Human ParasitologyPlasmodium

JASARAT ILYAS JOKHIOPhD ScholarSindh, Pakistan

Medical Protozoology

Introduction to Medical Protozoa

General Concepts of Protozoa: Generally unicellularEukaryotic organismsFound in every conceivable damp habitatApproximately 60,000 living speciesLargest visible to the naked eyesSmallest could only be seen with an EMcompleting all necessary life activities independently

Protozoa are one-celled animals found worldwide in most habitats. Most species are free living, but all higher animals are infected with one or more species of protozoa. Infections range from asymptomatic to life threatening, depending on species and strain of the parasites and resistance of hosts.

Medical ProtozoaThe protozoa habit in lumens, body fluid, tissues or cells and, according to the pathogenicity, can be categorized into: Pathogenic; Non-pathogenic (commensals); Whose pathogenicity are debatable.

StructureAll protozoa cells possess a variety of eukaryotic structures/organelles common to all eukaryotic cells, including cell membrane, nuclei, endoplasmic reticulum, mitochondria, Golgi bodies, lysosomes, centrioles, and food vacuoles.

Basic structureCell membrane:Cytoplasm:

Motile organelle (taxonomic marker of protozoa): pseudopodium(-dia) - amoeba; flagellum (-lla) - flagellate; cilium (-cilia) ciliate;Nucleus: two kinds of nuclei:

vesicular; compact.

Locomotion - grouping protozoa morphologically according to the mechanism of locomotionMotile with pseudopodium Amoeba, Entamoeba histolytica, Naegleria fowleri;Motile with flagellum Euglena, Giardia lamblia, Trichomonas vaginalis;Motile with cilia - Balantidium coli, Paramecium.

The General StructureFood vacuoleOuter ectoplasmInner endoplasmCytostomeCytopharynxMicronucleusFood reserveCiliaContractile vacuoleCytoproctTrophozoiteMacronucleus

1.psd

2.psd

Each cell is a self-sufficient unit capable of carrying out all of the metabolic functions of which multicellular organisms are capable

Classified under three phyla

The four major groups of protozoa parasite in human (conveniently listed as subphyla)

Life Cycle StagesTrophozoite: Actively growing and reproducing stageCyst: A dormant stage, enclosed in a cyst coat resistant to an unfavourable environment-medical importance of infection

Trophozoites of Entamoeba histolyticaCyst of Entamoeba histolytica

NutritionAll parasitic protozoa require preformed organic substances as holozoic as higher animals.

ReproductionBinary fission, the most common form of reproduction among medical protozoa, is asexual; Multiple asexual division occurs in some forms;Sexual reproduction: takes place within the definitive host and usually results in the formation of a zygote;Both sexual and asexual reproduction occur in the Apicomplexa.

Characteristics of PathogenesisProliferationOnly invading protozoa proliferate to a certain amount can they result to impairment to host. Disseminating effect (Diffusion)As soon as invading protozoa set up a primary focus, they could diffuse towards and impair to nearby tissues and organs. Opportunistic pathogenicityNot normally pathogensBecome pathogenic due to impairment of hosts resistanceClinical importance of the AIDS epidemic, cancer patients, Patients undergoing radiotherapy or chemotherapy and organ transplant patients.

Ecological Niches in the Human BodySkin: Leishmania; Eye: Acanthamoeba; Mouth: Amoebae and flagellates (usually non-pathogenic); Gut: Giardia, Entamoeba (and invasion to liver), Cryptosporidium, Isospora, Balantidium; G.U. tract: Trichomonas; Bloodstream: Plasmodium, Trypanosoma; Spleen: Leishmania; Liver: Leishmania; Entamoeba; Muscle: Trypanosoma cruzi; CNS: Trypanosoma, Naegleria, Toxoplasma, Plasmodium.

Plasmodium Malaria parasite

SEATTLE, WA Congressman Jim McDermott (D-WA) issued the below statement following Time magazine's article yesterday that a major advance toward the first-ever malaria vaccine was among the top 10 Medical Breakthroughs of 2011. The trial malaria vaccine was developed through the efforts of two Seattle-based organizations PATH and the Bill & Melinda Gates Foundation as well as GlaxoSmithKline.

I want to congratulate the dedicated people at PATH Malaria Vaccine Initiative, Bill & Melinda Gates Foundation, GlaxoSmithKline, and researchers in Africa for bringing us close to a first-ever malaria vaccine. It is fitting that Time magazine featured this remarkable achievement second on a list of top ten medical breakthroughs of 2011. On behalf of the people of Seattle, I want to say that we are especially proud of the work of PATH and the Gates Foundation recognized leaders in the field of global health that we are fortunate to have right here in Seattle. Now comes the critical part of sustained engagement the U.S. government should seize this historic opportunity to end malaria by dedicating resources to complete the work towards a vaccine. Now is not the time to pull back on funding for USAID, a major funding agency for malaria vaccine research.

Plasmodia habiting in RBCTwo cells burst open and merozoites released from themRupturedEnlarged;Pale;Alleviated density.

Children under 5 are the major at risk group in malarious regions.

Malaria is a major public health problem in warm climates especially in developing countries.

It is a leading cause of disease and death among children under five years, pregnant women and non-immune travellers and immigrants due to an anopheles mosquito taking a blood meal.

What is malaria ?

Malaria is a disease caused by the protozoan parasites of the genus Plasmodium. The 4 species that commonly infect man are:

Species Major featuresP. falciparum The most important species as it is responsible for 50% of all malaria cases worldwide and nearly all morbidity and mortality from severe malaria Found in the tropics & sub-tropicsP. vivax The malaria parasite with the widest geographical distribution Seen in tropical and sub-tropical areas but rare in Africa Estimated to cause 43% of all malaria cases in the worldP. ovale This species is relatively rarely encountered Primarily seen in tropical Africa, especially, the west coast, but has been reported in South America and AsiaP. malariae Responsible for only 7% of malaria cases Occurs mainly in sub-tropical climates

The burden of malaria The direct burden of malaria morbidity and mortalityEvery year, there are about 500 million clinical attacks of malaria. Of these, 2-3 million are severe and about 1 million people die (about 3000 deaths every day).Malaria in pregnancy accounts for about 25% of cases of severe maternal anaemia and 10-20% of low birthweight. Low birthweight due to malaria accounts for about 5-10% of neonatal and infants deaths.

The indirect burden of malariaHuman development: Impaired intellectual development, developmental abnormalities (especially following cerebral malaria), lost school attendance and productivity at workEconomics: Malaria retards economic development in the developing world. The cost of a single bout of malaria is equivalent to over 10 working days in Africa. The cost of treatment is between $US0.08 and $US5.30, depending on the type of drugs prescribed as required by the local pattern of drug resistance.

Geographical Distribution of MalariaAlthough previously widespread, today malaria is confined mainly to Africa, Asia and Latin America. About 40% of the worlds population is at risk of malaria. It is endemic in 91 countries, with small pockets of transmission occurring in a further 8 countries.Malaria is transmitted by the female anopheles mosquito. Factors which affect mosquito ecology, such as temperature and rainfall, are key determinants of malaria transmission. Mosquitoes breed in hot, humid areas and below altitudes of 2000 meters. Development of the malaria parasite occurs optimally between 25-30oC and stops below 16oC. Indigenous malaria has been recorded as far as 64oN and 32oS.Malaria has actually increased in sub-Saharan Africa in recent years. The major factor has been the spread of drug-resistant parasites. Other important factors include the persistence of poverty, HIV/AIDS, mosquito resistance to insecticides, weak health services, conflict and population migration.

About 30 million cases/year before 1949Distribution of malaria in China in 1995Distribution of malaria in China in 195024,000 cases reported with 39 deaths in 2000 in China

HistoryAn old disease, and an major health problems in the tropics today. 2000 years ago:Symptom and therapy about malaria were described in ancient Chinese medicine books In 1880: Laveran: found plasmodia in blood of a patient with malaria - Nobel Prize of 1907. In 1897: Ross --- found only anopheles mosquitoes could transmit malaria -Nobel Prize of 1902 (the first-ever medical Nobel Prize).

World wide Year Number of patients Morbidity(1/100,000) Death 1950 25 million 1000 2.5 million 2002 50 million 920 1.5-2.7 million China Year Number of patients Morbidity(1/100,000) Death 1950 30million 750 0.30 million 1992 74,000 0.64 52 1999 29,000 0.24 67 2002 3.5298 0.34 42 After 1950

EtiologyThere are four important species that infect humans, causing malaria:

*P. vivax - benign tertian malaria accounts for ~ 43% of cases;* P. falciparum - malignant tertian malaria accounts for ~ 50% cases;*P. malariae - quartan malaria accounts for ~ 7% of cases*P. ovale - mild tertian malaria accounts for < 1% of cases.

Morphology

P. v P. f P. m P. o

Wrights stain --- red nuclei, blue cytoplasm and brown malarial pigments;Morphological features of P. vivax1. Early trophozoite (ring form) 1 red nucleus on the ring-like light blue cytoplasm; single infection in a cell.

The infected RBCs were basically as same as normal RBCs.

2. Late trophozoiteIt was irregular in shape and alike amoeboid form with pseudopodia; within cytoplasm, brown pigment granules (malarial pigment --- haemozoin) appeared.

infected RBCs were pale in color, and had schuffners dots on it (fine red granules).

3. Immature schizontOval in shape; nucleus divided into 2-4 or more; malarial pigment began to concentrate in a mass.4. Mature schizontNucleus divided into 12-24, and cytoplasm also divided; each nucleus was surrounded by a portion of cytoplasm to form a merozoite; malarial pigment clumped.

5. Male gametocyteOval in shape; one loose nucleus in the centre; malarial pigments diffusing.6. Female gametocyteOval in shape; one compact nucleus in the side of it.

Morphological features of P. falciparumEarly trophozoite (ring form)1or 2 red nuclei on the ring-like light blue cytoplasm; multiple infection in a cell.

Infected RBC being alike normal RBCOnly the early trophozoites and gametocytes of P. falciparum can be seen in the peripheral blood .

Male gametocyteBanana in shape; 1 loose nucleus in the centre; malarial pigment diffusing.Female gametocyteNew moon in shape; 1 compact nucleus in the centre.

Life cycle

1. Sporozoite / liver,2-5. Mitosis, liver cell lysis,6. Trophozoite / red blood cell,7-11: Mitosis,12. Gametocytes (via meiosis),13,14. Gametes via mitosis (midgut),15,16. Ookinetes, zygotes via conjugation, cross the midgut epithilium,17. Oocysts, mitosis, 18-20. Cross salivary epithelium.Reproduction Patterns

Infective sporozoite in female anopheles

(exoerythrocytic phase)Schizont containing merozoites in human liver cells (reproduce asexualy)(intraerythrocytic phase)

Mature schizont (merozoites) in human RBC(reproduce asexualy)

RBC rupture release merozoites parasite debris, pigments and metabolites

Periodic paroxysmparoxysm

gametocytes

Anopheles (reproduce sexualy)

Life cycle of plasmodium in human (In female anopheles) infective sporozoite blood circulation of human human liver cells : schizont containing merozoites (tachysporozoites for 1-2 weeks, bradysporozoites for 3 - 6 months relapse, exoerythrocytic phase) pour into blood circulation by liver cell rupture invade RBC: merozoite ring form trophozoite schizont containing merozoites (intraerythrocytic phase) gametocytes female anopheles RBC rupture , release merozoites parasite debris, pigments and metabolites Periodic paroxysm

clinical paroxysm (chill and fever)human body

Development of plasmodium in anophelesGametocytes in blood circulation of human bitted by female anopheles, sexual reproduction: (gametocytes zygote ookinete oocyst containing sporoblasts infective sporozoite ) humans blood circulation by bite

Stage I : Upon infection by the mosquito, the malaria parasites move rapidly into the liver (within ~ 30 minutes ), and reproduce rapidly (mitosis) for 5 days or more, depending on the species ( P. falciparum or P. vivax).

Stage II : The malaria parasites release from liver cells, enter the bloodstream and within minutes invade red blood cells where they grow and divide. Every 48-72 hours (time differences depend on the species) a batch of infected red blood cells rupture and disperse more parasites along with waste products/toxins into blood stream of human. This step causes fever, chills and anemia in the victim. The released parasites then invade other red blood cells, begin the cycle again. Three Main (Human) Stages

Stage III: After invading red blood cells some parasites develop into a sexual form-male or female gametocytes. As soon as anopheles mosquitoes bite human hosts, the gametocytes are sucked, and then mate each oher and reproduce inside the mosquitoes. Afterwards, zygotes (ookinetes) make their way to the salivary glands of the mosquitoes and ready to infect another victim when the mosquitoes take their next blood meal.

Characteristic of life cycleIntermediate host: humanFinal host: female anopheles mosquitoInfective stage: sporozoiteInfective way: mosquito bite skin of humanParasitic position: liver cells and red blood cellsTransmitted stage: gametocyte Schizogonic cycle in red cells: 48 hrs/P.vSporozoite: tachysporozite (1-2 weeks) and bradysporozite (3-6 months)

The time for one intraerythrocytic cycleP. v.: 48hP. f. : 36-48hP. m.: 72hNumber and shape of merozoites in mature schizontP. v.: 12-24, irregular P. f.: 8-36, irregular P. m.: 6-12, daisy-like

Gametocyte form Intraerythrocytic phage of merozoites macrogametocyte and microgametocyte P. v.: 2-3d P. f.: 7-10d Without transmission significance as the number of gametocytes < 12 per 1mm3 blood

Morphological changes of parasited RBCsP. v.: enlarged; Schuffners dotsP. f.: normal; Maurers dotsP. m.: normal; Simons dots

The types of RBC chosen by malaria spp. P. v.: Immature RBCs P. f.: All kinds of RBCsP. m.: Aging RBCs

Nutritional metabolism Glucose metabolismthe main energy resource during intraerythrocytic phase;Protein metabolism: under the synergy of acidic endopeptidase and aminopeptidase, hemoglobin in red cells were digested and decomposed into globin and hemosiderin. The globin were redecomposed into several amino acids under function of several enzymes for synthesis of proteins necessary for the parasite. The remaining hemosiderin deposited and eventually formed malaria pigments. Nucleic acid metabolismLipid metabolism:

EndemicityEndemicity refers to the amount or severity of malaria in an area or community. Malaria is said to be endemic when there is a constant incidence of cases over a period of many successive years.

Endemic malaria may be present in various degrees. Recognised categories of endemicity include :

A. Hypoendemicity - little transmission and the disease has little effect on the population.B. Mesoendemicity - varying intensity of transmission; typically found in the small, rural communities of the sub-tropics.C. Hyperendemicity - intense but seasonal transmission; immunity is insufficient to prevent the effects of malaria on all age groups.D. Holoendemicity - intense transmission occurs throughout the year. As people are continuously exposed to malaria parasites, they gradually develop immunity to the disease. In these areas, severe malaria is mainly a disease of children from the first few months of life to age 5 years. Pregnant women are also highly susceptible because the natural immune defence mechanisms are impaired during pregnancy.

How is malaria transmitted?Malaria parasites are transmitted from one person to another by the bite of a female anopheles mosquito. The female mosquito bites during dusk and dawn and needs a blood meal to feed her eggs. Male mosquitoes do not transmit malaria as they feed on plant juices but not blood.

There are about 380 species of anopheles mosquito but only about 60 are able to transmit malaria. Like all mosquitoes, anopheles breed in water - hence accumulation of water favours the spread of the disease.

PathogenesisIncubation period:

The time necessary for completing the exoerythrocytic development in addition to the time needed to arrive the fever threshold.Fever threshold:

The lowest blood protozoa density to result in fever.Paroxysm:

Typical paroxysm: A periodic chills and fevers resulted from fission proliferation of intraerythrocytic phase of the protozoa;

1-2h of chills4-6h of fever 2-4h of sweating and bringing down a fever 40h of interval4 8hTypical paroxysm of P. v.

Relations between malaria fever types and the development during intraerythrocytic phase

Mechanism of typical paroxysm Merozoites Erythrocytic debrisMetabolic productions

Swallowed by WBC / MEndogenous heat-inducers Hypothalamic thermoregulatory center Chills and feversExogenous heat-inducers

Atypical paroxysm:Usually resulting misdiagnosis.Reasons: initial paroxysm of malaria; mixed infection; children and non-immunity population; improper treatment.Relapse (relevant to liver stage):It is a recurrence of symptoms which takes place after complete clear of initial erythrocytic infection without reinfection and implies reinvasion of the blood stream by merozoites transformed from activated bradysporozoites in liver.Recrudescence (relevant to erythrocytic stage):It is a recurrence of symptoms in a patient whose parasite density in blood stream is at such a low level that not to be clinically demonstrable or there is not apparent symptoms, which is induced by non-standard pathogenic therapy or drug resistant plasmodium (merozoites ).

Types of sporozoites and relapse Relapse --- Appear clinic signs of malaria about three to six months or longer after primary attack.P. vivax and P. ovale: Two types of sporozoites: Tachysporozoites --- induce primary attack Bradysporozoites --- result in relapseP. malariae and P. falciparum:Only tachysporozoite stage, without bradysporozoite stage, no relapse in malaria caused by P. malariae and P. falciparum.

AnemiaDirectly destroy red cells by plasmodium;Hypersplenism:Mechanism of self-protection demands spleen to produce more phagocytes to clear invaded red cells, debris and metabolism productions of plasmodium, which will result to hypersplenism;Phagocytes not only clear invaded red cells through recognition of receptors on the infected red cells but also swallow large number of normal red cells driven by incorrect identification mechanism;Big amount of red cells are sequestrated in enlarged spleen

Depression of born marrow function;Immunopathogenesis: exploration of hidden antigens on red cell debris will stimulate immune system to produce autoantibodies and further Ag-Ab complexes to resolve debris. Similarly, the autoantibodies will also identify the epitopes on normal red cells to lead to resolve normal red cells

SplenomegalyMechanism: Proliferation of mononuclear phagocytes results to hyperemia of spleen; Repeated infection leads to proliferation of fibrous tissue

Complications Hemolytic urinemic syndrome (Black water fever) Often occurs in patients with G-6-PD (Glucose -6 - phosphate dehydrogenase) deficiency and may be induced by primaquine treatment, heavy infection (high parasitemia) of P. falciparum or an atypical immune response during reinfection. Massive RBC rupture and hemolysis shows hyperhemoglobinemia, lumbago (backache), malarial hemoglobinuria, anemia, jaundice, acute renal failure.

Nephropathic syndrome Usually occurs in cases of p. malariae infection. Patients with hypertension, edema, massive protein in urine, etc.

Severity of disease and host factorsIn addition to parasite factors, several host factors determine the outcome of exposure to malaria:Naturally-acquired immunity: People who are constantly exposed to malaria gradually acquire immunity, firstly against clinical disease and later against parasite infection. Clinical manifestations of malaria are most severe in the non-immune. In holoendemic areas, these are children aged

Red cell and haemoglobin variants:

Well known examples of inherited factors that protect against malaria are Haemoglobin S carrier state, the thalassaemias and Glucose-6-phosphate dehydrogenase (G6PD) deficiency. Malaria provides the best known example whereby an environmental factor (malaria) has selected human genes because of their survival advantage.Foetal haemoglobin (HbF):

High levels of HbF occur in neonates, and in some people with inherited haemoglobin variants, protect against severe forms of P. falciparum malaria.Duffy blood group:

P. vivax requires the Duffy blood receptor to enter red blood cells. Therefore, people who do not carry the Duffy blood group are resistant to this malaria species. This explains the rarity of P. vivax in Africa, as most Africans are Duffy blood group negative.

Following a bite by an infected mosquito, many people do not develop any signs of infection. If infection does progress, the outcome is one of three depending on the host and parasite factors:Asymptomatic parasitaemia (clinical immunity) Acute, uncomplicated malaria Severe malaria

The clinical course of P. falciparum

This is usually seen in older children and adults who have acquired natural immunity to clinical disease as a consequence of living in areas with high malaria endemicity. There are malaria parasites in the peripheral blood but no symptoms. These individuals may be important reservoirs for disease transmission.Some individuals may even develop anti-parasite immunity so that they do not develop parasitaemia following infection.

A. Asymptomatic parasitaemia

B. Simple, uncomplicated malariaThis can occur at any age but it is more likely to be seen in individuals with some degree of immunity to malaria. The affected person, though ill, does not manifest life-threatening disease.

Fever is the most constant symptom of malaria. It may occur in paroxysms when lysis of red cells releases merozoites resulting in fever, chills and rigors (uncontrollable shivering).

Other features of simple, uncomplicated malaria include:VomitingDiarrhoea more commonly seen in young children and, when vomiting also occurs, may be misdiagnosed as viral gastroenteritis;Convulsions commonly seen in young children. Malaria is the leading cause of convulsions with fever in African children. Pallor resulting mainly from the lysis of red blood cells. Malaria also reduces the synthesis of red blood cells in the bone marrow. Jaundice mainly due to haemolysis.

Malaria is a multisystem disease. Other common clinical features are: Anorexia Cough Headache Malaise Muscle aches Splenomegaly Tender hepatomegaly These clinical features occur in mild malaria. However, the infection requires urgent diagnosis and management to prevent progression to severe disease.

C. Severe and complicated malariaNearly all severe disease and the estimated >1 million deaths from malaria are due to P. falciparum. Although severe malaria is both preventable and treatable, it is frequently a fatal disease.The following are 8 important severe manifestations of malaria:Cerebral malariaSevere malaria anaemiaHypoglycaemiaMetabolic acidosis

Acute renal failure Pulmonary oedemaCirculatory collapse, shock or algid malariaBlack water fever

Note: It is common for an individual patient to have more than one severe manifestation of malaria!

Summary of differences in the clinical features of severe malaria in adults and children Frequency of occurrence

Clinical ManifestationChildren AdultsSimilar in adults and children Prostration Circulatory collapse ++++++++More common in children Cerebral malaria Severe anaemia Multiple convulsions Metabolic acidosis Hypoglycaemia+++ +++ ++++++++++ ++++ / -More common in adults Jaundice Pulmonary oedema Haemoglobin uria Abnormal bleeding Renal failure+ + / - + / - + / -+ / -++++++++

Diagnosis Epidemiological data Clinical manifestations Laboratory findings

Epidemiological data History of living in or traveling to epidemic areas. History of blood transfusion. Neonates born by malaria mothers. Clinical manifestations Periodic paroxysms with shaking chills, high fever, sweating. Anemia and splenomegaly may present. Fever patterns may be irregular in some cases.

Laboratory findings WBC, RBC, Hb: Normal white blood cell count, decreased red blood cell count and hemoglobin level. Thick and thin blood smear (Giemsa stain) Plasmodium species are found in thick and thin blood smear, or bone marrow smear. --------Definitive diagnosis Thick and thin blood smear are very simple and important

Malaria Thick Smear

Plasmodium falciparum:Blood Stage Parasites - Thin Blood Smears1:Normal red cell2-18: Trophozoites ( 2-10: ring-stage trophozoites)19-26: Schizonts ( 26 is ruptured schizont)27, 28: Mature macrogametocytes (female) 29, 30: Mature microgametocytes (male)

Plasmodium vivax:Blood Stage Parasites - Thin Blood Smears1: Normal red cell2-6: Young trophozoites (ring stage parasites)7-18: Trophozoites19-27: Schizonts28, 29: Macrogametocytes (female)30: Microgametocyte (male)

Plasmodium ovale:Blood Stage Parasites - Thin Blood Smears 1: Normal red cell2-5: Young trophozoites 6-15: Trophozoites16-23: Schizonts24:Macrogametocytes (female)25:Microgametocyte (male)

Plasmodium malariae:Blood Stage Parasites - Thin Blood Smears1: Normal red cell2-5: Young trophozoites (rings)6-13: Trophozoites14-22: Schizonts23: Developing gametocyte24: Macrogametocyte (female)25: Microgametocyte (male)

Malaria is a multisystem disease. It presents with a wide variety of non specific clinical features: there are no pathognomonic symptoms or signs. Many patients have fever, general aches and pains and malaise and are initially misdiagnosed as having flu. P. falciparum malaria can be rapidly progressive and fatal. Prompt diagnosis saves lives and relies on astute clinical assessment: A good history Residence or a recent visit (in the preceding 3 months) to a malaria endemic area History of fever (may be paroxysmal in nature) Recognise significance of non-specific clinical features such as vomiting, diarrhoea, headache, malaiseDiagnosis

Physical examination Identify signs consistent with malaria: fever, pallor, jaundice, splenomegaly Exclude other possible causes of fever (e.g. signs of viral and bacterial infections) The diagnosis of malaria should be considered in any unwell person who has been in a malarious area recently

Investigations Blood Film Examination Thick and thin blood films (or smears) have remained the gold standard for the diagnosis of malaria. The films are stained and examined by microscopy.

Thick blood film - Used for detecting malaria: a larger volume of blood is examined allowing detection of even low levels of parasitaemia. Also used for determining parasite density and monitoring the response to treatment.

Thin blood film Gives more information about the parasite morphology and, therefore, is used to identify the particular infecting species of Plasmodium.

Serologic tests : not so important Test antibody against plasmodium Test DNA of plasmodium by PCR: high sensitivity Therapeutic trial is not advocated because of the side effects of chloroquine and primaquine.

Differential diagnosis septicemia leptospirosis typhoid fever bile duct infection Japanese encephalitis toxic form of shigellosis

Septicemia

Severe toxemia symptoms, with primary inflammation focus Positive blood bacterial culture. Without periodic paroxysm and intermittent period.

Leptospirosis The history of contacting contaminated water or wet soil; enlargement of lymph nodes, persistent high fever, myalgia of the calf muscle; Positive agglutination-lyse test for antibodies against leptospira species.

Typhoid fever: Insidious onset, sustained fever, relative bradycardia, rose spots, positive Widals reaction and positive blood culture for salmonella typhi. Biliary ducts inflammation: Sudden onset, with high fever, colic pain in right upper part of abdomen, jaundice. Utrasonography will be very helpful for making the diagnosis.

Japanese encephalitis and toxic form of shigellosis: Should be considered in differential diagnosis of cerebral malaria.

Prognosis Good in ordinary cases. Poor in cerebral malaria and Black Water Fever.

Treatment1. Symptomatic and supportive treatment2. Etiologic treatment:A. Control paroxysm treatment B. Prevent relapsC. Prevent transmission

Symptomatic and supportive treatment High fever, convulsion, cerebral edema, black water fever, etc. Keep warm for shaking chill; Physical and chemical defervescent methods for high fever, such as ice bag, air condition. Corticosteroid may be given , if necessary. Diazepam and wintermin for convulsion.

20% Mannitol injection fluid intravenous quickly for cerebral edema; Dextran also is useful for cerebral malaria. For black water fever, withdraw all anti malaria drug, and giving dexamethason, small amount of blood transfusion. Giving sodium bicarbonate, and must keep more than 2000ml urine output per day.

Etiologic treatment Treatment principle: 1. Combination anti-paroxysm treatment with preventing from relapse and transmission treatment 2. Ordinary examining G-6-PD before giving primaquine. Primaquine only is given in these patients without G-6-PD deficiency

Anti-paroxysm kill reproducting plasmodia in RBC Prevent relapse kill bradysporozoite; primaquine, for 8 days;Prevent transmission: kill gametocyte primaquine, for 3days

For P. vivax and P. ovale malaria

Anti- paroxysm drugs and primaquine ( for 8 days) must be given to control paroxysm, prevent from relapse and transmission.

For P. falciparum and P. malariae - caused malaria Anti-paroxysm drugs and primaguine (for 2-4 days) must be given to control paroxysm and to kill gametocyte for prevent from transmmision although prevent from relapse is not necessary.

Control drugs and treatment of paroxysm Drugs chloroquine - first choice for sensitive plasmodia artesunate - first choice for cerebral malaria artemisinine, pyromaridine phosphate, mefloquine, quinine sulfate, benflumethtolum, arteflene, naphthoquine phosphate.

Choice of drugsTreatment of vivax, malariae, ovale and chloroquine - sensitive falciparum malaria: chloroquineRadical cure of vivax or ovale malaria: chloroquine + primaquineTreatment of chloriquine - resistant falciparum malaria: artemisinin or mefloquine or quinine

Prophylaxis1. Treatment of patients and carriers2. Control mosquito vectors3. Individual protection

ImmunityCongenital immunity

Duffy-negative erythrocytes are resistant to P.v in West Africans.

ImmunityPremunition: (similar to concomitant immunity described in S.j)An acquired nonsterilizing immunity;Certain resistance against reinfection;Dynamic effects of immunity being positively related to protozoan burden in host;Being able to kill most protozoa.

Immune evasion :

An ability of malaria parasite to evade host immunity.Possible mechanism of evasion

1) Antigenic variation and antigen polymorphism;2) Histological sequestration (avoiding exposure to immune attack from host);3) Poor immunogenicity of its antigens (analogy exists between parasitic antigens and host molecules);4) Alteration of immune response of host.Immunity

Until now, a practical vaccine against malaria spp. isnt available. Undoubtedly, the news reported in Times will not only bring benefits to the people suffering from the disease, but also direct a right way for other researches. It should be believed that a effective vaccine is around the corner. vaccine

SummaryMalaria is a parasitic diseases caused by plasmodium species, and transmitted by the bite of infected female anopheles mosquitoes;Four top medical important species of plasmodium :

P. vivax, P. ovale, P. malariae and P. falciparum;Primarily cccur in tropic and subtropic area;All person are susceptible, and no last immunity;Life cycle of plasmodium:

two hosts, two types of reproductions

Summary The clinical features periodic paroxysm: shaking chills, high fever, heavy sweating. Anemia, splenomegaly and cerebral malaria in some of cases. Relapse and Recrudescence Definite diagnosis: Plasmodium species is found in thick and thin blood smear, or bone marrow smear.

Summary Etiologic treatment principle: 1.Combination anti-paroxysm with prevent replase and transmission treatment 2. Examining G-6-PD before giving primaquine. Control paroxysm treatment 1.chloroquine-sensitive plasmodia first choice: chloroquine 2.chloroquine -resistant plasmodia 3. Control paroxysm for cerebral malaria artesunate, first choice chloroquine (sensitive plasmodia) slowly intravenous drip ,then orally

Summary Prevent relapse: kill bradysporozoite: primaquine, for 8 days Prevent transmission: kill gametocyte: primaquine, for 3days primaguine only is given in the patients without G-6-PD deficiency. Prophylaxis: No vaccine is available 1.Treatment of patients and carriers 2.Control mosquito vectors 3. Individual protection: Avoid mosquito bite chemoprophylaxis