August 2022
Sexual Health
Hedda Fay

Types of STIs and How They Function

Part 2: Parasites, Fungi and Prevention

Sexually transmitted infections come in different categories, which makes them act differently, so we treat them differently. STIs can have a profound effect on the health of individuals and communities. Some are curable, others are treatable. In Part 1 (July) I covered bacteria and viruses. Now I'll get to the plant and animal world.


Parasitic STIs are caused by protozoans, nematodes and arthropods.

The most common is trichomoniasis vaginalis, a protozoan parasite. This is typically treated with metronidazole.

You can spot the egg, nymph and adult stages of pediculosis pubis, the crab louse or pubic louse, which is easily treated with the same medications you would use on head lice. We also have an itch mite called sarcoptes scabiei, aka scabies. These parasites reproduce by laying eggs in the pubic-hair region that take six days to hatch. Females can lay three to five eggs daily, and they live up to a month. Crabs feed excessively on blood, sipping four or five times each day.

Two other parasitic STIs are amebiasis, caused by entamoeba histolytica, and giardiasis, by giardia lamblia. These parasites are usually diagnosed with an examination of a stool specimen. Giardia is often found in people who engage in anal sex. Both are easily curable conditions.


Fungal overgrowths are the most commonly occurring STIs, which makes it great that they’re so easily cured. Fungal infections love the warm, wet, moist human body and its mucosa, ideal habitat for them to grow in.

Tinea cruris, aka jock itch, is a fungal infection more common in males than females. It likes warm, damp areas like the groin, including the skin between thighs and groin.

Vulvo-vaginal candidiasis (VVC), aka the yeast infection, is candida, a kind of yeast that occurs naturally in small amounts throughout the body, and there are over 1,000 species. At times an imbalance can cause the yeast to multiply, and we experience an overgrowth. This is easily cured with a topical cream or an anti-fungal pill. The vulva/vagina environment encourages candida growth and proliferation, with its dark, warm, moist mucosa. It is its own life form, part yeast, part fungus, parts vegetable, bacterium and animal. It can adapt and change form and shape, making it difficult to treat. It creates a biofilm made of proteins, plant cellulose, DNA, RNA and fats. It can reproduce sexually on its own, because each nucleus carries two copies of the chromosomes to create two separate cells that meet and fuse to create a new cell.

Yeast is either anerobic or aerobic. Lacking oxygen it produces energy by converting sugars to CO2 and ethanol, which is why some with systemic candida report feeling brain fog — it’s the alcohol!


To prevent these STIs you can use a condom correctly, and lubricant with the condom. If you don’t like that we recommend a full-panel STI test every three months, so when you do pick up something, you can get it cured in a timely manner and avoid long-term health problems from it.

I’m Hedda Fay reminding you that there are sexually communicable viruses, bacteria, fungi and parasites everywhere, and if you have enough unprotected oral, vaginal or rectal sex, you will meet one or more of them. Be responsible and get checked today to avoid problems later. Suit up, lube up, and be safe out there, it’s a microbial jungle!

Hedda Fay, the Community Outreach and Program Manager of Northland Cares, answers your questions about sex and sexual health.