Dr. Michael Blackwell is the senior director of Veterinary Policy for The Humane Society of the United States (HSUS). Blackwell contributed this article to Live Science's Expert Voices: Op-Ed & Insights.
As the Ebola virus continues to wreak havoc, especially in West Africa, many are concerned about the role animals, especially pets, may have in human infections. At this time, there is no alarming evidence concerning pets transmitting the Ebola virus to humans. However, we must continue to be watchful for any evidence of transmission.
According to the U.S. Centers for Disease Control and Prevention (CDC), approximately 75 percent of infectious diseases affecting humans also occur in animals. These are referred to as zoonotic diseases. The means of disease transmission between animals to humans can vary depending on the infection and usually involves a vector such as mosquitoes, or direct contact with a contaminated object, an infected person or with a contagious animal. [2014 Ebola Outbreak (Infographic )]
For national security planning, the CDC established three categories of diseases. Five of the six diseases in the highest risk category are zoonotic. Hemorrhagic fevers characteristic of the Ebola virus are included in that category.
How fragile is Ebola outside your body?
Disease-causing microbes have fairly predictable ways of surviving, and the Ebola virus is no exception. The Ebola virus can only be transmitted through direct contact with blood, secretions, organs or other bodily fluids from a sick individual.
Doctors also know that the Ebola virus is somewhat fragile. Like many other viruses, Ebola cannot survive for very long periods outside of the body. It also can be killed by exposure to ultraviolet radiation or by common household chemicals, such as chlorine bleach.
Since the disease's initial discovery nearly 40 years ago, the Ebola virus has been found to symptomatically affect mostly humans and other primates. According to the World Health Organization, fruit bats appear to be the primary natural reservoir for the virus. Other animals prone to infection include the forest antelope, chimpanzees, gorillas, monkeys and porcupines. Contact with these infected animals can lead to transmission and illness.
Test results examining the effect of the Ebola virus on dogs showed a positive correlation between infected dogs and the distances to the Ebola virus-epidemic area. According to a CDC study, during the 2001-2002 outbreak in Gabon, blood testing was done on dogs highly exposed to the virus — they had been eating infected dead animals. Blood serum tests showed approximately a 32-percent infection rate among dogs from villages with infected animal carcasses and people. The dogs tested in villages with human cases and infected carcasses appeared to yield a much higher infection rate compared to dogs from villages with human cases, but no identified infected carcasses. In villages where there were no identified infected carcasses, the infection rate was approximately 15 percent.
Though this study suggests dogs may become infected with the virus, it also appears that dogs are asymptomatic and may not shed the virus where they can transmit the infection to humans or other animals.
Two recent examples where dogs were exposed to humans infected with the Ebola virus were handled in very different ways. In Spain, Ebola patient Teresa Romero Ramos's dog Excalibur was euthanized. In contrast, Bentley, Nina Pham's dog in Dallas, Texas, was placed in quarantine for the obligatory 21 days, which ends on November 1. Bentley has tested negative three times for the virus and is reportedly doing fine. The Dallas officials took the proper course in their handling of Bentley.
While we still have much to learn about the natural course of Ebola virus in animals, let's not forget that its spread is controllable and that dogs living with ill people can be managed without euthanasia. In Texas, officials were sensible in their decision pay attention to the facts gathered on Ebola transmission, and to respond quickly, but not irrationally based unfounded fears. Let's work to help animals not become victims of over-reaction and hysteria.
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