Name the cestode life cycle stage present in the intermediate host.
Describe the morphology of an adult cestode.
Segmented, proglottids showing genital pore and reproductive organs,
Describe the morphology of a tapeworm egg.
Thick, brown embryophore containing the onchosphere, 40um
Outline the general lifecycle of a cestode.
Adults in the small intestine shed gravid proglottids into the hosts faeces. Proglottids disintegrate and eggs are dispersed. Eggs are ingested by the host species where they develop to the metacestode. Metacestodes are ingested by the definitive host and become adults in the small intestine.
Name four types of metacestode:
Cysticercus (taenia), coenurus, hydatid, cystercercoid
Tx of adult tapeworm.
Praziquantel or double dose of pyrantel
Which cestode has a cysticercus?
Cysticercus of these Taenia species are found where in the sheep (IH)? Ovis, hydatigena, multiceps.
Ovis - muscle, hydatigena - peritoneum, multiceps - brain
What is the intermediate hosts in a taenia lifecycle? Which species are associated with each host?
Sheep - ovis, hydatigena, multiceps. Rabbit - pisiformis, serialis Mouse - taeniformis
Cysticercus of these Taenia species are found where in the rabbit (IH)? Pisiformis, serialis
Pisiformis - peritoneum Serialis - connective/ sub-cut tissues
Strobilocercus of Taenia taeniformis are found where in the mouse (IH)? Which definitive host is this spp associated?
Which morphological feature is characteristic of Taenia taeniaformis?
Bell shaped proglottids
Some taenia species posess a rostellum. What is this structure and what is its function?
A retractable, muscular structure located at the end of the scollex. It may possess hooks. Involved in parasite attachment to the gut wall
True or false. Echinococcus spp. are zoonotic. Which species are relevant here, in the UK & continental EU?
True. UK - granulosis Rest of EU - multilocuralis
Definitive and intermediate host of Echinococcus granulosus?
D - Dog I - sheep, horse, camel, human
Name the two subspecies of Echinococcus and their intermediate hosts.
E. granulosus subsp granulosus - sheep, human, cattle etc E. granulosus subsp equinus - horse
Describe the morphology of E. granulosus.
Small adult tapeworm - 5mm Four suckers on scolex Rostellum present
What clinical signs are associated with human hydatid disease?
Slow growing, space occupying cysts of hydatids Liver - jaundice, cholangitis, abdominal pain Lung - pleurisy Anaphylaxis if rupture occurs
Alveolar echinococcosis is cause by which Echinococcus species?
Echinococcus multilocularis - fox tapeworm
Why is alveolar echinococcosis considered extremely pathogenic?
large, slow growing cysts difficult to diagnose and treat long incubation tume metastisize and spread
Which areas of EU are fox tapeworm usually found?
East and central - increasing urban fox population in UK may lead to greater risk here.
How long before entry into the UK must dogs receive a tapeworm treatment?
Describe the morphology of Dipylidium caninum.
Adults - 50cm long 4 unarmed suckers on the scolex Protrusable armed (4-7 rows of hooks) rostellum +++ Segments Barrel shaped gravid proglottids - 10-15 eggs per egg capsule Two genital pores per PG
Which flea species are implicated in transmission of D. caninum?
Ctenocephalides felis Also Trichodectes canis
What is the pre-patent period of D. caninum?
Outline the life cycle of D. caninum.
Adult tapeworm in the SI. Motile proglottids excreted in faeces. Eggs eaten by the flea and develop within to a cysticercoid. Infected flea is eaten as the animal grooms.
Dipylidium are considered to show little pathogenesis. Why then are they considered?
Owners often find the motile proglottids very distressing to observe. Motile proglottids may cause minor irritation