Like all sports that appeal to the extreme set, caving is risky. Beyond slips, falls and scrapes, spelunkers chance a host of rare, nasty diseases from cave critters. Typical threats are histoplasmosis, rabies, leptospirosis and tick-borne relapsing fever. Though most underground explorers understand the need for good ropes and headlamps, fewer think about the diseases they can catch beneath the surface, said Ricardo Pereira Igreja, a doctor and professor of infectious disease in Brazil. “People all over the world now are exploring caves for the nature and ecology. For some it’s very spiritual,” said Igreja, of the Federal University of Rio de Janeiro. “I think that’s good, but it does come with some threat.” For a casual tourist, like the 500,000 annual visitors to Carlsbad Caverns National Park in New Mexico, walking through a cave is essentially as safe as walking down the street. It is the sport cavers, those who crawl through muck and mud into little-explored crevices, that must protect themselves from things living on bats, rodents, ticks and other bugs, Igreja said. Igreja surveys the classic and emerging cave-borne diseases in the June 10 Wilderness and Environmental Medicine. We’ve collected a gallery of the offending cave fauna, along with tips about how to keep sickness away next time you’re slithering among the stalagmites. Note: None of these diseases are exclusive to caves. Strange bugs can strike almost anywhere. Image: Wikimedia

Histoplasmosis Once called “cave disease,” histoplasmosis poses the biggest risk to spelunkers. Some people who get infected never notice it, some have lungs so inflamed they have trouble breathing. Most people recover within 10 days, feeling like they’ve had tuberculosis or the flu. In very rare cases, untreated histoplasmosis can be fatal. The fungus, found around the world, infects bats and birds, and creates spores in their droppings. Humans become infected usually by walking through contaminated droppings, kicking up spores and breathing them in. Carlsbad Caverns is a part-time home to about a million migratory Mexican free-tailed bats. For their own protection, park visitors are not allowed near the roosting area, even when the bats are out of town. “There is the potential to catch something in our bat cave,” said Dale Pate, cave specialist at Carlsbad. “We limit who can go back there. Anyone who does has to wear respirators designed to keep histoplasmosis out and they need pre-exposure rabies shots.” Image: Ivan Kuzmin/NSF

Rabies While very rare, rabies is the most serious disease found in caves. Unless treated quickly, rabies inevitably leads to convulsions, coma and death. The disease takes weeks to years to progress and is found in nearly every corner of the world. Bats make up a quarter of the rabid animals reported to the Center for Disease Control; vaccination has helped the numbers of rabid dogs plummet. The humidity of a cave can be a perfect place for rabies to persist. “When you have hundreds of thousands of bats urinating, defecating and doing their daily thing in a very moist warm environment, the rabies virus can last for a period of time after it’s left their body,” said Pate. The most common infection route is a bite or a scrape, however a strange account from the 1950s raises the possibility the virus can travel through the air. A bat researcher and a mining engineer working in a cave caught rabies by breathing the virus in, it seems. However, no similar cases have been reported since. Regular cavers should be vaccinated for rabies, according to the CDC, but as of the latest numbers, only about 20 percent are. If handling or near bats, cavers should also wear gloves. If bitten, washing the wound immediately with soap and water can help. The bat should be examined for rabies, and the caver should see a doctor for early treatment. Image: soschilds/Flickr

Marburg Hemorrhagic Fever Cavers and miners in equatorial Africa risk catching a relative of the Ebola virus, known as Marburg hemorrhagic fever, from the African fruit bat. After incubating for about a week, the disease, which can be carried by many mammals, causes fever, chills and muscle pain. The CDC pinned outbreaks in Uganda and the Democratic Republic of Congo to bats living in mines, in the 2000s. Once sick, miners could transmit it from person to person. Depending on the outbreak, the fever kills 25 to 90 percent of those infected. Few tourists have contracted the fever from visiting caves, still the CDC recommends tourists avoid spelunking, or eating bats or bushmeat in areas where the disease has appeared before. Image: Wikimedia

Leptospirosis Cavers in the tropics can catch leptospirosis from water contaminated with the urine of rats and bats. Within a few days of exposure, a patient feels fever, headaches, sore muscles and their skin may turn yellow with jaundice. The disease responds to antibiotics, but it is far simpler to prevent an infection by not drinking cave water, and by wearing boots, gloves and masks, and washing exposed wounds. Image: Mediatejack/Flickr

Cave Fever Known as “cave fever” in Israel, tick-borne relapsing fever is especially common in Middle Eastern and Central Asian countries. However it is found in the Western U.S., South America and Africa too. The bacteria responsible or the disease lives in ticks found in dark, moist places like caves and abandoned buildings. Symptoms start with fever, chills, headaches, sore joints and stomach pain. After improving, a patient suffers a series of relapses. Patients usually receive a cocktail of the drugs and vaccines that exist, because none are completely effective. Simple insect repellent will help cavers avoid tick bites. And, if a tick is found, it should be removed gently with tweezers pushed close to the skin. Folk remedies using gasoline, kerosine, nail polish and lit matches are all bad ideas. Image: Wikimedia

Most cavers, to be sure, are able to crawl and climb through the earth’s nether regions without any problems. Matthew Kuhns, an engineer living near Los Angeles, has caved for nearly a decade, exploring land beneath Wisconsin, Iowa and Kentucky, and no one he knows has ever gotten sick. While slipping, falling and getting hypothermia is what he’s really worried about, he still takes simple precautions like wearing gloves and never drinking cave water. “You see quite a few salamanders, blind fish, lots of little mites and spiders, cave crickets and bats of course,” said Kuhns, who belongs to the National Speleological Society. “Bats you run into all the time, but they don’t bother you and you don’t bother them.” In Brazil, Dr. Igreja said he treats about one patient a year for histoplasmosis. In fact one of his colleagues studying the disease caught it. Physicians need to know about some of the rarer diseases too, he said, to help diagnose patients who’ve been traveling and caving. The sport, he thinks, will only get more popular. “Caving shows you the most amazing things,” Kuhns said, “beautiful underground rivers, gypsum flowers the size of your head. It’s about the thrill of going somewhere that potentially no one has gone before. And there is always the adrenaline rush if you’re doing something a little risky.” Image: archer10/Flickr