, and fibrinous thrombosis of the cerebrum (n = 4); necrotizing myocarditis (n = 3); and hemorrhagic enteritis (n = 3). The placenta and uterus of the cow as well as the kidney, pancreas, and liver of her aborted fetus contained H. somni DNA and demonstrated histopathological evidence of histophilosis. All fetuses contained H. somni DNA in multiple organs. Coinfections of H. somni with B. abortus (n = 2), N. caninum (n = 2), BVDV (n = 1), and BoHV-1 (n = 1) were identified; two fetuses demonstrated three pathogens. These findings suggest that H. somni was associated with the spontaneous abortions and reproductive problems of these herds. However, the exact cause of fetal death might not be attributed only to H. somni in all aborted fetuses, since some of these were infected with other abortifacient agents.

Aerosol infection of calves with Histophilus somni

The purpose of this study was to develop and evaluate an aerosol infection method with Histophilus somni that closely resembles the natural way of infection of calves. Another aim was to compare the virulence of two H. somni strains by collecting clinical and postmortem data of experimentally infected and control animals. Seventeen conventionally reared 3-month-old calves were divided into three groups. Two groups of six animals each were exposed to suspensions containing H. somni on three consecutive days using a vaporiser mask. The third group of five animals was used as control. The data of individual clinical examination were recorded daily. All animals were exterminated, and gross pathology of all lungs was evaluated on the 15th day after the first infection. Both H. somni strains caused an increase of rectal temperature, respiratory signs, decrease of weight gain, and severe catarrhal bronchopneumonia in both infected groups. Although some chronic lesions were detected in the lungs of the control animals as well, the histopathological findings in the infected and control groups were different. H. somni was recultured from all lungs in the challenged groups but it could not be reisolated or detected by PCR examination in the control group. This is the first paper on aerosol challenge of calves with H. somni using repeated infection and verified by detailed pathological, bacteriological and histopathological examination. The infection method proved to be successful. There was no difference in the virulence of the two H. somni strains used in the trial.

Haemophilus somnus bronchopneumonia in American bison (Bison bison)

Immunoperoxidase assays were performed on 21 archived formalin-fixed, paraffin-embedded tissues from from American bison (Bison bison) with bronchopneumonia. Seven of the 21 bison had positive staining for Haemophilus somnus in alveolar exudate, visceral pleura, lung parenchyma, and chronic necrotic lesions, and H. somnus was isolated from tissues from 1 of these 7 animals. Results suggest that H. somnus is a respiratory pathogen in bison.

Pathological, immunocytochemical and microbiological findings in calf pneumonias associated with Haemophilus somnus infection

Pathological, immunocytochemical and microbiological findings in 32 cases of calf pneumonia associated with Haemophilus somnus infection are described. The majority of cases were "found dead" or died after a sudden onset pneumonia of less than 24 h duration. Lesions of exudative bronchopneumonia were present and the cases could be divided into two main groups on the basis of histopathological and immunocytochemical features. In group A, cases were dominated by necrotizing bronchiolitis, degeneration and necrosis of airway and alveolar exudates, severe alveolitis with accumulations of degenerate basophilic cells, interstitial inflammatory changes and the widespread distribution of H. somnus antigen in airways and alveoli. In Group B, necrotizing and degenerative changes were much less extensive and less severe and the overall appearance was of suppurative bronchopneumonia with H. somnus antigen much less widespread within the lungs. Alveolar oedema, hyaline membrane formation and alveolar epithelial hyperplasia were present in caudodorsal lung areas of several calves. No major differences were seen between the histopathology of lungs where H. somnus was the sole isolate and that of lungs where H. somnus was isolated along with other bacterial pathogens.

Protective ability of antibodies against 78- and 40-kilodalton outer membrane antigens of Haemophilus somnus

The ability of concentrated antibody against the 78- or 40-kilodalton (kDa) outer membrane protein (OMP) of Haemophilus somnus to passively protect calves against H. somnus-induced pneumonia was determined. The 78- and 40-kDa OMPs were evaluated in passive protection experiments, because results of previous studies demonstrated their (i) immunogenicity for cattle, (ii) intense reactivity with convalescent-phase sera which passively protected calves against experimental H. somnus pneumonia, (iii) surface location and accessibility to antibody, and (iv) conservation among a wide range of H. somnus isolates obtained from animals with different diseases and from different geographic locations. The specificity of the two antisera evaluated in this study was verified by (i) immunoblots in which reactivity against the 78- or 40-kDa OMP was present in postimmunization but not preimmunization serum and (ii) immunoblots in which affinity-purified, surface-reactive antibodies in each antisera were used, which demonstrated that essentially only antibody to the 78- or 40-kDa OMP was reactive with the surface of H. somnus. In enzyme-linked immunosorbent assays, the antiserum against the 40-kDa OMP contained immunoglobulin G1 (IgG1), IgG2, and IgM against H. somnus, while the antiserum against the 78-kDa OMP contained IgG1 and IgM but no IgG2 against H. somnus. The antiserum against the 40-kDa OMP contained IgG1 and IgG2 specific for the 40-kDa OMP, as determined by Western blot analysis. Slight reactivity against H. somnus lipopolysaccharide was detected by enzyme-linked immunosorbent assay but not by Western blot analysis. In passive protection experiments, preincubation of bacteria with antibody against the 40-kDa OMP protected calves (P less than 0.025) against H. somnus pneumonia, while antibody against the 78-kDa OMP failed to protect calves against H. somnus pneumonia. Determination of the potential protective capacity of the 78-kDa OMP awaits resolution of the role of anti-78-kDa IgG2 in protection against H. somnus pneumonia. The 40-kDa OMP is, however, a good candidate antigen for evaluation of protective ability against H. somnus pneumonia following active immunization.

Experimental bovine respiratory tract disease with Haemophilus somnus

Eight calves were inoculated into the bronchus with H. somnus. Thirteen calves were inoculated with bovine respiratory syncytial virus (BRSV) and 8 days later with H. somnus. All calves developed necrotizing, suppurative, lobular bronchopneumonia and pleuritis. Clinical signs of disease and pneumonic lesions were significantly more severe in calves that were sequentially inoculated with BRSV followed by H. somnus. Pneumonic lesions in the inoculated calves were similar to those described for naturally occurring H. somnus-associated respiratory tract disease. Control calves inoculated with BRSV alone or sham-inoculated with medium did not develop clinical signs of respiratory tract disease. The BRSV-inoculated control calves developed minimal pneumonic lesions.