ISSN 2398-2977      

Getah virus disease

pequis

Introduction

  • Cause: Getah virus   Getah virus  , an arthropod-borne virus (arbovirus) that affects horses and pigs. First isolated from the mosquitoCulex gelidusin Malaysia in 1955. 
  • Disease associated with Getah virus infection was first reported in horses in 1978 in Japan.
  • Signs: infrequent, widespread occurrences of fever, dependent hindlimb edema and urticaria in horses with relatively high morbidity but no mortality.
  • Outbreaks of clinical disease in horses are uncommon, and only one has occurred outside Japan, in India in 1990.
  • No evidence of virus transmission to humans, even in individuals in contact with affected horses.
  • Diagnosis: serology, virus isolation, RT-PCR assay.
  • Treatment: supportive therapy.
  • Prognosis: excellent.

Pathogenesis

Etiology

  • Getah virus   Getah virus  , an arbovirus (arthropod-borne).
  • Family: Togaviridae.
  • Genus:Alphavirus.
  • The virus has three recognized subtypes:
    • Ross River.
    • Bebaru.
    • Sagiyama.

Predisposing factors

General
  • Not reported.
  • Since the disease has been reported in Thoroughbred racehorses it may be predisposed to by management factors, eg the stress of training.

Specific

  • As disease is primarily vector-borne areas of high mosquito activity enhance the risk of transmission of the virus.

Pathophysiology

  • Virus attached to cells via its lipid envelope.
  • Replicates in the cell cytoplasm.

Timecourse

  • Pyrexia develops 23 days after infection.
  • Viremia is present for 15 days post-infection.
  • Hindlimb edema develops on days 24.
  • Urticaria develops by day 78.
  • Each sign resolves 23 days after its appearance.
  • Virus neutralizing antibodies appear within 2 weeks.
  • Most affected horses recover fully within 12 weeks.

Epidemiology

  • Getahvirus is responsible for infrequent, widespread outbreaks in horses, particularly among racehorses in Japan. Antibodies have been found in healthy horses.
  • Transmission between horses is slow, but eventually led to ~40% morbidity in one reported outbreak.
  • CulexandAedesmosquitos are the primary vectors of the virus.
  • Transmission between horses is mainly by mosquitoes, but aerosol spread from nasal secretions is also thought to occur.
  • Antibodies have been found in many species, including healthy humans. Cattle, chickens and wild birds may possibly play a role in maintenance and transmission.
  • The pig is the most significant vertebrate host because it is kept in large numbers in virus endemic regions and it develops a viremia of significant magnitude and duration for it to act as an amplifying host of the virus.
  • Pigs are thought to be the reservoir for infection of mosquitoes and may act as virus amplifiers. They develop high titered viremia, but the virus is only mildly pathogenic in this species, causing occasional reproductive problems, including abortion and neonatal disease.
  • The virus is maintained year-round in tropical regions of Asia by continuously cycling between pigs and mosquitoes.
  • The mechanism of persistence in temperate regions is unclear, but may involve overwintering of infected mosquitoes or transovarial transmission in the vector. Alternatively, the virus may be reintroduced periodically.

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.
  • Fukunaga Y, Kumanomido T & Kamada M (2000) Getah virus as an equine pathogen. Vet Clin N Am Eqine Pract 16 (3), 605617 PubMed.
  • Brown C M & Timoney P J (1998) Getah Virus Infection of Indian Horses. Trop Anim Health & Prod 30, 241-252 PubMed.
  • Kamada M, Kumanomido T, Wada R et al (1991) Intranasal infection of Getah virus in experimental horses. J Vet Med Sci 53, 855-858 PubMed.
  • Kamada M, Wada R, Kumanomido T et al (1991) Effect of viral inoculation size on appearance of clinical signs in equine Getah virus infection. J Vet Med Sci 53, 803-806 PubMed.
  • Shibata I, Hatano Y, Nishimura M, Suzuki G & Inaba Y (1991) Isolation of Getah virus from dead fetuses extracted from a naturally infected sow in Japan. Vet Microbiol 27, 385-391 PubMed.
  • Morita K & Igarashi A (1984) Oligonucleotide finerprinting analysis of strains of Getah virus isolated in Japan and Malaysia. J Gen Virol 65, 1899-1908 PubMed.
  • Fukunaga Y, Ando Y, Kamada M et al (1981) An outbreak of Getah virus infection in horses clinical and epizootic aspects at the Miho Training Center in 1978. Bull Eq Res Inst (Japan) 18, 94-102 VetMedResource.
  • Imagawa H, Ando Y, Kamada M et al (1981) Sero-epizootiological survey on Getah virus infection in light horses in Japan. Jpn J Vet Sci 43, 797-802 PubMed.
  • Akiyama Y (1980) Getah virus infection among horses. J Jpn Vet Med Assoc 33, 567-581.
  • Kamada M, Ando Y, Fukunaga Y et al (1980) Equine Getah virus infection: isolation of the virus from racehorses during an enzootic in Japan. Am J Trop Med Hyg 29, 984-988 PubMed.
  • Sentsui H & Kono Y (1980) An epidemic of Getah virus infection among racehorses: isolation of the virus. Res Vet Sci 29, 157-161 PubMed.

Other sources of information

  • Calisher C H & Walton T E (1996) Getah Virus Infections. In: Virus Infections of Vertebrates. Vol 6; Infections of Equines. Ed: Studdert M J. Elsevier. pp 356. ISBN: 0444825274.

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