- German government funded scientists under Robert Koch, who thought he found the agent of malaria, which he
named Bacillus malariae,but which he later discarded because it could not be grown in labs.
- Ross then correctly recognized that Anopheles mosquitoes are carry malaria and that the life cycle in the human
was similar to that of the bird malaria that he had earlier studied.
- Ross demolished Koch`s theory and stated “It is not the mosquito’s children, but only the mosquito who herself
bites a malaria sufferer – it is only that mosquito who can give malaria to healthy people.”
- Grassi was jealous because his country Italy did not get the recognition.
- Ross and Laveran received the Nobel Prize, not Grassi.
- Grassi’s contribution was to recognize the vector as Anopheles.
- Malaria can be inducted in a host by the introduction of sporozoites (the type of parasite) through the bite of an
infectious female mosquito, but the parasites do not appear immediately in the blood.
The Disease Malaria (145) 00
- Plasmodium is parasitic protozoan of the genus Plasmodium that causes malaria in humans.
- The human malarias are caused by P. falciparum, P. vivax, P. Ovale, P. Malariae; four plasmodiums which are
specific to human out of the 170.
- All four of them are transmitted through the bite of an infected female anopheline mosquito when/during blood
feeding, she infects sporozoites from her salivary glands.
- The number of sporozoites inoculated is usually less than 25.
- They travel via the bloodstream to the liver (which takes less than an hour).
- Within the liver cell the parasites reproduced asexually to produce 10,000 or more infective offspring, which invade
- It is the asexual reproduction of parasites in RBC and their ultimate destruction with release of infectious
offspring (merozoites) that are responsible for the pathogenesis (origination and development) of this disease.
- Merozoites released from RBCs incade other red cells.
- In some cases, the merozoites enter red cells but do not divide. Instead, they differentiate into male or female
gametocytes (the crescent of Laveran). When ingested by the female mosquito, the male gametocyte divides into
eight flagellated microgametes, which escape from the enclosing red cell (exflagellation).
- The primary attack of malaria begins with headache, fever, anorexia, malaise, and myalgia. Followed by chills,
fever, and profuse (a lot) of sweating. There may be nausea, vomiting, and diarrhea.
-Such symptoms are not unusual for an infectious disease, malaria is therefore also known as “the great imitator”.
- Depending on the species, the paroxysms tend to assume a characteristic periodicity: In P. falciparum, P. vivax, P.
Ovale the period between fever bursts is 48 hours, and for P. Malariae, it is 72 h.
- The fever spike can reach up to 410C and corresponds to the rupture of the red cell as merozoites are released from
the infected red cell.
- Anemia is the most immediate pathological consequence of parasite multiplication and destruction of erythrocytes,
and there can also be suppression of red cell production in the bone marrow.
- During the first few weeks of infection, the spleen in palpable (palpation: The act of feeling or pushing on various
parts of a patient’s body to determine medical condition such as the normality of organs or the presence or absence
of tumors, swelling, muscle tension, etc.) because it is swollen from the accumulation of parasitized red cells and the
proliferation (rapid increase) of white cells.
- At this time, spleen is soft and easily ruptured.
- If the infection is treated, the spleen returns to normal size; however, in chronic infections, the spleen continues to
enlarge, becoming hard and blackened in color owing to the accumulation of malaria pigments.
- The long-term consequences of malaria infections are an enlarged spleen and liver and organ dysfunction.
- P. Falciparum infections are more severe and when untreated result in a death rate of 25% in adults.
- Complications of malaria: kidney insufficiency, kidney failure, fluid-filled lungs, neurological disturbances, and
- In pregnant women, it can result in stillbirths, underweight children, or abortion.
- Falciparum malaria accounts for 50% of all clinical malaria cases and is responsible for 95% of deaths.
- Relapse in this case is known as recrudescence for P. falciparum
- P. Vivax and P. Ovale malarias have the capacity to relapse also. Ex: parasites can reappear in blood after a period
when none were present. This type is known as recurrence and is due to the delayed liberation of merozoites from
preerthrocytic stages in the liver called hypnozoites. These two types are responsible for 45% of all clinical malaria
cases and are rarely fatal.