Malaria
Malaria is a life-threatening disease caused by parasites from the Plasmodium genus, which are transmitted to humans through the bites of infected female Anopheles mosquitoes.
When an infected mosquito bites a person, the parasites enter the human bloodstream and travel to the liver, where they mature and reproduce.
After multiplying in the liver, they re-enter the bloodstream and infect red blood cells.
The parasites then multiply inside the red blood cells, causing them to rupture and release more parasites that infect other red blood cells.
This process causes the symptoms of malaria,
Fever
Chills
Sweating
Headache
Nausea
Vomiting
muscle pain
Antimalarials
Antimalarials are a class of medications used to prevent and treat malaria.
They work by targeting various stages of the Plasmodium parasite's life cycle, thus inhibiting its growth and reproduction.
Antimalarial drugs are typically prescribed based on the specific strain of malaria, the severity of the infection, and the patient's medical history.
Additionally, antimalarials can be used prophylactically to prevent malaria in individuals traveling to areas where the disease is endemic.
Preventing malaria also involves vector control measures, such as the use of insecticide-treated bed nets, indoor residual spraying, and controlling mosquito breeding sites.
These measures, combined with prompt diagnosis and treatment, are crucial in reducing the global burden of malaria.
Etiology of malaria
The Etiology of malaria refers to the factors and processes that cause the disease.
Malaria is caused by single-celled, eukaryotic parasites from the Plasmodium genus.
The life cycle of the Plasmodium parasite involves two hosts: the Anopheles mosquito (the vector) and the human host (where the disease manifests).
Here, we will detail the etiology of malaria, focusing on the Plasmodium species, the mosquito vector, and the parasite life cycle.
1. Plasmodium species:
Five Plasmodium species are known to cause malaria in humans:
I. Plasmodium falciparum:
This is the most virulent and prevalent species, responsible for the majority of malaria-related deaths.
It is primarily found in sub-Saharan Africa.
II. Plasmodium vivax:
This species is less virulent but more widespread, occurring in Asia, Latin America, and parts of Africa. P. vivax can cause relapses due to dormant liver stages called hypnozoites.
III. Plasmodium ovale:
This species is primarily found in Africa and can also cause relapses due to hypnozoites.
IV. Plasmodium malariae:
This species has a worldwide distribution but is less common than P. falciparum and P. vivax.
It can cause long-lasting infections.
V. Plasmodium knowlesi:
This species primarily infects macaques but can also cause zoonotic infections in humans.
It is mainly found in Southeast Asia.
2. Anopheles mosquito vector:
Malaria transmission occurs through the bite of an infected female Anopheles mosquito.
Over 400 species of Anopheles mosquitoes exist, but only about 30-40 are efficient vectors for malaria.
The mosquito becomes infected when it feeds on a person carrying Plasmodium parasites in their blood.
Once inside the mosquito, the parasites develop and reproduce in the gut, eventually reaching the salivary glands.
When the mosquito bites another person, the parasites are transmitted through the mosquito's saliva.
3. Parasite life cycle:
The Plasmodium life cycle is complex, involving both sexual and asexual reproduction in the mosquito and human hosts, respectively.
I. Human infection:
When an infected mosquito bites a person, Plasmodium sporozoites are transmitted through the mosquito's saliva into the human bloodstream.
The sporozoites travel to the liver, where they invade hepatocytes (liver cells) and reproduce asexually, forming thousands of merozoites.
II. Liver stage:
In P. vivax and P. ovale infections, some parasites form dormant stages called hypnozoites, which can reactivate weeks or months later and cause relapses.
III. Blood stage:
Merozoites released from the liver enter the bloodstream and invade red blood cells. Inside the red blood cells, they multiply asexually, forming more merozoites.
The infected red blood cells rupture, releasing new merozoites that infect other red blood cells.
This cycle of invasion, replication, and rupture is responsible for the clinical symptoms of malaria.
III. Sexual stage:
Some merozoites develop into sexual forms called gametocytes.
When a mosquito bites an infected person, it ingests gametocytes, which then mature into male and female gametes in the mosquito's gut.
IV. Mosquito infection:
The male and female gametes fuse, forming a zygote that develops into a motile form called the ookinete.
The ookinete penetrates the mosquito's gut wall and forms an oocyst.
Inside the oocyst, the parasite multiplies, producing thousands of sporozoites.
The oocyst ruptures, releasing sporozoites that travel to the mosquito's.
Classification of antimalaria
Antimalarial drugs can be classified into different groups based on their chemical structure and mechanism of action.
Here, we will discuss the classification of antimalarial drugs in the categories of quinolines, biguanides, dihydrotriazines, and miscellaneous compounds.
