Helminths Flashcards
3 examples of helminths
Cestodes (tapeworms), trematodes (schistosomes), nematodes (hookworm)
What is schistosomiasis
Blood flukes - trematodes
What is a feature of schistosomes
two prominent suckers, oral and ventral
how many people have schistosomiasis worldwide
250M
What are the three major species of Schistosomiasis
S. Japonicum, S. haematobium, S. mansoni
How do you get infected with schistosomiasis?
Infected water. parasite burrows through skin, through bloodstream, into liver where they mature
sexually reproduce in blood vessels.
How is Schistosomiasis infection passed on?
Females are constantly shedding eggs that pass into the bloodstream, can be transmitted through faeces
How does the schistosome parasite penetrate the skin?
CERCARIAL penetration. Tail is cast off
- glycoalyx is shed via microvilli
- new double unit membrane is formed
What is a common symptom of schistosomiasis
Swimmer’s itch
Cercariae.
- 125µm long, 25µm diameter, 200µm tail
- covered in continuous syncital tegument
- primitive nervous system
- acetabular glands
How do cercariae penetrate skin
- they respond to gradients of fatty acid released by skin
- while on the skin they are positively reinforced by ceramides in the skin
- once they are deeper in the skin, they respond to different fatty acids
- once in blood, they transform to schistosomulum
What is the difference between the different schistosomes?
Haematobium = little tail thing
Mansoni = tiny weeny
Japonicum = oval shape
What is the intermediate host for schistosomes?
Water snail
What happens to the parasite once in the snail?
- differentiates into a sporocyst, with daughter sporocysts following sexual division
- cercariae form within sporocysts
What types of worm is a hookworm
Nematode - roundworms
intestinal dwelling
