Parasitologynotes

Parasitologynotes - Family: Heterophydidae Heterophyes...

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Family: Heterophydidae Heterophyes heterophyes Metagonimus yokogawai Tiny flukes (~1mm long) “tear shaped” Intestinal fluke (small intestine) Common in Africa, Asia, Middle and Far East-endemic in certain parts of Egypt) All species considered potential human pathogens Caused by eating undercooked or raw fish Life Cycle: 1 st intermediate host: aquatic snail; 2 nd intermediate host: fresh or brackish water fish (mullet); definitive host: fish eating birds and mammals Adults release embryonated eggs each with a fully-developed miracidium, and  eggs are passed in the host's feces . After ingestion by a suitable snail (first  intermediate host), the eggs hatch and release miracidia which penetrate the  snail’s intestine . Genera  Cerithidia  and  Pironella  are important snail hosts in  Asia and the Middle East  respectively. The miracidia undergo several developmental stages in the snail,  i.e. sporocysts , rediae , and cercariae . Many cercariae are produced from each  redia. The cercariae are released from the snail and encyst as metacercariae in  the tissues of a suitable fresh/brackish water fish (second intermediate host) .  The definitive host becomes 
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infected by ingesting undercooked or salted fish containing metacercariae . After  ingestion, the metacercariae excyst, attach to the mucosa of the small intestine  and mature into adults (measuring 1.0 to 1.7 mm by 0.3 to 0.4 mm) . In addition  to humans, various  fish-eating mammals (e.g., cats and dogs) and birds can be infected  by  Heterophyes heterophyes  . Clinical disease: gastric disease, fatigue, malaise, diarrhea Pathology: mild inflammation at site; heavy infection (mucosal damage and potential for ectopic parasite locations (so tiny gets into blood and disseminated)); affinity for heart Dx: eggs in feces (resemble C. sinensis eggs) Rx: Praziquantel Again don’t eat raw fish Platyhelminthes II Cestodes aka Tapeworms Dorsoventrally flattened
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No digestive system * No coelom No circulatory system No respiratory system Well developed muscular system Complex nervous system Hermaphroditic At least two different host in life cycle Host niche: intestinal tract in definitive host No pathology to gut mucosa in definitive host * Proglottid: segment that has sets of reproductive organs of both sexes Genitalium: term used for each set Strobila: long chains of proglottids Strobilization: growth of strobila from anterior to posterior - immature mature gravid - immature mature gravid senile Cestode Form - Scolex - Neck (contains germanal tissue gives rise to proglottids - Proglottids (immature, mature, gravid, senile **) Scolex - head - at anterior end - equipped with “holdfast” organs: suckers, hooks, grooves/slits, spines, tentacles,
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This note was uploaded on 04/03/2008 for the course BIOL 4105 taught by Professor Farrar during the Spring '08 term at LSU.

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Parasitologynotes - Family: Heterophydidae Heterophyes...

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