Plasmodium
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There are over 100 species of Plasmodium, some of which can infect humans and cause malaria. The four main species that infect humans are P. vivax, P. ovale, P. malariae, and P. falciparum. P. falciparum causes the most severe form of malaria and is responsible for over 1 million deaths per year globally. The life cycle of Plasmodium involves both sexual and asexual reproduction in humans and mosquitoes. Female Anopheles mosquitoes transmit the parasite between humans during blood-feeding. Laboratory diagnosis of malaria is usually done by examining thick and thin blood smears under a microscope to look for the parasite in red blood cells. Treatment depends on the species,
Plasmodium
- 2. Plasmodium • • > 100 species Both animals and humans 1. P. vivax Benign Tertian Malaria (humans) 2. P. ovale Benign Tertian Malaria (humans) 3. P. malariae Benign Quartan Malaria (humans/chimpanzees) 4. P. falciparum Malignant Tertian Malaria (humans)
- 3. Plasmodia
- 4. Geographical Distribution • P. vivax and P. falciparum more common P. ovale rarest of the 4 species • > 200 million people worldwide > 1 million deaths per year Most common lethal infectious disease
- 5. Geographical Distribution • Tropical & subtropical areas esp. Asia, Africa, Central and South America Certain regions in SE Asia, S. America, E. Africa Chloroquine Resistant strains of P. falciparum
- 7. HABITAT • Female Anopheles sexual cycle • Liver & RBCs of man asexual cycle RBC Age Variable: P. vivax youngest erythrocytes P. malariae oldest erythrocytes P. falciparum RBCs of every age
- 8. Anopheles, Culex and Aedes aegyptii
- 10. MORPHOLOGY • Peripheral blood stained with Leishman’s stain 1. Small Trophozoites (Ring forms): Infected RBC at first ring form a) b) c) Dot/rod shaped nucleus (red) Peripheral rim of cytoplasm (blue) Central clear vacuole like area (not stained) Different species have different rings
- 11. MORPHOLOGY 2. Large Trophozoite: • • Ring form Large trophozoite Fine grains of pigment Hematin 3. Schizont: Large trophozoite schizont N/C fragments merozoites 4. Gametocytes: • • • Male and female distinguishable Fully grown rounded occupies most of RBC P. falciparum sausage shaped crescent in RBC
- 14. LIFE CYCLE • HOST: Definitive Host Female anopheles (sexual cycle) Intermediate Host Man (asexual cycle) • VECTOR: Female Anopheles
- 15. LIFE CYCLE • Sexual cycle initiated in Humans Gametocytes (gametogony in RBCs) mosquitoes fusion of M/F gametes oocyst many sporozoites (sporogony) • Sexual cycle Sporogony (sporozoites) • Asexual cycle Schizogony (schizonts)
- 19. PATHOGENESIS • Usual Incubation periods: Vivax : 14 days Malariae: 28 days Falciparum: 11 days • Transmission: Mosquito bite I/V drug abuse Blood transfusion Transplacental (congenital) FEVER, ANEMIA, SPLENOMEGALY
- 20. PATHOGENESIS • Malarial Relapses: • P. vivax 2 years • Para-erythrocytic stage liver parenchyma dormant but viable • Resistance lowered released and activated complete erythrocytic cycle • Not in P. falciparum as no para-erythrocytic stage • Transmission other than mosquito bites no relapses
- 21. Natural Protection • Sickle cell trait (heterozygous) • Duffy blood group antigen –ve (homozygous recessive) (P.vivax) • G6PD deficiency • Premunition: • Partial immunity • Humoral antibodies block merozoites from invading RBCs • Low level of parasitemia low grade symptoms
- 22. PATHOGENESIS • Commonly Involved Organs: 1. 2. 3. 4. Changes in Blood Spleen Liver Bone Marrow
- 23. Signs and Symptoms • • • • • • • • • • • Abrupt fever, chills and rigors Headache Initially may be continuous then periodic Upto 41ºC or 106 ºF Nausea, vomiting, abdominal pain, anorexia, distaste of mouth Drenching sweats afterwards Well between febrile episodes Splenomegaly 1/3 hepatomegaly Anemia Falciparum fatal bcz of brain and kidney damage
- 25. Laboratory Diagnosis 1. Blood Exam: a. Microscopic Exam: • • • • • Take blood during pyrexia Not after even single dose of anti-malarials Thick and thin smears made, dried and stained Thick smear presence of organisms Thin smear identification of species
- 26. Laboratory Diagnosis • Thin Smear: • • • • • • Single drop of blood Spread to allow single cell layer Leishman’s stain Oil immersion lens Ring shaped trophozoites in RBCs P. falciparum gametocyte banana, sausage or crescent shaped • Other species gametocytes are spherical • > 5 % RBCs infected Dx of P. falciparum
- 27. Laboratory Diagnosis • Thick Smear: • • • • • 3-5 drops on slide allowed to dry Several cell layers thick Field’s stain or Giemsa stain Oil immersion lens Stain removes Hb from RBCs
- 28. Thin and Thick Smear
- 29. Laboratory Diagnosis 1. Blood Exam: b. TLC and DLC: • • TLC low leucopenia In fever may be high Monocytosis containing pigments
- 30. Laboratory Diagnosis 2. Biopsy: • BM and liver biopsies in difficult cases 3. Therapeutic Test: • Anti-malarials given if fever subsides Dx made 4. Serological Tests: • • • • Fluorescent antibody testing Complement fixation test Flocculation test Hemagglutination test
- 31. Treatment Falciparum easily treated before complications as no relapses and no paraerythrocytic stage Chloroquine is treatment of choice for sensitive strains of plasmodia (merozoites) Primaquine (Hypnozoites) Mefloquine or quinine and doxycycline (chloroquine resistant strains of falciparum) Atovaquone and proguanil (Malarone) (CR falciparum)
- 32. Prevention Chemoprophylaxis Mosquito netting Window screens Mosquito repellants Protective clothing Special care during night time DDT or kerosene oil spray over pools of water Drainage of stagnant water No vaccine presently available
- 33. Www.RCVetS.com