Ebola: can dogs catch and transmit the virus to humans?

A dog belonging to Nina Phan, one of the nurses infected with Ebola in Texas, has been placed under quarantine by US authorities in order to determine whether or not it is carrying the virus.

Last week, officials in Spain euthanised nurse Teresa Romero's dog, Excalibur, after she tested positive for the virus. These two cases have raised concerns that dogs and other animals may be potential carriers of the disease.

Can dogs get Ebola?

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Yes. After the 2002 Ebola outbreak in Gabon, researchers from the US Centres for Disease Control and Prevention (CDC) discovered that many of the animals that came into direct contact with disease, later tested positive for it.

It is believed the dogs contracted the virus by scavenging for infected bushmeat, but it could also have been transmitted through contact with the bodily fluids of an infected human.

However the virus had no harmful effect on the canines as they showed no symptoms and did not become ill or die.

What about other animals?

Ebola is a zoonotic disease, which means it can be transmitted between humans and animals. Scientists believe the Ebola virus originated from wild animals such as fruit bats living in tropical rainforests in equatorial Africa. The disease spread to humans when they came into contact with the organs, blood or other bodily fluids from infected animals through hunting.

This proves that cross-species transmission can - and does - occur. The disease has an almost identical fatality rate in humans and primates. It has also been observed in other domesticated animals such as guinea pigs, goats, and horses, but like in dogs, the virus is asymptomatic.

So, could they pass it on to humans?

In theory, yes. However, in its latest advice the CDC is careful to point out that there is no documented evidence of this and the risk remains "low".

Yet the Gabon report concluded that "given the frequency of contact between humans and domestic dogs, canine Ebola infection must be considered as a potential risk factor for human infection and virus spread". It suggested that dogs could pass the virus on to human through biting or licking or if a human came into direct contact with their urine or faeces.

Researchers believed that dog-to-human transmission could explain some human cases where there was no documented source of exposure to the Ebola virus.

Professor David Sanders, a biologist at Purdee University agrees. "The concept that viruses in animals can be transmitted to humans and can have potential harmful consequences, that's obvious," he told CNN. "So infected animals that are not showing signs of infection can potentially be capable of transferring virus to humans."