Sunday, March 21, 2010
When I was a freshman at Harvard, a wise alum gave me a piece of advice that I have carried with me throughout my life. "No matter how much you think you know about a subject," he warned, "someone who knows a whole lot more about it may be standing right behind you." For someone who's outspoken and loves to pronounce upon what little she knows, that's a potent life lesson, one that I learn again and again and again. Lest you be tempted to think it happens more at Harvard, I can attest that there are experts lurking in every corner. Here's a letter I got from Dr. Timothy Winship, who has been quietly reading my blog, but who couldn't get past Google's comment guard dogs to post this comment:
"As a professional virologist, with a background in animal viral disease, I appreciated your post about rabies in bats which contained a great deal of accurate information. A few points to clarify, though: the figure of 0.5% for rabies infection incidence in bats is cited quite a lot, but in fact this is based on a very limited sampling (it's surprising how little research on infection of bats with bat strain rabies viruses there is!). It probably isn't true, but what you must bear in mind is that 0.5% is NOT a low incidence given the number of animals we are talking about. That's one in two hundred animals, or 5 in 1000, or 50 in 10,000 and so on.
Because bats may roost in colonies of hundreds or thousands, this presents a problem. Dr. Winship continues:
"Also, most of the information we have regarding the pathology of rabies in bats is from laboratory infection of bats with canine strains of virus. Under those conditions bats develop a fairly typical pattern of disease seen in other mammals. However, very little is known about what happens when bats are infected with bat strains of the virus, and in particular how bats infect other bats. Your statement about not knowing the incubation period of the disease in bats is quite true but covers a lot of unknown ground! The actual level, or potential for asymptomatic carriage, of bat strain virus in bats is not known, i.e. I can't find any evidence in the scientific literature that anybody can tell you that an asymptomatic bat can't transmit rabies. Certainly these kinds of viruses, under the right conditions, can establish very persistent latent infections. I personally don't agree that we know that an asymptomatic bat cannot transmit the disease.
And as I think about it, who knows enough about normal bat behavior to say what's normal and what might be abnormal? Not me! Bats are bizarre little things.-JZ
Dr. Winship continues:
"The evidence from bite exposure records held by the CDC is disturbing--most cases are not from animals aggressively attacking and biting humans, i.e. acting rabid... You are right about health department records of bat testing being skewed towards unhealthy animals, but the statistics do tell us something about the geographic distribution of the disease, at least. If you haven't already seen it, here are the numbers and distribution of animal found in Ohio last year. It's also important to bear in mind that while the number of human rabies cases acquired within the US yearly is very small (averages something like one per year) the number of exposures is quite a lot higher (last I saw about 50 per year in Ohio). And, last I looked the cost of post-exposure prophylaxis was on the order of $12,000 per person. (Which makes the $700 pre-exposure shot series sound cheap). Anyway, I'm glad you're being careful. I enjoy your blog greatly and want to keep doing so for a long time! Thanks again--sorry this was so long-winded. "
This letter, like so many of your comments and emails, hit just the right note. I'm grateful to have knowledgeable and caring people reading this blog, and I'm doubly grateful when they speak up and add their own experiences to the discussion, holding up a light for us all to see by. That's one of the big reasons I can't seem to give it up--I learn so much.
Spurred by Dr. Winship's letter, I rooted around a bit to find out more about a case I'd heard about, of a Missouri man who'd had a bat get into his home in the Ozarks in October 2008 and gotten bitten by it. It's always tempting to think that someone dumb enough to handle a bat somehow has it coming to him if he gets bitten, but watching this video should persuade you otherwise. Here was a bat (the video shows file footage of a little brown, but it was more likely a big brown) that got into the living space of a home, acting normal. In the course of dealing with it, this good, intelligent, caring, wildlife-loving person allows it to climb up his coat. (Sound like something the Science Chimp might do?) It gets up next to his neck, he turns his head, hunching up his shoulder as you would; the bat gets frightened, squeezed by the coat, and nips him on the ear. Concerned, he keeps it around for a couple of days, but it acts normal and he decides to release it. His family is concerned, too, even teases him about getting rabies, but it just doesn't seem possible that anything bad could happen. It's just a bat, and people get all hysterical about bats.
Five weeks later, he falls ill, and dies painfully--all the more tragic, because his death could have been prevented by a series of injections administered immediately after the bite.
Here's the deal. If you get bitten by a bat or other rabies-vector species, you MUST get it tested and see a doctor immediately. Its brain tissue must be examined for the telltale ovoid bodies of the rabies virus. If it tests positive, you'll be given a series of shots, and you won't die. If you don't get it tested, and decide to take your chances, your family could be talking about you on a heartbreaking video like this one.
So, as enamored as I am of Dee Dee, and adorable and apparently healthy as she is, her welfare and her life is distinctly secondary to mine and my family's. The possibility that she may have a latent infection is small, but it's present, and we simply don't know enough about bat strains of rabies or normal bat behavior to say with any certainty that an asymptomatic bat is safe to handle. It's not. So if I mess up, and Dee Dee bites me, that's it. She dies, that I may live. Long sleeves and gloves for me, always, and nobody else handles her, ever.
Dr. Winship left me with a link to a terrific U.S. Geological Survey publication, available free and readable as a pdf file, that he describes as "the very best review of bat rabies I have ever found, and...recent as well." I concur wholeheartedly. Despite its foreboding title, Denny Constantine's "Bat Rabies and Other Lyssavirus Infections" is a great read.
Download it here.
Thank you, Dr. Winship, for bringing this issue into crystal-clear focus for me and my readers. It's good to have people like you, standing right behind me.