MALARIA

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Introduction:   

                1) Malaria is a common and often life-threatening disease and a major risk in the tropical and subtropical countries 

                2) The 2 most common types of species of malaria are P.vivax and P.falciparum.

Life cycle:

        1) Mosquitoes insert sporozoites in the skin when they bite humans through the skin.

           2) Within 30 minutes the sporozoites enter the bloodstream and the lymphatic system of hepatocytes and where they differentiate to form hepatic sporozoites which burst and release merozoites into the bloodstream and invade erythrocytes.

           3) merozoites develop from ring form to trophozoites and then to schizonts over 48 hours.

           4) After breaking down the host RBC membrane 24 to 32 erythrocytes enter the bloodstream each of which is capable of infecting a new erythrocyte.

           5) Fever occurs when RBCs rupture, leading to anemia and sequestration of infected erythrocytes in microvascular bed(cerebral malaria).

           6) In vivax malaria some of the merozoites re-enter the liver and remain dormant for weeks to months.

           7) This cycle can go on indefinitely and is responsible for causing relapsing malaria.

Clinical features:

             1) Patients present with symptoms of fever and prodromal symptoms of tiredness, abdominal pain, joint aches and loss of appetite, vomiting, and malaise

                 2) The typical vivax fever has 3 phases, the cold phase coinciding with severe chills, with chattering of teeth. Then the hot phase where a patient has a fever and finally the relief phase when the fever goes down and the patient suffers from sleepiness, fatigue and the patient is sweating.

                 3) These episodes may occur every 24-48 hours for vivax.

                 4) There is no specific fever pattern for falciparum.

                 5) Not all of the symptoms may be present in a single patient but the illness and symptoms may become better during relapses.

                 6) Patients may appear normal during the hot phase of malaria.

Diagnostic tests:

                          The diagnosis of malaria can be confirmed by a blood test and can be divided into microscopic and non-microscopic tests.

Microscopic:

                   1) Light microscopy of thin and thick blood smears is the golden method for diagnosing malaria.

                         2) The smears allow one to identify malaria species, quantify plasmodium, ad assess for the presence of schizonts, gametocytes, and malarial pigment in the neutrophils and monocytes. 

                         3) Thick smears are 20-40 times more sensitive than thin smears.

                         4) The diagnostic accuracy depends upon the quality of the blood smear and the experience of the laboratory personnel.

                         5) Appearance of the gametocytes on a smear is an indication that the trophozoites have cleared and there is an improvement, and by itself is not an indication of further treatment.

                         6) In Falciparum malaria, the RBCs are sequestrated in the tissue capillary beds resulting in a falsely low parasite count.

                         7) Smears should be repeated after every 6-12 hours if malaria is suspected.

Non-microscopic:

                          1) Rapid diagnostic tests (RDT also known as ICT) are now a point of care testing(POCT). Positive ICT can detect vivax, falciparum, or mixed infection.

                                   2) The sensibility and specificity of these tests vary with the kit used.

                                   3) The ICT tests from some kits may remain positive for around 2-3 weeks after treatment and should be repeated for follow-up.

                          4) If a patient is ICT negative and you suspect malaria, then you need to use thick and thin blood smears are required to rule out malaria 

                                   5) If malaria is strongly suspected then 3 M.P. smears should be repeated after every 8 hours. 


Other relevant tests for assessing severity are 

                   1) CBC: Anemia, thrombocytopenia, leucopenia.

                   2) Serum urea, creatinine, and electrolytes: Damaged in renal insufficiency.

                   3) Liver function tests: Hyperbilirubinemia(hemolysis), transaminitis

                   4) Chest X-ray to rule out ARDS.

                   5) Arterial blood gases: Metabolic acidosis.

                   6) Blood sugar: Hypoglycemia.

               
                                       

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