Experiment 14: Identification of Disease-Causing Organisms (Ascaris, Entamoeba, Plasmodium, and Ringworms)

AIM

To identify common human disease causing organisms like Ascaris, Entamoeba, Plasmodium and ringworms through permanent slides or specimens.

PRINCIPLE

Human diseases are caused by various pathogens including protozoans, helminths and fungi. Identification is based on morphological and diagnostic features observed under microscope or naked eye from permanent slides and specimens.

Entamoeba histolytica and Plasmodium vivax are unicellular protozoan parasites causing amoebiasis and malaria. Ascaris lumbricoides is a nematode helminth causing ascariasis with sexual dimorphism and distinct lateral lines.

Ringworm is caused by dermatophytes like Microsporum, Dermatophyton and Trichophyton infecting keratinised tissues. Study of characteristics, host interactions and symptoms helps in diagnosis and understanding disease transmission.

REQUIREMENTS

• Permanent slides of Plasmodium
• Permanent slides of Entamoeba
• Specimen of Ascaris
• Specimen of ringworm fungi (Microsporum, Dermatophyton, Trichophyton, etc.)
• Compound microscope
• Hand lens

PROCEDURE

1. Study the permanent slides under compound microscope.
2. Note down the identification characteristics of organisms in the practical record book.

OBSERVATION

a) Entamoeba histolytica

Characteristics

• It is unicellular protozoan and irregular in shape due to the presence of pseudopodia.
• It has single big nucleus, placed eccentrically in the cell.
• The cell shows the presence of few food vacuoles, but contractile vacuoles are absent.
• Ectoplasm, endoplasm, ingested bacteria, food vacuoles and nucleus are visible in stained preparation.

Interactions with Host

• It is an endoparasite of human intestine and causes amoebic dysentery or amoebiasis.
• Source of infection is through the contaminated food and water.
• The parasite feeds on RBCs by damaging the wall of large intestine and reaching the blood.

Symptoms

• Person affected with Entamoeba complaints of severe abdominal pain.
• Patient passes repeated motions filled with blood and mucus.

b) Plasmodium vivax

Structure of sporozoite shows sickle shaped body with pointed ends. It is an endoparasite seen easily within the RBC of the infected person. The Protozoa is known to cause malaria in humans.

Characteristics

• It is a unicellular organism.
• It has a big vesicle with cytoplasm accumulated at one place containing nucleus, which looks like a bag.

Symptoms

• The infected person suffers from headache, muscular pains and high fever, 102° to 103°F.
• The person suffers from alternate chills, shivering and high fever.
• Sleeplessness, restlessness and loss of appetite.

c) Ascaris lumbricoides

Characteristics

• The animal shows sexual dimorphism. The female is longer than male.
• Both the ends are pointed with the posterior end of male is curved ventrally.
• Single longitudinal lines are present on dorsal, ventral and other two lateral sides throughout the body. Lateral lines are more distinct than other lines.
• Ascaris is an endoparasite of small intestine of human beings causes Ascariasis.
• Male has cloacal aperture, pineal spicules, pre and post cloacal papillae; female has vulva, vagina and genital pore.

Symptoms

• Ascaris worm infests a single host and obstructs the intestinal passage thereby causing abdominal discomforts.
• The sufferer complaints of colic pain.
• There is impaired digestion, vomiting and diarrhoea in severe infestation.
• Person loses weight and feels tired and lethargic.

d) Microsporum - Ringworm Fungi

Characteristics

• Ringworm is an infectious disease caused by fungal infection of dermatophytes.
• On keratinised tissue, it produces fronds of hyphae which are waxy or cotton-like.

Interactions with Host

• The physical contact with infected persons, or their belongings may spread infections. Usually scissors, clips remain contaminated with fungal spores and cause infection in healthy persons.
• It infects keratinised areas of the body (hair, skin, scalp and nails) and the area gets more red on periphery than in centre creating ring-like appearance.

Symptoms on Scalp

• Yellowish cup-like crust appears on scalp. Hair become lustreless and grey. In severe cases, it leads to baldness.

Symptoms on Skin

• Round ring-shaped growing lesions appear on any part of the skin of the body.
• These lesions are very itchy which usually appear flat and keep growing if left untreated.

Symptoms on Foot

• It appears specially in between the toes because of the presence of moisture. A watery fluid leaks out from the infected areas.
• Cracking/scaling of skin of foot occurs due to the severe infection.

Symptoms on Nails

• Nails show discolouration, become chalky and thickened.

RESULT

Permanent slides and specimens show characteristic diagnostic features of Entamoeba histolytica, Plasmodium vivax, Ascaris lumbricoides and ringworm fungi. Each organism exhibits distinct morphology, host interaction and disease symptoms.

CONCLUSION

Entamoeba causes amoebiasis with blood and mucus in stool, Plasmodium causes malaria with high fever and chills, Ascaris causes ascariasis with abdominal discomfort and ringworm fungi cause circular itchy lesions. Hygiene, clean food and water prevent protozoan and helminth infections.

PRECAUTIONS

• The specimens should be examined carefully with naked eyes and with the help of hand lens.
• Prepared permanent slides should be thoroughly observed under microscope to see its diagnostic features.
• Make your observation first under low power followed by higher magnification.