ISSN 2398-2993      

Histophilus somni infection

obovis
Contributor(s):

Mike Reynolds

Paul Wood

Royal Dick School Veterinary Studies logo

Synonym(s): Hemophilosis


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.

Pathogenesis

Etiology

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.

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. The veterinary journal (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. The veterinary journal (203), 239–243 PubMed.
  • Wilkins P A & Woolums A R (2015) Diseases of the Respiratory System. In: Smith B P Large Animal Internal Medicine. 5th edn. Elsevier, St. Louis. pp 597-599.
  • 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. Veterinary record (160), 600 PubMed.
  • Wessels J & Wessels M E (2005) Histophilus somni myocarditis in a beef rearing calf in the United Kingdom. Veterinary record (157), 420-421 PubMed.

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