ISSN 2398-2993      

Winter dysentery

obovis
Contributor(s):

Tracy Anderton

Mike Reynolds

Synonym(s): Bovine Coronavirus


Introduction

  • Cause: Bovine Corona Virus (BCoV).
  • Signs: acute, explosive diarrhea in 50 – 90 % adult herd.
  • Diagnosis: clinical signs and exclusion of other causes of diarrhea in adult cows.
  • Treatment: self-limiting, supportive therapy.
  • Prognosis: good, low mortality.

Pathogenesis

Etiology

  • Caused by Bovine Corona Virus Bovine Corona Virus (BCoV).
    • 1 single serotype.
    • Also responsible for diarrhea in calves <3weeks old and mild respiratory disease in 2-6 month old calves.
    • Recently linked to BRD Bovine respiratory disease in older animals too.
  • Virus can cycle around cattle of all ages.
  • Most adult cattle are seropositive to bovine coronavirus.

Predisposing factors

General

  • Predominantly a winter disease.
  • Cattle in close confinement, poor ventilation.
Suspected concurrent risk factors include:
  • Changes in diet due to a shift in rumen microbial population which allows pathogens to colonise the rumen and lower gut Rumen function.
  • Presence of other microorganisms, eg Bovine Viral Diarrhea Virus Bovine Viral Diarrhea Virus (BVDv) due to a lowering of the cow’s immunity.

Specific

  • BCoV survive well in low temperatures, low ultra-violet light, ie winter.
  • Virus can build up during the colder months.

Pathophysiology

  • Fecal-oral transmission.
  • Possible respiratory transmission from respiratory secretions of clinical cases. 
  • Small intestine and colon are target site for BCoV.
  • Voluminous diarrhea produced as a result of hypersecretion caused by inflammatory mediators.
  • Destruction of epithelial cells in colonic crypts.
  • Transudation of extracellular fluid and blood -> hemorrhagic diarrhea.

Timecourse

  • Short disease course – typically 2-3 days.
  • Animals infected within 2-3 days of coming in contact with infected feces.
  • Disease in herd subsides in 1 – 2 weeks.
  • Milk yield takes longer to return to normal levels, may be months.

Epidemiology

  • High morbidity (20 – 100%), low mortality (1-2%).
  • Recovery within a few days is typical. 
  • Cows are infected via the fecal-oral route by ingestion of infected feces from clinical cases or carrier animals.
  • Highly contagious – animals show clinical signs within a few days of being in contact with an infected animal. Infected animals shed virus for 4 – 5 days.
  • Possible infection from visitors/fomites.
  • A similar winter dysentery has been seen in wild ruminants (deer, elk) which may provide a reservoir for infection.

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 VetMed Resource.
  • Smyth J A, Adour B M & Benko M (1997) Cattle Practice. 5 (3) pp 213. 

Other sources of information

  • Gruenberg W. Intestinal Diseases in Cattle – Digestive System. MSD Vet Manual (Merck) [online] Available at: www.msdvetmanual.com.

Organisation(s)

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