Plasmodium Malariae: Infection, Transmission & Diseases

Plasmodium malariae is a parasite of the genus Plasmodia. The protozoan is the causative agent of the infectious disease malaria.

What is Plasmodium malariae?

Plasmodium malariae is a protozoan that is classified as a parasite. This means that the Plasmodium lives at the expense of the host. Along with Plasmodium falciparum, Plasmodium ovale, and Plasmodium vivax, Plasmodium malariae is one of the causative agents of malaria. The single-celled organism causes malaria quartana. This form of malaria is comparatively benign and rarely has a fatal outcome. The causative agent of malaria was first described in 1880 by the French physician Alphonse Laveran. However, it was not until 1954 that the common name Plasmodium malariae was introduced by the International Commission on Zoological Nomenclature.

Occurrence, distribution, and characteristics

By the end of World War II, malaria had spread as far north as Europe and as far north as North America. Today, the infectious disease is a tropical disease. It occurs primarily in subtropical and tropical areas. Malaria is endemic in all continents, with the exception of Australia. Every year, around 200 million people fall ill. 600,000 of them die from the disease. The main distribution areas of Plasmodium malariae are in Africa, Asia and South America. The pathogen is not widespread in Germany. However, about 500 to 600 cases of malaria are imported each year. However, the proportion of infections caused by Plasmodium malariae is only about 10 percent. Most experts consider humans to be the only reservoir host for the pathogen. However, infected monkeys may also be a reservoir. Plasmodium malariae is transmitted by the anopheles mosquito. In the mosquito, the pathogen is present in the developmental stage of sporozoites. These have a diameter of 12 micrometers and enter the human bloodstream through a bite from the infected mosquito. From there, they migrate to the liver and invade liver cells. There, the sporozoites can reproduce asexually. The incubation period of this liver phase is about two weeks. The so-called liver schizonts produce many merozoites. These are released and infect the red blood cells. In the blood cells, they reproduce asexually again. At the end of the 72-hour multiplication cycle, there is the release of many new parasites that are washed into the bloodstream and again infect red blood cells. Only some of the plasmodia develop into sexual forms in the red blood cells. These sex forms are called microgametocytes or macrogametocytes. They are ingested by mosquitoes when they bite an infected person and continue to develop in the insect’s intestine. New sporozoites are formed, which then migrate to the mosquito’s salivary gland, from where they can be transmitted to another human.

Diseases and ailments

The infectious disease malaria, which is caused by the pathogen Plasmodium malariae, begins with uncharacteristic symptoms such as fever, headache, muscle aches and a general feeling of illness. At this stage of the disease, the misdiagnosis of flu-like infection is often made. As parasites are released into the blood at 72-hour intervals, febrile seizures occur every 72 hours. Typically, chills develop in the late afternoon hours. As it progresses, the fever rises very rapidly to levels above 40 °Celsius. After three to four hours, the temperature suddenly drops to normal levels. During this drop in fever, patients sweat profusely. It should be noted, however, that a lack of fever rhythm is not an exclusion criterion for the diagnosis of malaria. In malaria quartana, the kidneys can be severely damaged. This dangerous concomitant is called malarial nephrosis. Medically, it is a nephrotic syndrome. This is accompanied by a lowered serum protein. Serum proteins, also known as albumins, regulate the water balance in the bloodstream. A deficiency of albumins can lead to water retention in the tissues (edema) and to water retention in the abdominal cavity (ascites). To compensate for the loss of serum proteins, serum cholesterol levels rise. Malarial ephrosis occurs as a complication primarily in children between the ages of two and ten in tropical Africa.Plasmodium malariae, unlike the other plasmodia, continuously infects the blood. However, this ongoing parasite infestation is so small that it often cannot be detected with the microscope. Due to the parasitic load of the blood, recurrences can occur even after a long disease-free period. For example, there are malaria recurrences that have occurred more than 50 years after the original infection. The lack of microscopic detection is a risk for transfusion medicine in endemic areas. Even in donors who have tested negative for malaria, malaria can be transmitted when fresh blood is transfused. Refrigeration of blood supplies, on the other hand, kills Plasmodium malariae. Recurrences can also usually be stopped with medication. Malaria quartana must be treated as an inpatient. The drug of choice here is chloroquine. Since Plasmodium malariae does not form hypnozoites in the liver, follow-up treatment with primaquine is not necessary for malaria quartana, in contrast to the other forms of malaria. Travelers to malaria endemic areas should consider exposure prophylaxis. Mosquito-proof rooms with air conditioning and fly screens, sleeping under mosquito nets, and wearing long-sleeved clothing can reduce the risk of infection. The use of so-called repellents has also been shown to be helpful.