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| NEWER DIAGNOSTIC METHODS OF MALARIA |
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5th National CME of IAP Chapter on Pediatric Infectious Diseases, 23rd- 24th June 2007, Patna
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Dr. S.A.Krishna
HOD, Dept of Pediatrics, NMCH, Patna
Dr. A.K.Jaiswal
Asso. Professor , Dept of Pediatrics, NMCH, Patna
Dr. Anil Kumar
Senior Resident
Dept of Pediatrics, NMCH, Patna
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| DEFINITION |
Malaria is an acute and chronic illness characterized by paroxysm of fever, chills, sweating, fatigue, anemia and splenomegaly.
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| ETIOLOGY |
Malaria is caused by intracellular Plasmodium protozoa, transmitted to human by female Anopheles mosquitoes. Four species of Plasmodium cause malaria in human beings :
- P. Falciparum.
- P. Malariae.
- P. Ovale.
- P. Vivax.
Malaria also can be transmitted by blood transfusion, use of contaminated needles, by vertical transmission from a pregnant women to her fetus.
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| EPIDEMIOLOGY |
WORLD :
At present about hundred countries in the world are considered malarious, almost half of which is Sub-Sahara Africa.
INDIA :
During 2003 about 1.65 million cases were reported with 943 deaths. Malaria has been a serious problem in North-eastern states mainly Assam, Nagaland, Tripura and West Bengal. Contributes 8.5 to 11% of total malaria cases and 13 to 15 percentage of mortality.
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| LIFE CYCLE |
Sexual form :– In female Anopheles.
Asexual form :– In human beings.
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| LABORATORY DIAGNOSIS OF MALARIA |
Various method for diagnosis of malaria can be classified as under:
- CONVENTIONAL METHODS.
- NEWER TECHNIQUES.
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| CONVENTIONAL METHODS. |
- Peripheral blood film.
It is an oldest method. Two types of smear (thick and thin) are prepared from peripheral blood
- Thick film.
- Thick smears have more quantity of blood in small area.
- Chances of detection of malaria parasites are more in thick smear.
- Since morphology of the parasite is not clear, so species identification can not be done.
- Malarial pigment is easily detected in thick film.
- The thick film concentrates the parasites upto 40-times.
- So it increases the sensitivity of diagnosis.
- Thin film.
- Level of parasitaemia and malarial species can be detected.
- Count number of RBC containing asexual parasites per 1000 RBC.
- Mild -1 to 10%.
- Serious – 10 to 20%.
- Grave – 20 to 30%.
- Exceptionally Grave – more than 30%.
- In severe malaria, stages of parasite development can be detected.
- Neutrophils containing malarial pigment can be counted.
- It provides prognostic information.
- Parasite count.
- Parasite count denotes their concentration in blood at a particular point of time.
- A rough estimate of parasite concentration is as follows:
+ - 1 to 10 parasites/100 thick film field.
++ - 11 to 100 parasites/100 thick film field.
+++ - 1 to 10 parasites/thick film field.
++++ - more than 10/thick film field.
- Complete blood count.
- WBC – count
- Normal or low WBC count. Elevated in severe infection.
- RBC count
- Low RBC count with decreasing Hemoglobin % Normocytic, Normochromic anemia is the rule.
- Platelets counts
- Platelet count is almost always decreased – Thrombocytopenia.
- ESR
- Increased.
- Plasma viscosity
- Increased.
In severe infection – PT, PTT prolonged, thrombocytopenia is severe. CRP, CSF pressure, protein level is usually normal or elevated.
- Electrolyte level.
- mild cases.
- Normal
- In severe cases
- Lactic acidosis.
- Decreased plasma concentration
- Glucose, Na, HCO3, Calcium, Phosphate.
- Increased concentration
- Lactate, Blood urea nitrogen, Creatinine, Urate etc.
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| NEWER TECHNIQUES. |
- FLUORESCENT MICROSCOPY.
Fluorescent dye binds to parasite nucleic acids. Methods used are:
- Direct Acridine Orange staining.
- Acridine Orange stains cytoplasm orange and DNA green.
- Quantitative Buffy Coat (QBC) Technique
- In this method, due stains DNA green and RNA orange.
- BPC (Benzothiocarboxypurine) method.
- Immunological methods.
- Antibody detection
- Immunofluorescent Antibody absorption test (IFAT) – The main method for routine diagnosis.
- ELISA Test.
- Radioimmunoassay.
- Latex agglutination test.
- Solid phase dipstick and membrane dot blot.
- Antigen detection
- Based on the detection of circulating antigen specific for P. Falciparum in whole blood.
- PfHRP-II deep stick or ICT, Immunochromatographic card test
- This test utilizes affinity to purified sheep polyclonal antibody specific for P. Falciparum circulating antigen PfHRP-II.
- A drop of blood is placed on stick 01 card.
- Monoclonal antibodies captures the parasite antigen and read out as a colored band.
- Rapid, sensitivity is 0.001% parasitemia.
- Plasmodium LDH dipstick or card test
- A drop of blood is placed on stick or card.
- Monoclonal antibodies capture the parasite and read out a colored bands.
- Two bands-one band is genus specific and other is specific for P. Falciparum.
- Rapid, sensitivity similar to thick film upto 0.001% parasitemia.
- Molecular biological detection tests.
- Genetic probes.
- Two types of probes used are based on hybridization of probe DNA with genomic DNA or ribosomal RNA of parasites.
- In severe cases
- Lactic acidosis.
- Gene amplification technique or polymerase chain reaction (PCR).
- This technique is based on amplification of gene by PCR.
- More sensitive and specific than genetic probing.
- PCR is capable of detecting parasitemia of <0.00002%.
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Last created on 31-08-2007
Last updated on 31-08-2007 |
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