Morphology,classification and diagonosis of parasite

Geographical distribution

The parasite is distributed in tropic and subtropics.It is found in sanitation pore area .in developing country,it is distributed 50-60% but only 5%,it is distributed in developing country.It is common in worldwide.

Habitat

The parasite lives in everywhere.

Morphology

These are found in different forms: trophozoite,pre-cyst, and cyst.The cyst is considered as injunctive form and trophozoite is considered as a vegetative form.

Trophozoite:

It is the growing and feeding form of the parasite.It is about 10-14μm in diameter and irregular in shape.The cyst plasma is divided into two parts.The outer inner clear ectoplasm and inner granular endoplasm.Due to certain thrusting movement of one direction,pseudopodium is formed which helps in the motility of the parasite.The parasite has a typical motility called gliding motility.The endoplasm contains the nucleus,injected RCB,bacteria etc.The nucleus is not visible in fresh preparation due to the rapid motility of the parasite.Trophozoites divided by binary fission.Trophozitecan is killed by dry heat,chemical disinfectant and cannot survive long in outside environment.Therefore,infection is not transmitted by trophozoite.

Pre-cyst

It is the transient stage between trophozoite and cyst.It is about 10-20μm in diameter.Some of the pre-cyst might contain blood pseudopodium.Pre-cyst changes into the cyst.

Cyst

The cyst is about 10- 15μm in diameter and can live for the longer period in the favourable environment outside the human body.Therefore, the Mature cysts are the infected stage of this parThe mature cyst contains four nucleus(Qadri nucleus)where one mature cyst contains one or two nuclei.The cyst has thick resistant cyst wall which can resist gastric PH.

Mode of infection

The infection is transmitted through faecal-oral route.The infection is generally transmitted by using cyst contaminated food and drinks.

Classification of parasites

Parasites occur in two distinct forms:single called protozoa and multicellular metazoa called helminths or worms.For medical purposes protozoa can be subdivided into four groups:Sarcodina(amebs),Sporozoa(sporozoans),Mastigophora(flagellates) and ciliates.Metazoa is divided into two phyla :the platyhelminths and Nemathelminthis(roundworms,nematodes).The phylum platyhelminths contain two medically important classes:Cestoda(tapeworms)and trematodes(flukes).This classification is given as below:

• Parasites

1. Protozoa
2. Metazoa

• Protozoa

1. Sarcodina(amebas)
2. Sporozoa(sporozoans)
3. Mastigophora(flagellates)
4. Ciliata(ciliates)

• Metazoa

1. Platyhelminthes(flatworms)
2. Nemathelminthes(roundworms)

• Platyhelminthes

1. Trematoda
2. Cestoda

Laboratory Diagnosis of intestinal parasites

1. Serological parasitic examination
2. Indirect parasitic examination
3. Direct parasitic Examination

   Direct parasitic examination

• Sample :stool
• Physical consistency,odour,visible,blood,mucus,visible parasite
• Chemical examination ;Ph,occult blood
• Microscopic examination(wet mount)
• Normal saline
• Iodine

A large number of intestinal parasites such asGiardia lamblia,Entamoeba histolytic,Ascaris lumbricoides etc can cause intestinal infection.In order to detect this parasite in laboratory,three major approaches are as follows

1. Serological parasitic examination
2. Indirect parasitic examination
3. Direct parasitic Examination

• Direct parasitic examination

In the direct parasitic examination the ova,cyst, and trophozoites of the parasites are absence.The stool is considered to be the sample of choice.For the laboratory diagnosis of intestinal parasites.

• Collection of stools
• The patient is given a clean,dry screw capped container
• The patient is instructed on the collection process.
• The sample is collected and labelled.Those samples which are not sufficient are rejected and the patient is given the new container to recollect the sample.
• The sample is transported to the laboratory as soon as possible.In the case of delay,preservable such as potassium dichromate can be used.

Stool in laboratory examined as:

1. Physical examination:In physical examination,colour,consistency,odour,physical blood,mucus,visible parasites are observed.
2. Chemical examination:In a chemical examination ,Ph and occult blood are performed.
3. Microscopic examination:Microscopic examination of the stool is done in the order to detect cyst,trophozoites, and ova of the intestinal parasite.Microscopic examination is done by wet mount preparation.In wet mount preparation,normal saline preparation and iodine preparation is performed.

• Normal saline preparation:It is done in order to visualize the parasites in its original morphological forms.The following steps are applied in odor to execute this technique.

1. A clean dry grease free glass slide is taken and 2-3 drops of normal saline are kept in the centre of the slide.
2. A clean applicator is taken and a little amount of stool is emulsified and covered with a coverslip.Cave is taken in order to prevent the formation of air bubbles.Covers list can be kept by using the needle.
3. The slide is observed at 40×,diagnosis is based on the morphological forms of cysts,trophozoites,ova etc.

• Iodine preparation:It is done in order to stain the intracellular materials such as nucleus etc.This would further aid in the detection and diagnosis of intestinal parasites.

• Indirect parasitic examination

In this technique,other characteristics of parameters are observed ,For eg parasite, specific DNA can be detected by using the molecular technique such as a polymerase.

• Serological parasitic examination

In this technique, the antibody against parasites in serum and antigen can be detected in stool.Various serological techniques such as ELISA,RIA.immuno fluorescence etc can be used.For eg coproantigen of Giardia can be detected during Giardiasis.

Laboratory Diagnosis of blood parasites

A human of blood parasites causes infection in human beings.The most common blood parasites arePlasmodium vivax,Wuchereria Bancroft,Leishmania Donovan etc.These parasites can be detected in laboratory in three major techniques

1. Serological parasitic examination
2. Indirect parasitic examination
3. Direct parasitic Examination

• Direct examination

In the direct examination of blood parasites,microscopy is performed.The microscopic examination is done by collecting the blood sample.There are two different techniques by which microscopic examination of the blood smear is performed.

1. Thick blood stained smear
2. Thin blood stained smear

• Thick blood stained smear

This technique is performed in order to detect the presence of parasites.The technique is as follows

1. A clean dry grease free slide is taken
2. The finger tip of suspected patient is swab with alcohol and pricked with the sterile lancet.
3. A drop of blood is placed on the central of the slide.It is taken spread in an area of 1cm².A well-formed slide can be confirmed after the letters on newspaper can be visualized when observed from the formed smear.
4. The slide is then stained using Giemsa stain
5. After staining,the side is washed blotted and observed under the microscope.The parasites are detected on the basis of their morphological structures.

• Thin blood stained smear

1. A clean dry grease free slide is taken
2. The finger of suspected patient is swab with alcohol and pricked with the sterile lancet.
3. Then drop of blood is placed on the corner of the slide
4. A next slide is a hold at an angle of 45^•C or 35^•C and waits until the blood spread to edge of slide
5. The upper slide is rubbed against the lower slide and smear is prepared.A well-formed smear gives the shape of tongue
6. The slide is Dedham Eno globalized,stained,booted and observed under the microscope.
7. The parasites are detected on the basis of their morphological structures.

References

Arvind, Keshari K. and Kamal K Adhikari. A Textbook of Biology. Vidyarthi Pustak Bhander.

Michael J.Pleczar JR, Chan E.C.S. and Noel R. Krieg. Microbiology. Tata Mc GrawHill, 1993.

Powar. and Daginawala. General Microbiology.

Rangaswami and Bagyaraj D.J. Agricultural Microbiology.