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Eurosurveillance, Volume 10, Issue 45, 10 November 2005
Articles

Citation style for this article: Gupta RK. Recent outbreak of rabies infections in Brazil transmitted by vampire bats. Euro Surveill. 2005;10(45):pii=2831. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=2831

Recent outbreak of rabies infections in Brazil transmitted by vampire bats

Ravindra Gupta (ravi.gupta@hpa.org.uk), Centre for Infections, Health Protection Agency, London, United Kingdom

On 25 October 2005, the Brazilian ministry of health reported a new focus of human rabies infections transmitted by blood eating vampire bats (Desmodus rotundus) in northeast Brazil [1]. Twelve deaths were reported in Turiaçú, in the state of Maranhão in October 2005. Rabies deaths have also been reported in 2005 in Godofredo Viana (3), Cândido Mendes (2) and Carutapera (2) [1], and the local media reports that several hundred may have been bitten by bats. [4]. These areas are in the north of Maranhão, next to the focus of a bat-transmitted human rabies outbreak in the state of Pará in 2004 [1,5]. During the recent outbreak, media reports noted that nocturnal biting coincided with the failure of a regional generator which left people without electricity for six weeks [4].

Between 1986 and 2004, the ministry of health was notified of 743 human rabies cases in Brazil, most of which occurred in the north and northeast of the country [1]. Numbers of cases had been falling steadily from 1980 (over 170 cases) to 2003 (under 20 cases), mainly due to control of rabies in dog populations. Up to 2003, most human rabies infections notified in Brazil were transmitted in an urban setting by cats or dogs, but most infections since 2004 have been transmitted by bats in rural parts of the states of Pará and Maranhão [1,5]. Outbreaks of bat-related rabies have been linked to the continued deforestation of the Amazon region, which has displaced vampire bats across northern Brazil and increased contact with humans [2]. The ministry of health also notes that abandoned gold mines in Maranhão have provided favourable habitats for bat populations [5].

Vaccination and bat-catching teams are working in the region to try to prevent the spread of infection. A meeting between the authorities from two states affected in 2004 and 2005 was held in October to coordinate outbreak control activities.

Worldwide, rabies causes approximately 55 000 deaths per year [6]. Rabies viruses are transmitted to humans via saliva from bites of carnivores and chiropterans (bats). Bats may be frugivorous (fruit eating), hematophagous (blood eating), or insectivorous (insect eating). Transmission from carnivores has been controlled in Europe by vaccination of domestic cats and dogs and oral vaccination of wildlife. Vampire bats (Desmodus rotundus) feed on blood from warm blooded animals such as horses and cattle. They are not native to Europe and other species of bat found in Europe are not known to be reservoirs of classical (genotype 1) rabies. Bats with rabies may behave abnormally, which may partly explain the uncharacteristic behaviour of human biting exhibited in the Brazilian outbreaks.

Current World Health Organization guidelines on rabies pre-exposure prophylaxis state that rabies vaccine should be offered to visitors travelling or living in areas where rabies is endemic. The vaccine is given at 0, 7 and 21 or 28 days [7]. Following a bite or exposure of mucous membrane to saliva, vigorous washing with soap, water and application of ethanol or iodine to the wound is recommended to decrease the risk of rabies transmission. For previously unvaccinated people, the area surrounding the wound should be injected with rabies immunoglobulin (RIG) as soon as possible after washing, followed by intramuscular vaccination with five doses of inactivated cell culture or duck embryo vaccine [8].

The extent of the outbreak in Brazil is not yet fully understood, and therefore the risk to travellers is not completely defined. Vaccination should be considered for travellers to the affected area of the country, especially if they will be in remote areas for a long time [9]. Such travellers should be informed of the need for prompt treatment in the event of a rabies exposure. Sleeping in enclosed areas protected by an intact building structure or screening and netting should decrease exposure. Anyone returning from the Amazon region with a possible animal bite should be immediately referred for a specialist assessment regarding post-exposure prophylaxis.

References:
  1. Ministério Da Saúde. Raiva Humana transmitida por morcegos no Estado do Pará e Maranhão. 25 October 2005. (http://portal.saude.gov.br/portal/arquivos/pdf/nota_raiva.pdf)
  2. Promed. Brazil: 23 Deaths in Vampire Bat Rabies Outbreak in Maranhao State. ProMED-mail [online]. Boston US: International Society for Infectious Diseases, archive no. 20051102.3202, 2 November 2005. (http://www.promedmail.org)
  3. Rabies, human, vampire bats - Brazil (Maranhao)(02). In: ProMED-mail [online]. Boston US: International Society for Infectious Diseases, archive no. 20051027.3133, 27 October 2005. (http://www.promedmail.org)
  4. Rabies, human, vampire bats - Brazil (Maranhao). In: ProMED-mail [online]. Boston US: International Society for Infectious Diseases, archive no. 20051024.3100, 24October 2005. (http://www.promedmail.org)
  5. MINISTÉRIO DA SAÚDE, SECRETARIA DE VIGILÂNCIA EM SAÚDE (Brasilia). Raiva humana transmitida por morcegos no estado do maranhão. 25 July 2005 (http://portal.saude.gov.br/portal/arquivos/pdf/Nota%20Tecnica%20%20MA%20surto%20de%20raiva%20humana%2025%2007%2005.pdf)
  6. WHO Expert Consultation on Rabies. First report. (WHO technical report series 931 Geneva: World Health Organization; 2004. (http://www.who.int/rabies/trs931_%2006_05.pdf)
  7. Vaccine preventable diseases, vaccines and vaccination. In: WHO International Health and Travel Publication. Geneva: World Health Organization; 2005. (http://whqlibdoc.who.int/publications/2005/9241580364_chap6.pdf)
  8. Rabies [2005]. In: Immunisation Against Infectious Disease. London: Department of Health; 1996 (new chapters available online, May 2005) http://www.dh.gov.uk/assetRoot/04/11/09/70/04110970.pdf
  9. National Travel Health Network and Centre (NaTHNaC, London). Clinical update: rabies in Brazil. 9 November 2005 (http://www.nathnac.org/pro/clinical_updates/rabies_Brazil_091105.htm)

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