Parasitology (Trematodes & Cestodes) Study Objectives From the selected trematode and cestode parasites that follow, recall the basic physiology and morphology, pathogenesis, life cycle and transmission and subsequent host response (if given). Trematodes: −Fasciola hepatica −Opisthorchis sinensis −Paragonimus westermania −Schistosoma mansoni, S. haematobium, S. japonicum Cestodes: −Taenia solium, T. saginata −Echinococcus granulosus −Diphyllobothrium latum Randal K. Gregg, PhD READING: Medical Microbiology chapters 84-85

Life Cycle FascioliasisFascioliasis TransmissionTransmission −Foodborne/Waterborne −Ingestion of metacercariae in contaminated unwashed watercress (also water itself) Reservoirs = sheep, cattle also can complete life cycle Eggs passed in feces (mature 9-15 d in environment)…require light to hatch Fasciola hepatica 1 fluke = ~20,000 eggs/d 24 h SEXUAL ASEXUAL ~12 mo 5-10 yrs

Life Cycle OpisthorchiasisOpisthorchiasis −Also caused by O. felineus and O. viverrini TransmissionTransmission −Foodborne −Ingestion of metacercariae in contaminated raw fish (12 spp.) −Also contaminated frozen, dried, salted, smoked, pickled fish Reservoirs = dogs, cats Eggs do not hatch in water…require snail ingestion 50 yrs 1 fluke = ~4,000 eggs/d SEXUAL ASEXUAL Opisthorchis sinensis

Life Cycle ParagonimiasisParagonimiasis TransmissionTransmission −Foodborne / Fecal-oral −Ingestion of metacercariae in contaminated raw crustaceans (crabs, crayfish) Reservoirs = bird, pigs, dogs, cats (also can serve as definitive hosts) Eggs coughed out in sputum or swallowed and passed in feces Eggs have prolonged maturation in water Paragonimus westermani 5-20 yrs SEXUAL ASEXUAL ~3-4 mo ~ wks ~6-8 wks Survive only hrs Survive 1-4 d

Life Cycle TaeniasisTaeniasis −T. saginata (beef tapeworm) −T. solium (pork tapeworm) TransmissionTransmission −Foodborne / Fecal-oral −Ingestion of contaminated undercooked beef or pork containing cysticercus −Also ingestion of egg- contaminated food (T. solium) Attach in the jejunum Eggs of T. solium are infective for humans (intermediate host) Taenia spp yrs Can survive 5 mo Muscle of tongue, diaphragm, hindqtrs ~3-4 mo Survive 5 yrs Any tissue (brain, skin, muscle) Mature ~2-3 mo SEXUAL ASEXUAL 1 proglottid = 100,000 eggs (T. saginata); 50,000 eggs (T. solium)

Pathogenesis Cysticercosis  Humans as intermediate host  Cysticerci dispersed by circulation:  Subcutaneous  Muscles  Heart  Lungs  Liver  Brain  Eyes  Asymptomatic if:  Number of cysticerci is small  Cysticerci remain viable  Symptoms (death of cysticerci):  Inflammation in infested tissue  Fever  Arthralgia  Eosinophilia  Neurological sequelae (epilepsy, seizures,…)  Death (encephalitis, stroke, intracranial pressure)  50,000 deaths (1,000 cases in US annually) Taenia spp.

Life Cycle Agent of Human Echinococcosis (Hydatidosis, Hydatid Disease)Agent of Human Echinococcosis (Hydatidosis, Hydatid Disease) TransmissionTransmission −Fecal-oral −Ingestion of eggs (from soil, water, food) Definitive hosts = dogs, wolves, other canines Intermediate hosts = sheep, goats, camels, deer, caribou, moose, humans (or dead-end) Echinococcus granulosus 5 mo 1-3 mo 12 mo SEXUAL ASEXUAL Grow over 5-20 yrs Viable 1 yr

Life Cycle Agent of Diphyllobothriasis (Fish Tapeworm Disease)Agent of Diphyllobothriasis (Fish Tapeworm Disease) TransmissionTransmission −Foodborne / Fecal-oral −Ingestion of undercooked contaminated freshwater fish containing plerocercoid larvae Reservoirs = dogs, pigs, bears, cats, birds Attach to the ileum Eggs mature & hatch upon contact with water ZOONOTIC Diphyllobothrium latum 1 worm = >1,000,000 eggs/d Viable 3 yrs SEXUAL 5-20 yrs