Bovis ISSN 2398-2993

Bovine viral diarrhea virus: the virus

Synonym(s): diarrhea

Contributor(s): Tammy Hassel, Veronica Fowler

Introduction

Classification

Taxonomy

  • Family: flaviviridae.
  • Genus: pestivirus.
  • Species: Bovine viral diarrhea virus (BVDV).
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Clinical Effects

Epidemiology

Transmission

  • BVDV is transmitted by both the vertical (mother to fetus) and horizontal (animal to animal) routes.
  • A major source of BVD infection is when a pregnant animal becomes infected with BVDV which crosses the placenta and infects the developing fetus (vertical transmission).
  • Many fetuses however survive to term. Some suffer birth defects of the nervous system and eyes and have reduced development, but most are apparently normal. 
  • Surviving calves will be persistently infected (PI) with the virus as, due to exposure to the immature immune system, it is recognized by the animals immune system as ‘self’ and no immune response is generated.
  • PI calves are persistently viraemic (virus present in the bloodstream) and excrete the virus which can be rapidly transmitted to other cattle in close contact, either through aerosols or by oral ingestion of infectious particles. Virus is excreted in nasal discharge, saliva, semen, urine, tears, milk, and feces.
  • The disease can also be transferred by fomites; objects and materials that become exposed to the virus and can transfer it from place to place (equipment, boots, etc.).
  • Horizontal transmission leads to acute disease.
  • In persistently infected cattle conversion of the non-cytopathogenic biotype of BVDV to the cytopathogenic biotype results in the development of mucosal disease.

Pathological effects

  • In animals that are not pregnant, the symptoms of acute BVD infection are normally mild and may consist of depression, anorexia, occulo-nasal discharge, decreased milk production and oral lesions.  BVDV infection also has an immunosuppressive effect which may lead to secondary bacterial infections such as pneumonia caused by Mannheimia haemolytica Mannheimia haemolytica.
  •  Acute infection in pregnant animals elicits the same symptoms as described above for non-pregnant animals but the virus is able to cross the placenta and infect the developing fetus:
    • If the infection occurs at or around the time of insemination increased levels of infertility or death of the embryo may occur. 
    • Infection with BVDV between 100-150 days following gestation may result in teratogenic effects on the developing fetus. Such congenital defects can include brain damage and cataracts.
    • An additional effect of infection before 120 days is that calves become persistently infected with the virus.
  • Persistently infected calves are often weak or stunted and suffer from immunosuppression which can predispose the calf to acquire other infectious diseases and exacerbates the symptoms of these diseases, eg scour and pneumonia. PI calves may develop mucosal disease between 6 and 18 months of age:
    • Mucosal lesions in the mouth.
    • Diarrhea.
    • Ulcerations of the muzzle, the nose, the rim of the hoof and the interdigital cleft.
    • Lesions in the gut lymphoid tissues.
    • In most cases the disease is fatal within 2-3 weeks.

Control

Control via animal

  • Biosecurity control strategies for BVDV should centre on:
    • Only purchasing cattle from BVDV accredited herds.
    • If buying in cattle from non BVDV accredited herds, animals should be tested and isolated before introducing to herd.
    • If the biosecurity barrier Biosecurity is breached and BVDV infection is present the priority should be to isolate infected and exposed animals in order to prevent further transmission.

Control via chemotherapies

  • There is no treatment for BVDV infection itself. In acutely infected animals secondary infections are treated, as required.

Control via environment

  • In order to prevent fomite transmission equipment, footwear and any other materials which may have come into contact with BVDV infected animals should be appropriately disinfected.

Vaccination

  • Three inactivated BVD vaccines are available in UK. Initial vaccination comprises two doses 3-4 weeks apart before first service followed by booster vaccination at 6 or 12 months’ intervals. 
  • In 2015 a modified live virus vaccine was authorised for use in the UK. This vaccine requires a single dose and gives longer lasting immunity than the inactivated vaccine.

Diagnosis

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Pinior B, Firth C L, Richter V, Lebl K, Trauffler M, Dzieciol M, Hutter S E, Burgstaller J, Obritzhauser W, Winter P & Käsbohrer A (2017) A systematic review of financial and economic assessments of bovine viral diarrhea virus (BVDV) prevention and mitigation activities worldwide. Prev Vet Med 137, 77-92 PubMed.
  • Duncan A J, Gunn G J & Humphry R W (2016) Difficulties arising from the variety of
    testing schemes used for bovine viral diarrhoea virus (BVDV).
    Vet Rec 178 (12), 292 PubMed.
  • Givens M D & Newcomer B W (2015) Perspective on BVDV control programs. Anim Health Res
    Rev
    16 (1), 78-82 PubMed.
  • Ståhl K & Alenius S (2012) BVDV control and eradication in Europe--an update. Jpn J Vet Res PubMed.
  • Bratcher C L, Wilborn B S, Finegan H M, Rodning S P, Galik P K, Riddell K P, Marley M S, Zhang Y, Bell L N & Givens M D (2012) Inactivation at various temperatures of bovine viral diarrhea virus in beef derived from persistently infected cattle. J Anim Sci 90 (2),635-41 PubMed.
  • Stevens E, Thomson D, Wileman B, O’Dell S & Chase C (2011) The Survival of Bovine Viral Diarrhea Virus on Materials Associated with Livestock Production. The Bovine Practitioner 45 (2), 118-123.
  • Lindberg A, Brownlie J, Gunn G J, Houe H, Moennig V, Saatkamp H W, Sandvik T & Valle P S (2006) The control of bovine viral diarrhoea virus in Europe: today and in the future. Rev Sci Tech 25 (3), 961-79 PubMed.

Other sources

  • Talk by Professor Joe Brownlie at WBC 2018, Sapporo. Japan.

Organisation(s)


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