What Are Parasitic STIs?


What Are Parasitic STIs?

Parasitic STIs (sexually transmitted infections, also known as STDs), are parasites that are passed from person to person, most often during sex. A parasite is a small animal that survives by living off another living thing’s body.

Which STIs are parasitic?

There are three main parasitic STIs:

  • trichomoniasis
  • pubic lice (aka crabs)
  • scabies

All three parasitic STIs are fairly common, and all three can be completely cured with treatment!


You may have heard trichomoniasis referred to as trich. It often has very few symptoms or none at all. This is one reason why getting tested is important.

For people with vagina­s, the symptoms can include:

  • higher than usual amounts of discharge from the vagina
  • newly strong vaginal smell
  • pain during sex or peeing
  • tenderness or itchiness around the vagina

For people with penis­es, the symptoms of trichomoniasis can include:

  • discharge from the penis
  • irritation or redness around the penis head
  • painful peeing

It is even more common for people with penises to not have any symptoms of trichomoniasis.

You can get tested for trichomoniasis during a regular STI test in a clinic or at the doctor’s office. Most often, if you are tested for chlamydia or gonorrhea, they’ll also test for trichomoniasis. But you can ask to make sure.

You can usually treat trichomoniasis with a single dose of an antibiotic pill called Metronidazole. It is important to get treated, and make sure your partner(s) get treated as well. If trichomoniasis goes untreated, it can sometimes make bigger problems, like constant pain in your groin.

You can avoid trichomoniasis by using condoms.

Pubic lice (crabs)

Pubic lice are similar, but not the same as the lice that seem to be on everybody’s head in elementary school. The reason pubic lice are sometimes called crabs is because their shape makes them look like tiny crabs.

The symptoms of pubic lice include:

  • itchiness
  • redness
  • small blue spots on the skin of the pubic area
  • tiny black particles in the underwear

Testing for pubic lice is a pretty simple process. Doctors just look at the symptoms. You may also be able to see them using something like a magnifying glass.

You can treat pubic lice by washing with a special shampoo, which you can get without a prescription from a doctor or pharmacist. Usually just one shampooing will get rid of the pubic lice. You don’t need to shave to get rid of them. It’s important to let your partner(s) know you’ve been treated, and that they should get checked out too. This way, they won’t pass it on to other people, or pass it back to you.

Pubic lice transfer when people are close and touching intimately. This means a condom doesn’t protect against them. But, again, they’re pretty easy to get rid of.


Scabies are a parasitic STI that go under the skin. The symptoms for scabies include:

  • extreme itchiness, especially after baths or showers
  • a rash around creases in the pubic area, armpits, or nipples
  • small sores that can look like pimples in these areas
  • small scratches around these parts

Testing for scabies can be a little tricky because they are hard to see. But a healthcare professional can usually tell if you have them from close inspection, or by scraping off a bit of skin. If you have the symptoms of scabies, it is a good idea to go have a healthcare professional check it out.

You treat scabies by rubbing a special lotion all over your body. A doctor needs to prescribe this lotion. When you’re treating for scabies, it’s also a great idea to wash all your clothing and bedding. This way, you can make sure they’re completely gone.

Scabies, like pubic lice, is also transmitted by close contact. But scabies are tough and can survive on something like a used towel or shirt for up to three days. It’s much more common to get scabies directly from another person than from a sharing clothes.

Anything else I should know about Parasitic STIs?

Parasitic STIs can seem a little creepy, but not to fear! They are pretty easy to treat, and not a big deal at all. Everyone lives with dust mites and other small animals on their body; these ones are just more annoying. Like many STIs, they can carry a lot of stigma, and people can look down on people who have them. This can make it hard to deal with having them when you learn you do. Know that they are a lot like other parasites people can have. And most people who have had sex have put themselves at risk for them during their lives! Getting a parasitic STI doesn’t make someone less clean, and anyone who gets one deserves understanding and treatment without shame.

More info

Basics of each STBBI — Heart your Parts

Heart your Parts compiles a list of STBBIs (Sexual Transmitted and Bloof-Borne Infections), with a  quick description of each STBBI, whether it is curable and/or treatable,…

Types of STIs/STDs

SexualityandU’s webpage describing the most common STIs and STDs, grouped by family: Viral, Bacterial, and Parasitic/Fungal.–

Pubic Lice (Crabs)

Article on what pubic lice (crabs) is, the most common symptoms, and how to treat it.–


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