Vulture crisis deepens
Reports have been circulating concerning the disease factor that continues to decimate vulture populations in India and beyond (see World Birdwatch December 1998, p. 6).
Three species are now Critically Endangered; Indian Gyps indicus, White-rumped Gyps bengalensis and the recently recognised Slender-billed Gyps tenuirostris.
At least some populations of White-rumped Vultures are rapidly declining in Nepal and the first symptoms of the disease have been observed in White-rumped Vultures in Pakistan. A westward spread of the disease through Pakistan and beyond to Europe, the Middle East and Africa appears now to be inevitable. Pakistan is therefore considered a critical area for studies over the next year. Moreover it is the area where the White-backed Vultures come most into contact with Eurasian Griffons G. fulvus.
Experts are undecided as to what is the cause of the vulture fatalities, but it seems likely that it is a disease rather than changes in the processing of dead livestock, the misuse of pesticides or other factors. However, the nature of the disease is unclear although it is probably viral. Birds contracting the disease spend long periods (up to a month) perched with their heads held drooping down before dying.
In India, vultures have traditionally disposed of carcasses in the cities, villages and the countryside, reducing the risk of disease and maintaining sanitation. Identification of this disease, and the development of a remedy, are urgent priorities.
Preliminary studies in India have not detected any viruses or other disease factors known to infect either domestic or wild birds. An immediate priority must be to make available tissues of infected birds to any laboratory in the world that might contribute to the characterisation of the disease factor. Programmes currently being developed through the Peregrine Fund in Nepal and Pakistan are expected to be capable of providing such material soon.
The disease is probably one that has "jumped" from another species. If so, development of a vaccine may be possible and it is now essential to find laboratories that would be interested in undertaking such work. Other priorities include censusing of Eurasian Griffon colonies in the countries between India and the Middle East. These are the next populations most likely to be affected, and also the pathway of the disease to the Middle East, Europe and Africa. Captive breeding of the three species, to maintain a disease-free population, is also seen as a priority.
It is well known that the White-rumped Vulture population in South-East Asia plummeted in the early 20th Century, and there is speculation that whatever caused that decline could be causing the current problems. If so, surviving birds from South-East Asia may be immune to the disease and therefore hold the key to preventing its further spread.
World Working Group on Birds of Prey and Owls electronic newsgroup