Malaria

malaria

1. Plasmodium

2. Epidemiology According to estimates from the World Health Organization, over 200 million cases and about 655.000 deaths have occurred in 2010 due to Malaria. According to the World Health Organization (WHO) Malaria Report 2011, a total of 106 countries in the world are at risk of transmission of malaria infection.

3. Pathogenesis Malaria caused by Plasmodium falciparum is more severe than that caused by other plasmodia. It is characterized by far more red cells than the other malarial species and by occlusions of capillaries with aggregates of parasitized red cells. P. falciparum causes a high level of parasitemia because it can infect red cells of all ages.

4. This leads to life threatening hemorrhages and necrosis particularly in the brain further more extensive hemolysis kidney damage occur which result in heamoglobinuria . The dark color of the patient’s urine given rise to the term black water fever. The hemoglobinuria can lead to acute renal failure.

5. The timing of fever cycle is 48 hours for P. falciparum as well as P. ovale .

6. The vector and definitive host for plasmodia is the female Anopheles mosquito (only the female takes a blood meal). There are two phases in the life cycle: the sexual cycle , which occurs primarily in mosquitoes, and the asexual cycle , which occurs in humans, the intermediate hosts.

7. The sexual cycle is called sporogony because sporozoites are produced, and the asexual cycle is called schizogony because schizonts are made.

8. Life Cycle The life cycle in humans begins with the introduction of sporozoites into the blood from the saliva of the biting mosquito. The sporozoites are taken up by hepatocytes within 30 minutes. This " exoerythrocytic " phase consists of cell multiplication and differentiation into merozoites. P . vivax and P. ovale produce a latent form ( hypnozoite ) in the liver; this form is the cause of relapses seen with vivax and ovale malaria.

9. Merozoites are released from the liver cells and infect red blood cells. During the erythrocytic phase, the organism differentiates into a ring-shaped trophozoite . The ring form grows into an ameboid form and then differentiates into a schizont filled with merozoites . After release, the merozoites infect other erythrocytes. This cycle in the red blood cell repeats at regular intervals typical for each species. The periodic release of merozoites causes the typical recurrent symptoms of chills, fever, and sweats seen in malaria patients

10. The sexual cycle begins in the human red blood cells when some merozoites develop into male and others into female gametocytes.

11. The gametocyte-containing red blood cells are ingested by the female Anopheles mosquito and, within her gut, produce a female macrogamete and eight spermlike male microgametes . After fertilization, the diploid zygote differentiates into a motile ookinete that burrows into the gut wall, where it grows into an oocyst within which many haploid sporozoites are produced. The sporozoites are released and migrate to the salivary glands, ready to complete the cycle when the mosquito takes her next blood meal.

12. Incubation period 10-15 days for P. falciparum and vary weeks to month.

13. Clinical Features Fever Anemia Splenomegaly

14. Complications Severe anaemia Cerebral Malaria Renal failure pulmonary edema Intestine— diarrhoea Liver—jaundice

15. Intravascular haemolysis Black water fever Metabolic acidosis Spleenic rupture In pregnancy Maternal death, abortion, still birth,low -birth weight.

16. Laboratory Diagnosis Collection of Blood:- Blood should be collected s soon as malaria is suspected(it may be necessary to collect blood on several occasions to detect the parasites) Before the patient receives antimalarial drug.

17. Microscopic examination of Blood Films Two types of blood films(Thick and thin) are taken. It is a good practice to take both, the thick and thin films, at the same time either or same side or on two different slides so that the parasite may be quickly detected in thick film and then thin film examined for identifying the species.

18. Following steps are taken: Thick and thin films are made and allowed to dry. Thick, films are stained with field’s stain and giemsa’s stain. Films are washed and dried. Then examined under oil immersion objective lens.

19. If more than 5% of red blood cells are parasitized, the diagnosis is usually P. falciparum malaria.

20. Red cells: Crescent shaped. Banana shaped, Gametocyte with attached Red cell ghost. Seen in peripheral blood smear 10 days after infection.

21. Complete blood count Haemoglogin Level:- Low Eosinophilia ESR Raised

22. Total Bilirubin :- Raised CSF Examination:- In Cerebral Malaria Protein-Raised Glucose-Decreased

23. Urine Analysis Oliguria , protein casts and RBC’s in urine suggest Black water fever.

24. Bone Marrow Examination:- Chronic cases Other Rapid Diagnostic Test ( RDT ).

25. Chest X-ray helpful if respiratory symptoms are present. CT scan to evaluate Cerebral edema or hemorrhage. PCR to determine the specie.

26. Treatment Chloroquine -sensitive plasmodium falciparum => Chloroquine P. ovale => Chloroquine plus primaquine