People in parts of Africa could be at risk of catching the deadly Ebola virus from dogs, according to research published this month that suggests the animals could carry the virus without showing signs of disease.
The researchers, led by Eric Leroy, of the International Centre for Medical Research in Franceville, Gabon, say their findings mean that dogs should be taken into consideration during the management of Ebola outbreaks.
The Ebola virus causes a fever that kills between 50 and 90 per cent of infected people. There have been seven epidemics in Gabon and the Republic of Congo since 1994, affecting 451 people and killing 351. Uganda was also hit in 2000 by an outbreak that killed 224 of 425 affected people.
People can become infected by handling infected chimpanzees, gorillas and forest antelopes, or through contact with other people who carry the virus.
Leroy told SciDev.Net that his team decided to see whether dogs carried the virus after seeing them eat the carcasses of infected animals.
The team took blood samples from 300 dogs in three areas in Gabon: villages in the 2001 or 2002 epidemic zones; Mekambo City, where human cases were also reported; and two major towns (Libreville and Port Gentil) that are more than 600 kilometres away from the epidemic area but where several human cases had been reported during an earlier outbreak.
They found evidence that the dogs had been in contact with the Ebola virus in all three areas.
To show this, they measured the amount of Ebola virus antibodies — proteins produced by the immune system when it comes into contact with bacteria or viruses — present in the dogs' blood.
"What is important is that the presence of Ebola virus antibodies in the dogs' blood increases as you approach the zone of the epidemic," says Leroy.
This means that dogs could be used as an indicator both of Ebola virus activity in a region and of the risk of human infection there.
The researchers also suggest that the disease could be asymptomatic in dogs, although they caution that confirming this would require further research.
They add that the discovery of dogs showing signs of contact with the Ebola virus in areas that have not been declared to be affected by the disease suggests that the dogs might live "in close contact" with the virus's reservoir — the as yet unidentified animal species that acts as the source of the continuing outbreaks in susceptible species.
Finding this species is high on the agenda of public health authorities.Leroy and colleagues published their findings on 3 March in Emerging Infectious Diseases.
Link to full paper by Loïs Allela et al in Emerging Infectious Diseases
Reference: Emerging Infectious Diseases 11, 385 (2005)