ParasitologyTest4IntestinalNematodes

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  1. T. trichiura - common name, size, normal location, distinctive physical attributes (digestive tract, reproductive info)
    • whipworms (threadlike, but become thcik at posterior end)
    • size: females 30-50mm, males slightly smaller
    • location: adults live in large intestine and rectum of many mammals
    • digestive tract: mouth has simple opening, no lipssmall buccal cavity
    • esophagus is long (2/3 body length)
    • anus near tip of tail
    • reproduction: both sexes have SINGLE gonad
    • males - 1 spicule surrounded by spicule sheath
    • uterus - contains many unembyronated lemon-shaped eggs
    • eggs have two polar plugs
    • 5k-10k eggs produced per day (passed in feces)
  2. T. trichiura - egg embryonation info, human infection info, lifespan
    • eggs embryonate in 3-6 weeks (moist, warm, shady soil)
    • infection from ingesting embryonated eggs (salad, vegetables, children eating soil)
    • larvae hatches in small intestine
    • becomes adult in caecum
    • adults live for several years (large numbers may accumulate)
  3. T. trichiura - conditions that facilitate heavy population (and then infection)
    • Poor sanitation (human feces deposited on soil)
    • environment that facilitates their development (warm, humid, moist soil, shade)
  4. T. trichiura - geography, commonality in US, most commonly infected, threshold for symptoms
    • geography: global, especially tropical areas
    • 2nd most common infective nematode in US (#1 is pinworm)
    • children are most commonly infected
    • <100 worms rarely cause symptoms
  5. T. trichiura - symptoms
    • Symptoms: (heavy infections)
    • worms burrow inside mucosa (consume RBCs)
    • trauma to intestinal epithelium and submucosa (anemia and bloody stool)
    • abdominal pain, insomnia, vomiting, weight loss, nausea
    • retarded growth (due to malnutrition) in children
    • rectum prolapse
  6. T. trichiura - Easy way to differentiate males from females
    • Males have highly hooked tails (thicker portion)
    • females are straight
  7. T. trichiura - diagnosis, treatment, prevention/control
    • Diagnosis: finding worm or egg in stool
    • *NOTE - unique egg (polar plugs)
    • Treatment: difficult to treat w/ oral drugs (located in caecum, appendix, lower intestine)
    • Albendazole and mebendazole are drugs of choice
    • prevention: thorough washing of salad vegetables
    • training of children and adults in sanitary disposal of feces and washing of hands are necessary to prevent and control infection
  8. Name the intestinal nematodes w/ common name
    • Trichuris trichiura (whipworm)
    • Trichinella spiralis (trichinosis)
    • Necator americanus (hookworm)
    • Ancylostoma duodenale (hookworm)
    • Ascaris lumbricoides (large intestinal roundworm)
    • Enterobius vermicularis (pinworm)
  9. Trichinella spiralis - size, unique structures, digestive tract, reproductive info
    • *note - one of the most widespread and clinically important parasite
    • smallest nematode (human infecting)
    • males measure 1.5x.04mm
    • taper at anterior end 
    • Anus is nearly terminal
    • alae: large papilla at each side of anus
    • stichocytes: unicellular glands that encircle the esophagus
    • copulatory spicule is absent
    • tests in posterior 1/3 of body
    • vulva located near middle of esophagus (1/3 length of body)
    • Uterus filled with developing eggs (posterior end)... fully developed, hatching juveniles (anterior end)
    • *NOTE - DO NOT LAY EGGS (ovoviviparous)
  10. T. spiralis - cause of infection, life cycle in humans
    • *NOTE - same animal is both definitive AND intermediate host (diff organs)
    • infection: consumption of poorly cooked pork (infected with larvae)
    • excapusulate in small intestine
    • rapidly molt 4 times
    • enter intestinal mucosa
    • copulation occurs 24-30 hours after infection
    • males die shortly after copulation
    • females die after 9-16wks (~1500 juveniles produced)
    • juveniles are transported through body via hepatoportal system -> heart -> lungs -> arteries
    • *NOTE - they can end up in ANY tissue in body
    • tend to stop in striated muscle (diaphragm, jaws, eyes, tongue, etc)
    • abosorbs nutrients from host muscle
    • after ~3 months becomes encysted (nurse cell)
  11. T. spiralis - normal # infection, common sites of infection, calcification process
    • 1 worm per cyst is most common, up to seven have been seen
    • Most susceptible muscles - muscles of eye, tongue, jaw, diaphragm, and arms/legs
    • Calficiation occurs after ~1 year (host rxn)
    • *note these calcified cysts are what led to its discovery by James Paget (medical student)
  12. T. spiralis - describe infection of nonhuman animal, sylvatic trichinosis, urban trichinosis
    • infection occurs when muscle harboring the encapsulated larvae is eaten (larvae excysts)
    • most mammals are susceptible
    • sylvatic trichinosis: wild carnivores and prey (bears, foxes, raccoons)
    • Eskimos, indians, and those who feast on wild carnivores most frequently infected
    • Urban trichinosis: humans, rats, and pigs (triangle)
    • rats cannibalize, pigs eats rats, humans eat pigs
    • more important to humans
  13. T. spiralis - why is it especially important to cook meat?
    • heavily infected pork may contain >100,000 juveniles/oz
    • *NOTE - if half of them produce 1500 offspring, a single bit could contain 1.5million juveniles!!!!!
    • Tasting for flavor, raw sausage are major issues
  14. T. spiralis - worldwide prevalence
    • Occurs worldwide
    • widespread in Eastern Europe (4% in Poland)
    • Arctic region (Eskimos) (50% prevalence)
    • Relgious bans keep jews, hindus, and muslims disease free!
    • Vegetarians suffer from trichinosis
    • 150k-300k cases every year in US (most asymptomatic)
  15. T. spiralis - pathogensis
    • 3 stages
    • 1: mild, during penetration of adult females into mucosa
    • gravid females cause damage to host tissue (intestinal inflammation, pain, and symptoms of food poisonin)
    • respiratory difficulties may occur
    • facial edema
    • 2: severe during migration of juveniles (primary symptoms)
    • juveniles damage blood vessels, cause pneumonia, pleurisy, encephalitis, meningitis, nephritis, deafness, blindness
    • death (myocarditis) may occur at this stage
    • 3: moderate during penetration and encystment in muscle cells
    • intense muscular pain
    • breathing, circulatory, excretory, and nervous disorders
    • *NOTE - death caused by heart and kidney failure, respiratory complications
  16. T. spiralis - diagnosis, treatment, prevention/control
    • Diagnosis: muscle biopsy
    • immunological tests
    • xenodiagnosis
    • treatment: no treatment (management of symptoms)
    • mebendazole (muscle larvae) and pyrantel pamoate (adult worm)
    • prevention: very difficult to control, despite research
    • public education is best method
    • head meat above 60C
    • do not feed uncooked waste to pigs!!!!
  17. hookworms - why called hookworms, number of infected, intensity of infection, major problems caused by infection (symptoms)
    • called hookworms because anterior end is bent dorsally (looks like a fishhook)
    • ~500 million have hookworms
    • 1/4 have A. d.
    • 3/4 N. a.
    • one of the most widespread parasites
    • daily blood loss estimated as equivalent of 2million individuals
    • hookworms are intense bloodsuckers (feed on blood and tissue fluids in intestine)
    • this leaves patients weak, short of breath, showing physical exhaustion
  18. hookworms - digestive tract info, reproductive info
    • digestive: buccal cavity containing heavily chitinous ventral teeth and cutting plates
    • espohagus is stout and muscular (club shaped)
    • reproductive: males have single testis
    • umbrella-shaped copulatory bursa (envelopes vulva and anchors female during copulations)
    • females have simple, conical tail
    • females are didelphic
    • ~1000 eggs per day for as long as 9 years
  19. hookworms - two important species and general location
    • Ancylostoma duodenale (old world)
    • Necator americanus (new world)
  20. Describe experiment from Arthur Loss w/ Ancylostoma
    • accidentally spilled culture onto hand
    • noticed redness/swelling
    • after a few weeks saw eggs in feces
    • placed eggs on Egyptian boy's leg (to be amputated)
    • saw juveniles penetrating the skin
  21. What are the differences between A. duodenale and N. americanus (size, morphology, eggs, hosts, geography)
    • size: A. duodenale are slighly larger
    • vulva location: posterior 1/3 in A. d. | anterior 1/2 in N. a.
    • Buccal capsule: A. d. has 2 pairs of teeth on ventral wall | N. a. pair of dorsal and ventral cutting plates
    • Eggs: hard to distinguish, N. a. are slightly larger
    • hosts: dogs may also serve as host in N. a.
    • 500 million infected; 1/4 by A. d. (Asia, Europe, N. Africa, India) | 3/4 N. a. (America, Africa)
  22. Hoookworm - describe life cycle/ infection
    • mature and mate in host small intestine
    • embryos are several-cell staged by the time they are passed with feces
    • eggs require warmth, shade, organic environment, and moisture for further development)
    • Rhabditiform larvae hatch from shell, become L2 then L3
    • L3 is non-feeding filariform (infective stage)
    • filariform can survive in soil for 6wks, move to surface and extend during periods of rain/dew
    • infection occurs when the filariform larvae contact vertebrate skin (esp feet, legs, hands, buttocks)
    • migration in human: skin -> lymphatic system -> lungs (via heart and pulmonary circ) -> alveoli -> glottis -> cough up -> swallowed -> small intestine
    • attach to mucosa, grow, and become L4 (and then adult) in small intestine
  23. hookworm - 4 factors that lead to infection
    • shaded sandy/loamy soil
    • moisture
    • poor sanitation
    • contact with contaminated soil
  24. hookworm - epidemiology (stages of disease)
    • invasive: penetration of skin
    • slight hemorrhage and swelling 
    • intense itching (ground itch)
    • potential for introduced bacteria
    • pulmonary: during migration through the lungs
    • 2-4 weeks after entry
    • damage to lung tissues
    • burning sensation, dry cough
    • symptoms mirror pneumonia
    • intestinal phase: rapid maturation of juveniles in small intestine, invasion of tissues
    • *NOTE - most important period
    • change attachment sites often, causing massive blood loss
    • results in anemia, abdominal pain, loss of appetite, desire to eat soil, chronic malnutrition (permanent damage)
  25. hookwork - diagnosis, treatment, control/prevention
    • diagnosis: demonstration of hookworm eggs/worms (fecal smear on filter paper)
    • treatment: mebendazole + iron therapy (anemia)
    • Prevention: wearing shoes, washing salad vegetables
    • control: increase in sanity conditions, chemotherapeutic campaigns, proper elimination of dog feces (N. a.)
  26. What are creeping eruptions?
    • AKA cutaneous larval migrans
    • caused by invasion of non-human spp of hookworm
    • nearly identical to swimmer's itch
  27. A. lumbricoides - size, history, mophology, digestive tract info, reproductive info, location in host
    • *NOTE - this is the "mass exodus" one
    • Very large (>18")
    • may have been first parasite known to humans (Greek and Roman writing)
    • digestive tract info: 3 prominent lips
    • distinct lateral lines
    • reproductive: males are 26cm w/ ventrally curved posterior end and bluntly pointed tail
    • spicules are 3mm long, no alae
    • females are 40cm w/ straight posterior end
    • repr system lies in posterior 2/3 of body, vulva is 1/3 body length from anterior end
    • ovaries are extensive
    • uterus may contain >27 million eggs at a time, 200,000 laid per day
    • adults reside in lumen of small intestine, feed on semi-digested food (not blood)
  28. A. lumbricoides - life cycle
    • Fertilized eggs (ovalish w/ lumpy uterine layer)
    • *NOTE - uterine layer stains brown thanks to shiiiiiiiiiiiiiiiiiiiiiit
    • Egg development begins upon reaching soil, 2-3 weeks until L1 (idea conditions)
    • *NOTE - still inside egg
    • eggs highly resistant (low temp, desiccation, strong chemicals)
    • infection occurs when embryonated eggs are swallowed (contaminated food/water)
    • L2 hatch in small intestine -> penetrate mucosa -> lymph/circ system -> live -> right heart -> lungs (all in 1 week)
    • *NOTE - many worms "get lost" and accumulate in various parts of the body
    • in lungs, juveniles molt twice -> rupture pulmonary capillaries -> enter alveoli -> trachea -> epiglottis -> small intestine via coughing/swallowing
    • *NOTE - only L4 will survive gastric environment
  29. A. lumbricoides - why migrate if they end up in same place as start?
    • theory 1: migration simulates an intermediate host
    • theory 2: ancestor was a skin penetrator (L2-L4 developmental necessity)
  30. A. lumbricoides - global distribution,community risk factors, unique egg characteristics, most infected type of person
    • found globally, widespread (epidemic) in tropical and subtropical countries
    • 1 billion infected worldwide!!!! (75% in Asia and Africa)
    • 20-60% prevalence in southern US state (1956-1970)
    • poor sanitation practices (night soil) provide eggs that last for months/years
    • *NOTE - water is not the typical source for transmission
    • Ascaris eggs are highly resistant (formalin, K2Cr2O7, HCl, H2SO4) due to lipid layer
    • egg longevity makes it difficult to control
    • children are most likely to become infected
  31. A. lumbricoides -pathogensis (symptoms)
    • little damage is cause by intestinal penetration of newly-hatched worms
    • dead wandering juveniles cause inflammatory rxn
    • juveniles breaking out of lung capillaries cause hemorrhage
    • Loeffler's pneumonia: heavy infections cause blood to pool + WBC and dead epithelium to collect, making breathing difficult 
    • 85% of infected have minor symptoms and few worms (mean 6)
    • >100 worms result in digestive disorders, blockage of intestines
    • malnutrition common in children
    • Ascaris escape through any opening when in danger
  32. A. lumbricoides - diagnosis, treatment, prevention/control
    • Diagnosis: correct ID of eggs in feces (thick mammilated outer coat)
    • egg counts also help (200,000/female/day)
    • X-rays may reveal Ascaris in heavy infection
    • treatment: no treatment for migrating juveniles
    • Piperazine citrate, albendazole, and mebendazole are effective when density is high
    • intestinal obstruction should be treated with intravenous fluids or surgery
    • prevention: washing of salad vegetables
    • improvement of sanitary conditions
    • proper disposal of feces
    • regular chemotherapy to carriers
  33. E. vermicularis - AKA + reason, morphology of digestive + reproductive, general life cyle style, range of animals found in
    • pinworm or seatworm
    • females typically have slender, sharp pin-like tails
    • all pinworms have prominent muscular bulb on posterior end of esophagus
    • females 11mm, have wing-like alae surrounding mouth
    • males are 3mm, have sharply curved tail
    • direct lifecycle (no intermediate host)
    • common in mammals, birds, reptiles, amphibians (rare in fish, cats, and dogs)
  34. E. vermicularis - location, lifecycle in humans (detailed), important/unique info
    • Adults wander throughout GI tract (stomach to anus)
    • attach to mucosa where they feed on epithelia and bacteria
    • gravid female migrates out of anus at night and lays numerous stick eggs on anal skin
    • *NOTE - eggs are flattened on one side, develop ~6 hours at body temp
    • females die soon after ovideposition, males die after copulation
    • retroinfection: hatched juveniles wander back into anus and into intestine
    • new infection occurs when eggs containing L3 are ingested and hatch in small intestine (eggs usually picked up from clothing, towel, sheets, fingernails, etc)
    • eggs are micrscopic and can also be carried by air (they are everywhere)
    • *NOTE - eggs remain viable in cool, moist conditions for up to a week
    • after ingestion, L2 become adults by the time they reach large intestine (2-6 weeks)
  35. E. vermicularis - symptoms/pathology
    • pruritus: itching/swelling caused by eggs being deposited on skin
    • heavy infections in children result in sleeplessness, weight loss, hyperactivity, grinding of teeth, vomiting, abdominal pain
    • gravid females may migrate into vagina, become trapped in tissues, and produce nodules in uterus
  36. E. vermicularis - how common?
    • One of the most common of ALL parasitic infections in the world (most common nematode in US)
    • often causes group infection
    • extremely common in children
    • 500 million infected worldwide
  37. E. vermicularis - diagnosis, treatment, prevention/control
    • diagnosis: finding eggs or worms (in anus, not feces)
    • heavy infections can be discovered by examining perianus under bright light (sparkling worms)
    • treatment: albendazole and mebendazole
    • Pyrvinium pamoate and piperazine
    • cellophane tape to anus -> glass slide -> negative for 7 days = cured
    • prevention/control: diagnosis and cure are easy, preventing reinfection is difficult
    • personal hygiene is most important (hand washing, laundry in hot water, cleaning of rooms)
    • everyone is household should be treated

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