Phylum Nemathelminthes Flashcards
Class Nematoda
Roundworms Biohelminths - Trichinella spiralis -Enterobius vermicularis Geohelminths - Ascaris Lumbricoides - Trichuris trichuira
Trichinella spiralis - Morphology
Only non oviparous nematode (lay egg w/ little development) - vivparous female (living larvae instead of eggs)
Adult worms - minute and slender
F - up to 3 mm x 0.06m wide, slender ant nonpaillated mouth, post end cluntly rounded w/ sg ovary w/ vulva in ant 5th, long narrow digestive tract, viviparous and discharge larva instead of eggs
M - 1.5 mm x 0.04mm, slender ant nonpaillated mouth, post end ventrally curved w/ 2 caudal appendages (clasping papillae) on eitherside of cloacal orifice, long narrow digestive tract
The anterior part is filled with the stichocytes
Larvae - encysted w/i the muscle fibers are 1mm l x 36um d. Larva in cycst = coiled. stichocytes in the anterior part of body.
Cyst - 400x250um, +
Trichinella spiralis - Life cycle
Host - same intermediate and final host, all vertebrae who eat meat but major reservoir is swine
1 - infection mainly hrough poor cooked pork > larvae ingested > excyst in stomach + duodenum
2 - released in upper SI > invade (4 larval stage on 2nd day of infection)
3 - intestinal mucosa: develop into adult > m fertilize f [ male dies after mating]
4 - carried out of intestine (Lifespan here is 6 weeks), live intracellularly w/i superficial enterocytes
5 - F grow > produce larvae > deposit in mucosa/lymph vessel > thoracic duct > blood
6 - pass hepatic and pulmonary filters > larvae burrow into muscle all over (only encyst in striated muscle)
7 - larvae develop and liberated w/i 4-16 W
8 - develop into m + f worms > produce larvae
Trichinella spiralis - Disease
Trichinosis aka Trichinellosis
Intestinal phase - 1-7d = asymptomatic but sometimes D+V, consitpation, pain etc
Muscle phase - myalgia, palpabral oedema, eosinophilia, fever, myocarditis, meningitis, brochonpneumonia
Diagnosis - muscle biopsy, detect larvae in blood/CSF?stool, ELISA
Treatment - Thiabendazol
Prevent - cook meat thoroughly, inspect pigs
Enterobius vermicularis - Morphology
AKA pin worm - sm white worm, thread like appearance,
Adult - short white fusiform w/ pointed tail, mouth have 3cervical alae (cuticular expansions - transversly striated). DOuble bulb oesophagus
F - 8-13mm l, long point tail. Vulva infront of mid 1/3 of body > sg vagina > paired uteri > oviducts >ovaries. uteri of gravid female distended w/ eggs, oviparous
M - 2-5mm, tail curled ventrally, suprominent copulatory spicule
Eggs - translucent, non bile stained. oval, convex one side & flattened on one side. Outer albuminous layer ( make eggs sticky), contains tadpole shaped coiled embryo (fully formed) 50-60 ㎛ x 20-30 µm wide.
Enterobius vermicularis - Life cycle
Host - human only (monoxenous), common in children
Mode of infection
Fecal-oral route
autoinfection - eggs infective as soon as passed out of f worm > if hand contaminated > reinfect (maybe through itch anus)
Retroinfection - hatched larvae on perianal ski migrate to anus > worms
Aerosol inhalation - contaminated sheets/dusts
Life cycle
Entirely in lumen of GIT
lifespan of the adult worm around 2m
1 - Ingest eggs (infective stage w/i hours)
2 - eggs hatch in SI + molt 2x in jejunum and upper ileum
3 - larvae migrate to LI > mature (esp cecum or terminal ileum)
4 - copulation in terminal ileum (male dies after this)
5 - gravid female migrate nocturnally through anus and deposit eggs on perianal folds [oviposition] - fully infective w/i hours of deposition.
6 - Autotransmission + Transmission between hosts when another handles or touches contaminated items
Can persist outside of the host for several weeks if the environmental conditions allow
Enterobius vermicularis - Disease
Enterobiasis
Symptoms - mainly assymptomatic, perineal/perianal pruritus ( nocturnal mild itching pain), bacterial infection from scratching, may abstruct appendix > appendicitis
Diagnosis -
Eggs in stool
Perianal swab - look for eggs
Treatment
Mebendazole
Ascaris lumbricodes - Morphology
common name = round worm
Lumbricodi
Pink/white worm
Adult - lrg cylindrical w/ tapering ends, ant mouth has 3 finely toothed tips (1 dorsal, 2 venterlat)
F - 20-40cm, post= straight+conical, vulva mid ventrally near jct of ant + mid 3rds of body, vulvar waist (genital girdle) appear as groove surround worm at vulvar opening level). Vulva > sg vagina > branch into genital tubules (covuluted through post 2/3 body0
M - 15-30cm, post end curved ventrally to form hook + 2 copulatory spicules
Eggs -
fertilized; always bile stained, embryonated round-oval, tan coloured surrounded by a thick albuminous mamillated (lumpy) outer coat,
-> develop into infective eggs
unfertilized; laid by unisem f, non-embryonated + can’t become infective, elliptical shape, narrower + longer, thinner shell w/ irreg albumin coating, contain sm atrophied ovum w/ disorganized granules
Larvae
Ascaris lumbricoides -Lifecycle
Host - Man, no intermediate, live in lumen of SI
Infective stage + modes of Infection - egg w/ larva ingested w/ contaminated vegetable
1 - Ingest embryonated (2nd stage larva) eggs
2 - hatch in duodenum,
3 - larvae penetrate intestinal walls + circulate in blood + lymph
4 - -> liver, heart, lungs (infiltrate alveoli)
5- ascend to trachea > decend to oesophagus > reach sm I to develop into adults
6 - -> through intestine -> lay eggs around 200,00 eggs per day (unfertilized/fertilized 1 cell stage)> leave in feces
7 - develop into infective 2nd stage larva (10-14 days)
Ascaris lumbricoides -Disease
Ascariasis
Mainly assymp and usually related to larval migration stage/manifest as pullmonary disease
Symptoms relation of larvae conc, some develop allergic reactions, bado pain, intestinal obstruction (esp children)
Diagnosis
stool examination for eggs
Treatment Mebendazole, albendazole, piperazine
Trichuris trichiura - Morphology
Whipworm
Life span 5-10 yrs
Adult - m = 30-45mm, f - 40-50mm, flesh coloured, whip shape, ant 3/5 thin+ thread like, post 2/5 thick + fleshy (whip handle), ant portion cotain capillary oesophagus, post contain intestine and sg set repro organs
F = post end straight, blunt + rounded
M = post enf coiled ventrally, spicules
Eggs
lemon shaped, brown bile stained, 3x shell (outermost stained brown), mucus plug at each pole w/ unsegmented ovum (colourless), fetilized f lay 50,000 egg/day
Infective form = Embryonated egg w/
=rhabditiform larva (eggs develop in soil)
Trichuris trichiura - life cycle
Host - human only , lrg intestine - habitat
1 - 1 cell eggs passed w/ stool and develop in soil > 2 cell stage > advanced cleavage stage in ext environment (3 W) > embryonated (infectious stage)
2- Ingested by human (soil contam hands/food) > hatch in SI
3 - larvae migrate to LI . > mature (adolescent in 3-10 D) > caecum (survive here 4-6 yrs). Spear line projection anteriorly help embed in intestinal mucosa (supply nutrietnts)
4 - Mate > f lay immature eggs which are passed w/ stool
Trichuris trichiura - Disease
Trichuriasis (whipworm infection)
Symptoms - mostly assymptomatic, if worm load heavy sometimes dystentry (blood, mucus in stool w/ tenesmus), abdo pain, children often exp weight loss, anaemia from mucosal cleeding, chronic inflammation, rectal prolapse possible
Diagnosis -
Find characterist egg in stool
Treatment
Albendazole, mebendazole
