Why is rabies like a wedding?" Charles Rupprecht, known as the "rabies guru" of the Centers for Disease Control and Prevention, tells how he put the riddle to public health workers in Virginia recently, giving eight talks in two days.
Usually such talks focus on pet vaccination, dealing with strays, or raccoon rabies, which in Maryland has leapt from seven cases in 1981 to 346 last year. But this time there was an added incentive to come: A few months earlier, Virginia had something rare enough happen that most doctors never encounter it. A person died from rabies.
Last year might have passed without a single rabies death in the United States if not for the man who got sick about a week before Christmas. The Nottoway Correctional Center inmate complained of back pain, then of vomiting and cramps, then of muscle spasms and tremors. He was sent to Richmond for tests that ranged from a CAT scan to one for pesticide intoxication. Though he had no sign or history of an animal bite, his doctor considered rabies next. Tests were positive. The patient died Dec. 31. He was 29. The virus was traced to a bat bite.
Widespread pet vaccination of dogs, cats and even ferrets has created a public-health success story: Human rabies deaths in the United States are down to about three a year. That success comes at a yearly national cost of at least $300 million -- one CDC estimate is as high as $1 billion -- for rabies prevention and treatment.
Yet within these rare deaths is an emerging mystery. In 19 of the 27 deaths since 1990, neither doctors nor victims and their families could pin down how the victim caught the virus. All they knew for sure is what the tests showed: It was most often a rabies strain found in silver-haired bats, a reclusive and solitary species that usually avoids humans like, well, the plague. None came from the little brown bat, the species that people in the Baltimore-Washington area are most likely to see.
The last rabies death in Maryland, in 1976, came from a bat bite. The woman knew she was bitten, and the bat was caught and tested. Its species wasn't recorded. For her, the treatment failed. A more effective treatment used since the late '70s hasn't failed yet, according to the CDC.
The 19 deaths since 1990 didn't happen because of treatment failure but because there was no reason to suspect rabies. The victims didn't remember being bitten by any animal. Some didn't remember ever even seeing a bat. Yet there had to have been direct physical contact with one.
This puzzle is how rabies is like a wedding, Rupprecht says: "It's something old, and something new." Rabies is one of the oldest viruses known, but the new deaths today might be evidence of an evolving and possibly more virulent virus.
"It's quite a peculiar situation," says Rupprecht, chief of the rabies section at the National Center for Infectious Diseases. In North America, he says, "we're surrounded by rabies from raccoons, skunks, foxes." Yet, he says, the deaths most often have been caused not by these land animals but by the strain found in this obscure bat species.
A look at a CDC map tracking where rabid raccoons are found shows a strain that covers much of the eastern United States. Even 10 years ago, many of these states hadn't reported a single rabid raccoon.
Raccoons brought by hunters from the Deep South to West Virginia and Virginia brought wildlife rabies to Maryland, says Clifford I. Johnson, Maryland's public health veterinarian. "They just multiplied, and it spilled over."
Rabies apparently spreads among land animals far more readily than among bat colonies; the percentage of infected bats is usually pretty steady -- just half of 1 percent, bat experts say. And bats usually only infect other bats and sometimes horses, while land animals can pass infections easily among each other, to domestic pets and humans.
Once the symptoms show up, rabies is fatal. In recorded history, says Bela Matyas, medical director of the epidemiology program at the Massachusetts Department of Public Health, only four people have survived it, and three of these had had previous vaccinations.
"Rabies is an untreatable disease," says Matyas. "We don't treat rabies, we treat exposure to rabies. What we're actually trying to do is to destroy the virus before it can cause disease."
In the incubation period -- usually a few weeks, but sometimes several months -- as the virus works its way from the contact site into the nervous system, injections can almost always wipe it out. This used to mean a painful 26 shots in the stomach. The current and more effective treatment is usually five intramuscular shots over about a month, and one or more injections around the site of the bite or contact. It might make you feel a little ill, but there are no severe side effects. Its main drawback is its cost, which can be up to $4,000, depending on a person's size and hospital costs.
The problem is: You can be cured only if you realize you've been bitten.
The CDC Morbidity and Mortality Weekly Reports from the past nine years on human rabies deaths are oddly alike: A patient shows up at an emergency room, usually not terribly ill, with pain in one arm, nausea or a sore throat. Some patients are given throat spray. They're sent home, but they're seen again -- this time with fever, throat spasms, difficulty breathing, hallucinations, pain. Tests and treatment attempts are stepped up; everything from mad cow disease to alcohol withdrawal has been considered.
In cases where rabies began to be suspected, skin, saliva and blood tests were done. Sometimes the tests are negative; enough virus hasn't built up in the body to show up. The quickest way to diagnose rabies is through brain tissue. Suspected rabid animals are sometimes killed to examine the brain. That's not feasible with a sick human.
After a confirmation of rabies, it's probably too late for the victim, but not for those close to him. Family, living partners, health workers, all get preventive rabies treatment shots, even though the only documented U.S. case of human-to-human transmission of the disease has been through eye transplants, of an infected cornea.
Then there's the hunt for the cause -- the contact with the infected animal. In the case of bat contact, a bite can pass for a paper cut, a scratch from a thorn, or leave no trace at all, because a bat's teeth are so tiny and sharp.
Because viruses change to spread more easily, there's speculation that the bat strain of rabies might have adapted to be more easily transmissible though the tiny wounds a bat can make, that it could now be more virulent than that found in dogs or raccoons. But this is just a hypothesis, scientists say, and the rarity of the occurrences makes any proof unlikely.
Less rare: the chance of an encounter with a rabid raccoon, and the chance that person, and everyone close to him, will have to get the treatments. Costs can mount.
That's why much public health energy is directed toward controlling rabies in wild land animals. One of the latest weapons is a hit of rabies vaccine wrapped in a small fishmeal package -- tasty to raccoons. About 8,800 of these oral vaccine baits were tossed out of helicopters and car windows onto the Annapolis Peninsula in October. Anne Arundel County has the highest incidence of rabies, followed by Frederick; Baltimore County is fifth on the list. (Lower numbers in other counties might not mean the incidence is actually lower. Johnson points out that statistics can be skewed by more or less aggressive testing and animal control.)
When Annapolis-area raccoons were trapped, tested and released in November and December, 50 percent were found to have developed antibodies to rabies, says Joseph Horman, a veterinarian and consultant to the Anne Arundel County Health Department, "a pretty good response for the first time out."
Says Johnson: "I'm hoping we will have a regional program, because all the surrounding states have a problem. I think it's promising, if we can get funds to continue." He weighs the cost of the baits -- about $15,000 -- against the cost of rabies post-exposure shots -- at least 1,000 a year at about $1,500 a shot, he says.
If they can feed vaccine to raccoons, couldn't they feed it to bats, too? Rupprecht says problems are presented by bats' migratory patterns and diet of choice -- insects.
For now, he says, education is the least costly weapon. Maryland's health department is readying information on rabies for distribution, including to children's summer camps, says Johnson. Public health workers are spreading the word about new guidelines for bat contact.
And while it's intriguing medically, the problem of bat rabies is far outweighed by the value of bats to the ecosystem. One tiny bat can eat 1,200 mosquitoes in an hour -- and mosquitoes can carry diseases such as malaria and encephalitis.
If your pet is bitten
If your vaccinated pet is bitten by an animal, take it to the vet. Sometimes animals must be kept under observation after a bite.
Signs of rabies in a pet can vary. A pet may be hostile and bite at objects. More often, it will become passive, timid and shy, refuse food and water, or have difficulty swallowing.
Other signs include behavior changes, problems swallowing, excessive drooling and difficulty moving or paralysis.
Source: Centers for Disease Control and Prevention
If your pet is bitten
If your vaccinated pet is bitten by an animal, take it to the vet. Sometimes animals must be kept under observation after a bite.
Signs of rabies in a pet can vary. A pet may be hostile and bite at objects. More often, it will become passive, timid and shy, refuse food and water, or have difficulty swallowing.
Other signs include behavior changes, problems swallowing, excessive drooling and difficulty moving or paralysis.
Source: Centers for Disease Control and Prevention
Silver-haired bat
Many of the 27 rabies deaths in the United States since 1990 have been linked to a strain carried by silver-haired bats, which are about the size of mice and whose bites may go undetected. They usually roost under the bark of trees in old forests and almost never in houses.
Bats found most often in Maryland houses are brown bats, which come out of hibernation around March and seek warm spaces to bear and raise young through August. One case of rabies has been linked to the brown bat, but it's highly unlikely that its bite would go undetected.
Remember: Bats are the farmer's friend. In an hour, a bat can consume half its body weight in insects.
Raccoon
Raccoons are responsible for most rabies cases among land animals, including humans. In Maryland, rabies was confirmed in 346 raccoons last year, compared with seven in 1981. But because people tend to know if they've come in contact with a rabid raccoon, they seek treatment and death is extremely rare.
The bat problem
Most recent human rabies deaths have been due to a strain of rabies associated with silver-haired bats.
This species, difficult to see because of its coloration, often roosts in tree cavities or in bark crevices on tree trunks. They are reclusive and solitary and don't like competition, so if you see a group of bats flitting through your neighborhood in the evening, that's good, says Bat Conservation International, based in Austin, Texas. It's a sign that it's a healthy species of bats.
A couple of common questions about bats and rabies:
How can I tell if a bat has rabies?
Rabies can be confirmed only in a laboratory. However, any bat that is active by day, is found in a place where bats are not usually seen (for example, in a room in your home or on the lawn), or is unable to fly, is far more likely than others to be rabid. Such bats are often the most easily approached. Therefore, it is best never to handle any bat.
What should I do if I come in contact with a bat?
According to new CDC guidelines: If you are bitten by a bat -- or if infectious material (such as saliva) from a bat gets into your eyes, nose, mouth or a wound -- wash the area thoroughly and get medical advice immediately. If possible, the bat should be captured and sent to a lab for testing.
People usually know when they have been bitten by a bat. However, because bats have small teeth, bite marks are not easily seen, and there are situations in which you should seek medical advice even in the absence of an obvious bite wound. For example, if you awaken and find a bat in your room, see a bat in the room of an unattended child, or see a bat near a mentally impaired or intoxicated person, seek medical advice and have the bat tested.
People cannot get rabies just from seeing a bat or having contact with bat guano (feces), blood or urine, or from touching a bat on its fur (even though bats should never be handled).
Source: Centers for Disease Control and Prevention
Other tips
* Get your pets vaccinated. State vet Clifford I. Johnson says his biggest headache is unvaccinated cats and people who don't leave strays alone.
* Leave the wildlife alone. Besides raccoons, skunks and foxes, opossum and beavers have been found to have rabies. Squirrels, rats, mice or other small rodents are not known to have rabies.
* Drink pasteurized milk. Livestock such as horses and cows can have rabies, though the incidence isn't high. In November, Massachusetts had to give rabies treatments to 66 people who drank unpasteurized milk from a cow found to be rabid. The virus is fragile, though; heat from pasteurization or cooking kills it quickly.