Last October (2007) a 46 year old Minnesota man died of rabies, the only known victim in the US last year. Rabies is a rare disease in the US because we have good veterinary services. Most animals in routine and regular contact with humans are vaccinated against the disease. But bats have become a significant wild animal reservoir and the Minnesota case was a bat case:
Once rabies was suspected, the patient's family was interviewed on October 16 for a history of potential exposure. According to his family, the patient had handled a bat with his bare hands in a semi-open cabin porch in north-central Minnesota on August 19, 2007. He had reported feeling a needle prick sensation before releasing the bat. Because no blood or wound was visible, the patient concluded he had not been bitten and did not seek medical attention. Neither the patient nor his family was aware that this exposure constituted a rabies risk. (CDC, Morbidity and Mortality Weekly Reports)
The patient's illness started with a spreading numbness and tingling which started in the right hand. Within days he developed weakness in the right arm. Days after that the weakness had spread to the left arm, even as doctors were struggling to diagnose his worsening condition. He had not given his history of exposure to the bat. By the end of September he developed a fever, double vision and rapidly developing respiratory failure. He was intubated and put on a ventilator, still without a diagnosis. Tuberculous meningitis, West Nile and a variety of other agents were ruled out but not rabies. He lapsed into a coma and was transferred to a tertiary care hospital without a diagnosis. Eventually the diagnostic images suggested rabies and the diagnosis was made. Shortly after the patient died.
Rabies is caused by a virus present in saliva of rabid, biting animals. Its life cycle and underlying structure are somewhat similar to the flu virus (negative sense RNA virus with relatively few proteins) but is quite different in other respects. It infects nerve cells and travels up the long nerve fibers from the bite location to the spinal cord and central nervous system.
Rare in the US (25 cases in the eight years 2000 - 2007), it is not rare elsewhere, particularly in Asia which has 80% of the cases worldwide. The Indian sub-continent records more than 40,000 rabies deaths a year and recently China has suffered an exponential rise in human rabies cases, now numbering in the thousands annually. Feral dogs are the principal vector in Asia but in North America rabies virus is mainly found in wild life (raccoons, bats, skunks, foxes, coyotes). Among domestic animals cats are most frequent. followed by dogs and cattle. However less than one in ten animal rabies cases are in domestic animals (CDC).
Rare or not, once symptoms develop it is a virtual death sentence. There is no effective treatment for clinical rabies. Only six survivors have ever been recorded in the medical literature, and some of these had some form of prophylaxis prior to symptoms. But being bitten by a rabid animal it self is not a death sentence if you treat the exposed person with post-exposure prophylaxis (PEP). But how do you know if you are exposed? Here things get a little tricky. PEP, like many effective medical interventions, has its own side effects, mainly allergic reactions. CDC says that mere contact with an animal later shown to be rabid (e.g., a skunk or raccoon in a petting zoo) or contact with their blood, urine or feces does not require PEP. Rabid animals are more likely to make unprovoked attacks but being bitten while touching a feeding animal or an apparently healthy wild animal are not considered an unprovoked attacks. Don't do either one. If you are bitten by a
domestic animal (e.g., someone's pet) pet cat or dog you don't need PEP while the animal is being observed. Other mammals kept as pets may require timely PEP. [clarification hat tip commenter MoM]
Cats are the most frequent domestic animals with rabies because too many owners fail to have their pets vaccinated. They also roam freely and thus are more likely to come in contact with rabid wildlife (like raccoons).
The most difficult area is contact with bats. I'd stay away from bats if you aren't vaccinated against rabies. But you don't always have a choice. People can be bitten by bats without being aware of it, so awaking in your cabin to find a bat flying around presents a puzzle (assuming you haven't trapped the bat for testing). I know health officers who automatically refer these cases for PEP while many others do not.
What would I do in such a circumstance? I'd hope it doesn't happen to me. As with most US doctors I've never seen a clinical case of rabies but when I was in medical school we were shown a film of a young Iranian man with rabies. Forty years later I still remember his face and the look in his eyes. He was certainly dead by the time I saw his image. I was going to put up some YouTube clips of children with rabies, but on viewing them I decided not to. It broke my heart to look at them, knowing the truly terrible death those little ones were to suffer. They're dead, too, of course.
We're learning more about the basic science of rabies and maybe at some point we'll have an effective treatment. Until we do, we have to depend on good national veterinary services and timely prophylaxis for those suspected of having been bitten by a rabid animal.
I administered two PEPs last year to folks bitten by bats. Truly strange.
I can't recall any examples of cavers coming down with rabies (at least not domestically), although there may be some, and clearly they tend to have vastly more exposure to bats than the general public.
Maybe it's bats out of typical habitats?
Just to clarify -- is the onset of any symptoms too late? i.e., would PEP stand a chance of working if he'd gotten it when his hand went numb and tingly?
Assuming the allergic reactions to PEP are treatable, I think I'd risk them before death by rabies.
Speaking of vaccinations, is there a rabies vaccine for humans at high risk? (I'm thinking people who work with or near wild animals.)
caia: Yes, as far as I know any symptoms mean it's too late. The trade-off with PEP isn't allergy versus rabies (anyone would take that), it's how likely is rabies.
NJ: Regarding cavers, don't know the answer. Anyone else?
Yes, onset of symptoms is too late. PEP consists of a vaccine series and immunoglobulins, which needs to be administered before the virus penetrates the nerves.
High risk humans, such as vets (and vet students like myself), do receive a rabies vaccine. It consists of 3 shots and upon exposure they have a modified PEP: fewer shots and no immunoglobulin is necessary.
I can't quote particular cases of rabies in cavers, but I do know that cases of rabies in cavers in which no bite was known to have occurred led to the idea that rabies is capable of aerosol transmission. I don't think they've been able to prove that, but I am not sure.
Thanks, Revere and Rhabdo!
What's up with the induced coma treatment ... has there been any further publications since that 15 year old girl who was rescued that way? http://content.nejm.org/cgi/content/abstract/352/24/2508
Any idea what 'imaging' they're talking about here? "Eventually the diagnostic images suggested rabies and the diagnosis was made."
I'm only familiar with viral inclusion bodies in the brain - otherwise diagnosis seems to be made on history and presentation...?
-Crystal (another curious vet student)
Crystal: MRI. From the CDC Report:
MRI of the brain revealed new symmetric T2-signal abnormalities within the basal ganglia and medial temporal lobes, with subtle leptomeningeal gadolinium enhancement. The ascending paralysis and coma appeared atypical of idiopathic transverse myelitis, and the patient's clinical progression and brain imaging abnormalities were noted to resemble those observed in rabies encephalitis.
Thanks for this revere. We've had two cases of wild animal rabies so far this year in my county, racoon and skunk. I was just telling the wife I was thinking of putting up some bat houses around the barn to entice the little bug eaters to become permanent residents. This post nixed that idea. While I still want them around, perhaps now not so close.
I know that some states have used aircraft to drop vaccine-inoculated "bait" for raccoons and maybe skunks to consume, in an attempt to reduce the number of susceptible animals in the wild. Has that been successful enough to continue? I wonder if there would be a similar possibility of treating bats? One way would be to construct bat houses that could immunize any and all bats who enter; not sure that is possible.
I know here in NYS we had a tragic case in 1993, when a young girl died as a result of rabies.
Is there no way to find evidence of rabies exposure in an asymptomatic person, in those cases of finding the bat in your cabin? Also, I had believed that you could successfully treat a patient if you caught the early symptoms, like the tingling. How terrible that you can't. Is there a palliative treatment in place to somehow reduce the suffering?
Any vaccination can cause side effects (but not autism); however, in a previous job, I gave a lot of pre-exposure prophylaxis immunizations and boosters with Imovax, in healthy zookeepers and vets, w/o seeing any. Certainly better than getting rabies, and pre-exposure prophylaxis eliminates the need for post-exposure prophylaxis--a nice consideration if you're already feeling pain from an injury.
Other than the few cases mentioned, by the time a victim is symptomatic it's too late, wenchacha. In NY state, if you've received PEP due to possible job exposure, you need a titer every 2 years with a booster as needed.
Revere, I'd also heard that there was a concern that saliva alone, w/o a puncture (or with a very superficial one), is capable of transmission--have you heard anything similar? I do know that if I had a patient who woke up with a bat in their bedroom, I'd have a difficult time NOT giving PEP.
I recall seeing the video of the Iranian folks - heartwrenching. I was at a presentation on a case of rabies in a trekker who was bitten in Nepal, refused prophylaxis several times, and died horribly on return home. There's a monument just outside Ottawa for the Duke of Richmond, who died in 1819 after being bitten by a pet fox. Nasty, but worth remembering.
mnp: You can be infected via mucus membranes (eye) and some evidence via aerosol (mentioned also by another commenter earlier). Mainly, though, it's puncture wounds to watch out for.
Wow, vaccine truffers have invaded vet med too:
An anti-vax video for dogs.
A few years ago I was bitten by a bat that I thought had to be rabid. While pulling weeds during the day, I reached down near the ground and felt a sharp pain at the base of my thumb. There was a bat clinging to my hand and still biting. I threw it to the ground, stomped it, ran to get a plastic bag and immediately went to the emergency room. A bat on the ground during the day convinced me that it was likely rabid. A young girl only two blocks away had been bitten by a rabid bat a few years before (she was treated immediately after the bite).
At the emergency room I got shots of rabies vaccine in my arm at a several places around the site of the bat, immunoglobulin, and tetanus. A city animal control officer came to get the bat and take it to the state lab for diagnosis. The next afternoon I was informed that the bat was negative for rabies! No additional treatment was recommended, but I worried for some time that I did not get the full series of shots in case the findings at the state lab were wrong.
Lewis Thomas ("Lives of a Cell") claimed that the only truly horrid, torturous death he witnessed in his years of practice was a rabies death.
I once saw a raccoon that was probably rabid. It was walking down the middle of a city sidewalk in broad daylight, or rather not walking but moving in a series of intermittent leaps and twisting rushes. I called animal control but by the time they arrived they were unable to find the raccoon.
In the early '90s, I conducted contact interviews after two unconnected rabies deaths in Mexico.
The first was a 9-year-old boy who was bitten by a bat he tried to kick off the porch of an extremely rural home (some 12 hours to the nearest paved road). He died more than 3 months later in the care of a curandero who had no idea of what he was facing. I spent 14 days hiking, visiting less than 50 homes over some 250 square miles of canyons and ridgelines in the Barranca de Cobre teaching residents about rabies, while the zoo-techs with me captured bats (desmodus rotundus - vampire bats) and handed out cattle vaccines to the ranchers (many cows were falling over from "derengue"). We sent 54 desmodus to the lab and not one came up positive.
We caught many more desmodus alive and would smear them with warfarin. When they return to their group lairs (the theory goes) they would preen each other and many others would die from internal hemorrhaging (ironic way to kill a vampire).
The second case was a man who was bitten by a skunk at the waterhole of another extremely rural ranch and died at home less than a month later. After listening to 8 people described the lingering death of their neighbor/husband/brother/son I was convinced there is hardly a more horrible way to die. Those that tried to attend him in his last throes were exposed to a raving, rabid human animal. PEP was flown in and we prophylaxed 15 persons.
Bats are important means of insect control. They are losing habitat. People should not be afraid to put up bat houses. Less than 1% of randomly sampled bats carry rabies.
The key is to keep bats separate from people. That means: exclude bats from your house/cabin; do not handle bats; if you find a bat loose in a home where people have been sleeping or are otherwise incapable of knowing (or communicating) that contact has occurred, the bat should be submitted and tested for rabies. If the indoor-flying bat cannot be tested, PEP should be considered.
You notice that the key is "if contact has occurred". Bat bites may be inapparent, and it is easy to overlook the small puncture wounds that may occur during a bite.
An interesting article about how bats with a history of contact with people are more likely to be rabid than those randomly sampled (EID link below). Certauinly any wild animal that ventures close to people is suspect.
Nice post and a good discussion. I'd take issue with one point made early on:
If you are bitten by a domestic animal (e.g., someone's pet) you don't need PEP while the animal is being observed.
The 10 day waiting period is only for dogs, cats and ferrets. It is based on the premise that if the animal is adVanced enough in its disease process to be shedding virus in its saliva, it will be obviously symptomatic within the 10 day period. (Usually within 4 or 5 days) This is NOT the case for the other mammals that people may keep as pets, ESPECIALLY skunks and raccoons.
MoM: Thanks for the clarification. I got that from CDC but now can't remember if they restricted it only to cats and dogs. Anyway, it's good to have this made more precise. If the animal is being observed I would also hope there was someone who knew that if it were a raccoon or skunk you'd need to get PEP anyway, but I am correcting the post to make sure.
My nephew recently had half his face chewed off by a dog.
My niece took the border collie in, it was a problem dog but she had compassion for it. The nephew was rolling around on the floor with the dog playing with it and it attacked him.
My mother, who often gets information wrong, said they cut off the dogs head and will keep the head to see if rabies are an issue.
May be off track of this subject but if someone has clarification on keeping the head I'd be interested in hearing about it.
Lea: That is indeed how they check for rabies in an animal. That's about all I can say about it given the info you have.
As revere mentioned, if they destroyed the dog as a result of the bite (instead of wanting to keep the dog, in which case they would have kenneled & observed the dog for a couple of weeks) - they do indeed need a sample of brain tissue to test. Heads are sent to the state/county health department where a tissue sample is taken. Used to be they ran a fluorescent antibody test, but they may now test via PCR methodology - depending on the financial status of the PH lab.
Thank you very much Chromosome Crawl.
It wasn't a bite though, it was an attack and the kid has to have reconstructive surgery now.
That's really all I know for now, no doubt mom will have much more to tell me next week.
We actually just had 2 confirmed cases of rabies in skunks here in Northern NY. This is despite the oral rabies vaccination program , I guess there would be more cases if they weren't doing the oral vaccine drop flybys. I'm curious as far as the preventative human vaccines , I had gotten my series and when I had my titer checked (over a year later) found out it hadn't taken. I was then re-vaccinated & titer was fine when checked. I don't work with animals as I used to, I wonder how long the vaccine is actually good for? Also I believe the holding period (quaratine) for livestock, such as rabbits , ferrets etc. to be longer than the usual 10 days for cats & dogs. Any thoughts on this?
Vasha: the raccoon may have also had distemper. I believe it is more common.
CDC's advisory committee on immunization practices put out their updated recommendations for rabies last week on-line for those who want to read all the details of rabies vaccines and post-exposure prophylaxis
a good time to keep things in perspective. in 2002 (the year these figures were compiled)
66 fatlitie from lightning
54 from insect stings
3447 from drowning
16257 from falls
You are in far more danger from mundane things than you are from a rabid bat.
jayh: None of these bad outcomes are the result of bad luck, though. They all have important risk factors you can do something about. Similarly with rabies. And of course terrorism doesn't show up on your list at all. As it shouldn't. But think of all the money we spend on it. I'm more afraid of rabies.
What you do when you see an obviously rabid animal on the street. You don't want those things loose in your neighborhood because they can after all infect neighbors' pets as well as attacking people directly. Go inside, make the phone call, get a firearm, and then shoot to kill while waiting for animal control to arrive. This of course requires that you know how to use firearms safely in a populated area. And discharging a firearm in a populated area may also be a crime, but you can try a "competing harms" defense, claiming that the animal appeared as if it was going to attack someone and was rabid.
Or if you don't have a weapon or want to risk running afoul of the law, call 911 and get the police over there pronto, and let them take care of killing the rabid animal.
Stupid question department: I'm told that at one time the shots for rabies were very very painful. Is that still the case? And if so, why not apply local anaethetics or use TENS or some other means to make them less painful?