Helminths 2
Terms
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- Helminths
- multi-cellular animals (the worms)
- Characteristics of Helminths
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A) Specialized to live in hosts, but have nerves, muscles, digestive tracts like other eukaryotes.
B) Absorb nutrients from host food, body fluids or tissue.
C) Have reduced or complete lack of locomotion - Characteristics of Nematodes
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Member of Helminths.
A) cylindrical and tapered at end
B) either egg or larvae is infective - Enterobius vermicularis, lifecycle
- Entire life in human host. Adults found in large intestine, female lays eggs on perianal region. Eggs ingested by autoinfection, or fomites (sheets, dust, nightclothes).
- Enterobius vermicularis, treatment
- medendazole (Vermox). Treat whole family if one member is infected, clean house well.
- Enterobius vermicularis, clinical characteristics and diagnosis
- Infection often asymptomatic, but can have itching and irritability. Diagnose using "Graham Scotch tape test" to find characteristic (one side) flattened eggs on anal mucosa.
- Enterobius vermicularis, common name
- pinworm, due to female's pointy end
- Enterobius vermicularis, morphology and classification
- Member of Nematodes (roundworms). Eggs are infective to humans. Adult female has a pointy end.
- Ascaris lumbricoides, lifecycle
- Eggs ingested by host, hatch in small intestine. Juveniles access bloodstream and migrate to lungs. They then migrate from pulmonary capillaries to alveoli and are coughed up. The host then swallows the juveniles which complete development in the small intestine. There the females produce eggs (1:200,000/day!) which are passed in feces.
- Ascaris lumbricoides, epidemiology
- Causes ascariasis, most widespread helminthic disease in the world. 1/4 world infected. Pig farmers are at risk for pig ascarid (ascaris suum).
- Ascaris lumbricoides, morphology and classification
- Member of Nematodes (roundworms). Eggs are infective to humans. Can be up to 1ft in length.
- Ascaris lumbricoides, clinical characteristics and diagnosis
- Heavy lung infection causes pneumonia-like symptoms. Can see eosinophilia due to migrating worms. High worm burden can cause intestinal blockage, liver/gallbladder problems. Malnourishment common. Diagnosis is made by eggs in stool.
- Ascaris lumbricoides, treatment
- mebendazole (Vermox). Future prevention is a matter of good hygiene.
- Necator americanus, common name
- hook worm
- Necator americanus, lifecycle
- Larvae penetrate foot skin, migrate to lungs, are coughed up and end in intestine.
- Definitive host
- Home of mature parasite, location of sexual reproduction.
- Intermediate host
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Home of immature parasite.
Site of asexual reproduciton. -
What is the organism? -
Enterobius vermicularis -
What is this? - Eggs of Enterobius vermicularis. Characteristically flat on one side.
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Whose lifecycle? -
Necator americanus - Necator americanus, diagnosis
- Adult worms attached to intestine can cause blood loss, anemia, tiredness, and metal/physical retardation in children. Migrating larvae can cause pneumonitis.
- Necator americanus, treatment
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Prevention: wear shoes, practice good hygiene
Treatment: with mebendazole, iron replacement if anemic. -
What is this? - The egg of N. americanus shows a developing embryo
- Trichinella spiralis causes what disease?
- trichinosis
- Trichinella spiralis, clinical
- Cysts in commonly used muscles (eyes, speech, respiration, myocardium) cause them to weaken. Intense inflammatory responses are seen.
- Trichinella spiralis, lifecycle
- Human eats meat containing trichinella cysts. Stomach acid dissolves cyst covering, releasing worms. Worms mature in small intestine, mate and produce larvae. Larvae breakthrough intestinal wall and enter bloodstream. They penetrate into muscle cells and use them as a nursery for the larvae.
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What is this? - Trichinella spiralis cyst INSIDE muscle cell.
- Trichinella spiralis, treatment
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Symptoms: aspirin and corticosteroids.
Thiabendazole for adult worms in the intestine
No treatment kills the larvae. - Trichinella spiralis, diagnosis
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By blood test, muscle biopsy.
Eosinophilia often seen.
Splinter hemorrhaging under nails often diagnostic. - Wuchereria bancrofti, classification
- tropical nematode causing lymphatic filariasis (elephantiasis)
- Brugia malayi, classification
- tropical nematode causing lymphatic filariasis (elephantiasis)
- Onchocerca volvulus, classification
- tropical nematode causing onchocerciasis (river blindness)
- onchocerciasis treatment
- riverblindness treated by ivermectin. Control of blackfly vector also important.
- Life cycle of lymphatic nematodes, and name the organisms as well.
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Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus. - Cestodes, characteristics
- Member of Helminths. Intestinal parasites that lack a digestive system. Humans are definitive host.
- Cestodes, morphology
- Head (scolex) has hooks that attach to intestinal mucosa. It then produces proglottids containing either male or female reproductive organs that chain.
- proglottids
- Linked segments of male or female sex organs produced by the head of a cestode. Produced as long as the scolex is alive.
- strobila
- Chain of proglottids in cestodes.
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Whose lifecycle? -
Cestodes: Taenia solium and Taenia saginata - Taenia solium, common name
- pork tapeworm
- Taenia saginata, common name
- beef tapeworm
- Taenia solium causes what disease?
- cystercercosis: autoinfection by calcified larval stage leading to CNS or ocular problems.
- Taenia saginata, classification
- Cestode (tapeworm)
- Taenia solium, classification
- Cestode (tapeworm)
- Taenia solium, prevention & treatment
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Prevention: inspect meat for cysticerci, cook meat well
Treatment: Praziquantel - Taenia saginata causes what disease?
- None: does not autoinfect so cystercercosis is out. Symptoms are usually minimal.
- Taenia saginata, diagnosis
- Finding proglottids or eggs in feces.
- Taenia solium, diagnosis
- Finding proglottids or eggs in feces.
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What is this? - Scolex (head) of a cestode showing hooks and suckers.
- Trematodes, classification and common name
- Member of helminths, the parasitic flatworms. Commonly called flukes.
- Trematodes, members
- Schistosoma mansoni, Schistosoma japonicum, Schistosoma haematobium
- Trematodes, lifecycle
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See above - Trematodes, transmission vector
- snails
- Trematodes, treatment
- praziquantel
- Schistosoma mansoni, clinical and geography
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Initially allergic reaction, chronicly hepatic (hepatosplenomegaly) and intestinal abnormalities.
Africa and South America - Schistosoma japonicum, clinical and geography
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Allergic reaction, hepatic and intestinal abnormalities.
China, Japan, Phillipines - Schistosoma haematobium, clinical and geography
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Allergic reaction. Chronically, eggs deposited on bladder, end up in urine causing hematuria. Cause of bladder cancer.
North Africa, India, Portugal - Schistosoma hematobium, diagnosis and treatment
- Eggs in urine. Treat with Praziquantel.
- Schistosoma japonicum, diagnosis and treatment
- Eggs in stool. Treat with Praziquantel.
- Schistosoma mansoni, diagnosis and treatment
- Eggs in stool. Treat with Praziquantel.