Disease: Blue tongue

Pathogen

Bluetongue is caused by the bluetongue virus (BTV), a virus from the Orbivirus genus. Several serotypes of the virus exist, such as BTV-3 and BTV-12, which recently occurred in the Netherlands (Fabri et al., 2024; Santman-Berends et al., 2025). Bluetongue is a notifiable disease. If bluetongue is suspected, the Netherlands Food and Consumer Product Safety Authority (NVWA) is notified immediately (https://www.nvwa.nl/onderwerpen/dierziekten/melden-dierziekte#/).

Susceptible species

Domesticated and wild ruminants, camelids, elephants, and domestic and wild carnivores can become infected with BTV, with some susceptible to disease and mortality, and others subclinically infected (Saminathan et al., 2020).

Wild animal species naturally occurring in Europe susceptible to disease and mortality from BTV infection include the mouflon (Ovis aries musimon) (Fernandez-Pacheco et al., 2008), the Iberian ibex (Capra pyrenaica) (Gómez-Guillamón et al., 2021), the European bison/wisent (Bison bonasus) (Larska et al., 2025), and the Eurasian lynx (Lynx lynx) (Jauniaux et al., 2008).

In other species, the infection proceeds subclinical as far as has been observed, including red deer (Cervus elaphus), fallow deer (Dama dama) and roe deer (Capreolus capreolus). Based on the percentage of animals with detectable antibodies, infection would occur more frequently in red deer and fallow deer than in roe deer (Barroso et al., 2021; Falconi et al., 2011; Jiménez-Ruiz et al., 2022; Linden et al., 2010). The percentage of roe deer with BTV antibodies is generally low (see also https://dwhc.nl/en/2023/12/no-bluetongue-detected-in-roe-deer-in-october-and-november-2023/).

Signs in animals

Signs caused by BTV-infection in sheep and the white-tailed deer found in America (Odocoileus virginianus) have been thoroughly described (Falconi et al., 2011; Maclachlan et al., 2015):

  • Fever
  • Swelling of the head, including the lips, muzzle, and ears, due to fluid retention
  • Excessive salivation (in sheep)
  • Red mucous membranes in the mouth; very occasionally, a blue to purple discoloration of the tongue and oral mucosa (despite the name of the disease, this is not common); Bleeding and ulcers in the mouth, especially on the dental pads, which can be so painful that animals stop eating.
  • Profuse clear nasal discharge, which later becomes purulent and leaves crusts around the nose and muzzle
  • Lameness and stiffness due to inflammation of the coronary band and muscles
  • Hemorrhages, e.g., subcutaneous
  • Breaks in the wool (sheep)
  • Sometimes diarrhea, with or without blood
  • Severe difficulty breathing due to fluid retention in the lungs, sometimes secondary to a bacterial pneumonia

The course of the disease is difficult to predict. Severely ill animals can recover completely, but they can also become lethargic, unable to get up, and die. Sudden death can also occur in animals that appeared to be recovering, due to the death of cardiac muscle tissue.

Many of these symptoms have also been observed in European wildlife species susceptible to BTV-induced illness and mortality. Symptoms in mouflon infected with BTV-1 included inflammation of the mucous membranes, with congestion, swelling, and bleeding (Fernandez-Pacheco et al., 2008). In Iberian ibex infected with BTV-4, the symptoms included weakness, labored breathing, frothy nasal discharge, and subcutaneous edema of the head and jaws, neck, and chest (Gómez-Guillamón et al., 2021). In bison infected with BTV-3 in Poland, the illness lasted approximately 10 days, with initial symptoms including inappetence and withdrawal from the herd. In the 2–3 days before death, the animal was weak, apathetic, less mobile, and developed bloody diarrhea, and initially clear and then purulent nasal discharge (Larska et al., 2025).

Infection of animals

BTV transmission between animals occurs primarily through midges (small, biting insects of the genus Culicoides). A midge must first bite an infected animals to become infected and subsequently transmit the virus.

Infection of people

Blue tongue is not a zoonosis. Humans cannot get infected with the virus.

Geographical distribution

Blue tongue is found on all continents, except Antarctica (Maclachlan et al., 2015). In Europe, bluetongue occurs primarily in Mediterranean countries, such as Spain, Greece, and Italy (serotypes 1, 2, 4, 8, 9, and 16). Since 2006, outbreaks have also occurred in northwestern Europe, including the Netherlands, Belgium, Germany, France, and Denmark. In France, BTV-8 has been present since 2015, BTV-4 since 2017. And BTV-3 since 2024 (https://agriculture.gouv.fr/la-situation-de-la-fievre-catarrhale-ovine-fco-en-france; 10 aug 2025). Major outbreaks in captive animals (primarily serotype 3) occurred in the Netherlands and Belgium in 2023 and 2024 (National Government, September 6, 2023).

So far in 2025 (August 10, 2025), no cases of bluetongue have been confirmed in the Netherlands. See here for the current situation in the Netherlands.

Preventative measures

For livestock, there are measures in place to control midges. Vaccinations against specific serotypes can also help limit the spread among livestock. There is little cross-protection between BTV-serotypes, meaning that vaccination against one serotype offers little protection against another serotype (Maclachlan et al., 2015).

Sources

Barroso P, Risalde MA, García-Bocanegra I, Acevedo P, Barasona JÁ, Palencia P, Carro F, Jiménez-Ruiz S, Pujols J, Montoro V, Vicente J. Long-term determinants of the seroprevalence of the bluetongue virus in deer species in southern Spain. Res Vet Sci. 2021 Oct;139:102-111. doi: 10.1016/j.rvsc.2021.07.001. Bottom of Form

Fabri, N., van den Brink, K., van den Brom, R., Smits, D., Santman-Berends, I., ter Bogt-Kappert, C., Dijkstra, E., Snijders-van de Burgwal, N., Bunte, M. (Projectleider), & Roos, L. (Accountmanager). (2024). Monitoren van kliniek op BTV-3 besmette schapen- en rundveebedrijven in 2024: Resultaten (Projectnummer 3020003) [Rapport]. Royal GD. https://www.gddiergezondheid.nl/-/media/6513C403F63F4051AF5F6D003A0DFB93.ashx

Falconi C, López-Olvera JR, Gortázar C. BTV infection in wild ruminants, with emphasis on red deer: a review. Vet Microbiol. 2011 Aug 5;151(3-4):209-19. doi: 10.1016/j.vetmic.2011.02.011.

Fernández-Pacheco P, Fernández-Pinero J, Agüero M, Jiménez-Clavero MA. Bluetongue virus serotype 1 in wild mouflons in Spain. Vet Rec. 2008 May 17;162(20):659-60. doi: 10.1136/vr.162.20.659. PMID: 18487587.

Gómez-Guillamón F, Caballero-Gómez J, Agüero M, Camacho-Sillero L, Risalde MA, Zorrilla I, Villalba R, Rivero-Juárez A, García-Bocanegra I. Re-emergence of bluetongue virus serotype 4 in Iberian ibex (Capra pyrenaica) and sympatric livestock in Spain, 2018-2019. Transbound Emerg Dis. 2021 Mar;68(2):458-466. doi: 10.1111/tbed.13696. Epub 2020 Jul 7. PMID: 32573968.

Jauniaux TP, De Clercq KE, Cassart DE, Kennedy S, Vandenbussche FE, Vandemeulebroucke EL, et al. Bluetongue in Eurasian Lynx. Emerg Infect Dis. 2008;14(9):1496-1498. https://doi.org/10.3201/eid1409.080434

Jiménez-Ruiz S, Vicente J, Risalde MA, Acevedo P, Cano-Terriza D, González-Barrio D, Barroso P, García-Bocanegra I. Survey of Culicoides-borne bluetongue and Schmallenberg viruses at the wildlife-livestock interface in Doñana National Park (Spain). Transbound Emerg Dis. 2022 Sep;69(5):e1815-e1824. doi: 10.1111/tbed.14516. Epub 2022 Mar 25. PMID: 35304824.

Larska M, Orłowska A, Łopuszyński W, Skurka Ł, Nowakowska A, Trębas P, Krzysiak MK, Rola J, Smreczak M. First Detection of Bluetongue Virus Type 3 in Poland in 2024-A Case Study in European Bison (Bison bonasus). Pathogens. 2025 Apr 12;14(4):377. doi: 10.3390/pathogens14040377. PMID: 40333170; PMCID: PMC12030162.

Linden A, Gregoire F, Nahayo A, Hanrez D, Mousset B, Massart AL, De Leeuw I, Vandemeulebroucke E, Vandenbussche F, De Clercq K. Bluetongue virus in wild deer, Belgium, 2005-2008. Emerg Infect Dis. 2010 May;16(5):833-6. doi: 10.3201/eid1605.091217. PMID: 20409376; PMCID: PMC2953989.

Maclachlan, N. J., Mayo, C. E., Daniels, P. W., Savini, G., Zientara, S., & Gibbs, E. P. J. (2015). Bluetongue. Revue Scientifique et Technique-Office International des Epizooties, 34(2), 329-340. 10.20506/rst.34.2.2360

Rijksoverheid. (2023, 6 september). Blauwtongvirus vastgesteld op enkele schapenbedrijven in Midden-Nederland. Ministerie van Landbouw, Visserij, Voedselzekerheid en Natuur. https://www.rijksoverheid.nl/ministeries/ministerie-van-landbouw-visserij-voedselzekerheid-en-natuur/nieuws/2023/09/06/blauwtongvirus-vastgesteld-op-enkele-schapenbedrijven-in-midden-nederland

Saminathan, M., Singh, K. P., Khorajiya, J. H., Dinesh, M., Vineetha, S., Maity, M., Rahman, A. F., Misri, J., Malik, Y. S., Gupta, V. K., Singh, R. K., & Dhama, K. (2020). An updated review on bluetongue virus: epidemiology, pathobiology, and advances in diagnosis and control with special reference to India. The veterinary quarterly, 40(1), 258–321. https://doi.org/10.1080/01652176.2020.1831708

Santman-Berends, I., Paarlberg, N., van den Brink, K., Holwerda, M., Stegeman, A., Strous, E., Snijders, N., van Duijn, L., Dijkstra, E., Mars, J., & van den Brom, R. (2025). Binnenbedrijfsprevalentie en klinische verschijnselen van blauwtong serotype 12 op rundvee- en schapenbedrijven (Projectnummer 2080117). Royal GD. https://www.gddiergezondheid.nl/-/media/6DD8E01D3EA545109279DCF53B3BEFB6.ashx

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