The Good, the Bad and the Simply Irritating: Pictures of Parasites and More
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Creepy-crawlies like roaches and spiders might make you cringe, but there are more tiny bugs and bacteria around than you might realize -- and many take up residence right on your body and bedclothes. For example, dust mites feed on the dead skin cells we shed, and they live all over our homes, on sheets, pillows, curtains and clothing. A typical mattress may contain anywhere from 100,000 to 10 million dust mites.
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Demodex mites are also microscopic mites, but they hit even closer to home. These tiny arthropods are also known as "eyelash mites" because they take up residence on human hair follicles -- most often on the face. Fortunately, they're usually harmless and can be washed away with soap and water.
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It's hard to get through a summer of camping trips and barbecues without suffering at least a few itchy mosquito bites. There are nearly 4,000 varieties of these tiny blood-suckers around the world, and they feed not only on humans, but also other animals. While some carry malaria and other diseases, mosquitoes in the U.S. are usually just an annoyance.
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Some mites are so tiny they actually feed on other insects, including those that go on to feed on humans, like mosquitoes. Here, several miniscule mites (shown in red) hitch a ride on a cricket.
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The botfly infects people in South and Central America by attaching its eggs to blood-feeding insects like mosquitoes, which then transfer the eggs to human skin. The botfly maggot grows under the skin, forming a hard, painful bump. It takes about three months for the maggot to become a fly, but you'll probably want to have it removed by a doctor before that.
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Don't let the bedbugs bite! At less than a quarter-inch long, these bloodsuckers hide out in mattresses, box springs and even couches, and their bites leave itchy bumps on your skin. To avoid bringing them into your home after a trip, be sure to wash everything thoroughly after you stay in any hotel -- these days, not even high-class establishments are immune.
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If you've been hiking through tall grass or gardening around oversized weeds, it's a good idea to wash your legs and ankles thoroughly as soon as you can -- otherwise, chiggers may attack, leaving you with itchy red bites and a painful rash. Because they're too small to see with the naked eye, you won't know you've been bitten until the itch sets in.
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Staphylococcus bacteria are the most common of the 1 trillion bacteria that live on skin. Most types are harmless, but Staphylococcus aureus is the type that may cause staph infections, including blood poisoning, toxic shock syndrome and a variety of skin infections.
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Dutch scientist Antony van Leeuwenhoek is commonly known as "the father of microbiology." During his research in the 1600s, he developed and built his own microscopes and used them to observe single-celled organisms. Many of his observations were the first of their kind, including his recordings of bacteria and muscle fibers.
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People infected with tapeworms usually contract the infection from eating raw or undercooked meat. Once a tapeworm has ended up in the intestine, it may live for years without detection. Amazingly, a tapeworm can grow to more than 12 feet (3.7 meters) long -- in fact, the longest tapeworm removed from a human was about 37 feet (11.3 meters) long!
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Roundworms, or nematodes, are tiny worms that can infect humans and other animals, including dogs and cats. Ascariasis is the most common roundworm infection in people, and it affects millions worldwide. The eggs live in the soil and are transferred from hand to mouth to intestines, where they cause symptoms about a year after infection.
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Before the invention of modern antibiotics, fleas carried the bubonic plague and wreaked havoc on human populations. Today, these tiny parasites are more an annoyance than a dangerous threat. Fleas jump from host to host, often entering your home on your pets, and they can be difficult to get rid of due to their hardy nature.
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Keep those hands washed! While bacteria reside all over our bodies, the forearms and palms tend to carry the most, even more than those in the navel or armpits. You can never get rid of all the bacteria on your body, but don't worry -- most are harmless.
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There are billions of types of bacteria like these in the world, but less than 1 percent cause disease. Bacteria start taking up residence on the human body as soon as an infant emerges from the birth canal, and millions of bacteria grow and die on your skin each day.
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These nasty little microorganisms are known to cause Giardia, an unpleasant disease usually contracted by drinking untreated water. While the disease can occur everywhere, it's more common in underdeveloped countries where humans and other animals share water sources infected with the Giardia parasite.
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Most bacteria inside the human body are in the gut, or intestines. Many of these bacteria are helpful, aiding in the digestive process. Unfortunately, when you take antibiotics to help cure one ailment, you may be killing helpful bacteria, which are there to prevent further illness.
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More mites! Chicken mites, which are fairly common on domesticated poultry, are ectoparasites that live out their lives on the skin and feathers of the birds that host them. While chicken mites can't survive for long on human skin, they can bite and cause mild dermatitis.
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While head lice are usually associated with poverty and unclean living conditions, they actually affect people of all social classes. The wingless insects, which are about 2 to 3 millimeters long, cling to your hair and attack your scalp, leaving itchy bite marks. Unfortunately, they spread quickly and can be difficult to get rid of, although insecticidal shampoos can do the trick.
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Before lice start biting, they start out as nits -- lice eggs in your hair or on your clothes. Nits are "glued" to the hair follicle with a tight bond, making them hard to remove. Nits are generally off-white or brown, and smaller than a sesame seed.
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When you get home from a hike, be sure to check yourself and your gear for ticks: These tiny hitchhikers will attach to your skin and feed on your blood. While some are harmless, others can cause Lyme disease, which causes a wide range of symptoms and can be difficult to treat. A bulls-eye-shaped rash around the infected area is often the first sign of Lyme disease.
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Yeast infections don't just happen to women, and they can actually occur on different areas of the skin, basically on any moist part of the body. The fungal organism, called Candida albicans, thrives in mucous membranes and the gastrointestinal tract, and the chances of contracting a yeast infection can actually increase if you're taking antibiotics.
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Viruses love to infect the human body, and some, like human papillomavirus (HPV) are highly contagious. More than 100 types of the virus can live in and affect humans, and because it has become so common, many teenagers and young adults receive a vaccination to help keep the infection away.
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This lovely parasite, Trichomonas vaginalis, causes the sexually transmitted disease Trichomoniasis. About 7.4 million cases are reported in the U.S. each year, and while the disease affects both men and women, men usually don't exhibit any symptoms. Luckily, Trichomoniasis is easy to treat and usually clears up with no problem.
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Bacteria don't just stick to your skin! Dental streptococcus is a type of bacteria that takes up residence in the oral cavity and around the teeth, causing cavities and tooth decay. While it's impossible to eliminate all the bacteria inside your mouth, brushing and flossing can help!
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You may have suffered from the varicella-zoster virus as a child. Also know as the chickenpox virus, once it's contracted, it actually stays dormant inside you forever, and can cause shingles later in life. Both chickenpox and shingles result in unpleasant, itchy skin rashes.
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Athlete's foot: another parasitic fungus that loves to attack human skin. The parasitic microbial fungi that cause athlete's foot are called Trichophyton and Epidermophyton, and the fungus thrives in moist, warm areas. Athlete's foot is highly contagious, which is why it's often associated with gyms and locker rooms where sweaty athletes congregate.
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Did you know that Botox is actually a protein from a disease-causing bacteria? Before it was used in therapeutic and cosmetic applications, Botulinum toxin type A was just a toxin that came from bacteria that originated in improperly handled meat and was known to cause poisoning. Who knew that it would end up helping eliminate wrinkles?
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A project of the National Institutes of Health, the Human Microbiome Project (HMP) is working on characterizing the various microbial communities found on the human body. Analyzing microbes on the skin, in the gastrointestinal tract, in the nasal and oral passages, and more, the HMP is trying to determine the specific roles of each microbe in the health of the human body.
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With all the germs and bacteria that we're exposed to at home, in the office and elsewhere, many people turn to hand sanitizers to try to stave off infection. While hand sanitizers do kill healthy bacteria as well as the harmful ones you pick up on the go, the good bacteria should be able to regenerate quickly.
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Remember all those helpful bacteria that live inside your gut? These days, some people are turning to probiotics to help ensure these bacteria are active and doing their job. Probiotics, available in supplements and dairy products like yogurt, are actually live microorganisms similar to those friendly bacteria in the gut, and they can aid in digestion and help keep harmful bacteria at bay.
Learn about some more ways bacteria can be beneficial by checking out our list of 10 Reasons to Like Bacteria.
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