Various types of protozoan infective organisms are responsible for plenty of human misery. Ingested in contaminated water or injected by a feeding insect, they cause diseases ranging from malaria to encephalitis.
Protozoan is an inexact term for one-celled organisms with an internal structure more complicated than the bacteria, but lacking firm cell walls. Protozoan forms include flagellates, ciliates, sporozoans, amoebas, and foraminifers, according to the online Free Dictionary. They usually live in water or as parasites, and are a disparate group with members that are not all evolutionarily related.
The freeform Amoeba is an example of a protozoan organism. Animal-like, it moves around and feeds on other organisms, rather than making its own food like a plant. Though most amoebas don’t cause disease, some are very dangerous indeed. Infective protozoan organisms include:
Malaria plasmodium
There are 300 to 500 million cases of malaria each year. They are caused by a protozoan parasite transmitted by the anopheles mosquito. Injected plasmodium parasites travel to the liver, where they mature and release their merozoite form. These infect red blood cells, destroying them.
The results are anemia, high fever, chills, and flu-like symptoms. The CDC estimates that more than a million people die of malaria each year. Many malaria mosquitoes are now resistant to insecticides and many plasmodium parasites are resistant to antibiotics. One hopeful sign is the campaign to provide mosquito nets to protect sleeping children.
Giardia lamblia
Giardiasis is an infection with the protozoan parasite giardia lamblia. Symptoms include diarrhea, abdominal pain, bloating, headache, and nausea. The most commonly diagnosed intestinal parasite in the U.S. and Canada, in countries with undeveloped public health systems Giardiasis infection is very common.
The parasite spreads through contaminated water, during sexual contact, or from infected food handlers. Birds and small aquatic mammals provide reservoirs where the parasite spends part of its life cycle.
Treatments exist, but can cause unpleasant side effects. Avoid Giardiasis by drinking only water treated in a modern facility, or by filtering untreated water carefully. Don’t even brush your teeth with stream water, and wash hands frequently, especially if you change diapers or handle wet waste.
Cryptosporidium parvum
Cryptosporidium also causes diarrhea. According to the FDA, research shows that 80 percent of the people in the United States have had Crypto without knowing it, as a relatively mild illness lasting up to two weeks. However, immunocompromised people, including people with AIDS or in treatment for cancer, may have cryptosporidium for life.
Like giardia, crypto forms cysts that protect the organism in harsh conditions. Tougher than giardia, crypto can sometimes survive chlorination in modern water treatment plants. People can also pick up the infection in a public pool, lake, or stream.
Treatment for most people is quite effective, but young children and pregnant women are particularly vulnerable. Parents and potential parents should practice regular and thorough hand-washing, and teach their children to do the same.
Amoebae: Naegleria and Acanthamoeba
Naegleria fowleri is horrifying, and fortunately very rare. According to the CDC, only 32 infections were reported in the U.S. between 2001 and 2010. It lurks in warm waters, hot springs, and soil. It can occur in poorly maintained swimming pools and even in hot tap water. Microscopic, it makes its way up the nose, to infect the brain. Infected people generally die of primary amebic meningoencephalitis.
Acanthamoeba is another amoeba that causes severe infections. However, many people have been exposed to it, and not even felt ill. Their immune systems protected them.
Acanthamoeba can cause eye infections severe enough to damage vision. People who wear contact lenses should be especially careful to practice good hygiene to avoid this amoeba. In immunocompromised persons, Acanthamoeba can cause fatal infections. Early diagnosis and treatment is essential.
Leishmaniasis, sleeping sickness, and Chagas disease are other illnesses caused by infective protozoan organisms. Public health measures like sewers and water treatment plants effectively prevent the spread of disease. However, individuals also have a responsibility to look after their own health, and that of their family. Practicing good hygiene and teaching it to children can be lifesaving.
Bacteria, viruses, fungi, helminthes, prions, and protozoa are the major types of infective agents. All can make people sick, but all are also part of the totality that is our living world. We must protect ourselves, no doubt, but without harming the great web of life, of which humanity is only a part.
