2. CONTENTS
• INTRODUCTION
• MODE OF ENTRY
• SPREAD AND MECHANISM
• CLASSIFICATION
• CLINICAL FEATURES
• TREATMENT
• REFERENCE
3. INTRODUCTION
Helminth is a general term meaning worm.
The helminths are invertebrates characterized by elongated,
flat or round bodies.
In medically oriented schemes the flatworms or platyhelminths
(platy from the Greek root meaning "flat") include flukes and
tapeworms.
Roundworms are nematodes (nemato from the Greek root
meaning "thread"). These groups are subdivided for
convenience according to the host organ in which they reside,
e.g., lung flukes, extraintestinal tapeworms, and intestinal
roundworms.
4. Parasite modes of entryParasite modes of entry
• Ingestion
• Arthropod bites
• Penetration of intact skin or
mucous membranes
5. Spread and tropisms
• Some parasites must migrate to
certain locations within the host in
order to complete their life cycle
• Non-human parasites, in humans,
often fail to migrate properly and
become “dead-end infections”
7. • direct destruction of tissue
• hypersensitivity reactions
• eosinophilia
–occurs with helminths, not protozoa
–results from tissue migration
Tissue damage and host response
10. Roundworms (Nematodes)
• In contrast to platyhelminths, nematodes are
cylindrical rather than flattened; hence the
common name roundworm.
• The body wall is composed of an outer cuticle
that has a noncellular, chemically complex
structure, a thin hypodermis, and musculature.
The cuticle in some species has longitudinal
ridges called alae. The bursa, a flaplike
extension of the cuticle on the posterior end of
some species of male nematodes, is used to
grasp the female during copulation.
11. Generalized life cycle of
intestinal nematodes.
•
• острица
• хлыстовик
• аскарида
• анкилостома
•
20. • Most common:
– muscle pain and tenderness
– fever +/- chills
– edema (often periorbital)
• >10% eosinophilia (often ~50%)
• elevated CPK
• +/- chronic neurologic/myocardial
• self-limited (2% mortality)
Clinical features of trichinosis
21. Treatment of trichinosis
• antihelminthic (albendazole) to kill
any intestinal adults
• steroids to relieve inflammatory
reactions
• antipyretics
22. Flukes (Trematodes)
• Adult flukes are leaf-shaped flatworms. Prominent oral and
ventral suckers help maintain position in situ. Flukes are
hermaphroditic except for blood flukes, which are bisexual.
The life-cycle includes a snail intermediate host.
• A dorsoventrally flattened body, bilateral symmetry, and a
definite anterior end are features of platyhelminths in general
and of trematodes specifically.
• Flukes are leaf-shaped, ranging in length from a few
millimeters to 7 to 8 cm.
24. The life cycle of blood fluke, Schistosoma japonicum. This organism causes
chistosomiasis. Unlikesome flukes, S. japonicum does not have a redia stage, nor does it
enter an arthropod host.
25. Schistosomiasis - pathogenesis
• egg granuloma (type IV reaction)--> fibrosis
• morbidity ~ worm (egg) burden
• adult worms: invisible to the immune system
(survive for years)
26. Drug treatment of schistosomiasis
• Praziquantel increases permeability
of adult parasite to Ca++
.
• Tetanospasm --> death
27. Control of Schistosomiasis
REDUCE CARRIERS mass rx program
ELIMINATE SNAILS molluscicides
destroy snail habitats
snail-eating fish
PREVENT WATER
CONTAMINATION latrines, toilets
public health education
PREVENT HUMAN
EXPOSURE water systems
28. Tapeworms (Cestodes)
• Adult tapeworms are elongated, segmented,
hermaphroditic flatworms that inhabit the
intestinal lumen.
• Larval forms, which are cystic or solid, inhabit
extraintestinal tissues.
36. Treatment of cysticercosis and
echinococcosis
• Antihelminthic therapy (e.g.,
albendazole, praziquantel)
• (Echinococcus only)
– Surgical removal
– Irrigation-evacuation of cysts
37. REFERENCE
• "Neglected Tropical Diseases". cdc.gov. 6 June 2011.
Retrieved 28 November 2014.
• Jump up^ London Declaration (30 January 2012).
"London Declaration on Neglected Tropical Diseases"
(PDF). Retrieved 26 March 2013.
• ^ Jump up to:a
b
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d
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f
g
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Report of a WHO Expert
Committee (1987). Prevention and Control of Intestinal
Parasitic Infections. World Health Organization,
Technical Report Series 749.
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