KEY POINTS:
CENTRAL AFRICA - Ebola virus has killed more than 5000 western lowland gorillas in four years, according to scientists who warn that the world's largest ape is suffering a dramatic population decline that could soon lead to its extinction.
The virus is one of the deadliest infectious agents known. It also affects other primate species and its rapid spread among chimpanzees and gorillas in parts of central Africa has alarmed conservationists.
A study published in the journal Science is one of the first to put a figure on the number of western lowland gorillas affected by the epidemic, which appears to spread from ape to ape.
Before the latest study, scientists were not sure whether Ebola was spreading into apes from other animals in the forest which acted as natural "reservoirs" of the virus. The latest findings suggest direct transmission from one ape to another.
The type of Ebola virus killing the gorillas is known as the Zaire strain which has repeatedly infected people in Gabon and Congo, said Dr Magdalene Bermejo, of the Ecosystemes Forestiers d'Afrique Centrale, based in Libreville, Gabon.
"During each human outbreak, carcasses of western gorillas and chimpanzees have been found in neighbouring forests," said Bermejo, who did the latest study with colleagues from Germany and Spain.
Bermejo was part of a project looking at 10 social groups of gorillas, 143 in all, living near the Lossi Sanctuary in the Democratic Republic of Congo.
In late 2001, human outbreaks of Ebola flared up along the border between Gabon and the Democratic Republic of Congo. In June 2002 the first dead gorilla was found 15km from the Lossi sanctuary.
By October, gorillas were dying with the sanctuary and over the next four months the scientists counted 32 carcasses.
A dozen were tested for Ebola and nine tested positive for the Zaire strain.
Between October 2002 and January 2003, 130 of the 143 gorillas being studied had died - a mortality rate of more than 90 per cent. In the following months further carcasses were reported in other parts of the forest.
The virus appeared to be spreading from one gorilla group to another in a manner consistent with ape-to-ape transmission, the scientists said.
A survey of nesting sites used by gorillas living in a 2700sq km area surrounding the Lossi Sanctuary found that the number of occupied nests had fallen by 96 per cent.
The scientists estimated this would suggest about 5000 gorillas living in the region had been killed by the deadly Ebola virus since the epidemic began in 2002.
The deaths among the western lowland gorillas are mirrored among eastern gorillas, fewer than 5000 of whom remain.
- INDEPENDENT
