Malaria

Malaria is an acute infectious disease caused by Plasmodium and transmitted through the bites of female Anopheles mosquitoes.

I. Species of Plasmodium and its life cycle

1. Species
   • There are mainly four species of Plasmodium that cause human malaria: Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae, and Plasmodium ovale. Among them, Plasmodium vivax and Plasmodium falciparum are more common.
2. Life cycle
   • The life cycle of Plasmodium is quite complex and requires two hosts, humans and Anopheles mosquitoes.
   • In the human body, Plasmodium first invades liver cells for schizogony, a stage known as the exo – erythrocytic stage. Then, Plasmodium is released from liver cells and invades red blood cells, where it undergoes schizogony within the red blood cells, causing the red blood cells to rupture and release a large number of merozoites. This process leads to symptoms such as fever in patients and is called the erythrocytic stage.
   • When a female Anopheles mosquito bites a malaria patient, it sucks blood containing Plasmodium gametocytes. Inside the mosquito, Plasmodium undergoes sexual reproduction, followed by sporogony to form sporozoites. The sporozoites move to the salivary glands of the Anopheles mosquito. When the mosquito bites another person again, the sporozoites enter the human body and start a new cycle of infection.

II. Symptoms of malaria

1. Typical symptoms
   • The typical symptoms of malaria include cyclically occurring chills, high fever, and sweating.
   • The cycle of attacks is related to the species of Plasmodium. Plasmodium vivax and Plasmodium ovale usually have an attack every 48 hours, Plasmodium malariae has an attack every 72 hours, and the attack cycle of Plasmodium falciparum is more irregular.
   • The patient first feels chills and shivers all over the body, lasting from several minutes to several hours; then the body temperature rises rapidly, reaching above 40 °C, accompanied by symptoms such as headache, body aches, and fatigue; after a period of high fever, the patient sweats profusely, and the body temperature gradually drops, and the systemic symptoms are relieved.
2. Other symptoms
   • Long – term repeated infections with malaria may lead to complications such as anemia and splenomegaly. In severe cases, infection with Plasmodium falciparum may cause cerebral malaria, and patients may have neurological symptoms such as coma and convulsions. The condition is dangerous, and the fatality rate is relatively high.

III. Malaria – prevalent regions

1. Global distribution
   • Malaria is mainly prevalent in tropical and subtropical regions. Sub – Saharan Africa is a highly malaria – endemic area, accounting for about 90% of the global malaria burden. In addition, parts of Southeast Asia and South Asia in Asia, as well as some countries in Latin America, also have malaria epidemics.
2. The situation in China
   • Malaria was once widely prevalent in China. After years of prevention and treatment, malaria has been eliminated in most regions. However, local cases are still reported in Yunnan, Hainan, and other places, and there is a risk of imported cases.

IV. Diagnosis and treatment of malaria

1. Diagnostic methods
   • The diagnosis of malaria is mainly based on the patient’s epidemiological history (whether from a malaria – endemic area, a history of mosquito bites, etc.), clinical manifestations, and laboratory tests.
   • Laboratory tests include microscopic examination of blood smears for Plasmodium, which is the most commonly used method for confirming malaria. In addition, rapid diagnostic test strips for detecting Plasmodium – specific antigens can also be used. This method is rapid and simple and is suitable for use in primary – level medical institutions.
2. Treatment principles
   • The drugs for treating malaria mainly include chloroquine, artemisinin and its derivatives, etc.
   • Treatment plans vary depending on the species of Plasmodium infection and the severity of the condition. For example, for Plasmodium vivax and Plasmodium ovale infections, in addition to using drugs to kill Plasmodium in the erythrocytic stage, primaquine is also needed to eradicate the dormant forms of Plasmodium in the liver and prevent recurrence; for Plasmodium falciparum, it is necessary to quickly control symptoms to prevent the condition from worsening.