Bovis ISSN 2398-2993

Bluetongue

Synonym(s): orbivirus stomatitis rhinitis

Contributor(s): Belal Hossain , Jo Oultram

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Introduction

  • Bluetongue is an infectious viral disease. 
  • It is transmitted by adult female Culicoides spp (biting midges). 
  • Bluetongue can affect domestic and wild ruminants.
    • It can also affect camelids and other herbivores. 
  • The disease causes severe facial swelling, mortality, decreased production, affects fertility and places economic strain on producers. 
Bluetongue is a notifiable disease in many countries, including the UK.
  • Cause: bluetongue virus is a genre of genus Orbivirus in the family Reoviridae.
  • Diagnosis: clinical and pathological findings. Tests include: 
    • C-ELISA.
    • PCR. 
    • Isolation of the virus through inoculating an embryonated chicken egg with sub passage onto cell culture.
  • Treatment: no specific treatments other than supportive care. 
  • Prognosis: poor.

Pathogenesis

Etiology

Pathogenesis

  • There are quite similar pattern of pathogenesis in the host body but the magnitude of illness may vary from species to species.
  • The virus gain entry to regional lymph nodes, following cutaneous instillation (through inoculation or biting of the virus affected vectors) to the host body. 
  • The virus disperses to the mononuclear phagocytic cells, endothelial cells, lymphocytes and different parts of the body. 
  • The virus is closely associated with endothelial cell and with erythrocytes during the course of infection. 
  • Severe to moderate vascular endothelial damage resulting in changes to capillary permeability and fragility, with subsequent disseminated intravascular coagulation and necrosis of tissues supplied by damaged capillaries.
  • Infection in ruminants is prolonged and circulates for several weeks with a concurrent high titre of neutralizing antibody.
  • In cattle, clinical disease is thought to be a hypersensitivity reaction.
  • Bluetongue virus Bluetongue virus (BTV) has been shown to be an abortifacient and is teratogenic.
  • After transmission of BTV under natural and experimental conditions, the consequences of vertical transmission in pregnant cattle are variable.
    • Factors that influence reproductive consequences are the stage of gestation, characteristics of the virus, source and concentration of virus inoculum, placentation, season and the method and route of infection.
    • Reproductive consequences vary greatly in degree but in general include infertility, abortion, mummification of the fetus, stillbirths and congenital anomalies. 
  • Immunological unresponsiveness, sporadic viremia and development of "latent infection" were consequences of vertical transmission in offspring of infected cattle. 
  • Perpetuation of BTV through 3 generations in cattle has been documented.
  • The presence of BTV in semen of infected bulls has also been demonstrated.

Etiology

  • Bluetongue results from infection by Bluetongue virus Bluetongue virus, a member of the genus Orbivirus and family Reoviridae. 
  • To date (2017), 27 serotypes have been identified worldwide.
  • Isolates differ in virulence, and some strains seem to cause few clinical signs.
  • Like some other viruses such as Influenza virus Influenza virus, bluetongue viruses can re-sort and recombine to produce new variants. 
  • Bluetongue viruses are closely related to the viruses in the epizootic hemorrhagic disease (EHD) serogroup, a factor that can influence the development and/or selection of some diagnostic tests.

Timecourse

  • The incubation period is estimated to be approximately a week, with a range of 2-10 days.

Epidemiology

  • There are at least 27 serotypes worldwide, although not all serotypes exist in any one geographic area; e.g. 13 serotypes (1, 2, 3, 5, 6, 10, 11, 13, 14, 17, 19, 22, and 24) have been reported in the USA and 8 serotypes (1, 2, 4, 6, 8, 9, 11, and 16) in Europe. 
  • Distribution of BTV throughout the world parallels the spatial and temporal distribution of vector species of Culicoides biting midges Flies, which are the only significant natural transmitters of the virus, as well as the temperatures at which BTV will replicate in and be transmitted by these vectors.
    • Of more than 1,400 Culicoides species worldwide, fewer than 30 have been identified as actual or potential vectors of BTV to date.
    • Continued cycling of the virus among competent Culicoides vectors and susceptible ruminants is critical to viral ecology.
    • In the USA, the principal vectors are C. sonorensis and C. insignis, which limit the distribution of BTV to southern and western regions.
    • In northern and eastern Australia the principal vector is C brevitarsis.
    • In Africa, Southern Europe, and the Middle East it is C imicola.
    • In northern Europe, the major vectors are species within the C obsoletus-dewulfi complex.
    • In each geographic region, secondary vector species may attain local importance.

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.
  • Sharma R N, Beckford S, Tiwari K, Vinet E et al (2016) Seroprevalence of Bluetongue Virus Antibody in Ruminants from Grenada. Open Journal of Veterinary Medicine 6 (06), pp 99.
  • Maclachlan N J, Drew C, Darpel K & Worwa G (2009) The pathology and pathogenesis of bluetongue. Journal of comparative pathology 141 (1), pp 1-16 PubMed.
  • Schwartz-Cornil I, Mertens P P, Contreras V, Hemati B et al (2008) Bluetongue virus: virology, pathogenesis and immunity. Veterinary research 39 (5), pp 1 PubMed.
  • Mellor P S, Carpenter S, Harrup L, Baylis M & Mertens P P (2008) Bluetongue in Europe and the Mediterranean Basin: history of occurrence prior to 2006. Preventive veterinary medicine 87 (1), pp 4-20 PubMed
  • Billinis C, Koumbati M, Spyrou V, Nomikou et al (2001) Bluetongue virus diagnosis of clinical cases by a duplex reverse transcription-PCR: a comparison with conventional methods. Journal of virological methods 98 (1), pp 77-89 PubMed
  • Afshar A (1994) Bluetongue: laboratory diagnosis. Comparative immunology, microbiology and infectious diseases 17 (3-4), pp 221-242 PubMed.
  • Ellis J, Coen M, MacLachlan N J, Wilson W et al (1993) Prevalence of bluetongue virus expression in leukocytes from experimentally infected ruminants. American journal of veterinary research 54 (9), pp 1452-1456 PubMed
  • Luedke A J (1985) Effect of bluetongue virus on reproduction in sheep and cattle. Progress in clinical and biological research 178, pp 71-8 PubMed.
  • Erasmus B (1975) Bluetongue in sheep and goats. Australian veterinary journal 51 (4), pp 165-170 PubMed
  • Neitz W & Riemerschmid G (1944) The influence of sunlight on the course of bluetongue. Onderstepoort J Vet Sci Anim Ind 19, pp 69-70.  

Other sources of information

  • The center for food security and public health (2018) Technical fact sheet. [online] Last accessed 10th January 2018. Available at: www.cfsph.iastate.edu.
  • CABI (2017) Datasheet. [online] Last accessed 10th January 2018. Available at: www.cabi.org/isc/datasheet/91521.
  • The cattle site (2014) Bluetongue (BTV). [online] Last accessed 10th January 2018. Available at: www.thecattlesite.com.
  • OIE (2013) World Organization for Animal Health, OIE Technical Disease Card. [online] Last accessed on 01 November 2016. Available at: www.oie.int/fileadmin.
  • Merck Veterinary Manual (2012) Blue Tongue Disease: Introduction. [online] Last accessed on 22 November 2016. Available at: www.merckvetmanual.com.
  • Verwoerd D & Erasmus B (2004) Bluetongue In: Infectious diseases of livestock, 2nd Edn. Oxford Press, Cape Town, South Africa. 
  • OIE (2002) World Organization for Animal Health, OIE manual of standards for diagnostic test and vaccines. [online] Last accessed on 10th January 2018. Available at: www.oie.int/fileadmin.


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