Ask Emily

29 09 2011

Are there really worms living in our eyelashes?

Well, no, not worms, exactly. Exactly speaking, they are arachnids. And unless you’re in the estimated 5% free of these microscopic critters, there’s likely more than one living in that forest of hairs lining your eyes. I know, there’s a major ewww factor involved for a lot of people, especially when you see images of these things. By the way, obtaining those images appears to involve extracting the microscopic mites from hair follicles using “Krazy Glue” (see below).

Clocking in at a tiny 0.1  to 0.44 mm, the mites, if you’ve got ‘em, move around mostly at night on their four pairs of legs and dine sumptuously on surface skin cells (and yes, they poop). Many people walk around oblivious to their presence, but if the mites do cause symptoms, they generally are of the irritation sort, such as itching and scaling skin on the eyelids. These mites may not stay confined to the eye area and have been found in people who have rosacea, although whether or not they’re causative in that skin disorder remains unclear.

As with many organisms we host, it may be that disease or infection gives them a greater opportunity for colonization, especially if the immune system is suppressed or overtasked. They’ve also been implicated in conditions involving dry eyes, facial inflammation, and an eye disorder called blepharitis.

We’ve known about our cohabitation with these mites since at least 1840, when the primary species that inhabits us, Demodex folliculorum, was identified. It may make or may not make you feel better to know that this mite is the only parasite that hangs out in this specific area. Their presence appears to increase with age, with one study finding it in 84% of a population with an average age of 61 years, but in 100% of those older than age 70. They don’t seem to care at all whether you’re male or female. In spite of their ubiquity, though, these parasites are by no means off the hook when it comes to implications of their involvement in disease. As one publication has noted—and it’s worth quoting here—

As old-fashioned as mites may seem, and as low-tech is their removal from the follicle with Krazy Glue on a glass slide, the reader is cautioned that one of the great minds in dermatology suspected Demodex to be an unindicted coconspirator in several still poorly understood skin disorders. One could do worse than to further consider the possibility.

I supposed one could.

Do you have a question for Emily? Send it to:

By Emily Willingham

Image courtesy of Wikimedia Commons

World Rabies Day – 28 September

26 09 2011

Anyone who’s read Old Yeller knows (spoiler alert!) what happens to the title dog in the book. In this day of vaccinations against rabies, though, many people don’t give rabies more than the thought required to take their pets to the vet.

Yet rabies is still around, present in many mammals, including raccoons, skunks, bats, and foxes, and contact with any infected animal can mean infection for you or an unvaccinated furry pet.

In fact, about 55,000 people still die every year from rabies, which translates into a death every 10 minutes.

To make people more aware of the continued threat and precautions to take, national and international health organizations have designated September 28, 2011, as World Rabies Day.

Rabies is a viral disease. The virus attacks the central nervous system—the brain and spinal cord—and eventually is fatal (although there are extremely rare cases of survival). Symptoms, according the Centers for Disease Control and Prevention, are non-specific in the beginning—a fever, a headache, a general feeling of being unwell. But eventually, they progress to neurological symptoms, including hallucinations, confusion, paralysis, difficulty swallowing, and hydrophobia (as the disease is called in Old Yeller). Once these symptoms are present, death is only days away.

Usually, rabies is transmitted through a bite, transferred via the saliva of the infected animal, although rarely it transfers through other routes, such as via the air or transplantation of infected organs. The virus itself triggers no symptoms for up to 12 weeks even as it multiplies and invades the brain and spinal cord. When symptoms finally show up, an infected organism dies within about seven days.

Vaccines against rabies are available for animals, but worldwide, dogs remain the most common source of rabies infection in people, and children are at greatest risk. Vaccination could reduce or eliminate this risk, and a goal of the World Rabies Day campaign is to ensure more widespread vaccination of dogs. Since the campaign began in 2007, 4.6 million dogs have been vaccinated thanks to awareness events. This year’s goal is to grow that number even more.

Vaccinations also exist for people, especially post-exposure vaccinations. They once had a dire reputation as painful shots administered in the stomach, but now they’re shots in the arm and no more painful than other vaccinations. These shots include a shot given the day of exposure followed by more shots in an arm muscle on days 3, 7, and 14, according to the CDC. However, there is a short window of time for these vaccines to be effective; they must be administered preferably within a day of exposure. For people who have already had rabies vaccinations, a briefer round of further shots is required.

What should you do if you think you’ve come into contact with a rabies-infected animal? The CDC has a few guidelines:

  • Consider the situation urgent but not an emergency. Get medical help as soon as you can.
  • Wash a wound immediately with soap and water, which decreases the chance of infection.
  • Get immediate medical attention for acute trauma from a wound before worrying about rabies infection.
  • Once immediate considerations are addressed, your doctor and the relevant health department will determine if you need vaccination.

Remember, above all, keep your pets vaccinated against rabies, and stay away from wild animals, especially those known to carry the virus. For more information, see the World Rabies Day website.

By Emily Willingham

Image courtesy of

Mary Margaret’s Legacy

22 09 2011

My dad’s sister, Mary Margaret, died at age nine from laryngeal diphtheria.

One of the things Dad and I talked about when I became an immunization coalition coordinator was whether he would mind if I told his sister’s story in my work. He felt if her tragic story would help prevent anyone from losing a child to a vaccine-preventable disease, then it would be a wonderful tribute to her and it’d give her short life even more purpose.

Mary Margaret died a week before Christmas, 1927, after contracting diphtheria from schoolmates. This was three years before the diphtheria vaccine was available in the area, according to my grandmother’s recollection that came down to me through my dad.

She had home care by family, and a visit from a doc who visited the poor families, so they worried that maybe she could have had a more timely diagnosis and better care.

After her death, the family was put out of the house by the local board of health, and the house was roped off with a “do not cross” type of line and sulphur candles were burned in the house to rid it of any leftover contagion. They were treated like lepers.

Our family is and was Catholic.  Mary Margaret was allowed no funeral service (no stopping by the church) on the way to the cemetery located nine miles outside of Tulsa, Oklahoma. No last benediction or funeral rites from the church were given to her because of the contagious aspect of the disease. The grave wasn’t even marked until 1960, when my dad and his brother visited the cemetery to make arrangements for their mother’s burial. They were horrified to find it unmarked and ordered not one but two stones.

There was no money in 1927 for the family to mark it—the family, like most at the time, was living on the edge of poverty.

The summer after Mary Margaret died, my dad and uncle (ages four and five) were put on the train to Kansas City with notes pinned to their collars to let them off at Union Station there, as their aunt would pick them up and keep them for the summer—a rough summer for their parents who needed a break.

My grandparents coped as best they could, but my dad said he and his brother never saw the same sparkle in their parents’ eyes, and they couldn’t bring it back by themselves no matter how hard they tried.

Grandpa continued to work long hours as a baker, but coped by drinking. Grandma just carried on, never sharing her grief with the boys and never complaining.

My mother once talked to my grandfather (her father-in-law) about his daughter’s death, and it was the only time he said anything to her about it.

“For Christmas that year, my daughter had asked for a music box; instead, I had to buy a wooden box to bury her in,” he said, and then cried.

I have told Mary Margaret’s story to people occasionally since I have been the TAIC coalition Coordinator, and I have to tell you, even though my own grown sons are familiar with it, one of my daughters-in-law (and her mother) have bought into the false information about immunizations collected from the Internet and through their homeschooling network.

No matter what I can respectfully, carefully, or diplomatically say or try to teach, their attitudes of distrust about immunizations cannot be changed. So, their children, my grandchildren, remain unimmunized, much to my anguish.

On a cheery note, I can see the photo of Mary Margaret, the aunt I never knew, with that wonderfully whimsical orange clown nose on her face in celebration of Orange Nose Day.

And Grandma? She probably would have wanted to see something hopeful and meaningful come from the sharing of her daughter’s story. Maybe by relating our family’s story, today’s parents will realize just how serious vaccine-preventable diseases are, and make good, timely decisions about having their children properly immunized. Grandma would be AMAZED to know that several cancers can now be prevented with vaccines!

As to the diphtheria vaccine and my dad and uncle? When it was available in 1930 at the Tulsa Board of Health, Dad said his mother couldn’t get them there FAST ENOUGH to get both boys immunized. She wasn’t going to lose any more of her children to a preventable disease.

By Kathy Sebert, RN, BA/Coordinator, Tulsa Area Immunization Coalition & Tulsa Health Department employee

Autism Science Foundation

19 09 2011

[Autism Science Foundation is the place to go if you have questions about autism. We’re running their latest press release here to show our support for their work.]

Launch of NEW Website: Online Autism Research Destination for Parents, Individuals with Autism, Scientists and Teachers

(September 19, 2011—New York, NY)— The Autism Science Foundation (ASF), a nonprofit organization dedicated to supporting and funding autism research, announced today that it has re-launched its website as an enhanced, interactive resource for parents, individuals with autism, teachers, scientists and other autism stakeholders.

The website is the central distribution point for the latest in autism science and research. The site features:

Over the next few weeks, ASF’s team will be adding more features to the site including autism research sorted by topic area and a section about autism research studies seeking participants.

“It’s crucial that families, educators and scientists have access to up-to-date information that they know has been peer-reviewed or vetted by ASF’s Scientific Advisory Board,” said ASF co-founder Karen London. “Since ASF’s inception in 2009, we have aimed to be a central and trusted source of rigorous science information for the autism community.”

“We are pleased to be able to offer the autism community a broad and deep source of evidence-based information that integrates more interactive features and that reorganizes information to make it more useful and easier to find, in response to community feedback,” said Jonathan Carter, ASF’s operations manager. “The site offers ways for everyone who has a connection to autism to get involved in this important issue.”

ASF began funding research grants in 2009, its first year of operations, and has increased its funding levels each year. Since 2009, it has funded nearly half a million dollars in research grants. The organization was recently named the number one startup nonprofit in the “Disabilities” category by Philanthropedia/Guidestar.

ASF is a 501(c) (3) public charity. Its mission is to support autism research by providing funding to scientists and organizations conducting autism research. ASF also provides information about autism to the general public and serves to increase awareness of autism spectrum disorders and the needs of individuals and families affected by autism. To learn more about the Autism Science Foundation or to make a donation visit

Contact Info:
Dawn Crawford
Autism Science Foundation

HPV Vaccine: The Anti-Cancer Vax

15 09 2011

Have you or a loved one ever had an abnormal Pap smear result? If precancerous cells were identified, the cause was almost undoubtedly infection with human papillomavirus (HPV). Almost all cases of cervical cancer arise because of infection with this virus. Yet a vaccine can prevent infection with the strains that most commonly cause cervical cancer.

A vaccine against cancer. It’s true.

For the vaccine to work, though, a woman must have it before HPV infects her. You may find it difficult to look at your daughter, especially a pre-teen daughter, and think of that scenario. But the fact is that even if your daughter avoids all sexual contact until, say, her wedding night, she can still contract HPV from her partner. It happens to be the most common sexually transmitted infection.

About 20 million Americans have an HPV infection, and 6 million people become newly infected every year. Half of the people who are ever sexually active pick up an HPV infection in a lifetime. That means your daughter, even if she waits until her wedding night, has a 1 in 2 chance of contracting the virus. Unless it’s a strain that causes genital warts, HPV usually produces no symptoms, and the infected person doesn’t even know they’ve been infected.

Until the cancer shows up.

And it can show up in more places than the cervix. This virus, you see, favors a certain kind of tissue, one that happens to be present in several parts of you. This tissue, a type of epithelium, is a thin layer of the skin and mucous membranes. It’s available for viral invasion in the cervix, vagina, vulva, anus, and the mouth and pharynx. In fact, HPV is poised to replace tobacco as the major cause of oral cancers in the United States.

The virus can even sometimes pass from mother to child, causing recurrent respiratory papillomatosis, or warts in the throat that must be removed periodically and can sometimes become cancerous. It strikes about 2000 children each year in the United States.

How does a virus cause cancer? To understand that, you must first understand cancer. You may know that cells reproduce by dividing, and that cancer occurs when cells divide out of control. Behind most cancers is a malfunction in the molecules that tell cells to stop dividing. These molecules operate in a chain reaction of signaling, like a series of well-timed stoplights along a boulevard. If one starts sending an inappropriate “go” signal or fails to send a “stop” signal, the cell divides, making more cells just like it that also lack the right signals. If your body’s immune system doesn’t halt this inappropriate growth, we call it cancer.

The blueprint for building these “stop” molecules is in your genes, in your DNA sequences. As a virus, HPV also requires a blueprint to make more viruses. Viruses use the division machinery of the host cell—in you—to achieve reproduction by stealthily inserting their own DNA blueprint into the host DNA.

Sometimes, when it’s finished with the host, a virus leaves a little bit of its DNA behind. If that leftover DNA is in the middle of the blueprint for a “stop” molecule, the cell won’t even notice. It will use the contaminated instructions to build a molecule, one that no longer functions in stopping cell division. The result can be cancer.

Of the 150 HPV types or strains, about 40 of which pass through sexual contact, two in particular are associated with cancer, types 16 and 18. They are the ones that may persist for years and eventually change the cellular blueprint. The vaccines developed against those two strains are, therefore, anti-cancer vaccines.

Without a successful viral infection, viral DNA can’t disrupt your DNA. That’s what the HPV vaccine achieves against the two strains responsible for about 70% of cervical cancers. Recent high-profile people have made claims about negative effects of this vaccine, claims that have been thoroughly debunked. The Centers for Disease Control and Prevention as always offers accurate information about the side effects associated with available HPV vaccines.

This achievement against cancer, including prevention of almost 100% of precancerous cervical changes related to types 16 and 18, is important.

Worldwide, a half million women receive a cervical cancer diagnosis each year, and 250,000 women die from it. These women are somebody’s daughter, wife, sister, friend. Women from all kinds of backgrounds, with all kinds of sexual histories.

Women whose precancerous cervical changes are identified in time often still must undergo uncomfortable and sometimes painful procedures to get rid of the precancerous cells. These invasive procedures include cone biopsies that require shots to numb the cervix and removal of a chunk of tissue from it. Cone biopsies carry a risk of causing infertility or miscarriage or preterm delivery. A vaccine for your daughter could prevent it all.

HPV doesn’t care if your daughter has had sex before. It’s equally oblivious to whether the epithelium it infects is in the cervix or in the mouth or pharynx or in an adult or a child. What it does respond to is antibodies that a body makes in response to the vaccine stimulus.

Even if your daughter’s first and only sex partner passes along one of the cancer-associated strains, if she’s been vaccinated, her antibodies will take that virus out cold. It’s a straightforward prevention against a lifetime of worry—and a premature death.

For more info: Facts about the HPV vaccine from the National Cancer Institute

By Emily Willingham

Image courtesy of CDC

Using CAM? Tell Your Doc

12 09 2011

According to some estimates, one in three adults in the United States uses complementary or alternative medicine (CAM). CAM encompasses anything that’s not part of conventional medicine, such as herbal supplements and acupuncture.

In spite of this widespread use, however, many people neglect to tell their physicians about their CAM use. Some may think their doctor won’t approve or think the CAM treatments irrelevant to conventional medical care.

As many as 60% may not divulge this information, and in many cases, it’s because their doctor didn’t ask for it.

Leaving your physician in the dark on your CAM use—or, if it’s your child, any CAM your child may use—can be dangerous. It’s important to let your doctor know everything about your personal healthcare practices, whether it’s vitamins, herbal treatments, chiropracty, or acupuncture.

Why? Well, drugs are often either synthetic mimics of natural compounds or derived from natural compounds, as are herbal supplements. Just like drugs, herbal supplements can have active ingredients that may interact with other compounds, including those your doctor may prescribe. For example, grapefruit seed extract, a popular CAM intervention, can interfere with many medications’ effects, including the blood thinner coumadin.

There may be hidden reasons, such as an instability of your cervical spine, that would make it important to avoid certain chiropractic manipulations.

In addition to these fundamental medical reasons to tell your doctor everything you’re doing for your health—or your child’s, it’s also important for less tangible reasons. Your health professional may be able, for example, to help you decide which CAM therapy is a good fit for your needs, point you to good information about a target CAM intervention, or discuss the benefits and risks with you.

In addition, sharing with your health professional makes you all a part of a healthcare team taking care of you, with you in the driver’s seat.

The National Institutes of Health has provided a few tips for people who’d like to talk more with their healthcare providers about CAM therapies. These include:

  • Starting the conversation yourself. Take the initiative to talk about your healthcare practices.
  • Have a list available of the therapies—CAM or otherwise—you’re using, including dosing and frequency. This information should be included on any patient histories you complete, right along with prescription medications or therapies you use.
  • Make a list of any questions you may have about a specific CAM intervention, and ask those questions.
  • Don’t hesitate to take notes or ask for clarification as you converse with your healthcare provider.

The most important thing to remember is, CAM therapies are like any other intervention: They can interact with other treatments you’re taking, sometimes negatively, and that’s fundamental information your healthcare provider needs to have, about you or your child.

By Emily Willingham

Image courtesy of AAFP and Karen Woo

ECBT – Two Decades

8 09 2011

Every Child By Two (ECBT) celebrates its 20th anniversary this year. Former First Lady Rosalynn Carter and Former First Lady of Arkansas Betty Bumpers started ECBT with two goals: “. . . [to] raise awareness of the critical need for timely immunizations and to foster a systematic way to immunize all of America’s children by age two.”

ECBT offers a lot of direction to various segments of the population. For parents, they have sections on vaccine safety, tips on paying for vaccines, and descriptions of vaccines and the diseases they prevent.

Immunization advocates can find a huge amount of information on ECBT’s website, including surveys, reports, links, and a long list of national and regional resources.

Immunization registries are at the heart of ECBT’s work and they feature on their website how-tos, detailed explanations of registry benefits, and other tools helpful to those investigating such start-ups.

Healthcare professionals aren’t forgotten! They can find many links to patient educational materials and to strategies to improve vaccination rates.

Bringing Immunity To Every Community is an eLearning course developed by ECBT in partnership with the Colorado Foundation for Medical Care and the American Nurses Association and is worth checking out.

In the past few years, ECBT has created a second website, Vaccinate Your Baby, and a blog called Shot of Prevention. Vaccinate Your Baby is based on an awareness campaign of the safety of vaccines and the need to keep children’s immunization rates high. Actress Amanda Peet has been an ardent spokeswoman for ECBT and immunization and has kept the momentum going on this campaign.

The blog, Shot of Prevention, is led by Christine Vara, and has been both a leader in the arena of immunization blogs and a lightning rod for those with strong opinions. But they do love it when folks take time to comment on posts, so stop by when you have a minute to read these thoughtful opinion pieces.

It’s true that we’re fans of the people at ECBT, but for good cause. Kids would not be so well-protected today if, 20 years ago, two strong women hadn’t taken it upon themselves to lead the nation in immunizing our young.

Amy Pisani, Rich Greenaway and Jennifer Zavolinsky get up and go to work each day at ECBT, and because they do, they make the jobs of other immunization advocates so much easier. Thanks to all of you.

By Trish Parnell

Of Lice and Men: An Itchy History

1 09 2011

Originally published at Scientific American for Valentine’s Day. (September is Head Lice Prevention month, so they’re sharing this delightful article with us.)

Ponder the louse. Consider its plural, lice. Try now not to scratch the multiple itches that have just populated your head at the very thought of these near-microscopic insects crawling around in that forest of hair follicles, laying eggs, sucking blood, and generally creeping you out.

The thing is, your head may not be the likeliest place to feel the itch. After all, we’re home not only to the louse, but to lice, plural. As in two genera of lice, and three different kinds. One of those, the pubic louse, appears to trace back to contact between the Homo lineage and the gorilla, but more on that in a bit.

The history of lice and men is a long, itchy story that intertwines co-evolution not only with these blood-sucking little parasites but also with the microbes they carry. In fact, as visceral as our reaction can be to reading the “head lice” note our little darlings bring home from school, the insects themselves are nothing compared to the microbes they can harbor…and transmit to us. The lice and the microbes have driven us to death, to peace, to giving insects enemas. Yes, you read that right. They have, in short, been our co-pilots—or is it our head pilots?—for as long as Homo sapiens have been around.

Lice have been referred to somewhat mellifluously as “heirloom parasites.” They aren’t exactly heirlooms you’d want to inherit on Valentine’s Day…or any day, but they’re more than bugs that might be crawling around in your pubic hair. They and the microbes they carry have shaped fairly recent human history, and thanks to their close affinity for us, our hair, and our blood, we can use them to trace our deeper past.

That affinity is no joke. We host insects that are so desperately attached to us that they’d rather starve—and do—than dine on some other host. So when little Susie brings home the head lice letter, humans are the only mammals in the home that need to worry.

Our constant companions

Those lice-alert letters would bemuse our fairly recent ancestors, for whom lice were simply constant companions until about the 19th century. Along with their dancing lessons, the aristocrats of Europe learned the proper etiquette for disposing of one’s lice, absorbing these valuable lessons even into the 17th century. And in parts of the world where clothes stay on for days and hygiene is a tertiary consideration at best, body lice are not uncommon. As for pubic lice, they remain a worldwide presence, you know, down there.

Whether the host was a 17th-century prince or a modern human, there was at least one commonality: These insects, with a single bite, could give you something that could kill you.

Disease transfer

Lice likely benefited in Western culture from the religious-based aversion many had to bathing. Baths were such an anomaly that Queen Elizabeth I’s contemporaries blamed her near-fatal bout with smallpox on her foolish decision to bathe. Indeed, the parasites and their microbial passengers did flourish among the crowded, unwashed, often stressed and underfed masses that collected in villages, jails, army camps, and workhouses throughout the centuries (See application of DDT to a soldier, image left).

One of the best-known of these microbial passengers is the bacterium responsible for typhus, Rickettsia prowazekii (pdf). The name itself tells the story: the two researchers who were working to identify and isolate the pathogen, Howard T. Ricketts (d. 1910) and Stanislaus J.M. von Prowazek (pdf), each died as a result of typhus infection.

Dying from epidemic typhus was not a pleasant way to go. After a brutal onset involving excruciating headache and blistering fever, a rash would arise. The face would darken and swell, and a crazed delirium could send the sufferer leaping about naked and screaming, impossible to subdue. Following this period, which sometimes seemed to subside into a false recovery, the patient would enter a stupor, which gave the disease its name: typhos in Greek means “smoky” or “hazy.” Toward the end, gangrene could set in, rotting fingers and toes and driving away caregivers with the horrific stench. Death, when it came, would be a release.

Typhus and history

When we think of history, we usually consider first the people who shaped it. But microbes, with their ability to wipe out millions, have often played the greater role. Typhus permeates human history like the toxic haze that gave it its name, and rarely is its role one of beneficence.

One exception may be the interaction of Edward Winslow (pictured on the right), founder of Plymouth colony, with Massasoit, sachem of the Pokanoket people with whom the colonists had an uneasy peace. The source of that peace may trace to a Massosoit’s infection with typhus, from which he almost died. Winslow, arriving in the village, first gamely scraped the sachem’s furred tongue and then fed him some fruit preserves. Massasoit, feeling much better—which may well have been the misleading interim lull that typhus can bring—showed his gratitude to Winslow by asking the colonist to scrape the tongues of others in his village who were afflicted. Winslow did so, going well beyond any duty of a diplomat before or since, and the upshot was a shaky peace between the native Americans and the European colonists for 40 years.

But normally, typhus was no diplomat. While experts disagree, it may have been the agent in humanity’s first recorded plague, the Plague of Athens, during the Peloponnesian Wars. Pericles, Athens’ leader, decided to enclose the city in 431 BCE in a wooden barrier to withstand a Spartan siege. The only supply route was a single port, and with the siege, thousands of people surged into the town from the countryside, bringing their lice and microbes with them. The 10,000 dwellings of Athens were packed to bursting, and a plague exploded through the populace. Pericles himself died, as did much of his army, and the devastation marked the end of the golden age of Greek culture. That’s the kind of thing typhus can do.

Typhus marched its way through history in the habitus of the human body louse, Pediculus humanus humanus, and the louse itself was not immune to its influence. An infected louse turns red and dies within a few weeks of infection, but not before it bites and infects its human host. Before succumbing, however, the insect can also poop out millions of typhus bacteria, which can hang on clothing like a toxic dust, infecting others who never have a body louse near them.

Indeed, one researcher, Rudolf Weigl (image left), lost two of his fellow researchers to typhus as they were using solutions of typhus-infected poop to develop a vaccine. Part of the process involved infecting healthy lice with the bacteria. To do so, Weigl’s team would give the lice tiny enemas of the poop–water solution. Weigl himself contracted typhus twice, a demonstration that it could infect more than once. He ultimately succeeded in developing a vaccine in the 1930s, although as late as World War II, DDT was being used to fumigate soldiers against lice and other parasites.

In the first decade of the 20th century, Charles Nicolle (image right) sought to burn through the typhus haze and identify where the disease came from. He was the first to realize that lice stuck to clothing were the agents of disease transmission, and he immediately turned to experimentation on, yes, guinea pigs, followed by chimpanzees. In his fervor to develop a vaccine, he injected himself with a prototype. Finding that he did not develop typhus, he then tried out his vaccine on a few hapless children. They did develop typhus. In these days before the Declaration of Helsinki and human subjects research approvals, his only comment was (pdf), “You can imagine how frightened I was when they developed typhus; fortunately, they recovered.” Imagine. Nicolle received the Nobel Prize in Medicine in 1928 for identifying the louse–typhus connection.

The award reflected the significance of his discovery. Typhus was one of the greatest killers in human history. It shaped outcomes of war from the 16th century to the 20th, from Hungary and Turkey, and most of Europe and into the New World. In 1526, the French army had to end its siege of Naples because typhus had killed 28,000 of the besiegers in a month. For perspective, the failure to take Naples left Italy and the papacy in Spain’s power. The pope at the time, Clement VII, to avoid angering Charles V of Spain, declined to grant Henry VIII’s divorce (picture left) request from Catherine of Aragon…and the Protestant Reformation was born.

Typhus helped decimate the half-million strong Grand Armée of Napoleon (on the right) in 1812 to a mere 35,000 men and kept the great general from conquering Russia. Many of the dead met their fates not on the battlefield but in louse-infested hospitals packed with dead bodies.

Even into the 20th century, typhus was actively shaping human destiny. After it killed millions in eastern Europe around the first World War, Vladimir Lenin was driven to comment, “Either socialism will defeat the louse, or the louse will defeat socialism.” In the end, it was probably more about free-market economy than lice, but still.

As Hans Zissner, author of the seminal work Rats, Lice, and History, noted:

Soldiers have rarely won wars. They more often mop up after the barrage of epidemics. And typhus, with its brothers and sisters—plague, cholera, typhoid, dysentery—has decided more campaigns than Caesar, Hannibal, Napoleon, and the inspectors general of history. The epidemics get the blame for defeat, the generals get the credit for victory. It ought to be the other way around.

Human evolution

So, where did we pick up these unwanted blood suckers in the first place? All signs point to a human–ape connection, and “connection” may mean something more tangible than an evolutionary link. Some studies suggest interaction between early Homo species and gorillas, and also between early Homo species and us.

The lice we carry around are sucking lice. That’s pretty self explanatory. Two subspecies we harbor, head lice and body lice, belong to the Pediculus (picture left) genus (Pediculus humanus capitis and Pediculus humanus humanus, respectively). The other species we harbor, you know, down there, is a member of the genus Phthirus. Our closest living relatives, the chimpanzees, harbor Pediculus, as well, while gorillas are home to another Phthirus species.

In other words, we share a genus with each of them.

Sucking lice have been sucking primate blood for at least 25 million years. The big story, though, is what happened about 6 to 7 million years ago, and in the case of the gorilla, even later. Humans and apes are supposed to have parted evolutionary ways at about the 6 million year mark. The Pediculus genus seems to have split at the same time, with Pediculus schaeffi hitching a ride with the chimp lineage, and Pediculus humanus sticking with what would become the Homo line. The gorillas split off a little earlier, maybe about 7 million years ago, and the Phthirus may have done the same, sending Phthirus gorillae with the gorillas (natch), while Phthirus pubis eventually became a human problem.

Things get a bit, well, sticky when it comes to the Phthirus line (Phthirus pubis – picture right), however. The split between the gorilla and human lice seems to have happened around 3 to 4 million years ago, millions of years after the gorilla and human branches parted ways. That means that at the 3 to 4 million year point, human ancestors and gorillas must have had some kind of…contact.

The authors who uncovered this finding note in their paper that “How we might have acquired our pubic lice from gorillas is not immediately apparent, however it would be interesting to know whether the switch was very recent (say less than 100,000 years old) or whether it was considerably older” (Reed et al. 2007). Yes, that would be interesting indeed to know.

There are a couple of ways to explain why we carry around a chimp-related genus and a gorilla-related genus of lice. One idea, felicitously dubbed the “pair of lice lost” model, poses that after apes and humans parted ways, each lineage carried both Pediculus and Phthirus. Somewhere along the way, goes the pair-of-lice-lost idea, chimps dropped Phthirus and gorillas dropped Pediculus. Humans, being the avaricious little lineage that we are, held onto both.

But there’s a problem. This explanation just isn’t stingy, or parsimonious enough, and it doesn’t fit with the fact that the split for Phthirus happened 3 or 4 million years ago. In other words, the explanation that fits better is the “recent host switch” idea, as in it switched hosts from gorilla to us thanks to direct contact. Before anyone starts going all King-Kong freaky, it’s important to note that apparently, pubic contact is not required to explain this transfer from host to host. Predation or overlaps in habitats each species used also could have been a way the lice jumped from gorillas to us.

That transfer might have been possible thanks to a few changes the Homo lineage was experiencing, including loss of body hair. As their hirsute habitat decreased, the Pediculus subspecies that would become the head louse retreated to the head. That may have left a bit of an opening for a Phthirus invasion. Phthirus simply may have encountered the least competition, you know, down there.

Divergence from other Homos

Speaking of competition, the history of Pediculus humanus suggests a bit of fancy business happening between Homo sapiens and archaic Homo species, possibly Homo erectus. The Pediculus genus encompasses two lineages that trace back 1.18 million years. One of the lineages underwent a bottleneck—a severe population reduction—right about the time modern Homo sapiens did, 100,000 years ago. The other lineage, however, spent 1.18 million years isolated from its generic partner, until the two somehow had a reunion and both occur in us today. The only way for them to have gotten back together after that long hiatus was direct physical contact. Happy Valentine’s Day!

OK, the contact had to be direct, but it didn’t need to be sexual. It could have been more of that predation or shared hangout that let the two louse lineages reunite. But this re-pairing of a pair of parasites (pairasites?) in Homo sapiens is intriguing because it’s not the only instance: bedbugs, tapeworms, follicle mites, and a parasitic protozoan also exhibit this pattern of closely related pairs. The irresistible inference is that when the lice lineages reunited through the direct contact of Homo sapiens and archaic Homo, so did the lineages of several other unwelcome guests.


While the evolutionary history of lice helps us trace our deep past, we can also use them to explain more recent developments, such as the advent of attire. Body lice hang out—literally—in clothing, and pinpointing when this Pediculus subspecies separated from its head-bound brethren may have helped pinpoint when Homo sapiens decided to put on some clothes. Fig leaves aside, the question has been wide open, with ranges from 40,000 years ago to 3 million. But recent work indicates a divergence between the Pediculus subspecies at 170,000 years ago. This timing puts clothing far earlier than many estimates and well before humans would have needed them for warmth. It’s also well after humans lost their body hair, so for awhile there, our ancestors were wandering around naked and smooth, until a snake came out from behind a tree and…oh, never mind.


Speaking of the Bible, Egyptian mummies and mummies of other provenances have proved to be a wealth information about the evolution of the human-specific louse. They’ve helped researchers determine three separate lineages of Pediculus, one distributed globally, the other two only in certain regions. And the mummies also tell us a lot about what our ancestors had to deal with. In two Peruvian mummies dating to about 1025 CE, for example, one specimen had 407 lice on its head, while the other had 545.

Indeed, mummified lice are among the “best-preserved human parasites,” enthused one researcher, yielding not only adult lice but also nits and even eggs. Specimens from Israel dating back 2000 years were culled from hair combs, while crab lice…otherwise known as pubic lice or Phthirus pubis (the gorilla kind), have been found on South American mummies.

Pubic lice

In honor of Valentine’s Day, I’ve saved the pubic lice for last. For many years, lice experts thought that pubic lice were not a New World problem until the Europeans brought them, along with all of their other Old World threats. Then, in 2002, researchers found Phthirus pubis eggs attached to the pubic hairs of a 2000-year-old Chilean mummy, and adult pubic lice have been found in clothing from a 1000-year-old Peruvian mummy. The lice were stuck to the pleats of some cloth from a female mummy, and the enthusiasm of the authors in describing the louse specimens is worth transmitting in their own words (Rick et al., 2002):

Both are females. The foreleg is quite slender, with a long fine claw. The mid and hind legs are strong with thick claws, and the characteristically compressed abdomen is wider than it is long. … Crab lice are usually attached to the pubic and perianal hairs. It remains unclear why P. pubis and P. humanus were found in the same piece of cloth.

The louse with the “long fine claw,” they conclude, likely made its way to the Americas with early human migration.

Human pubic lice, also known as crab lice, can occur anywhere there’s hair, you know, down there, including the pubic and “perianal” hairs. It seems that they can also appear in other hairy places, including the legs, arms, armpits, and face. Yes, face. Crab lice can take up residence in the eyelashes, where they produce a crusty deposit and red, itchy eyes. Red is a Valentine’s color, right?

As is appropriate for a sexually transmitted (usually) organism, the slow-moving pubic louse is known for becoming attached to the same pubic hair for quite a long time. A true romantic, indeed.

References and Further Reading:

Gross, L. (1996) How Charles Nicolle of the Pasteur Institute discovered that epidemic typhus is transmitted by lice: Reminiscences from my years at the Pasteur Institute in Paris. Vol. 93, pp. 10539–10540.
Yong, Z., Fournier, P-E., Rydkina, E., Raoult, D. The geographical segregation of human lice preceded that of Pediculus humanus capitis and Pediculus humanus humanus. (2003) Microbiology: Parasitology pp. 565–574. doi:10.1016/S1631-0691(03)00153-7

Reed, D.L., Light, J.E., Allen, J.M., Kirchman, J.J. (2007) Pair of lice lost or parasites regained: the evolutionary history of anthropoid primate lice. BMC Biology 2007, 5:7. doi:10.1186/1741-7007-5-7

Toups, M.A., Kitchen, A., Light, J.E., Reed, D.L. (2006) Origin of clothing lice indicates early clothing use by anatomically modern humans in Africa. Molecular Biology and Evolution 28(1): 29–32.

Raoulty, D., Reed, D.L., Dittmar, K., Kirchman, J.J., Rolain, J-M., Guillen, S., Light, J.E. (2008) Molecular identification of lice from pre-Columbian mummies. Journal of Infectious Diseases 197(4): 535–543.

Reed D.L., Smith V.S., Hammond S.L., Rogers A.R., Clayton D.H. (2004) Genetic analysis of lice supports direct contact between modern and archaic humans. PLoS Biol 2(11): e340.

Robinson, D., Leo, N., Prociv, P., Barker, S.C. (2003) Potential role of head lice, Pediculus humanus capitis, as vectors of Rickettsia prowazekii. Parasitology Research 90(3): 209–211. DOI: 10.1007/s00436-003-0842-5

Mumcuoglu,, Y.K., Zias, J. (1988) Head lice, Pediculus humanus capitis (Anoplura: Pediculidae) from hair combs excavated in Israel and dated from the first century B.C. to the eight century A.D. Journal of Medical Entomology 25 (6): 545–547.

Rick, F.M., et al. (2002) Crab louse infestation in pre-Columbian America. Journal of Parasitology 88(6): 1266–1267.

Zinsser, H. Rats, Lice, and History. (2008) Transaction Publishers, New Brunswick, NJ. 301 pp.

McNeill, W.H. Plagues and Peoples. (1976, 1998) Anchor Press, NY. 365 pp.

Karlen, A. Disease and Plagues in History and Modern Times. (1995) New York: GP Putnam’s. 266 pp.

Crawford, D.H. Deadly Companions: How Microbes Shaped Our History. Dorothy H. Crawford. (2007) Oxford University Press. 250 pp.

Philbrick, N. Mayflower. ( 2006) Viking Penguin. 461 pp.

By Emily Willingham

Image Credits:: Pediculus humanus, public domain, Wikimedia Commons; Pthiris pubis, public domain, Wikimedia Commons; Rudolf Weigl, Wikimedia Commons; Charles Nicolle, Wikimedia Commons; Napoleon, Wikimedia Commons; Using DDT to combat lice and typhus, Wikimedia Commons; Henry VIII by Holbein, Wikimedia Commons; Human family tree (2003), Wikimedia Commons; Edward Winslow, Wikimedia Commons.