Ebola virus hysteria is taking hold of the northern hemisphere. The latest victim was a cross-bred dog called Excalibur, who was euthanased by the Spanish authorities even though he showed no signs of being infected with the virus, and despite the fact that there is no evidence that dogs can transmit Ebola to humans. The twelve year old rescued dog had the misfortune to belong to a Spanish nurse who became the first person to become infected with Ebola in Europe after nursing a Spanish missionary priest who had been repatriated from Sierra Leone to Madrid for intensive treatment. The priest died of the virus on September 25th,, and the nurse is thought to have picked up the virus after touching her face with a contaminated glove as she removed her protective suit after finishing her shift. Excalibur was a much loved pet in perfect health, and after Madrid's regional government obtained a court order to euthanase him, the nurse's husband put out a call for his life to be saved. An online petition rapidly gathered over 400000 signatures, and crowds of angry animal-loving protestors had to be restrained by police outside the apartment where the dog lived. Despite the protests, Excalibur was euthanased. The deed has been done. But was it really necessary? Did the animal present a risk, or was he just a scapegoat sacrificed to give the authorities a sense that they were doing something? There is scanty evidence to support killing a dog in a situation like this. Bats are thought to be the natural reservoir for the Ebola virus in central Africa, carrying the virus without showing signs of illness. Monkeys and apes become infected and fall seriously ill, like humans. But despite extensive research, there's been almost no evidence of other animals becoming infected or carrying the virus. There is one study that casts a cloud over the innocence of dogs: researchers investigating the 2001-2002 outbreak of Ebola in Gabon found low levels of antibodies in blood samples from dogs in areas where there had been cases of Ebola in humans and apes. This confirmed that the dogs had been infected with the virus, but it was impossible to know the source of their contact: from bats, apes, or from humans? It was also not possible to determine whether the dogs could have been infectious to humans at some point. In theory, the fact that they had been infected with the virus implies that at some point they may have shed the virus in their secretions, in the same way as infected humans pass on the infection. Some researchers believe that it would have been wiser to have kept Excalibur alive, not for sentimental reasons, but to learn more about the spread of the disease. If he had been kept in quarantine, serial blood samples could have been taken, monitoring his immune status. The question of whether or not dogs need to be included in Ebola virus control schemes could have been definitively answered in a safe environment. And if he had been clear of any sign of the virus after several months, he could have been released from quarantine to resume a normal happy doggy life. Sorry, Excalibur: the precautionary principle and the political need for action seized the initiative: we still don't know much about Ebola in dogs, and you'll never enjoy another happy walk with your owners.