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Rabies virus

obovis

Synonym(s): Lyssavirus


Introduction

Classification

Taxonomy

  • FamilyRhabdoviridae.
  • SubgroupLyssavirus - there are 16 different viral species of lyssavirus classified according to their genome sequence.

Etymology

  • Gk: rhabdos - rod; refers to the shape of the virus. Often described as bullet-shaped.
  • Lyssa - rage, fury.

Active Forms

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Clinical Effects

Epidemiology

Habitat

  • Particular reservoir species, usually a carnivore, important in each endemic region. Bats are implicated in many countries.

Lifecycle

  • Bite of rabid animal carrying virus in saliva → persists and replicate in local muscle tissue → enters and spreads in peripheral nerve cell axons → replication in spinal cord → spreads to brain → non-purulent polioencephalomyelitis with perivascular cuffing. From the brain, it spreads down nerves to salivary glands where virus is shed.

Transmission

  • Saliva: bites from infected animals.
  • Aerosol spread occurs uncommonly where the virus is high in concentration, as in caves populated by infected bats.
  • Transmission via blood is possible.
  • May be transmitted via open wound or mucous membrane.
  • Incubation period is widely variable from weeks to years depending on extent of tissue damage by and location of bite wound. OIE officially recognizes the incubation period as 6 months for the purpose of the Terrestrial Animal Health Code.

Pathological effects

  • In cattle, rabies usually manifests as excessive salivation, behavioral changes, muzzle tremors, vocalization (bellowing), appearance of choking (dysphagia), aggression or depression, hyperesthesia and/or hyperexcitability, paralysis of body parts (ear droop, limb paralysis, etc), pharyngeal paralysis and straining.
  • Death usually occurs within 1 week of clinical signs.
  • For further information on clinical rabies see Rabies.

Control

Control via animal

  • Prevention of rabies in cattle is challenging and control programs vary between countries.
Vets are advised to liaise with their local government veterinary advisor at the earliest opportunity if rabies is suspected.
  • Wildlife control should be considered (raccoons, etc) and steps taken to minimize wildlife access to feedstores, etc.
  • Elimination of stray dogs and cats and immunization of all mammalian pets and horses with inactivated vaccine or recombinant canarypox vectored vaccines to control urban rabies should be considered in countries where rabies is endemic.

Vaccination

  • A variety of vaccines are available (inactivated nervous tissue, modified live tissue culture, and modified live chicken embryo origin) but the choice of vaccine used varies between localities and species. However, these vaccines are prohibitively expensive for many farms.
  • Vaccination results in circulating neutralizing antibodies within 3 weeks.
  • T and B lymphocyte responses necessary for clearance.
  • Immune response from vaccination can prevent rabies, but response to natural infection does not aid in recovery.
In the UK, permission is needed from DEFRA prior to administration of a rabies vaccine and there must be a specific reason for its use.
  • Oral immunization of wildlife in some European countries and the USA has been successful.

Diagnosis

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Bassuino D M, Konradt G, Cruz R A et al (2016) Characterization of spinal cord lesions in cattle and horses with rabies: the importance of correct sampling. J Vet Diagn Invest 28 (4), 455-460 PubMed.
  • Harvey A M, Watson J L, Brault S A et al (2016) Duration of serum antibody response to rabies vaccination in horses. JAVMA 249 (4), 411-418 PubMed.
  • Green S L (1997) Rabies. Vet Clin North Am Equine Pract 13 (1), 1-11 PubMed.
  • Hudson L V, Weinstock D, Jordan T & Bold-Fletcher N O (1996) Clinical Features of Experimentally Induced Rabies in Cattle and Sheep. Zoonoses & Public Health 43 (1-20), 85-95 WileyOnline.

Other sources of information

  • Department for Environment Food & Rural Affairs (2018) Rabies Control Strategy for Great Britain. Website: https://assets.publishing.service.gov.uk.
  • Whittier W D (2006) Rabies in Cattle a Continual Threat in Virginia. Livestock Update Virginia State University. Website: www.sites.ext.vt.edu
  • Rupprecht C E (1996) Rhabdoviruses: Rabies Virus. In: Medical Microbiology. 4th edn. Ed: Baron S. Website: www.ncbi.nlm.nih.gov.
  • Dierks R E (1981) Disease of Cattle in the Tropics. In: Current Topics in Veterinary Medicine and Animal Science. Springer, Dordrecht. pp 107-121. DOI.
  • World Health Organization (WHO) Epidemiology and Burden of Disease. Website: www.who.int.
  • World Organisation for Animal Health (OIE) Terrestrial Animal Health Code. Website: www.oie.int.
  • World Organisation for Animal Health (OIE) Rabies (Infection with Rabies Virus and Other LyssavirusesWebsite: www.oie.int (pdf online).

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