Excalibur, the dog owned by the Madrid nurse who contracted Ebola, was euthanized on Wednesday. Reuters

Excalibur, the dog that became an Internet sensation after a sit-in, trending Twitter hashtag and Change.org petition that got more than 350,000 signatures, has been euthanized, reports the Madrid newspaper El Mundo. Spanish health officials decided to euthanize the dog that belonged to a Spanish nursing assistant infected with Ebola as a precautionary measure.

A group calling itself Partido Animalista (Animalist Party) staged a sit-in to save Excalibur. Javier Limon, the husband of the Spanish nurse, identified as María Teresa Romero Ramos, also pleaded to save the couple's dog in a video posted to YouTube. Partido Animalista's Twitter provided updates on the dog's condition, including a photo of the dog on the balcony earlier Wednesday.

The sit-in near the home led to some clashes with police. Firefighters and media also gathered at the couple's apartment. Earlier in the day, medical officials arrived at the scene to disinfect the apartment but were met by protesters, some of whom were carrying their own pets. "Murderers!" they yelled at the medical workers, according to NPR.

While the Ebola virus may be transmitted by bats, it is unclear if dogs can be infected and spread the disease to humans. The U.S. Centers for Disease Control and Prevention did test dogs in one study from the 2001-2002 Ebola outbreak in Gabon. The dogs were observed eating dead animals that were infected with the virus. Of the samples tested, 62 had developed Ebola-specific antibodies. "This study suggests that dogs can be infected by Ebola virus and that putative infection is asymptomatic," concludes the CDC. Dogs can be infected but do not show symptoms of the virus. The incubation period is also unknown in canines.

There are five strains of Ebola hemorrhagic fever; Ebola virus (Zaire ebolavirus), Sudan virus (Sudan ebolavirus), Tai Forest virus (Tai Forest ebolavirus), Bundibugyo virus (Bundibugyo ebolavirus) and Reston virus (Reston ebolavirus), according to the CDC. Four strains, Ebola, Sudan, Tai and Bundibugyo, can infect humans while the Reston strain has been found only in other primates.

Peter Cowen, a veterinarian at North Carolina State University, opposed Spain's decision to kill Excalibur, saying the dog should have been studied, reports the Associated Press.