• Homepage
  • Posts
  • West Nile Virus poses a threat to Bearded Vultures in captivity – and to humans too

West Nile Virus poses a threat to Bearded Vultures in captivity – and to humans too

Share This Post

Captive Bearded Vulture in Guadalentín/ illustrative (c) Junta de Andalucía

We here at the Vulture Conservation Foundation (VCF) manage the Bearded Vulture Captive Breeding Network in Europe, part of EAZA’s European Endangered Species Programme (EEP). This network is at the base of the important reintroduction projects for the species, starting with the Alps over 30 years ago, and expanding efforts to other regions including Andalusia, Grands Causses (Massif Central), Corsica (restocking) and Maestrazgo. Today, we collaborate with over 40 zoos and breeding centres, coordinating the breeding of Bearded Vultures for their eventual release to the wild. 

Managing this network brings a lot of veterinary and animal husbandry challenges, and this year was no different. The COVID-19 pandemic affected us all – personally and professionally. Within the Bearded Vulture EEP, we had to cope with, and find solutions, for the restrictions of movements across Europe. We did manage to transport chicks for reintroduction projects when the whole of Europe was confined and released them in the wild. Now that we thought the worst had passed, a new viral problem appeared: West Nile Virus (WNV) is a growing threat to captive Bearded Vultures in Europe, especially when centres or zoos are located at low altitudes. Unfortunately, this year alone, the network lost another Bearded Vulture due to this virus. 

West Nile Virus and the Bearded Vulture EEP

West Nile Virus does occur in Europe and may affect wild and captive birds. The vectors of this virus are mosquitos, and this disease coincides with the high peak of mosquito presence during the hot summer months. So, if any bird dies in this period of the year, a West Nile Virus analysis should be done. Furthermore, a few years ago, blood samples were compiled from the entire Bearded Vulture stock, and some showed antibodies against West Nile, confirming that the species can become immunized against this virus.

Most of the time, when they catch the virus, Bearded Vultures don’t exhibit strong symptoms or none at all, but eventually do get weak. As a consequence, they get other infections like aspergillosis that ultimately kills them. This threat has been growing in recent years as we can see from recent cases. 

  • In 2008, two birds died. A 20 years old female died from West Nile Virus infection and bacterial fibrinous to diphtheroid enteritis. A male who was 1,5 years old got the virus and died by secondary severe aspergillosis infection. 
  • In 2010, a female founder (originally from Greece) around 30 years old died again from West Nile Virus infection and severe secondary aspergillosis infection.
  • In 2017, two young six-month-old birds, a male and a female, died in Austria due to the same reason, West Nile Virus and secondary aspergillosis infection. 
  • This year, an imprinted 5-year-old bird died by aspergillosis, but again we suspect that he got WNV first. 

All these cases above, were observed at the Bearded Vulture specialized captive-breeding centre in the plains of Austria (Haringsee). Further, five birds from the specialized captive-breeding centre in Vallcalent (Lleida, Spain), managed by the VCF, tested positive to WNV in 2017. A breeding male named Tus died from aspergillosis, and he was suspected of suffering from WNV too that year. Furthermore, Kazajo, the human-imprinted male, had the same disease and was quite sick, but he fortunately recovered and is fine now, although he struggles to breathe well when it’s very hot. 

More recently, an adult Bearded Vulture died in Jerez Zoo based in Andalusia. A Cinereous Vulture from that facility also died and tested positive to this virus. As a preventative measure, Jerez Zoo has closed its doors to the public, as unfortunately, this outbreak has also developed into a public health issue in Andalusia, as the virus also infected people, with two deaths and about 23 hospitalized.

This outbreak in southern Spain alerted authorities and governments that are now monitoring the expansion of this viral disease. Health and veterinary authorities can consider more drastic measures, like the closing of facilities, culling of animals, etc., and thus the VCF is taking this issue seriously.

The VCF has been compiling information about Bearded Vultures and West Nile Virus for years. With the recent cases in Jerez Zoo, the Bearded Vulture EEP coordinator, Alex Llopis, who is a veterinarian and has extensive experience in breeding this species, will start an experimental vaccine test against WNV.

As we strive to produce as many fledglings as possible every year to increase the number of birds released in nature, these losses to West Nile Virus represent a severe threat for the Bearded Vulture EEP and its associated reintroduction projects. We also would like to help authorities to limit the spread of this viral disease that kills many animal species, but also humans. We are committed to tackling this threat and minimize such losses. 

Related Posts

Scroll to Top