of the organism inside the body in which tissue is consumed by the organisms is
referred to as the invasive stage. Transmission of the cyst is usually made by food
handlers in areas of poor sanitation, since the amoeba leaves its host in the cyst form in
feces. Perhaps the easiest way to remember the four modes of transmission of
Entamoeba histolytica are the "four F's": food, flies, fingers, and feces. It is estimated
that over 10 million persons are affected annually in the United States by amebiasis.
The last major outbreak of this condition in the US was in 1933 at the Chicago World's
Fair. Over 1400 cases (with four fatalities) were reported. While there are over 26
different species of amoebas known to man (several of which live normally within our
bodies), only six or seven amoebas actually cause disease in man.
(3) Plasmodium vivax, Plasmodium malariae, Plasmodium falciparum, and
Plasmodium ovale. Plasmodium organisms cause malaria. Malaria is one of the
prevalent diseases in the world. Fortunately, it is rarely seen in the United States. As of
1965, there were over 300 million new cases and approximately 3 million deaths
attributed to malaria. Malaria primarily infects the red blood cells, but it can secondarily
infect the liver. The vector (carrier) for malaria is the female Anopheles mosquito. The
protozoan lives and reproduces sexually in the female mosquito's gastrointestinal tract.
When the mosquito bites a human, the mosquito regurgitates digestive juices into the
site of the bite. In this manner, the protozoa are injected into the host's blood, where
the protozoa live and reproduce asexually in the host's red blood cells. Because of the
life cycle of the protozoa, killing the mosquito vector is the best method of controlling
malaria. Symptoms of malaria include sudden chills, fever, and sweating because of
destruction of red blood cells. The destruction of the red blood cells can lead to an
anemic state which often affects the spleen and liver. There are basically four types of
malaria produced by four different species of the protozoan: Plasmodium vivax,
Plasmodium malariae, Plasmodium falciparum, and Plasmodium ovale.
(a) Plasmodium vivax causes the most commonly occurring type of
malaria. If improperly treated, the patient may have recurring (relapsing) bouts of
Plasmodium malariae is a relatively rare form of malaria.
(c) Plasmodium ovale causes the rarest form of malaria, which is
limited to Western Africa.
(d) Plasmodium falciparum causes the most severe type of malaria, so
severe it can lead to death if left untreated. This form of malaria has also been known
to cause Blackwater fever, a condition in which red blood cells and the liver are
destroyed. Falciparum malaria is also the easiest form of malaria to treat.