Lecture 9 Flashcards
Whats another name for flatworms?
Platyheminths
Whats anther name for tapeworms?
Cestodes
Examples of these:
- Taenia solium (pork tapeworm)
- Echinococcus granulosus
- Echinococcus multilocularis
*- Taenia saginata (beef tapeworm)
*- Taenia multiceps
Taenia Tapeworms
- Tape-like, segmented body
- Hermaphrodite
- No digestive system
- Indirect life cycle
- Adult stages inhabit the small intestine of the definitive/final host)
- Larval cyst stages (metacestodes) in various organs and tissues of livestock, wildlife and humans (intermediate hosts)
Adult tapeworms
- Record sizes (50cm-15m)
- Continuous growth from the neck region
- At the posterior end: gravid segments break off and passed in the faeces
- Usually no clinical significance
Life cycle of Taenia solium
Unique zoonosis:
- Humans only known definitive/final host
- Pigs intermediate host
Humans carry:
- Both adult worms in the intestine
- larval cysticerosis in the muscle, other tissues
- Infection with adult worms in humans dangerous to host and other contacts
-Under-reported disease
Taenia multiceps
- Causes the disease ceonurosis
- Aka gid or staggers
- Dogs/foxes are the definitive host
- Sheep/humans intermediate host
- Circling behaviour in infected sheep
- Infection called Gid/Staggers/Ceonurosis
Taenia Ovis
Adult worms:
- In dogs and foxes
- Site: small intestine
- About 1m long
- No clinical significance
Larval cysts/metacestodes:
- In sheep and goats
- Site: cysts in muscle
- Up to 1cm in size
- ‘Sheep measles’ (meat condemnation)
Taenia saginata- Beef tapeworm
Adult worms:
- In humans
- Site: small intestine
- 5-15m in length
- Very long lived
- Often asymptomatic
- Huger pains, diarrhoea, nausea, weight loss
Larval cysts/metacestodes:
- In cattle
- Site: cysts in muscle
- Up to 1cm in size
- ‘Beef measles’ (meat condemnation)
Control of Taenia tapeworms: Preventing infections in livestock
- Prevent dog fouling on pastures
Control of Taenia tapeworms: Preventing infections in dogs:
- Prevent access to offal/uncooked meat
- Regular deworming of dogs
Control of Taenia tapeworms: Preventing infections in humans
- Meat inspection (also for T.ovis)
Liver fluke (Fasciola hepatica)
- Common parasite of cattle and sheep (zoonotic)
- Causes the disease fasciolosis
- Flat and leaf-shaped
- Indirect life cycle (intermediate host: mud snail)
- Most common on wet/muddy pasture
Rumen fluke (Calicophoron daubneyi)
- Steady increase in the prevalence of rumen fluke over the last 20 years
- Juveniles in the small intestine
- Adult flukes in the rumen
- Much less pathogenic than liver fluke (except for very rare cases of acute disease due to large numbers of juveniles)
- Same intermediate host as the liver fluke
- Climate affects the intermediate hosts ability to reproduce and move
- Encysted metacercariae are present on pasture from late summer
- Pre-patent period of 3-4 months
- In Ireland, infection in late summer results in a patent infection during winter
- Declining efficacy of F.hepatica control measures due to increasing resistance to triclabendazole
- Global climate change is predicted to extend the season of F.hepatica in northern Europe
Fasciola hepatica: clinical signs
- Juvenile fluke -> Liver damage
- Adult flukes -> Blood feeders
- Anaemia, lethargy, reduced growth and milk yield, bottle jaw
- Acute disease in sheep
- Chromic disease in cattle
- Zoonotic
