Intro & Ascaris

7/31/2019 Intro & Ascaris

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Helminthology

Parasitology Dept.


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Definitions

Helminthology is the science about helminthes

(worms).

Helminthes are divided into: Nemathelminthes

and Platyhelminthes


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Definitions

Due to living sites : Ectoparasites and

Endoparasites

Due to living habits: Facultative and Obligate

parasites Due to life cycle: Periodic and Permanent

parasites

Due to the host: Monoxen and Polyxen parasites


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Terminology

Host: definitive, reservoir, intermediate,

paratenic

Vector: biologic and mechanic

Parasitism

Commensalisms

Mutualism


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Nematodes

Half million species

50% free living

Animal & plant parasitesAnimal

vertebrate & invertebrate hosts

infection by ingestion or penetration


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Nematodes

Generally elongated, cylindrical & tapered

at each end (99%)

Fluid filled pseudocoelom longitudinal

muscle only

No vasculature or respiratory system

Usually sexual dimorphism (someparthenogenesis)


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Nematodes

Males usually smaller than females

Most between 1 mm and 150 cm

Colourless translucent to opaque with

an elastic cuticle


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Soil Transmitted Helminthiasis ( STH )

nematode infections

transmitted via soil medium either

1. Ingestion of embryonated eggs

2. Skin penetration by infective larvae

refers to these helminths:

Ascaris lumbricoidesTrichuris trichiura

HookwormsStrongyloides stercoralis

Toxocara spp.

Common

STH

agents


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Habitat of STH in host

Large intestine

Small intestine

Trichuris trichiura

A. lumbricoides

Hookworms

S. stercoralis


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Infections STH associated with:

Poverty and poor condition

Inadequate sanitation and water supplies

Soil quality and climate

Poor personal and environmental hygiene

Poor health awareness


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Ascaris lumbricoides


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Morphology


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Ascariasis

Etiology: Ascaris lumbricoides ( roundworm )

Habitat : small intestine, especially jejunum and upper ileum

Morphology:

Adult large, broad, cylindrical, tapers at both ends

- light cream pinkish whitish

- female bigger than male

Male

spicule

FemaleVulval opening

between anterior and

midlle 1/3 body


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Ascarismouth partventral view

3 fine toothed lips

2 ventral lips

1 dorsal lip

covered with sensory papillae


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Morphology

Egg consists of three layers (walls):

albuminoid (protein), hyaline, and lipoid

Due to the albumin layer: corticated ordecorticated eggs

Due to the content: fertilized, unfertilized,

or infectious eggsEggs resistant to desiccation


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Fertilized eggs:Rounded, have a thick shell, with anexternal mammillated layer that is oftenstained brown by bileSize: approximately 60 m in diameter

when spherical, and up to 75 m whenovoid.

Unfertilize:elongated and larger (up to 90 m in

length); their shell is thinner; and theirmammillated layer is more variable,either with large protuberance

Morphology:


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Ascariseggs

fertilized unfertilized

mammilated

semi-

decorticated


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Life Cycle

World-wide distribution

Ascaris lumbricoides requires no

intermediate host but only the final host

The essential host is human being, but it

also able to grow in swine and primate


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Life CycleAdult worms in small

intestine, produce eggswhich are excreted with

stool

tracheal migration

Lung passage

Eggs cleavage underoptimal condition in soil

embryonated eggs

Ingested/swallowed byhuman

Hatched in the upper part

of small intestine

Invade blood vessels
http://f/bahan%20kuliah%20ppt/Nematoda/hyperlink%20tracheal%20migration.ppthttp://f/bahan%20kuliah%20ppt/Nematoda/hyperlink%20tracheal%20migration.ppt


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3 weeks

Prepaten Period: 2 months


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