So today we venture into the current events vortex that is Ebola.
I live in Dallas. Well, actually I live 20 miles outside of Dallas, in the suburbs, but it might as well be ground zero given the level of hysteria that occurred when Dallas deputy Sergeant Michael Monning went to the local Care Now last week with Ebola-turned-stomach-flu.
I’m actually pretty tired of the topic and would just as soon never have to think about it again, but that’s just not how my brain is wired. I think about Ebola almost constantly. I suspect it’s a bit on the obsessive side, but at least I’m trying to be logical about it. Well, good luck trying to find actual facts on the topic, they are buried within media and public hysteria, conjecture and out right untruths.
I have the privilege of being directly involved in this frenzy to some degree as a veterinarian on account of the possibility of spread of Ebola from dogs to humans and vice versa.
One of the Dallas nurses currently fighting Ebola infection, Nina Pham, has a super cute one-year-old Cavalier King Charles Spaniel named “Bentley”. According to this report from CBS news, he’s just been moved to a decommissioned naval base to continue his luxury quarantine.
My understanding is he will remain in quarantine for 21 days. This is reflective of the only study that exists that demonstrates that “dogs could spread Ebola”.
Lets talk about that singular paper for a moment. Bear with me, as my volunteer editor has informed me that this part gets too “science-y”. Feel free to skim it. Hopefully you’ll get the point at the end.
The study was printed in the March of 2005 issue of the journal, Emerging Infectious Disease, by a French veterinary student, Lois Atella, and a team of scientists. They went to Gabon and “observed that several dogs were highly exposed to Ebola virus by eating [Ebola] infected dead animals”. Other dogs were seen to lick the vomit from Ebola-virus infected patients. Super gross, but we all know dogs are disgusting. We love them anyways.
The scientists took blood samples from 439 dogs in Africa and 102 French dogs (as controls). They looked for three things in the dogs:
- antibodies to Ebola virus (Antibodies are proteins floating around in the blood that indicate the immune system has been alerted to the presence of Ebola virus)
- viral antigen (any actual virus parts that can trigger immune response),
- viral DNA
What they found was that in Ebola epidemic areas, roughly 25% of the dogs tested had antibodies to Ebola circulating in their blood (feel fee to go to the article to get the hard numbers). According to the article abstract, this “suggests that dogs can be infected by Ebola virus and that the putative infection is asymptomatic”.
This statement has been translated by the media, public, and, notably the government of Spain who euthanized Excalibur, the dog belonging to an Ebola infected nurse (much to the horror of the world) to mean: DOGS CARRY EBOLA AND CAN INFECT PEOPLE!
I’m probably splitting hairs now, but here’s Important Part #1: the presence of antibodies in the system indicates that the patient or dog has been EXPOSED to the virus. Exposed means that the virus gets into the patient, the patient’s immune system sees it and destroys it. The virus may or may not have a chance to spread, reproduce or get the patient sick, we just don’t know. Exposure, basically means that the virus has been in the patient at some point.
Exposed is different from infected. According to the Free Dictionary, the definition of infection is: Invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may produce subsequent tissue injury and progress to overt disease through a variety of cellular or toxic mechanisms.
Translation: INFECTION indicates that the virus gets into your body, sets up a little home and replicates itself, making lots of new baby viruses to go off and infect others. You may or may not have symptoms (asymptomatic vs symptomatic infection).
Important part #2: I’m going to quote directly from the study here: “No circulating Ebola antigens or viral DNA sequences (tested by PCR) were detected in either positive or negative serum specimens, an attempts to isolate virus from these samples failed. ” The dogs tested negative for actual Ebola virus.
Said another way, the samples tested (and the study is unclear as to how many of the samples were PCR/antigen tested) did not show evidence of active Ebola infection. (The flip side of this is that animals known to actually spread Ebola, like fruit bats and monkeys test positive for the virus and are full of viral DNA.)
Bottom line is that this study DOES NOT PROVE THAT DOGS CAN SPREAD EBOLA. It doesn’t even prove that dogs shed the virus.
The study says that they “MAY excrete viral particles in urine, feces, and saliva for a short period before virus clearance as observed experimentally in other animals”. It doesn’t prove that they do.
The study DOES show that dogs can be massively exposed to gobs and gobs of Ebola virus particles, mount an impressive immune response to said exposure and NOT GET SICK FROM IT! Get that? Dogs might be immune to Ebola. At least in Africa.
Sounds to me like we need to be studying Ebola exposed dogs instead of killing them (Ahem, Spain?)
Back to Bentley, the nurses’ dog: one of my classmates, Dr. Kristy O. Murray, a notable human infectious disease expert(and veterinarian), observed that what they should have done was PCR test him for viral DNA as soon as they got their hands on him, 72 hours later, and at 1,2 and 3 weeks. The human test will work.
It’s too late for the initial testing, but how about starting now? While they are at it, they ought to go ahead and antigen/antibody test him too.
Furthermore (and if anyone can forward this to the “powers that be”, that would be great), what exactly is the end point determination for this twenty one day quarantine for Bentley? Data states he’s not likely to show signs of the disease. Is anyone going to test him for the virus at that point or are they just going to assume he is Ebola-free because he didn’t get sick? I’m not sure we should take that chance.
The study of dogs exposed to Ebola seems to me to be a golden opportunity to get some vital information regarding not only how the virus spreads, but maybe clues to prevention or treatment as well. We need that information here in the US, they really need it in Africa.