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In this article we will discuss about Plasmodia or Malarial Parasites:- 1. Morphology of Plasmodia 2. Life Cycle of Plasmodia 3. Laboratory Diagnosis 4. Serology 5. Treatment.
Contents:
- Morphology of Plasmodia
- Life Cycle of Plasmodia
- Laboratory Diagnosis of Plasmodia
- Serology of Plasmodia
- Treatment of Plasmodia
1. Morphology of Plasmodia:
2. Life Cycle of Plasmodia:
Human Cycle:
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Man, intermediate host, gets infected by the bite of infected female Anopheles mosquito. Sporozoites, infective forms, enter directly into liver cells (not in RBCs) for their development. This is (1) pre-erythrocytic schizogony. The merozoites are liberated. The micro-merozoites enter into RBCs whereas the macromerozoites reenter the liver cells. At this stage, there is no clinical manifestation.
2. In Erythrocytic Schizogony:
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In RBCs, the parasites pass through three stages trophozoites, schizonts, and merozoites. At this stage, there is clinical attack of malaria (overt malaria),
(3) Gametogony:
After the erythrocytic schizogony, the merozoites develop into gametocytes (sexual forms) which sexually reproduce in the mosquito and the individuals who harbour their gametocytes are called “carriers.”
(4) Exo-Erythrocytic Schizogony:
After the micro-merozoites infect RBCs the pre-erythrocytic schizogony disappears completely in P. falciparum—hence no relapse, but there is recrudescence due to improper treatment, whereas in P. vivax, P. ovale and P. malaria, there is relapse (liver cycle).
Mosquito Cycle:
Mosquito bites and ingests both asexual forms (that die) and sexual forms that transform into micro (male) and macro-gametocytes (female), zygote, ookinete (motile zygote), oocysts and, finally, infective sporozoites.
Clinical Features:
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The onset is usually sudden in vivax, shivering, fever, headache, malaise, muscular pain.
3. Laboratory Diagnosis of Plasmodia:
(a) Demonstration of Plasmodia in Leishman stained or Acridine Orange (AO) stained blood smear is the method of choice. Magnetic Resonance Imaging (MRI) is most recently used to diagnose cerebral malaria due to P. falciparum. Fluorescence microscopy using Acridine Orange stain can detect P. falciparum ring in smear.
4. Serology of Plasmodia:
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CFT, slide flocculation, latex agglutination, IHA, FA test are still under experimentation. Genetic engineering method and Polymerase Chain Reaction (PCR) are recent methods. In recent years, ELISA, ABC-ELISA (new test) immunoblot, DNA probes are useful epidemiological tools. A rapid manual test for P. falciparum. Para sight F test is simple, specific, sensitive and rapid (10 minutes) test in a single drop of blood.
5. Treatment of Plasmodia:
Chloroquine, quinine, primaquine are commonly used but halofantrine, pyronardine, mefloquine-sulphadoxine, pyrimethamine (Fangimel) are recent drug of choice for treatment of resistant malaria. Recently, Albendazole was found to kill cultures of P. falciparum.
