Dr. Greg Nelson, CVA’s senior vice president, was interviewed by Forbes magazine for an article on whether dogs can transmit the Ebola virus to their owners. In the article, Dr. Nelson pointed out that, although the virus can live within dogs, it is unclear whether they can transmit Ebola to their owners or to other humans.
As we learned that nurse Nina Pham contracted Ebola last week after taking care of Thomas Eric Duncan at Texas Health Presbyterian Hospital in Dallas, we also learned that her beloved dog, Bentley, a King Charles spaniel, was one of her contacts being placed into quarantine.
A stark contrast to the situation with nurse Teresa Romero’s dog, Excalibur, who was euthanized October 8th at the order of Spanish health officials.
While we know that dogs can harbor Ebola, and produce antibodies to the virus, it is unknown if they can transmit the disease.
“Basically, dogs produce antibodies to Ebola,” explained Dr. Greg Nelson, of Central Veterinary Associates, in Valley Stream, New York. “This means that the virus lives inside and multiplies within the dog and produces a response to eliminate the virus.”
“So, this is evidence that the virus lives and replicates inside the dog,” explained Nelson. “It is not known if the virus replicates in such numbers and finds a way to escape the dog and enter a human host.”
So the question becomes whether the virus can jump from dogs to humans.
“The only way to know this for sure, is to accidently have a person contract the disease while only being exposed to known dog carriers and no human carriers,” reasoned Nelson. “Then the virus must be isolated from the person for definitive identification.”
Gabon Outbreak, 2001-2002
A 2005 study of an Ebola outbreak in Gabon, Africa during 2001-2002 revealed that dogs can be infected with the virus, but may remain asymptomatic. While they remain asymptomatic during infection with Ebola, they may excrete viral particles in feces, saliva as well as urine before they clear the virus from their body, according to the study. Authors of the study caution that due to the “frequency of contact between humans and domestic dogs”, it’s still theoretically possible that canine infection with Ebola could be a potential risk factor for transmission. Humans could become infected through licking or biting as well as during grooming.
Another reason that Spain may have taken a more proactive and aggressive stance with Excalibur, Ms Romero’s euthanized pet, relates to the concern that dogs could be a potential source of human Ebola outbreaks as well as a route of spread among so-called “epidemiologically unrelated human cases”. Multiple outbreaks to this day have had an unknown source, including the 1976 Yumbuku outbreaks in the Democratic Republic of Congo, the 1995 Kikwit outbreaks, as well as multiple outbreaks in Sudan in 1976, 1979, and 2004. Authors of the study believe that with this uncertainty, dogs should be considered potential vectors of spread during human Ebola outbreaks. However, without a true outbreak in Spain, many have questioned whether health officials were premature to euthanize Excalibur.
In fact, authors of the study suggest that monitoring seroprevalence rates of Ebola in dogs can be a useful indicator of infection in cases where it may difficult to test for Ebola in humans directly.
Ebola is classified as a zoonotic disease meaning that it can be transmitted between humans and animals. Ebola’s natural reservoir is likely fruit bats, which remain asymptomatic during infection with the virus. Humans most likely became exposed to infected animals via their blood or bodily fluids during hunting.
Ebola is known to be highly lethal in chimpanzees, gorillas and humans, while other animals such as goats, horses or guinea pigs remain asymptomatic or develop only mild infection. It is important to note that Ebola has never been detected among goats, horses or guinea pigs living in wild populations. Ebola has also not been detected in African lions, so it’s possible that they may be immune.
Psychological Effects of Ebola
Placing Bentley into quarantine, and thus avoiding euthanasia, could potentially help Nina during this emotional and psychologically difficult period of her life. Pictures have been continuously sent to her to remind her that her dog is doing well thus far.
To be sure, the psychological effect of having Ebola can be devastating. Knowing that you have a potentially lethal disease where you must quarantined carries a high potential for developing depression, suicidal thoughts, and post traumatic stress.
The bottom line is that we do not know if dogs can transmit the virus to humans or to other dogs or wildlife.
At the same time, while infected dogs may be quarantined, it is also unclear for how long they remain infectious.
The CDC released a statement last week stating “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.”
That said, there are silent carriers for diseases such as typhoid, whereby asymptomatic persons can spread deadly infections to other people.
Pham reportedly called Dallas Animal Services last week to thank them for taking care of Bentley while he is quarantined at the Hensley Field Services Center. She was thankful and stated that it helped to provide comfort and reassurance. Dallas officials have also promised to do whatever possible to help spare Bentley’s life.
Bentley will be undergoing blood tests this week to determine if he has contracted the Ebola virus. The fact that Bentley is alive and doing well can only improve Pham’s mental outlook, hopefully helping her to get through this exceedingly difficult period of her life.
Meanwhile, the world will be watching closely to see if this was the right decision.
Source: Forbes.com “Can Dogs Transmit Ebola? Different Approaches Explained” 19 October 2014