Equis ISSN 2398-2977

Hendra virus disease

Synonym(s): Acute equine respiratory syndrome

Contributor(s): Graham Munroe, Vetstream Ltd

Introduction

  • Cause: Hendra virus (formerly Morbillivirus).
  • Signs: sudden death, shallow respirations, sweating, fever, nasal discharge - may be voluminous and frothy.
  • Diagnosis: virus isolation from tissue culture.
  • Treatment: none known; quarantine recommended.
  • Prognosis: grave.

Pathogenesis

Etiology

  • Hendra virus Hendra virus belonging to the genusHenipavirus in Paramyxoviridae.
  • Fruit bats (flying foxes)/Pteropus spp are suspected carriers of the virus. Virus is found in saliva, urine, and feces of infected bats. Clinical disease has not been noted in these species
  • Infection of horses is likely to occur from ingestion of contaminated fomites or pasture. Commonly sporadic, involving only a single horse within a group.

Predisposing factors

General
  • Geography - Queensland, Australia.

Pathophysiology

  • Initial viral replication in upper respiratory tract followed by viremia and systemic spread. The primary lesions are associated with vasculitis of smaller vessels in many tissues.
  • Capillary endothelium is damaged by the virus →  edema, fibrinous exudate and hemorrhage.
  • In the lungs: subpleural edema → acute interstitial pneumonia → consolidation of lungs.
  • Petechial hemorrhages → vascular lesions in many organs.
  • CNS edema → encephalitis. 

Timecourse

  • Incubation period 3-10 days, some report incubation periods as long as 2 weeks.
  • Death 1-3 days after onset of clinical signs.

Epidemiology

  • Seroconversion has been demonstrated in fruit bats excreting live virus in their urine, saliva and feces for approximately 1 week post-infection.
  • Virus has also been isolated from uterine fluid and fetal tissues of infected fruit bats.
  • The most likely route of infection in horses is ingestion of contaminated pasture or feed. 
  • Fourteen major outbreaks have been reported prior to 2011, with >70% mortality.
  • Five of these outbreaks involved humans, with 4 out of 7 cases dying; 3 of 7 cases were veterinarians.
  • In 2011 and 2012, 26 cases in horses occurred; the first field infection of a dog was noted.
  • Horses are considered potentially infectious from 72 h prior to the onest of disease until their death and the safe disposal of their carcass.
  • Virus is found in blood and secretions/body fluids of infected horses; attack rates for transmission has been estimated at 10% with a case fatality rate of 57%.

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.
  • Middleton D (2014) Hendra Virus. Vet Clin North America Equine Pract 30 (3), 579-589 PubMed.
  • Hess I M R et al (2011) Hendra virus: what do we know? NSW Public Health Bull 22 (5-6), 118-122 PubMed.
  • Hooper P T & Williamson M M (2000) Hendra and Nipah virus infections. Vet Clin North Am Equine Pract 16 (3), 597-603 PubMed.
  • Westbury H A (2000) Hendra virus disease in horses. Rev Sci Tech 19 (1), 151-159 PubMed.
  • Barclay A J & Paton D J (2000) Hendra (equine morbillivirus). Vet J 160 (3), 169-176 PubMed.
  • Williamson M Met al (1998) Transmission studies of Hendra virus (equine morbillivirus) in fruit bats, horses and cats. Aust Vet J 76 (12), 813-818 PubMed.

Other sources of information

  • Biosecurity Queensland (2011) Guidelines for Veterinarians Handling Potential Hendra Virus Infection in Horses. Version 4.1. Department of Employment, Economic Development and Innovation, Queensland Government. Website: www.dpi.qld.gov.au/4790_13371.htm.
  • Primary Industries and Fisheries, Queensland Government (2011) Hendra Virus. Website: www.dpi.qld.gov.au/4790_2900.htm.
  • Hodgson D R & Hodgson J L (1997) Acute equine respiratory syndrome. In: Current Therapy in Equine Medicine. Ed: N E Robinson. ISBN: 0-7216-2633-5.


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