I was on CNN – Talking Ebola, Dogs, and Bats

I appeared on CNN last night to help give context to the euthanization of Excalibur, the pet dog of the Spanish nurse who has contracted the ebola virus. My CNN interview is here:

I thought it might be helpful for me to follow up with some more thorough explanations:

Can animals get Ebola?
Yes Absolutely. Ebola affects humans, chimpanzees, and gorillas.

What animal first gave ebola to humans?
In the early 2000s, researchers went out in search of an answer to that question. They caught 1,030 animals living in the places where ebola outbreaks had occurred (679 bats, 222 birds, and 129 small terrestrial mammals), and tested their blood to look for signs that they’d been exposed to ebola. (Specifically, they looked for immunoglobulin G antibodies that match the ebola virus.) Of all those animals, the only positive hits were from three species of bats, and the geographic ranges of those three species overlap conspicuously with historical ebola outbreaks. [link to study]

Faces and geographic ranges of three bat species that might be the sources of ebola in humans. Hypsignathus monstrosus (blue), Epomops franqueti (red) and Myonycteris torquata (yellow). Figure taken from Leroy et al. (2005).
Faces and geographic ranges of three bat species that might be the sources of ebola in humans. Hypsignathus monstrosus (blue), Epomops franqueti (red) and Myonycteris torquata (yellow). Figure taken from Leroy et al. (2005).

Those data suggest that humans got ebola from bats, and that periodic outbreaks of the disease might result from new bat-human transmission events. The role of bats hasn’t been conclusively proven, but people eating bush meat often come into contact with the blood and guts of those fruit bats, so bats are the most likely candidate as ebola’s source.

(I should point out that the bats flying around your cabin in the summer eating mosquitoes have absolutely nothing to do with ebola and do not pose any risk.)

Can dogs get ebola?
Dogs eat parts of dead animals all the time (dead animals that might have died from ebola), and dogs also eat vomit (vomit that might have come out of people with ebola). So logic holds that dogs living where ebola outbreaks happen might become reservoirs for the disease. So can they get the disease?

Researchers tested blood from dogs living in Africa to see whether they had the immunoglobulin proteins that show up when an animal is exposed to ebola. They did.[link to study] This means that dogs can get the virus. Importantly, though, it doesn’t necessarily mean dogs can give the disease to humans.

Can dogs spread ebola to humans?
Simply put, we don’t know yet. I’ll give the researchers in that dog study the final word in this. This quote comes straight from their paper, and I think it’s very clear.

Although dogs can be asymptomatically infected, they may excrete infectious viral particles in urine, feces, and saliva for a short period before virus clearance, as observed experimentally in other animals. 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. Human infection could occur through licking, biting, or grooming. Asymptomatically infected dogs could be a potential source of human Ebola outbreaks and of virus spread during human outbreaks, which could explain some epidemiologically unrelated human cases. Dogs might also be a source of human Ebola outbreaks, such as the 1976 Yambuku outbreaks in Democratic Republic of Congo, the 1995 Kikwit outbreak, some outbreaks that occurred in 1996 and 2004 in Gabon and Republic of Congo, and the 1976, 1979, and 2004 outbreaks in Sudan, the sources of which are still unknown. Together, these findings strongly suggest that dogs should be taken into consideration during the management of human Ebola outbreaks (emphasis mine).