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Histophilus somni infection
Synonym(s): thromboembolic meningoencephalitis, Pneumonia, haemophilus somnus haemophilosis, bovine respiratory disease (BRD), pneumonia, conjunctivitis, laryngitis
Introduction
- Cause: Histophilus somni is a gram-negative aerobic bacteria of the family Pasteurellaceae. It is a bacterial commensal of mucus membranes of the bovine nasopharyngeal, lower respiratory and reproductive tracts.
- Signs: see below.
- Diagnosis: predominant or pure bacterial aerobic culture of trans-tracheal (TTA) or BronchoAlveolar Lavage (BAL), serum antibodies, immunohistochemistry.
- Treatment: antimicrobial agents and anti-inflammatory drugs.
- Prognosis: poor in chronic or advanced cases.
Geographic incidence
- Worldwide.
Age predisposition
- None.
Public health considerations
- None.
Cost considerations
- Morbidity and mortality can be high in disease outbreaks.
Special risks
- Respiratory compromise.
Pathogenesis
Etiology
- Histophilus somni is a gram-negative bacterial commensal of the bovine nasopharyngeal, lower respiratory and reproductive tract.
- It is a widely reported component of the bovine respiratory disease (BRD) complex Calf respiratory disease: overview Adult respiratory disease: overview.
Predisposing factors
General
- Physiological stress, for example, weaning events, recent animal movements, disbudding/dehorning Disbudding and dehorning cattle, mixing of multi-sourced animals or viral incursion may all precipitate a respiratory disease outbreak.
Specific
- Episodes of physiological stress, concurrent BRD pathogen infection, for example, a synergism between Histophilus somni and bovine respiratory syncytial virus (BRSV) Bovine respiratory syncytial virus, has been reported.
- Housing/environmental conditions which increase aerosol challenge of infective agents and predispose animals to adverse physical conditions; such as poor air quality, increased dust and fluctuations in temperature and humidity may all contribute to disease incidence Ventilation in cattle housing.
Pathophysiology
- Histophilus somni strains differ in their ability to induce BRD in calves and may be found commensally in the genital and respiratory tracts.
- Respiratory outbreaks are thought to proceed the other manifestations of disease by weeks or months.
- Histophilus somni possess virulence factors which aid colonisation of the airways, evasion of the host defense mechanisms and may confer resistance to antimicrobial therapy. These include a lipooligosaccharide responsible for mediating endothelial cell apoptosis. Immunoglobulin binding proteins which help evade the host’s immune system, histamine which contributes to tissue inflammation and a biofilm which helps confer antimicrobial and immune system resistance.
- The ability of Histophilus somni to adhere to endothelial cells allows the activation of platelets and thrombus formation.
Timecourse
- Hours to days.
Epidemiology
- Exposure to Histophilus somni is common, with 25% to 100% of cattle having serum antibodies.
- Disease outbreaks are normally associated with a period of physiological stress or poor environmental conditions.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed Papers
- Recent references from PubMed and VetMedResource.
- Murray G M, O’Neill R G, More S J, McElroy M C, Earley B & Cassidy J P (2016) Evolving views on bovine respiratory disease: An appraisal of selected key pathogens – Part 1. Vet J 217, 95–102 PubMed.
- Goldspink L K, Mollinger J L, Barnes T S, Groves M, Mahony T J & Gibson J S (2015) Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia. Vet J 203, 239–243 PubMed.
- Panciera R J & Confer A W (2010) Pathogenesis and pathology of bovine pneumonia. Vet Clin Food Anim 26, 191–214 VetMedResource.
- Scott P R (2010) Bovine respiratory disease - the importance of veterinary involvement. Cattle Practice 18, 159-162.
- Van der Burgt G, Clark W & Knight R (2007) Cattle fertility problems and Histophilus somni. Vet Rec 160, 600 PubMed.
- Wessels J & Wessels M E (2005) Histophilus somni myocarditis in a beef rearing calf in the United Kingdom. Vet Rec 157, 420-421 PubMed.
- Oliver et al (2022) Bovine thrombotic meningoencephalitis Cattle Quarterly Autumn Edition pp4-5 BCVA
Other sources of information
- Wilkins P A & Woolums A R (2015) Diseases of the Respiratory System. In: Large Animal Internal Medicine. Ed: Smith B P. 5th edn. Elsevier, USA pp 597-599.
- APHA Disease surveillance (2023) Disease surveillance in England and Wales, March 2023 Vet Rec 192 (7) p281