medical parasitology lab

Staining of Parasites

Medical Parasitology Lab.

Cryptosporidium parvum

Raed Z. Ahmed, Medical Parasitology Lab.,2012

Intestinal Protozoa

Cryptosporidium parvum

Infect human and most mammals. The infective stage is oocyst containing sporozoites

measuring 4-6µ in diameter. The diagnostics stage is sporulated oocyst containing 4

sporozoites. Diagnosis:– Detecting oocyst in stool.– Acid-fast stain.


• The most common method of diagnosing Cryptosporidiosis is acid-fast staining methods or the Ziehl-Neelsen stain.

Cryptosporidium parvum oocyst

http://gut.bmj.com/content/41/6/801/F2.large.jpg

Cryptosporidium parvum oocyst


Intestinal Protozoa


Isospora belli

Isospora belli• Isosporiasis is a human intestinal disease caused by the parasite

Isospora belli.• The coccidian parasite Isospora belli infects the epithelial cells of

the small intestine, and is the least common of the three intestinal coccidia that infect humans.

• Infection causes acute, non-bloody diarrhea with crampy abdominal pain, which can last for weeks and result in malabsorption and weight loss. In immunodepressed patients, and in infants and children, the diarrhea can be severe. Eosinophilia may be present (differently from other protozoan infections).

• Diagnosis:– Acid- fast stain


Isospora belli oocyst


Tissue Nematodes


Trichinella spiralis

Trichinella spiralis

Trichinella spiralis • Cause trichinosis, trichiniasis or trichinelliasis..• Adult inhabit the small intestine of the rats and pigs. Both

males and females lie freely in the lumen of the intestine of pigs and rats.

• Fertilized female only penetrate the mucosa where the larviposit, they do not lay eggs.

• Larvae is the infective stage, live encysted in the flesh of the host, and they represent the infective stage.

• Human infected by eating undercooked pork containing infective encysted larvae.

• Human is dead end host.


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• Diagnosis:– By finding the adult parasites in early days of infection.– Finding larvae in the blood during migration or in

muscle after encystation.– Immunological tests.– X- ray to detect the calcified larvae in muscle.


Trichinella spiralis larvae encysted in muscle


Intestinal Nematodes


Entrobius vermicularis

Entrobius vermicularis

Entrobius vermicularis• Also named as human pin worm and seat worm, cause

oxyurdiasis.• Young and mature worms are present in small intestine (at

terminal ileum till fertilization).• Gravid females are present at lower rectum where they lay ova

at perianal region around anus (oviparous).• The female is 0.88-1.3 cm long, it has a long tapering tail

resembling 1/3 its length, its strait.• The male is shorter than female (2-5 mm) the tail is curved

strongly to ventral side, and has a single spicule.• Infective stage: Embryonated Eggs.• Definitive host: human.


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• Diagnosis:– Egg in stool is rarely detected but adults present after

purgative.– Egg can be detected at perianal area as follow:• N.I.H method (National Institute of Health), its based on

swabbing the perianal area with a cellophane paper.• The adhesive cellulose tape (scotch tape), better result.• The Vaseline cloth wiping, the collected ova examined.

• Egg morphology:– 20-50u, transparent with double walled shell, it may show

one side convex and the other flat.



Entrobius vermicularis Eggs

http://upload.wikimedia.org/wikipedia/commons/5/5d/Eggs_of_Enterobius_vermicularis_5229_lores.jpg

Entrobius vermicularis Adult


malefemale



Trichuris trichiura

Trichuris trichiura • Its commonly called whip worm because of the shape of

this worm (anterior thin and posterior thick).• Adult inhabit the large intestine in the caecum of man.• The adult male smaller than female, male 3.4-4.5 cm,

female 4-5 cm.• Trichuris trichiura eggs have distinct shape. (oviparous)• Diagnosis:– Stool examination to detect eggs.


Trichuris trichiura Eggs


Trichuris trichiura Adult


http://upload.wikimedia.org/wikipedia/commons/a/a7/Trichuris_trichiura.jpg



Strongyloides stercoralis

Strongyloides stercoralis • Adults lives in the small intestine (duodenum and jejunum),

fertilized females are deeply embedded in the mucosa, where they also oviposit.

• Male have a pointed curved tail associated with two spicules.• Female have straight tail without spicules.• In contrast to the Anclystoma spp., both sexes have short

buccal cavity.• Infective stage: Filariform larvae.• Diagnosis:• Based on recovery of the rhabditiform larvae passed in

stool.• If diarrhea is present, eggs may also be recovered.



Strongyloides stercoralis Larvae


Rhabditiform

Filariform

S. Stercoralis Adult Male


spicules

spicules

S. Stercoralis Adult Female




Ancylostoma duodenale



Anclystoma duodenale

Ancylostoma duodenalae (Hookworm)

• Inhabit human intestine ( jejunum, ileum, and rarely duodenum ) and cause Anclystomiasis.

• Male shorter than female and have copulatory bursa and two spicules.

• Female is long and has pointed end.

• Both sexes have long buccal cavity with two pairs of teeth.

• Infective stage: Filariform larvae.

• Diagnosis:

– Based on finding ova in fresh stool sample.

– In old sample, larvae present and must be differentiated from larvae of Strongyloides stercoralis.



Hookworm Eggs


Hook worm eggs like insects or mites egg, therefore must be differentiated

Mites egg Hook worm eggPlant material

Hookworm Larvae


Filariform Rhabditiform

Hookworm Adult


MaleFemale

Ancylostoma duodenalae copulatry burasa


Ancylostoma duodenalae buccal capsule


Comparison between Ancylostoma duodenalae and Necator americanus


Ancylostoma duodenalae Necator americanus

Old world hookworm New world hookworm

Larger (male 8-11mm) Smaller (male 7-9mm)

Anterior end bent in same direction of general curvature of body

Anterior end bent in opposite direction of general curvature of body

Prominent buccal capsule with 2 pairs of teeth

Smaller buccal capsule with 2 pairs of semilunar cutting plates

Copulatory spicules not fused Copulatory spicules fused at ends to form a barbed tip

Copulatory bursa vs Copulatory Spicules


Necator americanus copulatory spiculesAncylostoma duodenalae copulatory spicules

Comparison between S. stercoralis and Hookworm


Aspect Anclystoma spp. (Hook worm) Strongyloides stercoralis

Rhabditiform larvae

Buccal cavity Long Short

Esophagus One – third of the body One – third of the body

Genital permordium Absence Prominent

Filariform larvae

Esophagus One – third of the body Half of the body

Tail Pointed Notched

larvae Striated sheath Unsheathed

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