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How many species of mites live on the human body?

How many species of mites live on the human body?


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How many known species of mites regularly live on the human body?

I've always heard that most people have eyebrow mites. This source mentions 2 species of face mites, Demodex folliculorum and D. brevis, that also regularly live on humans, but I'm wondering if there are in fact other species of mites that also call human bodies home. If so, how many? And where do they live?

Note: I'm not talking about disruptive mites such as scabies, but mites that go less detected.


The answer is 2-3 human mites.

This page says that 2 mites specialize on humans: http://www.bbc.com/earth/story/20150508-these-mites-live-on-your-face https://link.springer.com/article/10.1007/s10493-009-9272-0

Another page I found said there are 3 common human mites, adding scabies to the list.

This page talks about bites from a variety of dust and house mites: https://link.springer.com/article/10.1007/s10493-009-9272-0

My biology lecturer from university of Edinburgh told us that we have hundreds of species of detrital nematodes living on and inside us and that nematodes can be a few microns long. About 800 million humans have a 30cm large nematode inside them according to the WHO.


These microscopic mites live on your face

You almost certainly have animals living on your face.

You can't see them, but they're there. They are microscopic mites, eight-legged creatures rather like spiders. Almost every human being has them. They spend their entire lives on our faces, where they eat, mate and finally die.

Before you start buying extra-strong facewash, you should know that these microscopic lodgers probably aren't a serious problem. They may well be almost entirely harmless. What's more, because they are so common they could help reveal our history in unparalleled detail.

There are two species of mite that live on your face: Demodex folliculorum and D. brevis.

They are arthropods, the group that includes jointed-legged animals such as insects and crabs. Being mites, their closest relatives are spiders and ticks.

Scientists have known that humans carry face mites for a long time

Demodex mites have eight short and stubby legs near their heads. Their bodies are elongated, almost worm-like. Under a microscope, they look as though they're swimming through oil, neither very far, nor very fast.

The two species live in slightly different places. D. folliculorum resides in pores and hair follicles, while D. brevis prefers to settle deeper, in your oily sebaceous glands.

Compared with other parts of your body, your face has larger pores and more numerous sebaceous glands, which may explain why the mites tend to live there. But they have also been found elsewhere, including the genital area and on breasts.

Scientists have known that humans carry face mites for a long time. D. folliculorum was spotted in human earwax in France in 1842.

You may have around two mites per eyelash

In 2014, it became clear just how ubiquitous they are. Megan Thoemmes of North Carolina State University in Raleigh and her colleagues found, as had previous studies, that about 14% of people had visible mites. But they also found Demodex DNA on every single face they tested.

That suggests we all have them, and probably in quite large numbers. "It's hard to speculate or quantify but a low population would be maybe in the hundreds," says Thoemmes. "A high mite population would be thousands." Put another way, you may have around two mites per eyelash.

The populations may well vary from person to person, so you might have many more than your neighbour or far fewer. You may also have more mites on one side of your face than the other.

Yet it's not clear what the mites are getting from us. For starters, we're not sure what they eat.

"Some people think they eat the bacteria that are associated with the skin," says Thoemmes. "Some think they eat the dead skin cells. Some think they're eating the oil from the sebaceous gland."

They've never been known to eat one another

Thoemmes and her colleagues are currently looking at the microorganisms that live in the mites' guts. That could help determine their diet.

We also don't know much about how they reproduce. Other species of mite get up to all sorts of things, from incest and sexual cannibalism to matricide and fratricide. But so far it seems Demodex are a little less extreme.

"They've never been known to eat one another," says Thoemmes. "It appears that they come out at night to mate and then go back to their pores."

The only thing we know about is their eggs.

"We have caught a Demodex laying an egg on camera," says Thoemmes. The video is available on YouTube.

Female Demodex mites lay their eggs around the rim of the pore they are living in. But they probably don't lay many.

"Their eggs are quite large, a third to a half the size of their body, which would be very metabolically demanding," says Thoemmes. "They're so large they're probably laying one at a time, as I can't imagine that more than one can fit in their bodies based on the size."

Speaking of objects that Demodex need to push out of their bodies, these mites also don't have anuses.

They still need to poo, so it's been said that they 'explode' with waste at the end of their lives. However, that's "a bit of an over-exaggeration", says Thoemmes.

All their waste builds up over time and then there's one large flush of bacteria

They do save it all up until death, though. When a Demodex dies, its body dries out and all the built-up waste degrades on your face.

"It's not an exploding action necessarily, but it's true that all their waste builds up over time and then there's one large flush of bacteria," says Thoemmes. "It's not just coming in discrete units over time, it's a lot built up that comes out."

That may sound terrible. But surprisingly, it looks as though these mites are not harmful.

"I would think that they're not harming us in a way that's detectable," says Thoemmes. "If we were having a strong negative response to their presence, we'd be seeing that in a greater number of people."

People suffering from rosacea tend to have more Demodex mites

The one thing they have been linked to is a skin problem called rosacea. This mainly affects people's faces, and begins with flushing before sometimes progressing to permanent redness, spots, and sensations of burning or stinting.

Studies have found that people suffering from rosacea tend to have more Demodex mites. Instead of 1 or 2 per square centimetre of skin, the number rises to 10 to 20.

But that doesn't mean the mites cause the problem.

"The mites are involved in rosacea, but they're not causing it, "says Kevin Kavanagh of Maynooth University in Ireland. In a study published in 2012, he concluded that the root cause was changes in people's skin.

Our skin gradually changes over the years, for instance due to ageing or exposure to the weather. This alters the sebum, an oily substance produced by the sebaceous glands that helps keep our skin moist.

When the mites die, they release their internal contents

Demodex are thought to eat the sebum, and the change in its makeup may cause a population boom. "This causes irritation in the face, just because there are so many mites around," says Kavanagh.

There also seems to be a link between rosacea symptoms and the big flush of bacteria released when a mite dies.

"When the mites die, they release their internal contents," says Kavanagh. "This contains a lot of bacteria and toxins that cause irritation and inflammation."

There may also be a link with the immune system, which normally protects us against infections. Thoemmes says the mites have been found to be particularly abundant on people with immune deficiencies, such as AIDS or cancer.

"I think mites are exploding because you're having an immune response to something else," she says. "Rosacea is another response to that."

For most people, most of the time, they're harmless

It's still not clear what sort of relationship we have with our Demodex mites. We can be sure they are not parasites, which take things from us and cause harm in the process.

The relationship might instead be commensal, meaning that they do take something from us but not in a way that normally causes harm. For most people, most of the time, they're harmless.

They may even be beneficial. For instance, they may clear dead skin off our faces or eat harmful skin bacteria.

But suppose you really wanted to get rid of them. Could you?

Although there are therapies that kill Demodex mites, we can't get rid of them forever.

They rebound after about six weeks, says Kavanagh. "We pick them up from people who we are in contact with. We pick them up from sheets, pillows, towels. There's good evidence that we transmit them between each other."

We may pick up Demodex very early in life

It looks as if there is something special on our faces that they need. Even if you kill them off, you're going to get them again, because they're everywhere and they want to be on your face.

In line with that we may pick up Demodex very early in life. "Demodex mites have been found in mammary tissue," says Thoemmes. As a result, she suspects they travel from mother to baby, perhaps through breast-feeding or even at birth.

We may then pick up a few more from the people we know as we grow older. Thoemmes's study found more mite activity on adults over 18 than on 18-year-olds.

It also seems our species has carried Demodex mites for a long time.

Humans have long had a close relationship with domestic dogs

Thoemmes speculates it might be "since we evolved from our hominid ancestors". That would mean we've been carrying these animals for 20,000 years.

We might have picked them up from other animals. D. brevis is particularly similar to a species that lives on dogs. Humans have long had a close relationship with domestic dogs, and with their wild relatives, wolves. Thoemmes suggests our ancestors "lived closely with them, for hunting purposes or that kind of thing", and picked up the mites as a result.

As well as our relationships with animals, the mites could reveal a lot about our relationships with each other. Their genes contain clues to our history.

When Thoemmes looked at the mites' DNA, she found that mites collected from Chinese populations were distinctly different from those collected from North and South American populations.

Because these differences exist, studying the mites could tell us how our distant ancestors migrated around the planet, and reveal which modern populations are most closely related.

"We might be able to figure out human associations&hellip we weren't able to figure out or see before," says Thoemmes.

She is particularly interested in finding out about the colonisation of Central and South America. "There's been a lot of speculation as to which populations of humans colonised Brazil and inter-bred," she says.

Demodex could also allow us to peer much further back in time, and investigate how we evolved. If they've lived with us for so long, it is possible our immune systems have changed as a result. These little mites may have helped shape how we respond to disease.

Our bodies are seething with microorganisms

"They most certainly have an effect on us, as we do on them," says Thoemmes. "We could be having immune responses to them, which could have been having an effect on our health and immune systems."

For now, this is all speculation. But even if none of these ideas pay off, the story of Demodex is a reminder that we humans are home to a multitude of species.

Some, such as head lice and fleas, hop aboard occasionally, or only live on certain populations. Others, like Demodex and the microorganisms in our guts, are with all of us throughout our lives. Our bodies are seething with microorganisms: they make up 90% of our cells.

There is a simple lesson here. You are not just you: you are a walking, talking community, an entire ecosystem held within one body.


Scabies Mites

Biology

The scabies mite (Figure 4) or human itch mite burrows into the outer layers of the skin of humans causing human mange or scabies. Different varieties of scabies mites are specific for certain mammals including man, domestic animals, and wild animals.

The female mite makes long burrows in folds of skin. The female lays from 40 to 50 eggs in the burrow. The larvae and nymphs develop and burrow in the skin. The total life cycle takes one to three weeks depending on the environment.

Transmission

Scabies mites are transmitted from one person to another by direct contact or also by two people who share the same bed. People are most likely to become infested when living in crowded quarters with other people. Dog scabies often can be transmitted to man under ideal conditions.

Symptoms

Persons infested with scabies suffer severe itching. A rash may develop later as the person becomes sensitized to the mites. The rash usually occurs around armpits, the wrists, the waist, and back of the calves. Even though only a few mites may be present, the rash may spread over much of the body.

Control

If scabies mites are suspected, a physician should be consulted for diagnosis and treatment. If dog scabies transmission to man is suspected, a veterinarian should be consulted for treatment of the dog at the same time that the human is treated.


Scientists say face mites evolved alongside humans since the dawn of human origins

Scientists have discovered a universal human truth about our bodies: they all, without exception, have mites. A landmark new study, led by scientists at Bowdoin and the California Academy of Sciences, explores the fascinating, little-known natural history of the face mite species Demodex folliculorum, using genetic testing to link the microscopic animal's evolution to our own ever-evolving human story. By zooming in on a type of genetic material (called mitochondrial DNA) in mite samples from around the world, scientists discovered that different human populations have different mites, that those mites follow families through generations, and that they are not casually transferred between humans. The study is published today in the Early Edition of the journal PNAS.

Dr. Michelle Trautwein, Academy curator of entomology and senior author of the new findings, says improving the understanding of the mites that live in human hair follicles helps shed light on human evolution and may allow scientists to pinpoint mites' role in human health. Dubbed "face mites," D. folliculorum are actually tiny arachnids that inhabit hairs throughout the human body and consume skin cells and oils. Mites exist in human ears, eyebrows, and eyelashes as well as hairs that cover nipples and genitals.

For most people, mites are harmless. For some, however, mites can be associated with various skin and eye disorders including rosacea and blepharitis. Trautwein says this is one reason among many that scientists need to learn more about these constant human companions.

"It's shocking that we're only just discovering how deeply our histories are shared with the mites on our bodies," says Trautwein, who has traveled the world to sample mites and learn more about their cryptic lives. "They aren't just bugs on our faces, they are storytellers. Mites tell us about our own ancient history--it's a complex story, and we've only just scratched the surface."

To understand how and why mites vary geographically, study authors sampled 70 human hosts from around the world. For some subjects, intact mites were collected by drawing the curved end of a bobby pin across a participant's forehead in others, metal laboratory spatulas were used to take samples that included a mix of hair and skin cells (including mites) from cheek and outer nose. The scientists then sequenced mite DNA to look at the mitochondrial DNA of each subject's mites.

"We discovered that people from different parts of the world host different mite lineages," says Trautwein. "The continent where a person's ancestry originated tended to predict the types of mites on their faces. We found that mite lineages can persist in hosts for generations. Even if you move to a faraway region, your mites stick with you."

The study revealed that, in some cases, African Americans who had been living in the U.S. for generations still hosted African mites. These results suggest that some mite populations are better able to survive and reproduce on hosts from certain geographic regions. Differences in mite lineages, the authors suggest, are consistent with the divergence of human populations and support the "Out of Africa" hypothesis. This widely accepted theory about the origins of humanity states that every living human today is descended from a group that evolved in Africa and dispersed into the wider world. Though the study results suggest that mites predated the dawn of modern humans, Trautwein says that mites were likely along for that much later series of journeys off the continent.

"Another exciting mite revelation from our work is that mites aren't shared easily," says Trautwein. "Mites are not casually transferred to passersby on the street. We seem to share mites primarily with our family, so it likely takes very close physical contact to transmit mites."

Going forward, Trautwein and her multidisciplinary colleagues will continue to research the strange lives of mites and how they relate to human evolutionary history and health. Trautwein is in the midst of a multi-year project sampling arthropods (and collecting mite samples) alongside citizen scientists in homes on all seven continents, exploring the overlooked life that shares our homes and bodies on a daily basis. Past expeditions include Sweden, the Peruvian Amazon, and houses in the Academy's own San Francisco backyard. Trautwein will continue sampling mites and collecting house-dwelling arthropods in Australia, Mozambique, China, and Antarctica in 2016-17.


How to Get Rid of Mites on a Human

Six types of mites commonly affect humans these include scabies mites, straw itch mites, bird mites, chigger mites, clover mites and dust mites. A common misconception about mites is that they are insects. According to North Carolina State University, mites are not insects but more closely related to arachnids, such as spiders. The Illinois Department of Health claims that most mites do not make any contact with humans, but mites that do come into contact with human skin can cause mild to severe reactions 1.

See a physician immediately if you are experiencing symptoms such as a rash or severe itching that may indicate a mite infestation. A doctor may need to prescribe an insecticide lotion for the skin of an affected person. Mites may affect other household members. If you are living with someone being treated for mites, you should also seek treatment.

Mattress Care for Scabies

Kill mites with tick repellents as the two insect-like creatures are similar. Spray repellent on clothing to kill mites.

Clean the home thoroughly as some mites can live off a host for a number of days. This creates an ongoing infestation problem. Vacuum often and thoroughly. Vacuum carpets and mattresses, as well as any other upholstered furniture daily for several weeks.

How to Get Rid of Turkey Ticks

Wipe hard surfaces with a cloth dampened with alcohol. This will kill any mites that are too small to see but may crawl along these surfaces.

Change disposable filters on air-conditioners and furnaces, or clean air filters often to inhibit dust mites from infesting the home. You can also place filters inside of heater grates for added protection and cleanliness. These filters will catch dust and dust mites that may enter through the vent system.

Place pillows and mattresses inside plastic zip-up coverings to prevent mites from nesting and breeding in bedding. Clean infested mattresses with the upholstery attachment on a vacuum cleaner. Clean pillows and other bedding in the washing machine.

Removing host-animals, such as birds and rodents, from the home may reduce the risk of mite infestations.

Use tick repellents on clothing (especially shoes and pant legs) when walking through heavily weeded areas that may contain mites. Chiggers are known for living in the same densely weeded areas that ticks are typically found in.

Warnings

Avoid the use of chemical insecticides when trying to rid the home of dust mites. According to the North Caroline State University Department of Entomology, dust mites can cause respiratory irritation and pesticides may aggravate respiratory conditions.


Belly button bugs

Two of the main stories in the first episode focus on belly button bacteria and on the many varieties of lice.

A person’s belly button contains hundreds of bacterial species. The belly button is rarely well-washed and is a cosy place for these bacteria to settle. The bacteria here are probably not critical to our existence, but their presence does provide a quick and easy way to sample the great variety of bacteria living on the rest of human body.

Scientists can take a simple swab and quickly build up a profile for the sort of bacteria to which you’ve been exposed. As they build up profiles from many people, it becomes possible to tell the difference between good and bad bacteria. Your belly button bacteria can then help predict which diseases you might get and, if you do get one, how easily you may fight it off.

The story of the human louse and its various specialities is also a good one – and is examined with stunning new electron microscopy videos. It is an evolutionary tale that explores how lice migrated across the body during our hairier past. It explains how they had to specialise to live in different environments as we became less hairy, as head lice can’t survive on any other part of the body.

Microscopic scabies mites live on the skin. SBS

The documentary links our loss of hair (to get rid of these parasites) with the lighter coloured skin of cooler climate people. It even looks at why we have some lice that came from our nearest simian neighbours – in this case, there must have been some close physical contact. Despite some aspersions cast on our early ancestors, this makes for a complex and interesting tale.


The Organisms That Make Us Who We Are

From bacteria to viruses, mites to fungi, our bodies are literally riddled with life. Perhaps to a greater extent than you ever thought imaginable. But are these guests up to mischief should we throw them out for trashing the house? Or do we welcome them with open arms and beg them not to leave. From assisting your immune system to having sex on your face (wait, what?!), this article is going to explore the organisms that have set up camp on and inside our bodies.

The Human Microbiome

Let’s start with microbes. Microbes are microscopic organisms such as bacteria, archaea, protozoa and fungi, and these microorganisms that reside on or within your body are referred to as the human microbiome. This microbial colonization begins during and shortly after birth. Your body is composed of about 10 trillion human cells, but bacteria outnumber them by at least ten to one. Microbes actually make up around 1 to 3% of your total body mass. These microbes colonize lots of different areas of the body including your skin, gut, mouth, eyes, and genitals.

What&aposs lurking in your gut

You can find anywhere between 500 to 1,000 different species of bacteria in your gut alone, and they actually make up 60% of the dry mass of your feces- yummy. Common bacterial species found includes E. coli, B. bifidum and E. faecalis. These bacteria are far from just being gate crashers we have developed a symbiotic relationship with them. We provide these bacterial species with a nice home to live and replicate in, whilst they provide us with a myriad of benefits. For example, they assist in the breakdown of food, and they help to prevent harmful species from colonizing which could adversely affect our health. They also assist in the production of hormones and vitamins, namely vitamins B and K. It is also becoming increasingly apparent that the bacteria present in your gut play a role in modulating and training your immune system to be able to recognize friend from foe. 

Scanning electron micrograph of E. faecalis​, found in the human colon. Wikimedia commons. 

But do these bacteria only do good things? Apparently not. There is an increasing amount of evidence to suggest that certain bacterial species colonizing the gut are actually associated with obesity. These microbes are more commonly found in those living in colder northern areas of the world, compared to warmer southern areas. It seems that certain types of bacteria found in leaner individuals are better at breaking down certain types of food.   

Spotty Skin and Smelly Pits

Your skin also has plenty of microbes, especially your hands- it&aposs amazing what you can grow in a petri dish if you stick your finger on one. Bacteria present on your skin can sometimes associate with oil glands, playing a role in the development of acne. Your sweat is also naturally odorless it’s the bacteria found on the skin that make it smell. Interestingly, your unique body odor correlates with the presence of specific microbes, as they break down non-volatile compounds into volatile compounds with characteristic scents. It was discovered that the higher the density of a group of bacteria called coryneforms, the more the underarms smelt. 

The skin microbiome. Wikimedia commons.

Recently the bacterial species living in our navels (belly buttons) was investigated it was found to be colonized to an extent greater than scientists could have ever predicted. They swabbed 60 bellybuttons and found a whopping 2,368 phylotypes of bacteria, which probably corresponded to an even bigger number of bacterial species. It was thought that 1,458 of these bacterial species could be new to science. Amazingly, one volunteer harbored a species of bacteria that has only ever been isolated in Japanese soil- and he had never been to Japan! Another (who admitted to not washing very much. ) had a species of extremophilic (thrives in extreme environments) bacteria that is often found in deep sea hydrothermal vents and ice caps. Intriguing or disgusting, but our bellybuttons are turning out to be a microscopic jungle, and it&aposs exciting microbiologists a great deal. Just imagine what could be in yours! Or maybe don&apost.

Most of the bacterial species found in our bodies don’t do us any harm, and so are referred to as commensals. But they can become opportunistic pathogens, for example if immunity is lowered or natural barriers become compromised, such as the blood brain barrier. This is where they can go rogue and cause problems.

Organisms That Can Alter Your Behavior?

So, we know that organisms can affect your health, in positive and negative ways. But what about your personality? There has been some very interesting research emerging on a protozoan organism called Toxoplasma gondii which is found in 22-84% of the human population (depending on the country). The most intriguing effect of toxoplasmosis is the apparent �tal attraction syndrome” which occurs in infected rodents. T. gondii can only productively replicate in cats, but it can infect humans and rodents. Amazingly, it has found a way to alter the brain signaling of the rodents to make them more likely to be consumed by the cat. Infected rodents in studies had slower reaction times and displayed no aversion to the scent of cat urine, which rodents usually have an innate fear of.

But what’s perhaps more interesting is what they have found in humans. It was discovered that people with toxoplasmosis had slower reaction times and actually enjoyed the smell of cat urine! No other types of urine (they tested a few), just cat urine, whereas uninfected individuals did not like the smell. Is the organism trying to alter the behavior of the human to make it more likely to be eaten by cats?! It goes on they studied people involved in road traffic accidents in Prague. They found that those involved in accidents, whether they were a pedestrian or driver, were more likely to be infected when compared with residents not involved in accidents. This suggested that those individuals were perhaps sometimes more reckless. This research has certainly been met with raised eyebrows, and confounding factors are always a possibility. For example, it may not be that toxoplasmosis affects your personality, but perhaps people with a particular personality are more susceptible to toxoplasmosis.

Your Face As A Breeding Ground

So what other weird things live on your body? There are some very interesting creepy crawlies alongside these microbes. Mites, or more specifically Demodex, live in places such as your eyelash and eyebrow follicles. They&aposre the most common ectoparasite (parasite that lives on the surface of the host) on the human skin. Usually these critters will do you no harm, although in some instances they have been found to cause skin disease. They can leave the follicles and walk around the skin at night, meeting others to then mate at the follicle opening. Once they’ve done the dirty deed, they go back to the inside of the hair follicle to lay eggs. You give these mites a comfy bed and what do they do? Have sex on your face. They&aposre worse than teenagers. Perhaps even more disgustingly, Demodex don&apost actually have an anus. This means they have no way of getting rid of their feces, so when they die they explode all of this feces into your pores. Some scientists may believe that this is sufficient to stimulate an immune reaction, and may be the cause of the acne-like skin condition rosacea.

Nobody Loves Me. Think I&aposll Go And Eat Worms. 

Although worms are not found in everyone, they&aposre surprisingly common in the human population. There areਃ main typesਏound in humans flatworms such as tapeworms, flukes such as blood flukes, and roundworms such as threadworms, pinworms or hookworms. 

The largest of the intestinal worms found in humans is the roundworm Ascaris lumbricoides, whichꃊn reach a whopping 35 centimeters. After ingesting the eggs they hatch and bury into the intestinal wall, entering the blood stream. From here, they travel to the lungs where they&aposre coughed up and swallowed again, returning to the gut once more.

Tapeworms are transmitted via infected food, and once inside the body it attaches to the intestine via hooks found on its head. Here, it can survive for up to 25 years! If you&aposre unlucky enough to become infected with hookworms (Necator americanus), these intestinal parasites actually drink your blood and can cause a type of anemia. 

And finally my favorite, the pinworm. These little guys are only a few millimeters in length, and once again live in the intestines. They mate by traumatic insemination- the male stabs the female with his penis, and then dies. At least they die happy.  

Let&aposs Not Forget Viruses!

It might surprise you to learn just how many viruses there are in our bodies. It recently emerged that like the human microbiome, humans also have a virome. Our human viromes have been suggested to be even more diverse than our microbiomes, and they also vary considerably between people. In one study investigating twins and their mother, they found between 52-2773 different viruses. We also have a surprising amount of viruses in our bodies that infect bacteria- these are called bacteriophages. For every bacterium in your body, it is estimated that there is a whopping 100 bacteriophages. Going back to poo- there is approximately 10 billion in each gram. Wow. 

Just like how it has been suggested that the bacteria in your gut can contribute to obesity, there has been some interesting, if very controversial, research to suggest that perhaps viruses can also play a role. A small number of researchers have been investigating a particular type of adenovirus, and they found that infection correlated nicely with obesity. This was triggered by observations in animal models where this virus was found to dramatically increase the amount of fat found in the body. Not everyone is convinced by this virus, but some people are beginning to take it more seriously. The idea that obesity could be an infectious disease, possibly spread by a simple cough or sneeze, has met some raised eyebrows. 

Just like bacteria, viruses can live harmlessly in the body, but can then go on to cause problems when the person becomes immune suppressed. 

I could go on, but simply there’s just too many things living inside you to talk about them all. You are literally riddled with life, but these organisms play a big part in your life, and most of them are quiet do-gooders that we wouldn’t even know were there. You can thank some of these organisms for helping to shape who you are. 


How many species of mites live on the human body? - Biology

Arthropods form a huge assemblage of small coelomate animals with “jointed limbs” (hence the name arthro-pods). They exhibit segmentation of their bodies (metamerism) which is often masked in adults because their 10-25 body segments are combined into 2-3 functional groups (called tagmata). They exhibit varying degrees of cephalization whereby neural elements, sensory receptors and feeding structures are concentrated in the head region. Arthropods possess a rigid cuticular exoskeleton consisting mainly of tanned proteins and chitin. The exoskeleton is usually hard, insoluble, virtually indigestible and impregnated with calcium salts or covered with wax. The exoskeleton provides physical and physiological protection and serves as a place for muscle attachment. Skeletal plates are joined by flexible articular membranes and the joints are hinges or pivots made from chondyles and sockets.

Biodiversity
The main arthropod assemblages include crustaceans (crabs, lobsters, crayfish, shrimp), arachnids (spiders, scorpions, ticks, mites) and insects (beetles, bugs, earwigs, ants, bees, termites, butterflies, moths, crickets, roaches, fleas, flies, mosquitoes, lice). Most parasitic arthropods belong to 2 main classes: the 6-legged insects, and the 8-legged arachnids.

Insects have 3 distinct body parts, commonly called the head, thorax and abdomen. The head has 2 antennae and the thorax has 6 legs arranged in 3 bilateral pairs. Many insect species also have 2 pairs of wings attached to the thorax. Parasitic insect species include fleas, flies and lice which actively feed on host tissues and fluids at some stage in their life-cycles.

Arachnids have 2 body parts known as the prosoma (or cephalothorax) and opisthosoma (or abdomen). The cephalothorax has 8 legs arranged in 4 bilateral pairs and arachnids do not have wings or antennae. Important parasitic assemblages include the ticks and mites which bite into tissues and feed off host fluids.

Collectively, arthropods account for a substantial share of global biodiversity, both in terms of species richness and relative abundance. There are over 1,000,000 species of insects and over 50,000 species of arachnids. They are very successful and adaptable organisms and are capable of forming large populations due to their rapid and fertile reproduction rates. Many species are also able to withstand adverse environmental conditions by undergoing periods of developmental arrest (diapause). The protection afforded by their exoskeletons allows them to colonize many habitats and they overcome the problem of growing larger in a non-expandable exoskeleton by undergoing periodic moulting (or ecdysis) which is mediated by hormones. Developmental stages between moults are referred to as instars. Moulting is a complex process and its timing is mediated by many environmental and physiological cues. It involves detachment of the hypodermis from the procuticle, partial resorption of the old cuticle, production of a new epicuticle, dehiscence (splitting) of the old cuticle, emergence of the animal, stretching and expansion of the new cuticle by air and/or water intake, and then sclerotization of the new cuticle.

Life-cycles
Adult arthropods are generally small in size, most are visible but some remain microscopic. Arthropod sexes are separate and fertilization is internal. A wide range of mating behaviours, insemination and egg production strategies are involved. In most species, the egg develops into a larva: i.e. a life-cycle stage that is structurally distinct from the adult and must undergo metamorphosis (structural reorganization) before becoming an adult. This metamorphosis may be complete (involving major changes during a pupation stage) or incomplete (involving gradual changes in nymph stages). For example, the grub-like larval stages of flies and fleas form cocoon-like pupae where they undergo complete metamorphosis and emerge as radically-different adult insects. In contrast, the larval instars (or nymphs) of lice, ticks and mites undergo incomplete metamorphosis through a series of moults gradually becoming more adult-like in appearance.

Arthropods are involved in nearly every kind of parasitic relationship, either as parasites themselves or as hosts/vectors for other micro-organisms (including viruses, bacteria, protozoa and helminths). They are generally ectoparasitic on, or in, the skin of vertebrate hosts. Many species are haematophagous (suck blood) while others are histophagous (tissue-feeders) and bite or burrow in dermal tissues causing trauma, inflammation and hypersensitivity reactions. Infestations are transmitted from host-to-host either by direct contact or by free-living larvae or adults actively seeking hosts.


Direct transmission of infective stages occurs when hosts come into close contact with each other or share quarters, bedding or clothing. Larvae, nymphs or adults may cross from one host to another, while eggs or pupae may contaminate shared environments. Insects (fleas and lice) and arachnids (mites) rely on close contact between hosts.

Many adult insects actively seek hosts in order to feed or lay eggs. Winged insects (mosquitoes, flies) fly to new hosts to feed while fleas jump onto passing hosts. Some adult flies (botflies) do not feed on their hosts but deposit eggs from which larvae emerge and feed on host tissues and exudates.

Tick larvae actively seek hosts by climbing vegetation and questing for passing hosts. Some species complete their life-cycle on the same host (one-host ticks) while others detach after feeding and drop to the ground to moult before seeking new hosts as nymphs or adults (two-host or three-host ticks).

Taxonomic overview
Insects exhibit extraordinary biodiversity, both in terms of species richness (numbers of species) and relative abundance (population sizes). Most parasitic species belong to three main groups: the jumping fleas (Siphonaptera) the winged flies (Diptera) and the wingless lice (Phthiraptera).

fleas are bilaterally-flattened wingless insects with enlarged hindlimbs specially adapted for jumping (up to 100 times their body length). Jumping feats are accomplished using elastic resilin pads which expand explosively when uncocked from the compressed state. Fleas undergo complete metamorphosis whereby grub-like larvae form pupae from which adult fleas emerge. The larvae are not parasitic but feed on debris associated mainly with bedding, den or nest material, whereas the adult stages are parasitic and feed on host blood. There are some 2,500 flea species, most parasitic on mammals (especially rodents) and some on birds. They vary in the time spent on their hosts ranging from transient feeders (rodent fleas) to permanent attachment (sticktight fleas and burrowing chigoes).

flies and mosquitoes are winged insects with two pairs of wings attached to the thorax and a well-developed head with sensory and feeding organs. They undergo complete metamorphosis involving a pupation stage. Different species vary in their feeding habits, both as adults (parasitic or free-living) and larvae (parasitic or free-living). There are over 120,000 species belonging to 140 families. Two main suborders are recognized on the basis of structural differences, Nematocera (adult stages parasitic, larval stages often free-swimming) and Brachycera (adult stages parasitic or free-living, larvae stages often predaceous).

lice are small wingless insects, dorsoventrally flattened, with reduced or no eyes and enlarged tarsal claws for clinging. All lice undergo gradual metamorphosis and there are no free-living stages. Eggs are cemented to hair/feathers whereas nymphs and adults cling to hair/feathers. Two orders of lice are recognized on the basis of their mouthparts: the Mallophaga (chewing/biting lice) with some 3,000 species infesting birds and mammals and the Anoplura (sucking lice) with 500 species found on mammals.

Many non-spider arachnids (subclass Acari) are found as parasites on animal or plant hosts. They belong to two main groups: the macroscopic ticks and the microscopic mites. Many species are important in human and animal medicine as causes of disease or as transmission vectors for other pathogens.

ticks are epidermal parasites of terrestrial vertebrates that may cause anaemia, dermatosis, paralysis, otoacariasis and other infections (transmit viral, bacterial, rickettsial, spirochaete, protozoal and helminth pathogens). They feed mainly on blood and their mouthparts are armed with small backward-facing teeth to aid in attachment. All ticks undergo gradual/incomplete metamorphosis whereby larval and nymphal instars resemble adults. The integument is relatively thick and respiration occurs via spiracles (usually only one pair) and trachea. Two major families of ticks are recognized on the basis of many morphological features: the Ixodidae (hard ticks with a tough cuticle and a large anterodorsal scutum) with some 650 species that infest mammals, birds and reptiles and the Argasidae (soft ticks with a leathery integument and no scutum) with 160 species that infest mainly birds and some mammals.

mites are microscopic arachnids which undergo gradual or incomplete metamorphosis. Adults and nymphs have 4 pairs of legs whereas larvae have 3 pairs. Over 30,000 species of mites have been described, many are free-living species, some are plant parasites while others are parasitic on terrestrial and aquatic hosts. Most parasitic species feed on skin debris or suck lymph, some burrow into the skin, some live in hair follicles, and some in the ear canals. Their mouthparts are variable in form but the hypostome is never armed with teeth. The integument is usually thin and three orders are recognized on the basis of their respiratory systems: the Mesostigmata with respiratory spiracles (stigmata) near the third coxae the Prostigmata (Trombidiformes) with spiracles between the chelicerae or on the dorsal hysterosoma and the Astigmata (Sarcoptiformes) without tracheal systems as they respire through the tegument.


Scientists say face mites evolved alongside humans since the dawn of human origins

A close-up on a Demodex folliculorum face mite, the focus of a new study that uses genetic testing to reveal the microscopic animal's evolutionary link to our own ever-evolving human story. By zooming in on mitochondrial DNA in mite samples from around the world, scientists discovered that different human populations have different mites, that those mites follow families through generations, and that they are not casually transferred between humans. Credit: © California Academy of Sciences

Scientists have discovered a universal human truth about our bodies: they all, without exception, have mites. A landmark new study, led by scientists at Bowdoin and the California Academy of Sciences, explores the fascinating, little-known natural history of the face mite species Demodex folliculorum, using genetic testing to link the microscopic animal's evolution to our own ever-evolving human story. By zooming in on a type of genetic material (called mitochondrial DNA) in mite samples from around the world, scientists discovered that different human populations have different mites, that those mites follow families through generations, and that they are not casually transferred between humans.

The study is published today in the Early Edition of the journal PNAS.

Dr. Michelle Trautwein, Academy curator of entomology and senior author of the new findings, says improving the understanding of the mites that live in human hair follicles helps shed light on human evolution and may allow scientists to pinpoint mites' role in human health. Dubbed "face mites," D. folliculorum are actually tiny arachnids that inhabit hairs throughout the human body and consume skin cells and oils. Mites exist in human ears, eyebrows, and eyelashes as well as hairs that cover nipples and genitals.

For most people, mites are harmless. For some, however, mites can be associated with various skin and eye disorders including rosacea and blepharitis. Trautwein says this is one reason among many that scientists need to learn more about these constant human companions.

"It's shocking that we're only just discovering how deeply our histories are shared with the mites on our bodies," says Trautwein, who has traveled the world to sample mites and learn more about their cryptic lives. "They aren't just bugs on our faces, they are storytellers. Mites tell us about our own ancient history—it's a complex story, and we've only just scratched the surface."

To understand how and why mites vary geographically, study authors sampled 70 human hosts from around the world. For some subjects, intact mites were collected by drawing the curved end of a bobby pin across a participant's forehead in others, metal laboratory spatulas were used to take samples that included a mix of hair and skin cells (including mites) from cheek and outer nose. The scientists then sequenced mite DNA to look at the mitochondrial DNA of each subject's mites.

Dr. Michelle Trautwein, senior author and curator of entomology at the California Academy of Sciences, samples face mites from guests at NightLife, the museum's weekly after-hours event for guests 18 and over. The 70 international study subjects, however, donated mites through a different process. For some subjects, intact mites were collected by drawing the curved end of a bobby pin across a participant's forehead in others, metal laboratory spatulas were used to take samples that included a mix of hair and skin cells (including mites) from cheek and outer nose. The scientists then sequenced mite DNA to look at the mitochondrial DNA of each subject's mites. Credit: © California Academy of Sciences

"We discovered that people from different parts of the world host different mite lineages," says Trautwein. "The continent where a person's ancestry originated tended to predict the types of mites on their faces. We found that mite lineages can persist in hosts for generations. Even if you move to a faraway region, your mites stick with you."

The study revealed that, in some cases, African Americans who had been living in the U.S. for generations still hosted African mites. These results suggest that some mite populations are better able to survive and reproduce on hosts from certain geographic regions. Differences in mite lineages, the authors suggest, are consistent with the divergence of human populations and support the "Out of Africa" hypothesis. This widely accepted theory about the origins of humanity states that every living human today is descended from a group that evolved in Africa and dispersed into the wider world. Though the study results suggest that mites predated the dawn of modern humans, Trautwein says that mites were likely along for that much later series of journeys off the continent.

This is another view of a Demodex folliculorum face mite, the focus of the new international study. Results show that, in some cases, African Americans who had been living in the US for generations still hosted African mites. These results suggest that some mite populations are better able to survive and reproduce on hosts from certain geographic regions. Differences in mite lineages, the authors say, are consistent with the divergence of human populations and support the 'Out of Africa' hypothesis. This widely accepted theory about the origins of humanity states that every living human today is descended from a group that evolved in Africa and dispersed into the wider world. Though the study results suggest that mites predated the dawn of modern humans, Dr. Michelle Trautwein from the California Academy of Sciences says that mites were likely along for that much later series of journeys off the continent. Credit: © California Academy of Sciences

"Another exciting mite revelation from our work is that mites aren't shared easily," says Trautwein. "Mites are not casually transferred to passersby on the street. We seem to share mites primarily with our family, so it likely takes very close physical contact to transmit mites."

Going forward, Trautwein and her multidisciplinary colleagues will continue to research the strange lives of mites and how they relate to human evolutionary history and health. Trautwein is in the midst of a multi-year project sampling arthropods (and collecting mite samples) alongside citizen scientists in homes on all seven continents, exploring the overlooked life that shares our homes and bodies on a daily basis. Past expeditions include Sweden, the Peruvian Amazon, and houses in the Academy's own San Francisco backyard. Trautwein will continue sampling mites and collecting house-dwelling arthropods in Australia, Mozambique, China, and Antarctica in 2016-17.


Flies

Flies are common insects present throughout the world. Most of us know the housefly which can sometimes cause diseases such as typhoid and dysentery by contaminating the food that people eat. However, it is the biting flies that are more likely to cause diseases. Some of these flies feed on human blood but in the process transmit pathogens similar to the way mosquitoes spread disease. There are thousands of species of flies and the size and other physical features vary greatly apart. These two-winged insects can travel great distances and hide in different modes of transport thereby allowing it to move across countries and even continents.

Two species of blood-sucking flies that are known to cause serious disease is the tsetse fly and the sandfly. The tsetse fly may transmit the protozoan Trypanosoma brucei which causes African trypanosomiasis (sleeping sickness). Sandflies may transmit the Leishmania protozoan which causes the disease leishmaniasis or Bartonella bacilliformis bacteria resulting in bartonellosis. These diseases are not usually seen in the mainland United States but travelers to endemic regions need to be aware of the dangers as flies are often thought to be harmless insects.


Watch the video: DISGUSTING Things That Live on Your Body! Brit Lab (November 2022).