Platyhelminths as Human Parasites Images from the CDC

Trematode Parasites Clonorchis sinensis Fasciola hepatica Schistosoma spp. mansoni japonicum Haematobium Paragonimus westermani Dicrocoelium dendriticum

Clonorchis sinensis Chinese Liver Fluke 20 Million Infected People Infection by eating raw or udercooked fish (pickled fish) Flukes live in bile ducts Symptoms Pain in upper rt. Quadrant Hepatosplenomegaly Gall Stones Obstructive Jaundice Bile Duct Cancer

Clonorchis sinensis

Fasciola hepatica Sheep Liver Fluke Human infection from eating wild aquatic plants Symptoms Hepatosplenomegaly Anemia Jaundice Abdominal Pain Fatty Food Intolerance

Schistosoma spp. Dioecious Large males with split bodies forming a longitudinal groove Females housed in groove of male Adults may live for 10-30 years

Schistosoma spp. Schistosoma mansoni Schistosoma japonicum Egg with large subterminal spine Adults in veins of large intestine Schistosoma japonicum Egg with diminutive subterminal spine Adults in veins of small intestine Schistosoma haematobium Egg with terminal spine Adults in veins of urinary bladder

Schistosomiasis

Intermediate Hosts of Schistosomes Schistosoma mansoni Africa, S. America, West Indies Int. Host - Biomphalaria Schistosoma japonicum Asia Int. Host - Oncomelania Schistosoma haematobium Africa Int. Host - Bulinus

Schistosome Cercaria Cercariae penetrate skin of definitive host Schistosomes that normally parasitize birds may produce the rash known as swimmer’s itch. The rash is the result of an immune response to the cercariae.

Schistosomiasis Blood Flukes 200 Million people infected in Africa and Asia Symptoms Ascites Symmer’s Fibrosis Death via hemorrhage

Control of Schistosomes Proper disposal of body waste Avoid contact with contaminated water Vaccine? Biological Control? Aswan High Dam Electricity Agriculture Schistosomiasis

Paragonimus westermani Lung Fluke Widely Distributed >10 million people infected in China Infection by eating raw or undercooked crustaceans Symptoms Chronic Cough Purulent, blood-streaked sputum Jacksonian Epilepsy, meningitis (cerebral infection) Death (pericardial infection)

Dicrocoelium dendriticum Liver fluke of livestock Humans are accidental hosts Mind-controlling effect on ants

Cestode Parasites Taenia saginata Taenia solium Diphyllobothrium latum Echinococcus spp.

Taenia saginata Beef Tapeworm Cows are intermediate host Scolex without hooks Motile proglottids

Taenia solium Pork Tapeworm Pigs are intermediate host Scolex with hooks

Taeniasis

Diphyllobothrium latum Broad Fish Tapeworm Single worms up to 20 meters Most severe adult tapeworm disease Vitamin B12 absorption by worms leads to anemia

Diphyllobothriasis

Cysticercosis Infection by juvenile tapeworms Symptoms related to location of cysticerci Brain Eyes Heart

Echinococcus spp. Hydatid Disease Infection by close contact with sheep dogs Cysts may grow for many years Surgical removal after scolicidal flush