Malaria

Life cycle of malaria

1. MALARIA DR. SUMESH KUMAR DASH PG RESIDENT, DEPARTMENT OF MICROBIOLOGY, IMS & SUM HOSPITAL.

2. INTRODUCTION Malaria is one of the oldest documented diseases of mankind. The name “Malaria” (“Mal” means bad and “aria” means air) was derived from the ancient false belief that “disease is spread by air pollution through stagnant water and marshy lands” French army surgeon Alphonse Laveran (1880) was the first to discover the causative agent Plasmodium , in the red blood cell (RBC) of a patient in Algeria. Golgi had described the asexual cycle of the parasite in RBC. Sir Ronald Ross, in 1897 had described the sexual cycle of the parasite in female Anopheles mosquito in Secunderabad, India.

3. causative Agent P. vivax causes benign tertian malaria. (periodicity of fever is once in 48 hours, i.e. recurs every third day) P. falciparum causes malignant tertian malaria. (severe malaria, periodicity of fever is once in 48 hours, recurs every third day) P. malariae causes benign quartan malaria. (periodicity of fever is once in 72 hours, i.e. recurs every fourth day) P. ovale causes ovale tertian malaria. (periodicity of fever is once in 48 hours, i.e. recurs every third day) P. knowlesi causes quotidian malaria. (fever periodicity is once in 24 hours, i.e. recurs every day).

4. Life Cycle Host: Plasmodium completes its life cycle in two hosts: Female Anopheles mosquito is the definitive host where the sexual cycle (sporogony) takes place. Man acts as intermediate host where the asexual cycle (schizogony) takes place. Male Anopheles doesn’t feed on man and feeds exclusively on fruit juices, i.e. why male Anopheles doesn’t transmit the disease. Whereas female Anopheles needs at least two blood meals before laying eggs.

5. Infective form: Sporozoites are the infective form of the parasite. They are present in the salivary gland of female Anopheles mosquito. When Plasmodium species is transmitted by blood transfusion or through placenta , Merozoites act as infective form. Mode of transmission: Man gets infection by the bite of female Anopheles mosquito. Sporozoites from the salivary gland of the mosquito are directly introduced into the blood circulation. Rarely, it can also be transmitted by: Blood transfusion Transplacental transmission.

6. HUMAN CYCLE In humans, the asexual cycle takes place through the following stages: Pre-erythrocytic schizogony Erythrocytic schizogony Gametogony .

7. Pre-erythrocytic Schizogony This stage occurs in liver and it is so named because it occurs before the invasion of RBC. The motile sporozoites leave the circulation within 30 minutes and enter liver. After entering into hepatocytes, the spindle shaped sporozoites become rounded and lose their apical complex and transform into trophozoites. Trophozoite is the feeding stage of the parasite which later on undergoes several nuclear divisions (schizogony) and transforms into pre-erythrocytic schizont. Pre-erythrocytic schizont contains several merozoites; which are released outside on rupture and attack RBCs to perform erythrocytic schizogony. Some sporozoites of P. vivax and P. ovale don’t develop further and may remain in liver as hypnozoites and cause relapse of malaria after many years.

8. Erythrocytic Schizogony The hepatic merozoites after released from pre-­erythrocytic schizont, attack RBCs. The process of entry into RBC takes about 30 seconds . Trophozoite: Soon the pear shaped hepatic merozoites round up, lose their internal organelle and transform into trophozoites. Ring form: Early trophozoite form is known as ring form. It is annular or signet ring appearance containing a central vacuole and peripheral thin rim of cytoplasm and a nucleus. Late trophozoite: Ring form enlarges and becomes more irregular due to amoeboid movement and transforms into late trophozoite or amoeboid form. Schizogony: Late trophozoite undergoes multiple nuclear divisions (erythrocytic schizogony or merogony) and produces 6–30 daughter merozoites arranged in the form of rosette.

9. RBCs then rupture to release the daughter merozoites, malarial pigments and toxins into the circulation which result in malarial paroxysm of fever at the end of each erythrocytic cycle. Each merozoite is potentially capable of invading a new RBC and repeating the cycle. The time interval between entry of the parasite to the body and appearance of the first clinical feature is known as incubation period. It varies between the species: P. vivax - 14 days (ranges 8–17 days) P. falciparum - 12 days (ranges 9–14 days) P. malariae - 28 days (ranges 18–40 days) P. ovale - 17 days (ranges 16–18 days)

10. Gametogony After a series of erythrocytic cycles, some merozoites after entering into RBCs, instead of developing into trophozoites, they transform into sexual forms called as gametocytes. The gametocytic development takes place in the blood vessels of internal organs such as spleen and bone marrow and only the mature gametocytes appear in the peripheral blood. The gametocytes of all the species are round in shape except in P. falciparum in which they are crescent or banana shaped . They are of two types—(1) Male gametocyte (or microgametocyte) and (2) Female gametocyte (or macrogametocyte) Neither gametocytes don’t cause any clinical illness nor they divide. Individuals harboring gametocytes are considered as carriers or reservoirs of infection and play an important role in the transmission of the disease.

11. Mosquito Cycle A female Anopheles mosquito during the blood meal, takes both the asexual forms and the sexual forms. The asexual forms get digested whereas the sexual forms, i.e. the gametocytes undergo further development. Hence considered as infective form of the parasite to mosquito

12. CLINICAL MANIFESTATION Fever Chills Sweats Headaches Nausea and vomiting Body aches General malaise.

13. How Malaria Present Clinically FEBRILE PAROXYS Cold stage: Lasts for 15 minutes to 1 hour. The patient feels lassitude, headache, nausea, intense cold, chill and rigor. Hot stage: Patient develops high grade fever of 39–41°C and dry burning skin. Headache persists but nausea diminishes. Sweating stage: Fever comes down with profuse sweating. Skin becomes cold and moist. Patient feels relieved and often asleep. This stage lasts for 2–4 hours. ANEMIA: After a few paroxysms of fever, patient deve lops a normocytic normochromic anemia SPLENOMEGALY: After a few weeks of febrile paroxysms, spleen gets enlarged and becomes palpable. Splenomegaly is due to massive proliferation of macrophages that engulf parasitized and nonparasitized coated RBCs.

14. Laboratory Diagnosis Microscopic tests Peripheral blood smear - Gold standard Fluorescence microscopy (Kawamoto’s technique) Quantitative buffy coat examination (QBC) Non-microscopic tests Antigen detection tests (RDTs) or ICTs Antibody detection – ELISA Culture - RPMI 640 medium Molecular diagnosis - PCR

15. Peripheral Blood Smear Collection of blood Best prepared directly from capillary blood In EDTA bulb (used within 30 mins) Time of collection As soon as possible if malaria is suspected Before administering antimalarials During pyrexial phase Type of blood film Thick film Thin film

16. THICK FILM 30 to 40 times more sensitive than thin films More suitable for detection of malarial parasite when they are few in number Blood is not fixed, RBCs are lysed during staining (only parasitic forms will be seen) THIN FILM To confirm the plasmodium species Assists in the identification of mixed infections Blood is fixed, parasites are seen within the RBC s Also helps in assessing the response to treatment especially in areas where drug resistance is suspected (by counting the number of parasitised RBCs before & after the treatment)

17. Making Of Film

18. Fixation & Staining Fixation – thin films are fixed with absolute alcohol for 1 to 2 mins. Staining – films are stained with Romanowsky stain: Giemsa, Field’s, Wright’s Giemsa - 10% solution for 10 mins

19. Reporting Of Blood Film Look for the different morphological forms of parasite in blood smear: Trophozoites / ring forms Schizont Gametocytes Identify species – differences in the characteristics of morphological forms in different species

20. Quantitative Buffy Coat Capillary tube is coated with an anticoagulant & Acridine orange fluorescent dye. After centrifugation, the tube can be used for two purpose: Complete blood count Identification of malarial parasite using a fluorescence microscope

21. Rapid diagnostic tests detect malaria antigens

22. treatment Chloroquine can be used for P.vivax . P.Falciparum is resistant to chloroquine, mefloquine used. Artemisinin is being used increasingly and has been found to be useful the parasite is resistant, and hence is the drug of choice.

23. complications Cerebral malaria: Occurs due to plugging of brain capillaries by the rosettes of sequestered parasitized RBCs leading to vascular occlusion and cerebral anoxia. Pernicious malaria : It is characterized by blackwater fever, algid malaria and septicemic malaria Black water fever: This syndrome is characterized by sudden intravascular hemolysis followed by fever, hemoglobinuria and dark urine. Algid malaria: Characterized by cold clammy skin, hypotension, peripheral circulatory failure and profound shock. Pulmonary edema Hypoglycaemia Renal failure Bleeding/disseminated intravascular coagulation Severe jaundice

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