Malaria is the best known protozoal disease, caused by one of four species of the sporazoa type – Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. The parasite survives only in the Anopheles mosquito, which transmits the protozoa as she bites. Worldwide, there are about 380 species of this type of mosquito, but only about sixty are able to transmit the parasite responsible for malaria. P. vivax and P. ovale can survive and grow at lower temperatures than P. falciparum. As a result, P. vivax has been known to be transmitted as far north as the UK and the Netherlands. None of the parasites can complete its breeding cycle in temperatures below 15C (50°F).
The Anopheles mosquito bites only at night. The parasite produces larvae (sporozoites) inside the intestines of the female mosquito. (Males are vegetarians and do not require blood for survival.) The larvae are then discharged into the mosquito’s saliva at the time of a “bite.” These sporozoites will congregate in the liver and start multiplying (a 30,000 fold multiplication) into a form called merozoites. About two to four weeks later, the merozoites begin attacking red blood cells (RBCs) and feed on hemoglobin multiplying still further into more merozoites as well as a smaller number of gametocytes. Destruction of the RBCs releases a toxin that brings on the paroxysmal chills and fevers – symptoms of the disease. This is the reason that it is advised to continue with antimalarial medication for at least a month after returning from an endemic area.
The cycles of infection become synchronized. Each cycle produces more and more infected cells, which then burst. With each bursting, cellular debris, parasites, and by-products are released into the bloodstream, triggering a malarial paroxysm (periodic sudden recurrence of symptoms). The paroxysms start with chills that last for fifteen minutes to an hour, accompanied by a headache, vomiting, and overwhelming nausea. These symptoms can increase in severity to mild delirium. The paroxysm lasts eight to twelve hours and terminates as the exhausted person goes to sleep. On awakening, the patient will feel much better.
The growth of the parasite inside the red blood cells occurs at fixed intervals. It is this factor that determines the frequency of the paroxysms. The interval is about forty-eight hours for P. viva and P. ovale. The interval varies between thirty-two and forty-eight hours for P. falciparum, and every seventy-two hours for P. malariae. In addition, the severity of clinical symptoms varies among the different species. P. falciparum produces the severest symptoms, with fevers climbing as high as 43.3°C (110°F). With the continual destruction of red blood cells, concurrent damage to the capillaries, RES (reticuloendothelial system), various internal organs, plus an increasing resistance to medications. Death is the only outcome. The mildest form for humans is P. malariae, whose replication is much slower. P. falciparum produces the severest and deadliest form of the disease.
The two complications of malaria are lung edema and cerebral malaria. Of the four species of malaria, only Plasmodium falciparum makes the red blood cells stick to the walls of the blood vessels. Normal RBCs are smooth and flexible enough to squeeze through the tiniest of capillaries. But RBCs, carrying this particular parasite, become sticky and stiff, forming plugs that leave the tissues starved for oxygen. Damaged lungs can lose their seal, causing a person to literally drown in the very fluids being administered for his recovery. Similar destruction can happen in the brain, causing a lack of oxygen, followed by coma and death. Death can also result from multi-system failure, including renal failure and a ruptured spleen.
The matured parasites stay in the blood and do not reenter the liver. Those that do remain in the liver do so in a dormant state to be released months or years later, causing relapses in those thought to be cured. Although most who have been exposed to malaria protozoa develop symptoms within six weeks, some may not for a year or two after exposure. The disease is not passed from person to person. However, an infected person can transmit it to a mosquito, which, in turn, passes it on to another human. Interestingly, mosquitoes that become infected with the malarial parasite and bite an HIV-infected person cannot become infected with the HIV virus or pass it on. Malaria can be transmitted by transfusion, but only as long as the sporozoites stay in the bloodstream. Only one species has been known to remain viable for more than forty years.
Identification of the parasites is fairly easy because all four of the species differ enough to allow for certain diagnosis. The disease is most commonly found in Africa, South America, and Southeast Asia, although recent cases have been reported in the US and Britain. The parasite has now become resistant to the best anti-malarial drugs, and can now be found in at least 100 tropical and subtropical countries, with millions being affected worldwide. According to WHO, one out of every seventeen people alive today will die from a disease transmitted by the bite of a mosquito. Worldwide, malaria infects 300-600 million people, killing about three million – one million in Africa alone.
Malaria can pose a particular threat to pregnant women, causing either a premature birth, a stillborn birth, or spontaneous abortion. However, the infection is usually more severe in non-pregnant women. Those taking antimalarial drugs as a preventative should be aware that they do not always prevent the disease. Those women who do take the drug and are breastfeeding should realize that a small amount of the drug is transferred to the milk, but not enough to protect the infant. Infants will be required to take the drug individually, but it is essential that the correct dosage be given that is according to the size and weight of the child. An overdose of an antimalarial drug can be fatal.
Many cultures have developed herbal medicines to combat malaria. Some Mediterranean cultures use the fava bean in their diet. The Hausa of Nigeria have at least thirty-one anti-malarial plant medicines. The people of Madagascar have used hundreds of plants to combat malaria. The Chinese used theArtemisia annua plant. Quinine, also known as Jesuit’s bark, is made from the bark of the cinchona tree. It was found amongst the Peruvian Incas and introduced to the rest of the world.
A supplemental treatment for malaria consists of taking the temperature every fifteen minutes, and, at the first sign of an elevated body temperature, the person should be put into a Russian steam bath, a whirlpool, a hot tub, etc. to elevate the body temperature to about 39°C (102-103°F). This brings the white blood cells out into the bloodstream to attack the parasites before they can enter a new red blood cell. This method will not get rid of all of the parasites, but it will at least reduce the number, according to Weintraub. Using this method with proper timing, and repeating it every time the temperature elevates, is said to reduce the numbers of organisms.
During the American Civil war, southern troups suffered the most from malarial outbreaks. Almost 1.25 million cases were reported during that time, which also included General Grant. Malaria was so ferocious around the city of Rome, and along the west coast of Italy, that some areas remained uninhabitable until the 20th century. Archaeologists have recently found evidence that malaria may have contributed to the downfall of Rome. Since it is known that the mosquito cannot fly more than 100 meters and could not have come from Africa by this means, this theory was long thought ridiculous. It is now presumed that the mosquito came from Africa aboard ships. DNA of skeletal remains found in Roman villas, proved beyond a shadow of a doubt that malaria was indeed the cause of death in that area. That, and the fact that sixteen sunken ships were found in the harbor, led to speculation that the ships were scuttled as the “barbarians” approached the city because there were not enough healthy sailors to protect them from capture.