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193 Cards in this Set
- Front
- Back
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How does the body structure of nematodes differ from that of Platyhelminthes on the one hand and coelomates on the other?
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Body structure is round;
Pseudocoelomate with no living mesothelial lining |
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What is characteristic about the following features of nematodes digestive tract?
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Complete digestive tract
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What is characteristic about the following features of nematodes muscles?
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Longitudinal muscles only, running front to back
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What is characteristic about the following features of nematodes presence of cilia?
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No moving cilia -amoeboid sperm
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What is characteristic about the following features of nematodes reproductive systems?
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Dioecious
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What is characteristic about the following features of nematodes body surface?
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Body surface is covered with cuticle (non-living tissue)
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What is the function of spicules and gubernaculum?
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of taxonomic and functional importance - used to differentiate different species; gubernaculum used to grasp female
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What is the common name of Trichuris trichiura?
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whip worm
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What are stichocytes?
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segments around the esophagus
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Describe the life cycle of T. trichiura.
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Adults located in ileocecal region (sm intestine); produce 3000 to 30,000 eggs per day; unembryolated eggs in soil for 21 days then become infective; ingested eggs hatch and enter crypts of ileocecal region; posterior protrude into lumen; adults in ileocecal region of the sm intestine
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How do humans become infected with T. trichiura? At what larval stage?
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fecal contamination; shady moist soil; poor hygiene
eggs ingested |
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Infections of T. trichiura occur:
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worldwide
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What are the medical consequences of infection with T. trichiura?
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Sx depend on intensity of the infection; can cause mechanical damage to mucosa; toxic/inflammatory response to worms
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What factor determines whether no or severe symptoms occur with T. trichiura?
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intensity of infection: <100 worms = asymptomatic; 100-1000 worms indicates heavy infection with diarrhea, tinesmus, stunting growth, cognitive deficits, anemia, rectal prolapse
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Alarming Sx with heavy infection of T. trichiura?
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rectal prolapse
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What steps can be taken to control infection with T. trichiura?
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prevent fecak contamination of food; wash hands and food
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Describe the lifecycle of Capillaria hepatica.
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Adult worms in liver migrate to eggs in the liver; the host dies or is eaten or unembryolated eggs are left on the ground for 2-6 weeks; infective eggs are ingested then hatch in the intestine and penetrate the wall; migrate to the liver in the blood (molt 4 times)
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What part of the world do C. hepatical infections occur?
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occur worldwide
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What are the consequences of infection with C. hepatica?
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mechanical destruction of the liver
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How is C. hepatica infection diagnosed?
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liver biopsy
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How do humans become infected with C. hepatica?
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ingest contaminated soil
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Is ingestion of uncooked tissues from infected hosts a risk factor in C. hepatica?
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Yes - raw fish or anything contaminated with eggs
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In what part of the world do Capillaria philippinensis infections occur?
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Philippine islands
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How do humans become infected with Capillaria philippinensis?
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Eat raw fish that is infected or ingest food that contains eggs
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How do heavy and life threatening infections occur in Capillaria philippinensis?
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zoonosis; piscivorous bird reservoir; associated with consumption of raw fish;
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What are the medical consequences of infection with Capillaria philippinensis?
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mechanical destruction of mucosa leads to electrolyte imbalance, bacterial infection and death
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How does Trichinella spiralis give birth to its offspring?
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eggs hatch in utero
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What type of host is the human in Trichinella spiralis?
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Humans are intermediate host
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Are infections with Trichinella spiralis variable and unpredictable?
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No - symptoms follow a predictable sequence
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Any infection with Trichinella spiralis is serious but a lethal dose is:
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5 juvenile worms per gram of body weight
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Trichinella spiralis mechanisms?
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bacterial infection of mucosa; cell death from penetrating Juvenile worms; toxemia
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How are Trichinella spiralis infections diagnosed?
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symptoms and recent history of eating pork; immunological tests; biopsies
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Why is it obvious that trichinosis is a zoonosis, with humans not being an important host for the parasite?
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humans don't play a major role in the lifecycle of this parasite; humans not a good host; infection is passed on by dying
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How are infections with Trichinella spiralis contracted?
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Eating undercooked pork or another animal (horse) that is infected, or eating wild carnivorous animals
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How are infections with Trichinella spiralis treated?
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None. Anti-inflammatory drugs
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How can Trichinella spiralis be prevented?
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Cook pork (meats) and/or freeze (except Arctic strain)
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What is unusual about the location of Dictophyme renale in the definitive host?
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located in the right kidney
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Lifecycle of Dictophyme renale
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Adult resides in the kidney where it produces unembryolated eggs in urine; eggs passed to water and ingested by small annelid in the gut; penetrates gut wall and juveniles move to ventral blood vessels; eaten by fish or frog (parentenic hosts) and resides in muscle; ingested by defnitive host; moves from stomach to liver then to kidney
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Besides the definitive host, what other types of hosts are involved in Dictophyme renale?
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fish and frogs are parentenic hosts; cats and dogs are normal reservoir hosts
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Two routes of human infection with Dictophyme renale?
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fish or frogs eaten; swallowed in water
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What mechanism of of pathology in D. renale infections?
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mechanical destruction of the right kidney
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How are Dictophyme renale infections diagnosed and treated?
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surgical removal is treatment; diagnosed by eggs in urine
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How can Dictophyme renale infections be prevented?
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Filter water; cook fish and frogs before eating
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Describe the life cycle of Strongyloides stercoralis.
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Adult female in small intestine; produces unembryolated eggs that hatch in the intestine producing juveniles in feces and are deposited in stool; contaminate soil or penetrate gut; then move to blood, into the lungs, trachea and finally back to the small intestine
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What is unusual with respect to occurrence of both sexes in Strongyloides stercoralis, and occurrence of free living stages, about this life cycle?
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Can produce both homogonic or heterogonic cycles; switch between free living and parasitic
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How are human infections with Strongyloides stercoralis typically contracted and by what stage?
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fecal contamination of soil; moist soil; not wearing shoes
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At what stage of Strongyloides stercoralis do symptoms occur and by what mechanisms?
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migratory phase: inflammation and mechanical damage to lungs -- intestinal phase: diarrhea; abdominal pain; eosinophilipa; dermatitis; wanders under the skin; autoinfection around the anus
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What is a Strongyloides stercoralis hyperinfection and in what population of hosts does it occur?
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infection throughout the body; bowel perforation, brain invasion, respiratory failure, septicemia. Occurs in immunocompromised individuals
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How are infections with Strongyloides stercoralis diagnosed?
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rhabiditiform larvae in stools
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In what part of the world do Strongyloides stercoralis infections occur?
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in the tropics
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Are there any epidemiologically significant reservoir hosts in Strongyloides stercoralis?
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Dogs are reservoir host
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How can human infection be controlled in Strongyloides stercoralis?
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kill all the dogs; eliminate fecal contamination of soil; wear shoes
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Can free living nematodes post a health threat?
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nn
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Why are hookworms given their distinctive name?
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Distinct morphology with curved dorsal anterior and armed buccal capsule; copulatory bursa with rays
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What are the 2 species of hookworms infecting humans?
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Ancylostoma duodenale
Necator americanus |
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Which is the most prevalent hookworm and in what parts of the world?
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Necator americanus found worldwide
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What is distinctive about the morphology of the anterior and posterior ends of these hookworms?
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anterior end has lips and posterior end is slender and pointed
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Describe the general hookworm life cycle.
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adults in sm intestine produce eggs which are deposited as unembryonated eggs on the soil where they hatch; go through 2 molts and produce filari (within 5 days); these penetrate the skin, then move to the blood, lungs, trachea and are swallowed where they end up in the sm intestine
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How do humans become infected, and by what stage?
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worm penetrates the skin and matures in the lungs
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When comparing the life cycles of Ancylostoma duodenale and Necator americanus, how do they differ with respect to obligatory development in the lungs and ability to undergo arrested development?
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Time in the lungs is required for americanus but not for duodenale; duodenale can get to adults by two methods whereas americanus only has one
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What are the pathological mechanism by which hookworms cause disease?
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worms must penetrate the skin
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What factor determines whether no symptoms or severe symptoms occur?
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intensity of infection; .3 to .26 M per day = light infection; 1,000 worms approximate 200m/per day = heavy infection
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What are the most severe symptoms of hookworm infection?
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protein deficiency
iron deficiency anemia |
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Do these symptoms with hookworms affect all races equally?
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more prevalent in caucasian
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How are hookworm infections diagnosed?
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eggs found in stool
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How can transmission of hookworm infection be controlled?
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wear shoes, prevent fecal contamination of soil; practice good hygiene
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What species of dog and cat hookworms cause problems in humans, and what are the problems?
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Ancylostoma braziliense, A. caninum;
braziliense causes creping eruptions with cutaneous larva; caninum causes eosinophilic enteritis |
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What is the name of the condition that results when dog and cat hookworms cause problems?
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cutaneous larva migrans
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Describe the life cycle of Trichostrongylus spp.
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not on test
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How does Trichostrongylus spp. differ from that of hookworms and S. stercoralis?
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Not on test
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How are humans typically infected, and by what larval stage with Trichostrongylus spp.?
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not on test
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What are the reservoir hosts of this zoonotic infection (Trichostrongylus spp)?
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not on test
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Can free living nematodes post a health threat?
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yes
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Why are hookworms given their distinctive name?
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They have an armed buccal capsule
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What are the 2 species of hookworms infecting humans?
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Ancylostoma duodenale
Necator americanus |
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Which is the most prevalent hookworm and in what parts of the world?
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Necator americanus is found worldwide
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What is distinctive about the morphology of the anterior and posterior ends of these hookworms?
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the anterior end of the worm contains the barbs that allow them to penetrate the skin; the posterior end of these worms is very thin
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Describe the general hookworm life cycle.
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adults live in sm intestine and produce eggs which are deposited on unembryonated eggs on soil; eggs hatch and molt two times producing filari which penetrate the skin and travel via blood to the lungs, trachea and are swallowed where they end up back in the sm intestine
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How do humans become infected with hookworms and by what stage?
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humans become infected with J3 (filari form) by penetrating the skin
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When comparing the life cycles of Ancylostoma duodenale and Necator americanus, how do they differ with respect to obligatory development in the lungs and ability to undergo arrested development?
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Ancyclostoma duodenale life cycle has two methods of infecting adults (mammary, neonatal) or through the lungs; Necator americanus requires development in the lungs for development to adult stage
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What are the pathological mechanisms by which hookworms cause disease?
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worms (filari) penetrate the skin
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What factor determines whether no symptoms or severe symptoms occur in hookworm disease?
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intensity of the infection - 0.3 to 0.26 M worms per day = light infection
1000 worms --> 200M/day = heavy infection |
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What are the most severe symptoms of hookworm infection?
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most severe Sx:
severe protein deficiency iron deficiency anemia |
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Do the symptions (with hookworm disease) affect all races equally?
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worse in caucasians
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How are hookworm infections diagnosed?
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diagnosed by finding eggs in stool
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How can transmission of hookworm infection be controlled?
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wear shoes, prevent fecal contamination of soil; practice good hygiene
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What species of dog and cat hookworms cause problems in humans, and what are the problems?
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Ancylostoma braziliense and
A. caninum Cause creeping eruption (cutaneous larva migrans) and eosinophilic enteritis |
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What is the name of the resulting medical condition (dog and cat hookworms)?
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creeping eruption (cutaneous larva migrans)
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Describe the life cycle of Trichostrongylus spp.
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not on test
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How does Trichostrongylus spp. differ from that of hookworms and S. stercoralis?
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not on test
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How are humans typically infected with Trichostrongylus spp., and by what larval stage?
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not on test
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What are the reservoir hosts of this zoonotic Trichostrongylus infection?
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not on test
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In whatpart of the world is Trichostrongylus spp. especially prevalent?
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not on test
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What are the pathological effects of Trichostrongylus spp.?
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not on test
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How is Trichostrongylus spp. infection diagnosed?
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not on test
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What is the intermediate host and the normal definitive host for Angiostrongylus cantonensis?
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not on test
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How does the definitive host become infected with Angiostrongylus cantonensis?
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not on test
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Where does the definitive host become infected with Angiostrongylus cantonensis?
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not on test
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Where in the definitive host does larval development occur with Angiostrongylus cantonensis?
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not on test
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Where to the adults reside, and how do their progeny escape from the definitive host in Angiostrongylus cantonensis?
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not on test
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How to humans typically become infected (with Angiostrongylus cantonensis) and what are the medical consequences?
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not on test
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What are the symptoms of severe infection with Angiostrongylus cantonensis?
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not on test
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Where is Angiostrongylus cantonensis most prevalent?
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not on test
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What is the intermediate host and the normal definitive host for Angiostrongylus costaricensis?
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not on test
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How does the definitive host become infected with Angiostrongylus costaricensis?
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not on test
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Where in the definitive host does larval development occur in Angiostrongylus costaricensis?
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not on test
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Where do the adults reside, and how do their progeny escape from the definitive host in Angiostrongylus costaricensis?
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not on test
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How do humans typically become infected with Angiostrongylus costaricensis and what are the medical consequences?
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n
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What are the symptoms of severe infection with Angiostrongylus costaricensis?
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not on test
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Where is the Angiostrongylus costaricensis infection most prevalent?
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not on test
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Describe the life cycle of Ascarius lumbricoides.
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adult worms reside in sm intestine produce 200,000 eggs/day/worm which are deposited unembryonated on soil; after 2 weeks the molt and produce infective egg (j2) which hatches and is ingested; penetrates blood and moves to the lungs where it becomes j4 then goes to trachea and is swallowed and moves to sm intestine
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What is the infective stage of Ascarius lumbricoides?
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J2 in this parasite, J3 in most others
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In what sense does part of the life cycle in the definitive host seem unnecessary in Ascarius lumbricoides?
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the stop in the lungs
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How do humans become infected with Ascarius lumbricoides?
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humans ingest infective eggs (J2)
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Where are Ascarius lumbricoides infections most prevalent?
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Found worldwide, especially Southeast United States
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What structural feature of the egg of A. lumbricoides makes it extremely resistant to harsh environments?
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the outer coating of the egg consists of a protein, chitin and lipid layers making it resistant to harsh environments (can live for 10 years in soil)
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What medical problems does A. lumbricoides cause during different phases of its life cycle?
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causes Ascaris pneumonitis in the lung phase;
causes malnournishment, intestinal blockage, verminous intoxication, and wandering in the intestinal phase |
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What factor determines the severity of disease with A. lumbricoides?
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intensity of the infection - Sx rare in light infections and worse in heavy infections
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How can transmission of Ascarius infection be controlled?
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proper disposal of human feces and proper washing of hands and food
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What medical problems result from infection of humans with Toxocara canis or T. cati?
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death of larvae in tissue results in inflammation (liver= fever, eosinophilia; brain=neuropathology, death; eye=blindness
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How are infections of Toxocara canis or T. cati contracted?
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eggs are ingested by humans, penetrate the mucosa and J2s wander in tissues (visceral larva migrans)
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What is the name of the medical condition when infected with Toxocara canis or T. cati?
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ascarid worm infection
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How is the infection with Toxocara canis or T. cati diagnosed?
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ELISA
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Which of the species Toxocara canis or T. cati represents a greater threat to humans, and why?
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Toxocara canis most threatening to humans
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What steps can be taken to control Toxocara canis or T. cati transmission to humans?
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Deworm pets, cover sandboxes, keep children off ground
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What role do rodents play in the life cycle of Toxocara canis or T. cati?
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rodents are paratenic hosts
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What is the normal definitive host of Baylisascaris procyonis?
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raccoons
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Why is Baylisascarius procyonis of public health concern?
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rare in humans but can be dangerous due to visceral larval migrans
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What are the normal intermediate, paratenic, and definitive hosts of Anisakid nematodes?
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crustaceans (definitive host) eat eggs, ingested by fish or squid (paratenic host) and then ingested by larger fish Iintermediate host) which are eaten by marine mammal
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How do humans become infected with Anisakid nematodes and what are the potential medical consequences?
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eat undercooked fish (including salted, picked fish); consequences include mechanical trauma to mucosa, perforation of bowel causing peritonitis; and misdiagnosis
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Where is the prevalence of human infection greatest with Anisakid nematodes?
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Japan, Skandanavia, and US
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What is the best method of diagnosis and treatment with Anisakid nematodes?
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diagnosis by endoscopy
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Why is Baylisascarius procyonis of public health concern?
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not on test
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What are the normal intermediate, paratenic, and definitive hosts of Anisakid nematodes?
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intermediate - crustaceans
paratenic - fish, squid definitive - marine mammal |
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How do humans become infected with Anisakid nematodes and what are the potential medical consequences?
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eat undercooked fish; causes mechanical trauma to mucosa, inflammation, perforation of the bowel and misdiagnosis
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Where is the prevalence of human infection greatest with Anisakid nematodes?
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Japan, Skandanavia and US
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What is the best method of diagnosis and treatment with Anisakid nematodes?
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diagnosis by endoscopy
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How can Anisakid nematode infection be prevented?
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cook or freeze fish
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Describe the life cycle of Enterobius vermicularis.
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common name: pinworms
lifecycle: adults in sm intestine gravid female migrates to anus at night; oviposition on perianal skin where they embryonate and produce infective eggs (J3) on skin then transmitted hand to mouth, or inhaled or contaminated food or H2O |
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What is the infective stage and how do humans become infected with Enterobius vermicularis?
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J3 is infective stage and humans become infected by consuming or inhaling contaminated food or water
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What are the medical consequences of infection and what is the most recognizable symptom of Enterobius vermicularis?
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most visible symptom is itching
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How is Enterobius vermicularis diagnosed and why are stool specimens not the preferred choice?
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diagnosed by perianal swab (scotch tape method) - worms only appear at night
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How can infection with Enterobius vermicularis infections be prevented?
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good hygiene; drug therapy for entire family
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What are typical drugs used to treat intestinal nematode infections?
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mebendazole and ivermectin are very common treatment
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What is the normal definitive host of Gnathostoma spinigerum?
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not on test
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What other hosts normally occur in the life cycle of Gnathostoma spinigerum?
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not on test
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How do humans become infected and what are the medical consequences of of Gnathostoma spinigerum infection?
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not on test
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What is the medical condition called (infection with Gnathostoma spinigerum)?
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not on test
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In what part of the world does the Gnathostoma spinigerum parasite occur?
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not on test
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How are human infections with Gnathostoma spinigerum treated?
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not on test
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How do humans become infected with Gongylonema ingluvicola and what are the medical consequences?
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not on test
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Describe the life cycle of Dracunculus medinensis.
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adult female in subcutaneous tissues migrates to dermis and release J1s to form blister, water contact ruptures blister releasing J1s in water where they are ingested by cyclops (crustacean) and penetrate the gut of the Cyclops then move to hemocoel (crustacean blood), undergoes 2 molts and forms J3s in hemocoel which are digested by definitive host and end up in intestine
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How does the female worm release her progeny to the outside in Dracunculus medinensis?
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blister ruptures on contact with water
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How do humans become infected with Dracunculus medinensis?
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drinking water contaminated with infected copepods
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Does fecal contamination play any role in the Dracunculus medinensis life cycle?
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no
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Are there are reservoir hosts in Dracunculus medinensis?
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dogs and cattle
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In what parts of the world does Dracunculus medinensis occur?
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found in Africa and the Middle Eastern countries (ponds) and India and Parkistan (step wells)
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What are the medical consequences of infection with D. medinensis?
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allergic reaction during blister formation
skin ulcer with secondary infections death of adult worms in joints produce arthritis or spinal cord paralysis may produce prolonged debilitation |
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How is the D. medinensis infection treated?
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treated by winding worm out on a stick or by surgery
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How can D. medinensis infection be prevented?
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prevent contamination of drinking water; kill the copepods with insecticide
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Describe the life cycle of Wucheraria bancrofti.
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adults reside in lymphatic ducts of human and produce microfiliae in blood, ingested by mosquito (lose sheath) and produce microfiliarial in mosquito gut, these penetrate gut and migrate to flight muscles where they become J3s (infective) and migrate to proboscis and enter human by bite wound
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What is a microfilaria (Wucheraria bancrofti)?
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produced by females as offspring
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What is the intermediate host in Wucheraria bancrofti?
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mosquito
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Where does the Wucheraria bancrofti parasite occur?
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found worldwide, especially in the tropics
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Are there any reservoir hosts in Wucheraria bancrofti parasite life cycle?
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no reservoir hosts
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What is meant by the "periodic strain" of W. brancrofti?
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shows nocturnal periodicity (found in blood only at night)
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What pathology is caused by microfilariae in the W. bancrofti parasite?
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bancroftian filariasis
microfilariae and adults |
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What pathology is caused by adult worms in W. bancrofti?
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inflammatory response around lymph vessels; damaging lymph vessels; painful lymphatic chills and fecer (lymphedema); blockage of lymph vessels result in elephantiasis, chyluria (lymph in urine) and disappearance of microfilaremia)
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What is the immunological mechanism for this pathology in W. bancrofti?
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immune system response eleminated Juvenile parasite
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What are the methods of diagnosis, treatment and control of W. bancrofti?
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diagnosis: microfilariae in peripheral blood smear
treatment: diethylcarbamizine (DEC) or surgery control: mosquito control and mass chemotherapy |
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What is the main difference between W. bandrofti and Brugia malayi?
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Brugia malayi is found only in SE Asia and the pathology is the same except there is no nocturnal periodicity in Brugia malayi
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How does Onchocerca volvulis differ from Wucheraria bancrofti in terms of adult location, microfilaria location and vector?
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Adult worms in Onchocerca volvulis are pretty benign, located in subcutaneous nodules and produce microfiliarae in the dermis which are taken up by the blackfly when biting host
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What pathology is caused by adult worms in Onchocerca volvulis, and what pathology is caused by microfilariae?
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adult worms are pretty benign but cause subcutaneous nodules at bite site and may also cause elephantiasis
microfilariae present no problem if alive but if dead cause severe inflammation of skin and eye; dermatitis, intense itching, blindness |
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Where do the adults develop in Onchocerca volvulis?
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adults develop in cutaneous nodules
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How is the Onchocerca infection diagnosed?
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skin snip (biopsy)
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In what part of the world does Onchocerciasis occur?
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most severe in Africa and Central America
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In Africa, what regions show the greatest severity of the disease Onchocerciasis?
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Blindness occurs by age 40 in Africa, age 20 in Central America
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Why does Onchocerca volvulis occur close to rivers and streams?
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these locations are where the blackfly larvae develops
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How is Onchocerca volvulis treated?
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treated with DEC which kills microfiliariae and causing anaphylaxis (not a good option)
Ivermectin suppresses release of the microfiliarae without anaphylaxis removal of adult worms by surgery |
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What drug has revolutionized treatment of onchocerciasis?
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Ivermectin
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What are the strategies for control of onchocerciasis in Africa?
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mass chemotherapy
insecticide treatment of water |
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Are there any reservoir hosts in onchocerciasis?
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no reservoir hosts
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How does Loa loa differ from Onchocerca volvulis in terms of adult location, microfilarial location, vector, and development within the vector?
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Loa loa adults wander in subcutaneous tissue (not nodules); microfilariae in blood, vector is deer fly, parasite develops in fat body instead of flight muscles
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What medical condition results from infection with L. loa and what is the pathological mechanism?
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hypersensitivity to wandering worms cause calabar swelling; migration of adult worms into the cornea
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In what part of the world do infections of L. loa occur?
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infections found in W. Africa and the Sudan
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Are there any reservoir hosts in the L. Loa life cycle?
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no reservoir host
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How is infection with L. loa treated?
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treated with surgical removal of adults and microfilariae with DEC, Ivermectin
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What is the strategy for control of the L. loa infection?
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control not feasible
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What is the normal definitive host(s) for Dirofilaria immitis, and where in the definitive host does the adult develop?
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dogs; adult develops in the pulmonary artery and right ventricle of the heart
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What is the vector, and where in the vector does larval development to the infective stage occur with Dirofilaria immitis?
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vector is night biting mosquito
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What harmful effects occur in dogs or humans infected with D. immitis?
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can cause pulmonary inflammation and heart failure in dogs; in humans causes lung granulomas
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How is D. immitis infection prevented in dogs?
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Ivermectin or DEC
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Why is treatment of heavy infections in dogs a problem with D. immitis?
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often fatal doses of medication required to kill pararsites
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