chapter 9
TRANSCRIPT
HDL 113: Clinical Parasitology I
CHAPTER 9:TRICHURIS TRICHIURA
© 2010 Cosmopoint
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Chapter 9: Trichuris trichiura
© 2010 Cosmopoint
Topic Outlines
9.1 Introduction
9.2 Disease, geographical distribution, habitat
9.3 Morphology
9.4 Life cycle
9.5 Transmission and pathogenesis
9.6 Laboratory diagnosis
9.7 Treatment and prevention
© 2010 Cosmopoint
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Chapter 9: Trichuris trichiura
© 2010 Cosmopoint
Learning Outcomes
At the end of this chapter, students should be able to:
Briefly describe Trichuris trichura.
Explain morphology, habitat, life cycle, mode of transmission & pathogenesis, laboratory diagnosis, treatment and prevention.
Topics© 2010 Cosmopoint
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Chapter 9: Trichuris trichiura
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9.1 Introduction
INTESTINAL NEMATODES Phylum Aschelminthes
Class Nematoda
Intestinal nematodes / roundworms.
Round / cylindrical shape, covered by a tough outer covering (cuticle), a complete digestive system, including a mouth and an anus.
Male and female forms exists.
Female larger than males.
Topics
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Chapter 9: Trichuris trichiura
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9.1 Introduction
Most adult nematodes are not found in human feces, ova and larvae are the most common diagnostic forms.
Size and shape of intestinal nematode ova are constant for a given species.
Ova may be round or oval, and the shape may vary in fertilized and unfertilized eggs.
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Chapter 9: Trichuris trichiura
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9.2 Disease, geographical distribution, habitat
Trichuris trichiura
Disease: Trichuriasis
Geographic Distribution: The third most common round worm of humans. Worldwide, with infections more frequent in areas with tropical
weather and poor sanitation practices, and among children. It is estimated that 800 million people are infected worldwide.
Trichuriasis occurs in the southern United States.
Intestinal nematode
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Chapter 9: Trichuris trichiura
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9.3 Morphology
Trichuris trichiuraMorphology Whipworm
Adult males – 30-45mm long, with a coiled posterior end.
Adult females - 35-50mm with a straight posterior end.
Both sexes have a long, whip-like anterior end.
Eggs - Bile-stained and oval or barrel-shaped, with a thick, smooth shell, and a clear, prominent polar plug at each end. Length: 50-55 µm, Width: 20-25 µm.
Topics
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9.4 Life cycle
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LIFE CYCLE
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9.4 Life cycle
The unembryonated eggs are passed with the stool (1). In the soil, the eggs develop into a 2-cell stage (2) , an advanced cleavage stage (3) , and then they embryonate (4); eggs become infective in 15 to 30 days. After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae (5) that mature and establish themselves as adults in the colon (6). The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year.
Topics
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9.5 Transmission and pathogenesis
1. Whipworm infection occurs worldwide, but especially in developing tropical countries and the rural southwestern part of the United States.
2. Infection: after ingestion of embryonated eggs in contaminated food or water, or directly from soil.
3. Most infections are asymptomatic with a heavy worm burden, nausea, diarrhea, abdominal pain, and weight loss may occur.
4. Blood loss in serious infections may result in anemia, and serious infections may lead to rectal prolapse.
5. Simultaneous infections with Ascaris are common.
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9.5 Transmission and pathogenesis
Figure: Rectal prolapse
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Chapter 9: Trichuris trichiura
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9.6 Laboratory diagnosis
Lab diagnosisMicroscopic identification: Typical, oval eggs, displaying prominent polar plugs at each end.
Distorted eggs may be present in patients receiving antihelminthic treatment.
Routine concentration methods for detection of ova and parasites have been recommended.
Adult worms rarely seen in feces.
Adults usually reside in the large intestine, cecum and appendix of the host. Examination of the rectal mucosa by proctoscopy (or directly in case of prolapses) can occasionally demonstrate adult worms.
Topics
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9.6 Laboratory diagnosis
Topics
Figure: T. trichiura egg in an iodine-stained wet mount.
Figure: T. trichiura egg in an unstained wet mount.
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9.6 Laboratory diagnosis
Topics
Figure: T. trichiura egg in an unstained wet mount.
Figure: Two T. trichiura eggs, showing the variability in size of the species.
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9.6 Laboratory diagnosis
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Figure: Cross section of an adult female T. trichiura stained with hematoxylin and eosin (H&E), showing numerous eggs. Image taken at 100x maginification. Image courtesy of the Oregon State Public Health Laboratory.
Figure: Close-up of an egg taken at 1000x magnification.
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9.6 Laboratory diagnosis
Topics
Macroscopic (Gross) Observations
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9.7 Treatment and prevention
Treatment and prevention
TREATMENT: Drug of choice: Mebendazole Alternative: Albendazole
PREVENTION: Adherence to good personal hygiene. Avoidance of contaminated food or water. Avoidance of the use of
human feces as fertilizer.
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Chapter 9: Trichuris trichiura
© 2010 Cosmopoint 1804/08/2023
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