Protozoa are single celled beings, some of which cause diseases in humans. The protozoan diseases vary from mild to life threatening. Almost all human beings have protozoa in their body at some point in their lifetime. However, in this age of acquired human immune deficiency syndrome (AIDS), certain protozoa that once caused mild or no disease have become life threatening. A good example is Pneumocystis carinii. This protozoa is found in the lungs of many healthy people. However, in patients with "AIDS" it can cause fatal pneumonia.
The deadliest of the protozoan diseases, malaria is one of the top five "killer" infectious diseases. The causative agent is the genus plasmodium of the phylum protozoa. It includes P.vivax, P.falciparum, P.ovale and P.malariae. Nearly, 800,000 people die of malaria every year. It is transmitted by the female anopheles mosquito. Once they enter the human body, they undergo maturation in the liver and blood cells. Symptoms include fever with chills and rigor followed by excessive sweating. P.falciparum, if not detected early, can cause cerebral malaria and death.
Treatment is with 4-aminoquinolines, which include chloroquine and the newer sesquiterpine lactones like artesunate and artemether.
Amoebiasis is a group of protozoan disease caused by entamoeba histolytica. It includes the common amoebic dysentery and amoebic abscess in the liver, lungs, spleen and skin.
Amoebic dysentery is characterized by loose stools with blood and mucus in them. Spasmodic abdominal pain is common. It is diagnosed by examination of stools under a microscope. If not treated, it can cause ulcers in the large intestines and abscess elsewhere in the body.
Amoebic dysentery is usually treated with nitroimidazoles like metronidazole and tinidazole.
This disease, caused by the protozoa trypanosoma brucei, is transmitted by the tsetse fly. Symptoms begin with fever, headache and joint pain. If not treated early, it can involve multiple organs, including the heart and the kidney. Finally, the organism crosses the blood brain barrier, causing the typical symptoms of confusion, day time somnambulism and night time insomnia.
Sleeping sickness is treated with drugs containing arsenic, such as suramin.
This protozoan disease is caused by Toxoplasma gondii. Infection is caused by eating contaminated meat, accidental ingestion of cat feces or possibly by eating unwashed vegetables. In healthy persons, it is asymptomatic or may cause flu-like illness. However, in people with HIV it can be fatal. It can cause encephalitis or necrotizing retinochoroiditis.
Treatment is usually with clindamycin and spiramycin.
Trichomonas vaginalis, a protozoa, causes (the usually sexually transmitted) trichomoniasis. Although asymptomatic most of the times, it needs attention as it is known to facilitate HIV transmission.
Symptoms include vaginitis leading to white discharge in women and urethritis leading to burning micturition in men.
Trichomoniasis is treated with metronidazole.
Giardiasis caused by giardia lamblia and spread by contaminates in water and, Kala azar, caused by Leishmania, and spread by sand flies, are a few of the other types of protozoan diseases.