Malaria

Malaria is a serious and potentially fatal disease caused by parasites that are spread to humans through the bites of infected female Anopheles mosquitoes. It continues to pose a major health threat, particularly in tropical and subtropical areas around the world.

1.0 Introduction

• Malaria is an infectious disease caused by Plasmodium parasites, which are transmitted to humans through the bites of infected mosquitoes.
• After entering the body, the parasites first multiply in the liver before attacking the red blood cells.

2.0Transmission

• Malaria is primarily transmitted through the bite of an infected female Anopheles mosquito. 
• It can also be transmitted through blood transfusions, organ transplants, and the use of shared needles.
• In rare cases, malaria can be passed from mother to unborn child.

3.0Types of Malaria Parasites

There are five types of Plasmodium parasites known to infect humans:

• Plasmodium falciparum (most severe form)
• Plasmodium vivax (Most widely spread)
• Plasmodium ovale
• Plasmodium malariae

Symptoms

Early Signs of Malaria

• Fever
• Chills
• Sweating
• Headache
• Nausea
• Vomiting

Severe Malaria Symptoms

• Seizures
• Confusion
• Severe anemia
• Difficulty breathing
• Organ failure

Incubation Period

• Symptoms typically appear 10 to 15 days after the mosquito bite. 
• However, the onset can vary depending on the type of parasite and individual health factors.

4.0Life Cycle of Malaria

• The life cycle of the plasmodium is spent in two hosts’ man and anopheles mosquito. 
• The mosquito is the definitive host as the sexual development and multiplication of the parasite occurs in it. 
• Man is the intermediate host. 
• Sporozoite is the infective form of malarial parasite which is passed on to man through the bite of infected vector, the female anopheles mosquito. 

5.0Development in the Human (Primary Host) ( Asexual stage)

• Anopheles Mosquito inject sporozoite to human  enter the liver  the liver release merozoite enter the RBC (ring stage) and cause the main pathology which is blood haemolysis and anemia 
• Mosquito inject sporozoite to human (infective stage) 
• Mosquito suck gametocytes from human 
• Some parasites develop into male + female gametocytes . 
• The various stages of the parasite in man are:- 

(a) Pre-erythrocytic schizogony 

• This phase lasts for 8 days. Sporozoites are elongated and spindle shaped. 
• The sporozoites enter the liver parenchymal cells and become rounded. 
• They undergo multiple divisions and develop into schizonts. 
• One schizont contains 20,000 – 30,000 merozoites. 
• The liver cells ruptures and releases the merozoites into blood. 

(b) Erythocytic schizogony

• This has a duration of 48 hours. The merozoites penetrate the red blood cells. 
• The merozoites enlarge in size and develop into trophozoites. 
• The trophozoites develop into schizont which further develop into merozoites. 
• There may be 6-24 merozoites in red blood cells.
• In the case of Plasmodium falciparum the schizonts aggregate in the capillaries of the brain and other internal organs. 
• So that only ring forms are formed in the peripheral blood. 

(c) Gametogony

• Some merozoites enlarge and get transformed to microgamete and macrogamete. 
• The malarial parasite now becomes infective as the presence of gametocytes is a must for sexual development in the mosquito. 
• The mosquito gets these gametocytes after taking a blood meal from a patient of malaria. 

 (d) Exo-erythrocytic schizogony

• This phase resembles pre-erythrocytic schizogony. 
• Some sporozoites after entering the liver cells do not undergo multiplication but go into resting phase. The resting stage of the parasite is known as hypnozoite. 
• These can reactivate up to after 2 years and become schizonts and release merozoites. This phase is responsible for relapse of malaria.

(ii) Development in the mosquito(Secondary Host or Sexual stage)

• Male and female Gametocytes are taken up from the blood of an infected human by biting a mosquito .
• Further sexual development takes place in the mosquito gut to produce sporozoites.
• The female anopheles mosquito takes a blood meal from a malaria patient and the plasmodium gametocytes (Both microgametes and macrogametes) reach the gut of the mosquito. 
• Only the mature gametocytes undergo further development. 
• Microgametes penetrate the macrogametes and fertilize it leading to the formation of a zygote. 
• In the midgut of the mosquito one microgamete develops into 4-8 filamentous structures called microgamete. The zygote matures into an ookinete. 
• The ookinete further develops into oocyst. The oocyst further matures and increases in size. A large number of sporozoites (100-1000) develop inside the oocyst. 
• The oocyst ruptures and releases the sporozoites in the body cavity of the mosquito. The sporozoites go to all the organs but prefer to go to the salivary glands. 
• The mosquito is now infective to man.

6.0Malaria Diagnosis and Treatment

Diagnosis

Malaria is diagnosed through:

• Microscopic examination of blood smears
• Rapid diagnostic tests (RDTs)

Treatment

• Treatment depends on the type and severity of the infection. Common medications include:
• Artemisinin-based combination therapies (ACTs)
• Chloroquine
• Mefloquine
• Quinine

Malaria Around the World

• Sub-Saharan Africa bears over 90% of the global malaria burden. India, Indonesia, and Papua New Guinea are also heavily affected.

Geographic Regions Where Malaria Is Common

• Malaria is prevalent in:
• Sub-Saharan Africa
• South Asia
• Southeast Asia
• Central and South America
• Some parts of the Middle East and Oceania