How many organisms live inside you?
A lot. Scientists estimate that the number of microbe cells living in our bodies outnumber our human cells 10 to 1. Microbe cells can live almost anywhere in or on us, with the exception of the lungs, brain and circulatory system, which need to be kept sterile. Most of these organisms are harmless to us and many of them are critical to our survival—helping complete our daily functions. In other cases, an organism takes too much from a person and the human host will start to suffer. When an organism survives at the expense of the host, it’s called a parasitic relationship.
Parasites are incredible. They have adapted methods of survival that involve stealing from hosts, who do most or all of the hard work for them. Consider that there might be parasites stealing your hard-earned nutrients right now, or making a home in your cells, organs or follicles.
These organisms can come in a variety of forms, from microscopic single cells to 20 foot-long tape worms. Many human-loving parasites come from tropical regions, such as the plasmodium in malaria, the guinea worm and the human bot fly. Here in Canada there is a very slim chance that you will encounter any of these parasites. Don’t feel too left out though, there are some parasites that you can find right here in Vancouver, these are included in the illustration below. I have also indicated with an arrow where in your body they may take up residence and wreak havoc. Have you ever been infected with one of these organisms?
I have been host to at least four of these parasites, some of which I’ve been able to get rid of and some of which are still living happily in my body today. One of the most common and least harmful is demodex, also known as the eyelash mite. This microscopic mite lives on your face, in your hair follicles or sebaceous glands. Approximately 1/3 of children are observed to have these mites, increasing to about 2/3 among seniors. Are they living on your face too? You can check yourself, all you need is a magnifier and a glass. A light microscope works best, 40X–60X power can be used to detect them, 400X will give you lots of detail. For detection, a smart phone or tablet magnifier adapter (like the proscope) would also work. To see if tiny arachnids are living in your eyebrows, follow these steps:
- Use your fingernails to press firmly on the skin between your eyebrows, with a little more pressure than you would use to pop a pimple. This will push some sebum (what makes your face oily) out of one of the glands the mites live in. The more sebum you can push out, the better your chances of seeing a mite. You can do this on a few areas around your forehead and nose.
- Use a tool with a solid surface (a butter knife for example) to gently scrape the sebum off your face and onto a glass slide. Mix the sebum with one drop of vegetable oil to help dissolve the sebum, and apply a plastic cover slip if you have one.
- Observe the slide using your magnifier. Use a low power (40X–60X) to search your slide to try and find some mites. If you find some, enhance the power to get more details. The image below shows a demodex mite at 400X magnification under a microscope.
If you found some mites, congratulations! You and your mites will be together for the rest of your days, along with countless other organisms living on and in you. These mites are typically symptomless, but if you suspect you may be hosting other, more invasive parasites, go talk to a doctor. some of the most common undesirable parasites are found in the digestive tract and can cause symptoms like nausea, diarrhea and abdominal pain—these are often easily treatable.
Parasites can seem unnerving, but thinking about our body as their entire world is pretty interesting. We host countless small creatures who are born, live and die in our bodies each day. So take a moment to consider the approximate 90 trillion microbes, and how you are working harmoniously with almost all of them in a biological balancing act. Although some of these invaders can hurt us, the majority help us by providing essential functions like helping us to break down food. They can strengthen our immune system and promote production of signaling proteins. You may think of yourself as an individual, but you are actually a whole community with billions of different genomes and thousands of species coming from dozens of families.
Parasites can do amazing things. Find out about parasites that can take over animal brains and make hosts do their bidding. Parasitic plants are also pretty tricky. Find out how they sneak their way into your garden.
Photo credit for feature image: “Male human head louse” by Gilles San Martin