Ebola, Aids, and Pets
My sister, a long-retired RN, wrote me, in order to ask her doggie-dedicated brother this question: “Because Ebola seems to be transmitted the same way HIV is, do you know of any case where an animal has contracted or otherwise been involved with the transmission of AIDS or HIV?”
Keeping in mind that there are a few variants of each, the major epidemiological difference between Ebola and AIDS (Acquired Immune Deficiency Disorder) is this: Ebola is extremely contagious, and easily transmitted via contact with secretions and excretions in the eyes, nose, mouth, and other exits from the body. AIDS (including HIV in humans) is not so easily spread via the first two or three of these.
Both are caused by viruses, which are disease molecules or particles with considerable ability to mutate. Most mutations in nature never survive, and thus go unnoticed, even those in higher animals. In mammals and others, it is usually because of an incompatibility of two parents with different numbers of chromosomes, but even here, survival and reproducibility vary. Crosses between zebras and horses may not work, while zebra-donkey crosses do; some cross-species combinations are even fertile (bison-bovine, to some extent). Even within genera, some such as canines are genetically very plastic (develop many variations) and others not. We know far less about the unsuccessful virus mutations because those just do not appear.
Both Ebola and HIV (or AIDS) have high human mortality rates (are extremely deadly), but as in every pathogen, it would be self-defeating if it were 100% successful in a short time. So we see some survival rates such as under 50% in Ebola and much less in HIV (until modern medicines/therapy). Ebola thins out the herd in one way; HIV allows non-promiscuous, non-infected populations to survive. Neither of these monsters could survive if their “food supplies” or vectors were eliminated.
Other than by human contact, Ebola so far has been spread mostly by contaminated or carrier animals, with greatest effect via bats (urinating or dropping food they were snacking on) and bushmeat (any animal including primates, caught by hungry natives), and easily enters the victim through orifices such as cuts/scratches or by wiping one’s eyes or mouth. Ebola virus has been found in human semen for up to 3 months, even in otherwise recovered victims. The “safe sneeze distance” of three feet is ridiculous—I have seen pictures of aerosol particles traveling much farther, especially where there is air movement.
According to Centers for Disease Control and Prevention (CDC), “The US Department of Agriculture, and the American Veterinary Medical Association do not believe that pets are at significant risk for Ebola in the United States, but CDC is currently working with them and many other partners to develop additional guidance for the U.S. pet population.” While dogs and house cats can become infected with Ebola virus, there is no evidence that they develop disease. However, there have been innumerable instances of other-disease transmission from one person to another via handling of the pet. We do not yet know how long virus particles can survive on tongue, fur or other surfaces before being acquired by someone touching them. While highly unlikely that pets in civilized countries will pass along such particles to other humans, it is certainly possible. Currently, routine testing for Ebola is not available for pets. Still, there should be some balance between the action by Spain (immediately euthanizing a victim’s pet dog) and letting such a pet have normal contact with humans before it is proven “clean.”
In the case of HIV, if there is no hint of bestiality, there should be no concern. Nervous Nellies could simply give the dog a bath and sleep soundly. My sister’s concern was, “Ebola seems to be transmitted the same way HIV is,” but that’s not quite accurate. By contact with virus particles, yes, but there’s a big difference in the mechanism of such contact—and in the tissues most likely to transfer them. Five species within the genus Ebolavirus are known but we are most worried about those than can affect us. In a some of them, every time the virus copies itself, a few mutate to some degree. Also, there are many examples in which a disease particle or parasite can enter one species and change so that it is incapable of infecting the next species to which it is passed, but that barrier to transmission does not seem to be confirmed in all animal species as yet. Some other epidemic diseases are easily transferred between species, such as pig-human-duck in the case of SARS.
“Bird flu” (H5N1 avian influenza virus) has probably circulated through many billions of birds for at least two decades without changing mode of transmission. Some variety of Ebola might mutate into an easily-airborne form but that is speculation at this point. To my knowledge, experts have not yet documented any other virus infecting humans that has mutated from non-airborne to airborne, and Ebola probably will not make that jump. But it certainly is possible, given Ebola’s rapid mutation rate. It is an RNA virus, so as it splits to make copies of itself, it includes a few mutations. Many of those mutations will not survive, but some of them might, and some of those could affect the functioning of the human body. No one is keeping track of the mutations happening across West-central Africa, but in Sierra Leone early in the outbreak, before it was spreading as fast as it is now, over 300 genetic changes were found.
A mid-October 2014 item on VetMed (a chat group populated by pet lovers) decried the lack of studies re pets as Ebola vectors, but that is only partly because most Ebola workers are frantically so busy caring for human victims that they have little or no time for that question. And the news media typically has tunnel-vision and broadcast a relatively limited variety of stories. According to Loïs Allela, veterinary inspector with the Ministry of Environment of Gabon, “Dogs appear to be the first animal species shown to be naturally and asymptomatically infected by Ebola virus.” But we don’t yet know if such a pet can be a “carrier” and spread Ebola to people or other animals. Purdue University Biology Professor David Sanders says that fruit bats and some other animals without symptoms can transmit the virus and infect other species including humans.
For now, I would feel safe in taking care of a (bathed) pet obtained from an AIDS-HIV patient, but would want to quarantine one from an Ebola household. Right now, dogs and cats are not being affected by current mutations of Ebola, but we don’t know if that resistance will continue as it mutates, or even if they can spread it without symptoms of their own, something like the way “Typhoid Mary” did. There are many instances in which one individual or species spreads disease vectors to others without themselves being affected.
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