INTRODUCTION TO HELMINTHS Flashcards
Classification by Infection Mode: What are the different modes of infection for helminths?
①By ingestion
②By penetration of skin
③By blood sucking insects
④By inhalation of dust containing eggs
Which helminths are associated with ingestion of eggs?
①Enterobius
②Ascaris
③Trichuris
(EAT)
Which helminths are associated with ingestion of Larvae within intermediate host?
Dracunculus
Which helminths are associated with ingestion of Encysted larvae in the muscle?
Trichinella
Which helminths are transmitted by penetration of skin？
①Ancylostoma
②Necator
③Strongyloides
Which helminths are transmitted by blood sucking insects？
Filariae
Which helminths are transmitted by inhalation of dust containing eggs?
①Ascaris
②Enterobius
Egg Laying/Larvae Types: Can you describe the differences between oviparous, viviparous, and ovoviviparous helminths?
①Oviparous: Egg laying nematodes
②Viviparous: Producing larvae
③Ovoviviparous: Laying eggs containing fully formed larvae which hatch out immediately
Oviparous: Egg laying nematodes
①Unsegmented eggs: Ascaris & Trichuris
②Segmented eggs: Ancylostoma & Necator
Viviparous: Producing larvae:
①Trichinella
②Wuchereria
③Brugia
④Dracunculus
Ovoviviparous: Laying eggs containing fully formed larvae which hatch out immediately:
Strongyloides
Helminth Groups: What are the two main groups of helminths and what distinguishes them?
①Nemahelminths
Nematodes – Roundworms
②Platyhelminths ( Flatworms)
- Trematodes - flukes
- Cestodes - tapeworms
Nematode Habitats: How are nematodes classified based on their habitat？
①Intestinal nematodes
②Blood and tissue nematodes
Intestinal nematodes；
①Soil transmitted helminths (STH)
②Others Non – soil transmitted helminths ( Non- STH)
Blood and tissue nematodes
Filaria and drucunculus
INTESTINAL NEMATODES
Small intestine: ①Ascaris
②Ancylostoma
③Necator
④Strongyloides
⑤Trichinella
Large intestine: ①Enterobius
②Trichuris
TISSUE NEMATODES (Somatic nematodes)
①Lymphatic: Wuchereria, Brugia
②Sub-cutaneous: Loa loa, Onchocerca, Dracunculus
③Mesentry: Mansonella spp.
④Conjunctiva: Loa loa
⑤Zoonotic filariasis: Dirofilaria spp.
Soil transmitted helminths；
- These require period of development and maturation during their life cycle in the soil
①Ascaris lumbricoides
②Trichuris trichiura
③Hookworm ( Necator americanus and Ancylostoma duodenale)
④Strongyloides stercolaris
Non – soil transmitted helminths；
①Enterobius vermicularis
②Trichinella spiralis
Filaria and drucunculus
①Wuchereria bancrofti
②Brugia malayi
③Brugia timori
④Onchocerca vovulus
⑤Drucunculus medinensis
HUMAN FILARIAL WORMS
thread-like worms transmitted by blood sucking arthropods
they are zoonotic
Cause FILARIARIS
Morphology of filarial worms
①Adult worm
②Microfilariae(embryo)；
Sheathed microfilarie or
unsheathed microfilariae
How many species of filarial worms infect humans ?
eight
Definite hosts of filarial worms
Humans
Classification of human filarial worms
①Lymphatic filariasis
②Subcutaneous filariasis
③Serous cavity filariasis
Lymphatic filariasis agents
①Wuchereria bancrofti (bancroftian filariasis)
②Brugia Malaya (Malayan filariasis)
③Brugia timori
Subcutaneous filariasis
①Loa loa(calabar/fugitive swelling)
②Oncocerca volvulus（river blindness, dermatitis)
③Mansonella streptocerca(skin diseases)
Serous cavity filariasis
①Mansonella ozzardi（asymptomatic)
②Mansonella perstans（asymptomatic)
Tapelike and segmented helminths
Cestodes
Leaflike and unsegmented helminths
Trematodes
Elongated, cylindrical and unsegmented helminths
Nematodes
Sexes not separate
, monoecious, hermaphrodite
Cestodes
Sexes not separate
, monoecious, except for schistosoma
Trematodes
Sexes separate
, diecious
Nematodes
Head end has suckers, often with hooks.
Cestodes
Head end has suckers, no hooks.
Trematodes
Head end has no suckers, with no hooks, well developed
Nematodes
No alimentary canal
Cestodes
Incomplete alimentary canal with no anus
Trematodes
Alimentary canal present
Nematodes
No body cavity
Cestodes and Trematodes
Body cavity present
Nematodes
。。。do not multiply in man or host
Nematodes
