The association between Ebola and dogs has been all over the news lately. After potentially being exposed by their infected owners, a Spanish dog, Excalibur, was euthanized, while a Texas dog, Bentley, is being held in isolation at an undisclosed location. The disparate handling of these two cases raises the question — what risk do dogs really pose when it comes to the transmission of the Ebola virus?
We do know that Ebola has the ability to infect certain types of animals in addition to humans. Antibodies to the virus are widespread in African fruit bats. Many scientists think that fruit bats may be the natural hosts for Ebola since they do not appear to become sick from the virus, but they do shed it. Nonhuman primates react like people when infected with Ebola, becoming very sick and often dying. Forest antelope can also become infected. Researchers noted that during an Ebola outbreak in Gabon in 2001-2002, “unexplained deaths of animals had been mentioned in the nearby forests” and “samples taken from their carcasses [primates and antelopes] confirmed a concomitant animal epidemic.” Pigs can become infected with the “Reston” variant of Ebola, but this strain does not make people sick.
Contact with fruit bats and/or wild animals hunted for food are the most likely initial sources of infection in human Ebola outbreaks. Ebola is a zoonotic disease (a disease that can be transmitted from animals to people) even though by far the most common route of transmission once an outbreak has started is person to person.
All of this means that concerns about dogs living in close contact with Ebola victims are not unreasonable. In fact, research looking at the Gabon outbreak showed that approximately 25 percent of the dogs in the region had produced antibodies against the Ebola, indicating they had been exposed to the virus. This does not mean, however, that the dogs actually “had” Ebola or could transmit it to people or other animals. As the Centers for Disease Control says on its website, “At this time, there have been no reports of dogs or cats becoming sick with Ebola or of being able to spread Ebola to people or animals.”
A few weeks ago, I spoke to Dr. Ronald Harty, associate professor of microbiology at Penn Vet, about his research into a potential drug to combat Ebola. I think he explains the situation best. As quoted in Delaware Online, The News Journal:
“The dog's immune system reacted to the virus it came in contact with but did not replicate it," Harty said. That means the dog's body recognizes there was a threat present and created antibodies to fight it, but the virus didn't create more copies of itself and spread, as a viral infection does. "It is highly unlikely a dog, cat or any other domestic animal could contract or transmit the disease.”
Because of this extremely low chance of disease transmission, the World Small Animal Veterinary Association recommends that, in cases like Excalibur’s and Bentley’s, dogs be quarantined and tested but not immediately euthanized. Kudos to the authorities in Dallas who let science rather than unfounded fear guide their decision making.
Dr. Jennifer Coates
Ebola virus antibody prevalence in dogs and human risk. Allela L, Boury O, Pouillot R, Délicat A, Yaba P, Kumulungui B, Rouquet P, Gonzalez JP, Leroy EM. Emerg Infect Dis. 2005 Mar;11(3):385-90.
Reston ebolavirus in humans and animals in the Philippines: a review. Miranda ME, Miranda NL. J Infect Dis. 2011 Nov;204 Suppl 3:S757-60.
[Multiple Ebola virus haemorrhagic fever outbreaks in Gabon, from October 2001 to April 2002]. Nkoghe D, Formenty P, Leroy EM, Nnegue S, Edou SY, Ba JI, Allarangar Y, Cabore J, Bachy C, Andraghetti R, de Benoist AC, Galanis E, Rose A, Bausch D, Reynolds M, Rollin P, Choueibou C, Shongo R, Gergonne B, Koné LM, Yada A, Roth C, Mve MT. Bull Soc Pathol Exot. 2005 Sep;98(3):224-9. French.