Trematoda 1-3 PDF

M.A. Freeman Parasites of veterinary importance Helminths: parasitic worms, large and multicellular The term "helminth" includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities: -they are vermiform or “worm-like” in form-  Phylum Nematoda (ro...

M.A. Freeman Parasites of veterinary importance Helminths: parasitic worms, large and multicellular The term "helminth" includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities: -they are vermiform or “worm-like” in form-  Phylum Nematoda (roundworms)  Phylum Platyhelminthes (flatworms)  Class Cestoda (tapeworms)  Class Trematoda (flukes: endoparasites)  Class Monogenea (skin flukes: ectoparasites)  Class Turbellaria (free-living flatworms, some parasitic forms)  Phylum Acanthocephala (thorny-headed worms)  Phylum Annelida (segmented worms) not parasitic (leeches) Trematodes are often referred to as digeneans or digenean flukes Digenea: a subclass of trematodes in the Platyhelminthes, consisting of parasitic flatworms (known as flukes), they typically have two suckers, one ventral and one oral. Adults are particularly common in the digestive tract, but occur throughout the organ systems of all classes of vertebrates. Once thought to be closely related to the Monogenea, it is now recognised that they are closest to the Aspidogastrea and that the Monogenea are more closely allied with the Cestoda. Around 6,000 species have been described to date. Wiki- Aspidogastrea: is a small group of flukes comprising about 80 species. It is a subclass of the trematoda, and sister group to the Digenea. Species range in length from approximately one millimeter to several centimeters. They are parasites of freshwater and marine molluscs and vertebrates (cartilaginous and bony fishes and turtles). Maturation may occur in the mollusc or vertebrate host. None of the species has any economic importance, but the group is of very great interest to biologists because it has several characters which appear to be archaic. Trematodes Lecture Objectives  Key characteristics  Life cycles  Fasciola hepatica Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode of the class Trematoda, Phylum Platyhelminthes. It infects the livers of various mammals, including humans Trematodes (flukes) Dorso-ventrally flattened, leaf-like Oral and ventral suckers for attachment and feeding Hermaphroditic but can cross-reproduce Large operculate eggs – sedimentation Do NOT have direct life cycles Typically broad host spectrum (except gastropod 1st IH) As in other flatworms, there is no anus, and waste material must be egested through the mouth, or via specialized cells – known as flame cells Trematodes (flukes) – Fasciola sp. Fasciolosis/iasis Fasciola hepatica infecting the bile ducts in sheep liver (pipestem liver) The larval stages, metacercaria, burrow through the lining of the intestine and into the peritoneal cavity. They then migrate through the intestines and liver, and into the bile ducts. Inside the bile ducts, they develop into adult flukes Trematodes (flukes) Fasciola hepatica http://www.biologydiscussion.com/invertebrate-zoology/phylumplatyhelminthes/fasciola-hepatica-habitat-structure-and-life-history/28888 Trematodes (flukes) Oral sucker Testes Vitelline glands Genital pore Ventral sucker Ovary Oviducts Trematodes (flukes) Amphimerus sp. High prevalence of the liver fluke Amphimerus sp. in domestic cats and dogs in an area for human amphimeriasis in Ecuador. Calvopiña M. et al. PLoS Negl Trop Dis. 2015;9(2):e0003526. doi: 10.1371/journal.pntd.0003526 Kidney fluke: Phyllodistomum conostomum in H&E section of ureter Host: arctic char Salvelinus alpinus A few from fish: adult trematodes (often called digeneans) Trematodes (flukes) – ‘Simple’ life cycle Final Host (DH): Adult Environment: egg – miracidium Intermediate host: rediae – cercaria Environment: metacercaria Final host: immature adult to adult Final host consumes metacercaria in the environment Fasciola hepatica, has a global distribution and has been known as an important parasite of sheep and cattle Trematodes (flukes) – life cycle (CDC, 2012) Trematodes (flukes) – eggs Operculate Sedimentation in diagnostics DPDx, Division of Parasitic Diseases and Malaria, CDC http://dpd.cdc.gov/dpdx/ Trematodes (flukes) -- miracidium Penetrate into the snail intermediate host Trematodes (flukes) -- IH Intermediate hosts of Fasciola hepatica are freshwater snails from the family Lymnaeidae. This stage can be quite host specific Trematodes (flukes) -- rediae Developmental stage in the IH Trematodes (flukes) -- cercaria Photo: Thomas Nolan Free-swimming: encysts as a metacercaria in the environment or in a 2nd IH Swimmer's itch, also called cercarial dermatitis, appears as a skin rash caused by an allergic reaction to certain parasites that infect some birds and mammals Schistosoma is a genus of trematodes, commonly known as blood flukes. They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis Trematodes (flukes) -- metacercaria Photo: Thomas Nolan 2nd IH - fish Trematodes (flukes) – life cycle (CDC, 2012) Trematodes (flukes) – ‘complex’ life cycle  Adult : final and definitive host  Egg : environment – miracidium  Rediae : Intermediate host (snail)  Cercaria: (into environment again)  Metacercaria : 2nd IH; PH; or environment  Young adult to adult : final and definitive host  Final host consumes metacercaria in the 2nd IH or PH or in the environment Halfbeak – Hemiramphus brasiliensis (ballyhoo) Encysted metacercarial stage in the liver What might be the definitive host? Or possibly a bird: many digeneans are found in water associated birds, and ballyhoo are often found swimming very near the water surface Trematodes (flukes) – life cycle Cercaria penetrate the 2nd second intermediate host (tadpoles) becoming infective mesocercariae Tadpoles or frogs (following the metamorphosis), may be ingested by a number of paratenic hosts (e.g., other frogs, snakes) or directly by the definitive host, e.g. the dog. Common in North American mammals with a wide range of definitive hosts known, including cattle, lynx, martens, skunks, bobcats, foxes, coyotes, and wolves Alaria americana Cercaria Alaria americana : trematode in the family Diplostomatidae. All species infect carnivorous mammals, living in their small intestines as mature worms Development via the lungs Uses intermediate and paratenic hosts Trematodes (flukes) – location Adults  Species dependent  Rumen/intestine, liver, lungs, blood, kidney Pathology  Usually adults  Immature migration, mechanical disruption  Induce inflammatory reactions Trematodes – Fasciola hepatica Final Host: ruminant  Mode of infection: consumes metacercaria in the environment  Location: liver, bile ducts  Pathology: “pipestem” liver with chronic infection  Clinical signs: anemia, bottle jaw  Diagnosis: clinical signs + egg in feces (sedimentation) or fecal antigen test Intermediate host: snail Trematodes – Fasciola hepatica J. Ketzis and RUSVM Trematodes – Fasciola hepatica https://www.youtube.com/watch?v=Eu8h93n2jkE&feat ure=em-share_video_user Parasites of veterinary importance Helminths: parasitic worms, large and multicellular The term "helminth" includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities: -they are vermiform or “worm-like” in form-  Phylum Nematoda (roundworms)  Phylum Platyhelminthes (flatworms)  Class Cestoda (tapeworms)  Class Trematoda (flukes: endoparasites)  Class Monogenea (skin flukes: ectoparasites)  Class Turbellaria (free-living flatworms, some parasitic forms)  Phylum Acanthocephala (thorny-headed worms)  Phylum Annelida (segmented worms) not parasitic (leeches) Review: Trematodes Trematodes Dorso-ventrally flattened, with oral and ventral suckers for attachment Hermaphroditic but can cross reproduce Heavy large operculate eggs, diagnosis in sedimentation Example Fasciola hepatica: liver fluke/sheep liver fluke (zoonotic) Life cycle: environmental stages x 2 (egg and metacercaria), IH: rediae (snail) Indirect / complex life cycle, some with more than one IH Know various stages and pathology: pipestem liver – chronic infections in Faciola hepatica Clinical signs (anaemia, bottle jaw)