Dr. Germs, Defender of Health - Learn all about which protozoan parasites classify as germs, how they are transmittedd, and which diseases and symptoms they can cause

Protozoa are single-celled organisms that live in soil and water and play an important role in their ecology. They have animal-like characteristics of movement and consumption of other organisms and most often thrive as parasites.

Protozoa	Transmission	Disease & Symptoms
Cryptosporidium	Water-borne: Ingestion of fecally contaminated swimming pools, water supplies, or food	Cryptosporidiosis Watery diarrhea, abdominal cramps, slight fever
Malaria parasites (Plasmodium falciparum, vivax, ovale, and malariae)	Blood-borne: Mosquitoes transmit malaria parasites into the bloodstreams of humans	Malaria Fever, anemia, chills, flu-like illness, and in severe cases, coma and death.
Pediculus (lice) humanis (body) humanis capitis (head) Pthirus pubis (pubic lice)	Person-to-person: Head lice are spread through head-to-head contact with an infested person; body lice through direct contact with the body or clothing of an infested person; pubic lice (crabs) are most often spread through intimate contact with an infested person	Pediculosis Itching
Taenia sollum (tapeworm)	Food-borne: Ingestion of undercooked pork contaminated with larvae	Cysticercosis (aka neurocysticercosis) Worms migrating into various body parts leave cysts. In muscles, they cause swelling or nodules under the skin; in eyes, they float around, impairing vision or and cause retinal swelling and detachment that lead to blindness; in the brain, they cause swelling, seizures, headaches, confusion, attention deficit, and difficulty with balance. When the worm dies, the host's immune system attacks its remains, causing swelling and scarring. Spinal cord lesions can lead to weakness and partial or full loss of motor control.
Toxocara canis (dog roundworm) or Toxocara cati (cat roundworm)	Hand-to-mouth: Humans typically ingest roundworm eggs by eating with contaminated hands	Visceral larval migrans (VLM) Eggs in the human intestine develop into larvae, which penetrate the bowel wall and migrate through blood vessels to reach the liver, muscles, lungs, and sometimes the eyes and brain, causing itching, rash, breathing difficulty, abdominal pain, brain damage, meningitis, encephalitis, or epilepsy, loss of visual acuity, or blindness.
Toxoplasma gondii	Food-borne: Ingestion of raw or undercooked meat contaminated with cysts Hand-to-mouth contact: Humans typically ingest cysts by eating after touching cat feces Blood-borne: Transmitted from an infected mother to her fetus	Toxoplasmosis Swollen lymph nodes, muscle aches
Trichinella spiralis (trichina worm, a roundworm)	Food-borne: Ingestion of raw or undercooked game or pork contaminated with larvae	Trichinosis (aka Trichinellosis or Trichiniasis) Intestinal infection causes nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort. As the worms encyst in other parts of the body cause headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, pinpoint hemorrhages, itchy skin, and heightened numbers of white blood cells. Worms penetrating nervous tissue cause difficulty coordinating movements and respiratory paralysis.
This sample list of parasitic protozoa and the diseases they cause is far from all-inclusive. For complete information about any disease, we encourage you to visit the Center for Disease Control and Prevention (http://www.cdc.gov/). This content is intended for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease or to replace the advice or diagnosis of your physician or health care provider.