Easily remember the life cycle malaria parasite: P.falciparum vs. P vivax

I am writing this blog post to help you remember the most important stage of malarial parasite which differs between two most important species: P. facliparum and P.vivax. I hope after going through this post, you will discover some fascinating things and their arrangements in a word with the help of which you can recall or write the life cycle of both P. faciparum and P.vivax individually or even write the most important differences between their life cycle.
Note:To get the best of this blog post: you must have some idea about general life cycle of malarial parasite and its stages.
Lets begin with this magic word “FALCIPARUM”. For now only focus on this word and the alphabets there

• F: Fatal (Plasmodium falciparum cause most severe (dangerous) or life threatening types of malaria)
  

Prevention and Control of Visceral Leishmaniasis

The current strategies for Visceral Leishmaniasis rely on reservoir and vector control, the use of insecticide impregnated materials and active case detection and treatment, anti-leishmanial vaccines are still being developed. 

Reservoir Control
Since man is the only reservoir of kala azar in Nepal, active and passive case detection and treatment of those found to be infected (including PKDL) may be sufficient to abolish the human reservoir and control the disease.

Vector Control
The application of residual insecticides has proved effective in the control of sandflies. DDT is the first choice since the vector of kala azar P. argentipes is susceptible to DDT. Insecticide spraying should be undertaken in human dwellings, animal shelters and all other resting places up to a height of 6 feet from floor level. Spraying should be preceded and followed by an assessment of susceptibility. Any sign of resistance in vector should lead to an immediate change in insecticide. BHC should be kept as a second line of defence.

Antibody/Antigen Detection Tests for the diagnosis of Kala-azar (Visceral Leishmaniasis)

Antibody detection tests

Antibody based tests must be used in combination with a standardized clinical case definition for Visceral Leishmaniasis diagnosis. Serological tests based on indirect fluorescent antibody (IFA), Enzyme Linked Immunosorbent Assay (ELISA) or Western Blot have shown high diagnostic accuracy in most studies but are poorly adapted for field settings. Two serological tests have been specifically developed for field use and have been sufficiently validated-the direct agglutination test (DAT) and the rK39 based immunochromatographic test (ICT).

Direct Agglutination Test (DAT)

Direct Agglutination Test (DAT) another test widely used for serodiagnosis of kala-azar is based on antigen-antibody reaction. Trypsin treated, stained and formalin preserved promastigotes are used as antigen which show agglutination with specific antibodies present in patients serum. The test is performed at room temperature though the antigens are stored under controlled temperature in freezer.

The usefulness of the above mentioned serological tests is limited by, their variable sensitivity or specificity, requirement of electricity, refrigeration, or a well equipped laboratory and high cost.

Recently developed rapid dip-stick test – rK39 is the option available now to diagnose kala-azar cases at the grass roots in conjunction with the clinical diagnosis.

Laboratory Diagnosis of Leishmaniasis: Visceral Leishmaniasis (Kala azar): Part One

Diagnosis of Visceral Leishmaniasis may require taking a blood sample and/or taking a biopsy from the bone marrow or splenic puncture to show the parasite.

Diagnosis of Cutaneous Leishmaniasis will require a small biopsy or scrapping of ulcer.

Diagnosis of Mucocutaneous Leishmaniasis requires a biopsy of the affected tissues.

Biopsy samples are examined by microscopy, culture and other methods to look for the parasite and identify the specific kind of leishmania causing the ulcer.

Sample for Visceral Leishmaniasis

1. Blood:Blood film/Blood Culture and Serological Tests.
2. Bone Marrow: Biopsy material obtained by sternal or iliac crest puncture.
3. Splenic Pulp: Biopsy material obtained by splenic culture.

Different factors involved in the transmission of (Visceral Leishmaniasis) kala-azar

Mode of Transmission

Kala-azar is transmitted from person to person by the bite of the female phlebotamine sandfly, p.argentipes which is a highly anthrophilic species. Transmission may also take place by contamination of the bite wound or by contact when the insect is crushed during the act of feeding. Transmission of Kala-azar has also been recorded by blood transfusion, veneral and transplacental but are very rare.

Different factors involved in the transmission of kala-azar
Agent Factor:

1. Agents: Leishmania donovani, are intracellular parasites that infect and divide within macrophages is the causative agent of kala-azar.
2. Reservoir of infection: There is a variety of animal reservoirs e.g. dogs, jackals, foxes, rodents and other mammals. Indian kala-azar is considered to be a non-zoonotic infection with man as the sole reservoir.

Class note: Life Cycle: Leishmania Spp.

Class Note: Leishmaniasis: Introduction, Epidemiology and Transmission

Leishmaniasis is a parasitic disease caused by several species of genus Leishmania (protozoa) and transmitted by the bite of sand flies.Sand flies are primarily infected by animal reservoir, but humans are also a reservoir for some Leishmania species.

Leishmaniasis currently threatens 350 million men, women and children in 88 countries around the world. The leishmaniases are parasitic diseases with a wide range of clinical symptoms:

1. Cutaneous leishmaniasis: Involving the skin at the site of a sandfly bite. Cutaneous forms of the disease normally produce skin ulcers on the exposed parts of the body such as the face, arms and legs. The disease can produce a large number of lesions-sometimes upto 200 causing serious disability.  
2. Visceral Leishmaniasis: Involving liver, spleen and bone marrow. It is also known as Kala azar and is characterised by irregular bouts of fever, substantial weight loss, Hepatomegaly and Splenomegaly and anaemia. If left untreated, the fatality rate in developing countries can be as high as 100% within 2 years.
3. Mucocutaneous Leishmaniasis: Involving mucous membrane of the mouth and nose after spread from a nearby cutaneous lesion.Lesions can lead to partial or total destruction of the mucous membranes of the nose, mouth and throat cavities and surrounding tissues.
   

Rapid Diagnostic tests for the Laboratory Diagnosis of Malaria

Rapid Diagnostic tests for the Laboratory Diagnosis of Malaria

A rapid diagnostic test (RDT) is an alternate way of quickly establishing the diagnosis of malaria infection by detecting specific malaria antigen (e.g. HRP2- Histidine Rich Protein-2, or Specific PLDHL-Parasite Lactate Dehydrogenase (specific for Falciparum malaria diagnosis).

Technique: A blood specimen collected from the patient is applied to the sample pad on the test card along with certain reagents. After 15 mins, the presence of specific band in the test card window indicate whether the patient is infected with Plasmodium falciparum or one of the other three species of human malaria.

Advantage of Rapid Diagnostic test for Malaria diagnosis)
High quality malaria microscopy is not always available in every clinical settings where patients might seek medical attention. The laboratories associated with these health care settings may now use an RDT to more rapidly determine if their patients are infected with malaria.

Disadvantage of Rapid Diagnostic test (for Malaria diagnosis)
The use of the RDT does not eliminate the need for malaria microscopy. The RDT may not be able to detect some infections with lower number of malaria parasites circulating in the patient's bloodstream. All negative RDT must be followed by microscopy to confirm the result. 

In addition, all positive RDT's should also followed by microscopy. The currently approved RDT detects two different Malaria antigen; one is specific for P. falciparum and the other is found in all four human species of malaria. Thus microscopy is needed to determine the species of malaria that was detected by the RDT. In addition, microscopy is needed to quantify the proportion of RBC's that are infected, which is an important prognostic indicator.  

Download Free: Malaria Diagnosis Tutorials, Resourcess and Books

Download Free Malaria Diagnosis Tutorials, Resourcess and Books

1. Basic Malaria Microscopy: Part TwoTutors Guide: World Health Organization
2. Diagnosis of Malaria Infection
3. Malaria Microscopy Quality AssuranceManual Version One: By World Health Organization

Class Note: Laboratory Diagnosis of Malaria

Once malaria is suspected on clinical grounds, it is mandatory to obtain the laboratory confirmation of the presence of malaria parasites in the patient’s organism, whenever possible. The diagnosis of malaria may in fact be pursued by the direct demonstration of the parasite whole cell or of parasite’s nucleic acid or products in the blood (direct diagnosis) or by the demonstration of the patient’s immune response to the infection (indirect diagnosis or immunodiagnosis)

The direct demonstration of the whole parasitic cell may be accomplished by several methods, from the old and simple (but still golden standard!) direct microscopic observation of stained blood specimen to the more recent and sophisticated concentration and staining techniques (Quantitative Buffy Coat ®, acridine orange method). Finally, the detection of the presence of the genome of the parasite is now possible by the Polymerase Chain Reaction (PCR) technique. New and sensitive immunological methods to detect P. falciparum antigens have yielded promising results for the individual diagnosis of malaria infection.

Asexual Life Cycle of Plasmodium Falciparum

plasmodium spp possess a life cycle which shows an alternation of generation accompanied by an alternation of host. Man represent the intermediate host of malarial parasite, i.e. Asexual life cycle (cycle of schizogony) occurs in Man. The gametogony also starts in the RBC of man and is completed in the Female Anopheles mosquito.

Pre-erythrocytic schizogony

1. It comprises a single cycle and lasts for six days
2. The mature pre-erythrocytic schizont measures 60 micro meter in length and 30 micro meter in breadth

Resistance to Malaria (falciparum and vivax malaria) Infection

A number of genetic factors provide some resistance to the various plasmodium spp. Hemoglobin S, thalassemia, and glucose-6-phosphate dehydrogenase deficiency are associated with increased resistance to P. falciparum.

Microscopic Diagnosis of Malaria

Microscopic Diagnosis of Malaria

The direct microscopic visualization of the parasite on the thick and/or thin blood smears has been the "gold standard" for malaria diagnosis.

Thick Blood smear
Thick smears consist of a thick layer of dehemoglobinized (lysed) red blood cells (RBCs). Thus, thick smears allow a more efficient detection of parasites (increased sensitivity). However, they do not permit an optimal review of parasite morphology.
Allow the smear to dry thoroughly. Insufficiently dried smears (and/or smears that are too thick) can detach from the slides during staining. You can accelerate the drying by using a fan or hair dryer. Do not fix thick smears with methanol or heat. If there will be a delay in staining smears, dip the thick smear briefly in water to hemolyse the RBCs.

Thin Blood Smear:
Thin smears consist of blood spread in a layer such that the thickness decreases progressively toward monolayer. Fix the smear by dipping them in absolute methanol.

Microscopic examination:
First screen the thick/thin smear at a low magnification (10× or 20× objective lens), to detect large parasites(microfilaria) then examine the smear using oil immersion objective. NCCLS recommend examination of at least 300 oil immersion fields for the determination of "No Parasite Seen".

Thin Smear Showing Plasmodium Falciparum

Diagnostic Points for Plasmodium falciparum

1. Red Cells are not enlarged.
2. Rings appear fine and delicate and there may be several in one cell.
3. Some rings may have two chromatin dots.
4. Presence of marginal or applique forms.
5. It is unusual to see developing forms in peripheral blood films.
6. Gametocytes have a characteristic crescent shape appearance. However, they do not usually appear in the blood for the first four weeks of infection.
7. Maurer's dots may be present.

Diagnostic Points for P. vivax

1. Red cells containing parasites are usually enlarged.
2. Schuffner's dots are frequently present in the red cells as shown above.
3. The mature ring forms tend to be large and coarse.
4. Developing forms are frequently present.

Parasitology Note

Name of the organism	Sample	Microscopy	Blood examination	Direct examination	Other
Ascarisis lumbricoides	Stool or vomit. Bile by duodenal intubation.	- Egg: direct microscopical examination of a saline emulsion of the stool. - Concentration: flotation method - Unfertilized eggs don’t float in salt solution. - Solitary male harbouring: no egg. - Egg in bile.	Eosinophilia during early stage of invasion. If present in the intestinal phase suggests associated strongyloidiasis and toxocariasis.	Finding of adult worms. Antihelminthic drug increase expulsion of worms.	X-ray with barium emulsion. Allergic dermal rxn(scratch test) with powdered Ascaris antigen.
Giardiasis	Freshly passed stool. Bile (duodenal intubation)	Demonstration of Giardia trophozoite (in diarrhoeic stool) and cyst.
Intestinal amoebiasis	Stool Blood (blood shows moderate lecocytosis)	Cellular exudates: scanty, containing only nuclear mass (Pyknotic bodies) of only a few pus cells, macrophages and epithelial cells. Clumped RBC:reddish yellow or yellow green in color Charcot-Lyden crystals.    *not pathognomonic.     *Suggests careful examination of stool.      *Diamond shaped or whetstone shaped crystals, clear and refractile (5-50µm in size). Demonstration of E.histolytica by examining trophozoites in acute cases, characteristic movement & presence of ingested RBC. Moderate leucocytosis.		An offensive dark brown, semifluid stool, acid in rxn, admixed with blood, mucus and presence of much fecal matter.	Serology always negative. Although there is tissue invasion, it has not existed long enough to produce detectable antibody.
Amoebic live abscess	Pus by exploratory puncture. Liver biopsy in miliary amoebic hepatic abscess. Stool.	Demonstration of trophic form of E. histolytica. Present in less than 15% cases of amoebic liver abscess.	Leukocytosis (15,000-30,000 per mm3) of blood. DC shows Neutrophil granulocytes to be 70-75%.	OTHERS: Intradermal test: erythema. Radiological Examination: shows evidence of basal pleurisy. Hepatic Photoscan.	Presence of specific antibodies circulating in the blood of infected individual. CFT, precipitin test, immobilization test, Test of Goldman, IHA, Passive cutaneous anaphylaxis.
Pulmonary amoebiasis	Sputum	Demonstration of trophozite of E. histolytica. Expectorated pus when examine fresh, may demonstrate the motile form(trophozoite) of E.histolytica.