(i) Fever with chills and rigors after 48 hours.
(ii) Intermittent fever and discharge of fever with sweat.
(iii) 2-3 days after each other.
(iv) Fever usually occurs in the morning and afternoon.
(v) Three conditions of malarial fever are noteworthy. Cold condition, heat condition and sweating condition.
(vi) Body temperature is lower than normal when fever is gone. It is cold. Cold conditions last from 20 minutes to 1 hour.
(vii) Body temperature is very high in heat condition and temperature is up to 104-105 degrees Fahrenheit. This condition lasts for 2-4 hours.
(viii) Excretes toxins through sweat. The sweat condition lasts for 2-3 hours.

(i) Nausea occurs. Sometimes there is vomiting.
(ii) Headache and insomnia.
(iii) Loss of appetite and aversion to food.
(iv) Muscle pain and joint pain.
(v) The body feels cold.
(vi) Very thirsty.
(vii) Patient takes less food and becomes weak.
(viii) Difficulty breathing.
(ix) The patient is constipated.

1. Early symptoms of the disease
(i) Nausea occurs. Sometimes there is vomiting.
(ii) Headache and insomnia.
(iii) Loss of appetite and aversion to food.
(iv) Muscle pain and joint pain.
(v) The body feels cold.
(vi) Very thirsty.
(vii) Patient takes less food and becomes weak.
(viii) Difficulty breathing.
(ix) The patient is constipated.
2. Secondary symptoms of the disease
(i) Fever with chills and rigors after 48 hours.
(ii) Intermittent fever and discharge of fever with sweat.
(iii) 2-3 days after each other.
(iv) Fever usually occurs in the morning and afternoon.
(v) Three conditions of malarial fever are noteworthy. Cold condition, heat condition and sweating condition.
(vi) Body temperature is lower than normal when fever is gone. It is cold. Cold conditions last from 20 minutes to 1 hour.
(vii) Body temperature is very high in heat condition and temperature is up to 104-105 degrees Fahrenheit. This condition lasts for 2-4 hours.
(viii) Excretes toxins through sweat. The sweat condition lasts for 2-3 hours.
3. Final symptoms of the disease
(i) Red blood cells are destroyed. Anemia occurs. In this condition, hemolytic anemia occurs.
(ii) Spleen and liver of the patient become swollen and enlarged day by day. Lysolecithin is secreted from the spleen.
(iii) Parasites produce antibodies called Haemolysin which destroy red blood cells.
(iv) Digestion of the patient is disturbed.
(v) Patient may die due to brain damage.

Organisms that are partially or completely dependent on other organisms for survival are called parasites. Like Plasmodium vivax, Plasmodium ovale, Plasmodium falciparum, Plasmodium malariae etc.

Organisms that carry disease germs are called vectors. Humans and mosquitoes are carriers of the malaria parasite. There are about 430 species of Anopheles mosquitoes in the world. Among them, 19 species of mosquitoes are vectors of malaria. The total number of mosquito species in Bangladesh is 113, the number of Anopheles mosquito species is 34 and the number of malaria vector species is 8. Notable Anopheles mosquitoes are Anopheles dirus, Anopheles annularis, Anopheles aconitus, Anopheles sundaicus, Anopheles philipnensis, Anopheles minimus, Anopheles vagus etc.

The period from the time the pathogen enters the host until symptoms of the disease appear is called dormancy. The latency period of Plasmodium species is Plasmodium vivax 12-20 days, Plasmodium ovale 11-16 days, Plasmodium falciparum 08-15 days and Plasmodium malariae 18-40 days.

Plasmodium is the causative agent of malaria. All species of mosquitoes of the genus Anopheles alone carry Plasmodium. Anopheles mosquito is the sole carrier of Plasmodium in terms of lifespan, environmental conditions, temperature and duration of bite. Anopheles mosquitoes are good for gamete formation, fertilization, zygotes, oocysts and sporogony of Plasmodium. A crop of Anopheles mosquito is a favorable environment for the growth of bacteria.
Other species of mosquitoes contain toxic substances in their bodies. These toxins are harmful to Plasmodium. The intestines of all those mosquitoes contain trypsin-like substances. These substances inhibit the growth of Plasmodium ookinetes. As a result sporozoites are not formed. But the Anopheles mosquito has no harmful components for Plasmodium. The crop of Anopheles mosquito is a perfect environment for the germs to reproduce. Therefore, only female Anopheles mosquitoes carry malaria.

1. Vertebrate (human) requirements
(i) New host: Sporozoites of malaria parasite require human as new host.
(ii) Merozoite Formation: Merozoites are not formed without a vertebrate host. Therefore, a vertebrate host is required for merozoite formation.
(iii) Schizogony: Hepatic and erythrocytic schizogony of malaria parasites is accomplished in humans or vertebrates.
(iv) Easy availability: Humans are readily available as vertebrate hosts.
(v) Continuity of the species: Production of male and female gametophytes is necessary to maintain the continuity of the species. Gametophytes are produced in human blood. Therefore, vertebrates are essential to prevent species extinction.
2. Invertebrate host (meshki) requirement for sex cycle
(i) Sex cycle: Malaria parasite requires mosquito for sex cycle.
(ii) Carrier of sporozoites: After sexual reproduction, the mosquito carries the sporozoites.
(iii) Easy availability: As an invertebrate host, muskrats are readily available in the vicinity of settlements.
(iv) Nutrition: The sporozoites obtain nutrition from the body of the mosquito.
(v) Life span: The mosquito lives longer than the time required for the malaria parasite to complete its sexual cycle.

Merozoites of the malaria parasite are released from the liver and enter the bloodstream. It disrupts the normal environment of the blood. White blood cells release pyrogens to destroy them. The hypothalamus of the brain is stimulated due to excess pyrogens in the blood. Because of this, chemical substances like prostaglandin, monoamine etc. are secreted from the brain. This message or stimulus reaches the peripheral regions of the body through vasomotor nerves. Peripheral blood vessels are narrowed. Therefore excess heat cannot escape from the body. As a result, body temperature rises more than normal and fever occurs.

The periodic alternation of haploid and diploid states in the life cycle of an organism is called a cycle. The genealogy of the malaria parasite is discussed.
1. Haploid status
(i) Sporozoites: When an Anopheles mosquito biting a healthy human, the sporozoites enter the human body through the saliva of the mosquito. Sporozoites are mobile, slightly curved and both ends of the body are straight. The sporozoites penetrate human liver cells and grow within 30-45 minutes.
(ii) Metacryptomerozotes: Metacryptomerozotes are formed successively from sporozoites. Metacryptomerozites are of two types. Micrometacryptomerozites and macrometacryptomerozites. Micrometacryptomerozites are small in size and have large nuclei. Macrometacryptomerozotes are large in size and have small nuclei. Macrometacryptomerozites invade new liver cells. Micrometacryptomerozites enter the bloodstream and invade red blood cells.
(iii) Merozoite: 12-18 small cells are seen in the cytoplasm of the germ. A nucleus enters each segment. They are arranged in two layers like petals. This condition is called rosette. Each part, including the nucleus, becomes a merozoite.
(iv) Gametocytes: Some merozoites develop into gametocytes. Gametocytes are of two types. Microgametocyte and Macrogametocyte. Microgametocytes are small in size and have large nuclei. Macrogametocytes are large in size and have small nuclei.
(v) Gametes: In the process of exflagellation, the nucleus of each microgametocyte divides into 4-8 pungametes or microgametes. Each macrogametocyte gives rise to one strigamete or macrogamete.
2. diploid state
(i) Zygote: The microgamete enters the macrogametocyte through the fertilization cone. Later their nuclei fuse to form a zygote.
(ii) Uokinete: After 12-14 hours the quiescent spherical zygote becomes elongated and motile. It is called wokkinet or vermicule. Uokinetes are 18-28 microns in length and 3-5 microns in width.
(iii) Oocyst: Within 24 hours the oocinets break through the wall of the mosquito crop and come out and become spherical. It is then covered with a thin film. It is called a oocyst. The oocyst later transforms into a sporozoite.