Nematoda Flashcards
what newly classified group does nematodes belong to and why
Ecdysozoa
Three layer cuticle and they molt when they grow (ecdysis)
Nematodes are the first group that can be terrestrial. They are also parasitic. Where are they very abundant in?
soil
What do nematodes possess that flatworms dont ?
Body cavity
between single mesodermal layer and endoderm.Called pseudocoelom
Full of liquid and the pressure supports muscle; hydrostatic skeleton
Why doesnt nematodes need scolex for attachment?
They are MOTILE so they dont need to attach to small intestine to move.
They use peristalsis from oesophagus action to force them down
Structure of nematodes
lips=touch and sense
acellular cuticle layer
2 openings of digestive tract: mouth and anus
Excretory system – two lateral ducts that run longitudinally down either side of the body
Nervous system: dorsal and ventral nerve cords
No circulation or respiratory system so no filtration of blood
Separate sexes: fem bigger than male. Male has coiled posterior end
Are nematodes protosomes or deuterosomes
Protosomes
Difference between protosomes and deuterosomes
protosomes: blastophere becomes mouth first then anus develops
deuterosomes: blastophere becomes anus then mouth develops
humans are deuterosomes
what are soil transmitted nematodes called
geohelminths
adult geohelminths are anaerobic but larval stage aerobic
intestinal paarasites
infection through fecal contamination of soil or food, water
no intermediate host
Ascaris lumbricoides are the largest intestinal nematodes. What size can they get to
female: 40cm
male:15-30cm
Why is the nematode Ascaris lumbricoides important
most common human helminthic infection
can be spread in europe
*this and eccinhoccus granulosas endemic to this region
diagnostic stage of ascariasis
eggs in faeces
Life cycle Ascaris lumbricoides
- eggs released in faeces
- larvae forms in soil. Another host injests eggs
- larave hatches in small intestine but it needs oxygen
- It goes to lungs and grows there
- Goes along bronchial tree to oesophagus and is swallowed
- develops into adult worm in small intestine
Name some geohelminths
Ascaris lumbricoides
Trichiurus trichiura (whipworm)
Strongyloides stercoralis
Ancylostoma duodenale (hookworm)
Enterobius vernicularis (pinworm)
Why cant you cant get autoinfection from Ascaris lumbricoides
after ingestion of eggs, 2-3 months required for new egg production
Life cycle of Trichiurus trichiura (whipworm)
- eggs shed from human faeces to soil
- eggs become embryonated after 2-3 weeks
- Human injests eggs and hatch in small intestine (growth and molting here) Infective larvae penetrate villi
- Young worms penetrate the mucosa of cecum (large int) Develops into worms
- injestion to maturity=3 months
NO AUTOINFECTION
2 stages of Strongyloides stercoralis in its life cycle
parasitic stage in human
free living stages in soil
Life cycle of Strongyloides stercoralis
FREE LIVING:
* Rhabditiform larvae in the intestine are excreted in stool
- Develops into free living adult worms (male and fem)
- eggs are produced by fertilized female worms. Rhabdidiform larvae hatch
- Rhabditiform develop into filariform
PARASITIC:
* If infective filariform larvae penetrate skin, it migrates to small intestine to become adults
- Develops into parasitic FEMALE worms. Lays eggs in intestinal mucosa
*Rhabdidtiform larvae hatch and migrate to intestinal lumen
AUTOINFECTION: rhabditiform in large intestine become filariform, penetrate intestinal mucosa + migrate
which nematode is the old world hookworm
Ancylostoma duodenale
How big are the males and the females in A.duodenale
fem: 13 mm
male:11mm
whats the infective stage of S.stercoralis
larvae passed in stoop
NOT EGG IN FAECES
life cycle of Ancylostoma duodenale (anaemia)
- eggs passed in poo, Rhabditform larvae hatch
- they grow in feces/soil and develop into infective filariform larvae
*Penetrates skin, carried through blood vessels
- Ascend bronchial tree and pharynx then swallowed
- larvae matures in small intestine
- attach to intestinal wall sucks blood, caises ANEMIA
what can hookworms cause in children in the tropics
chronic anemia and stunts growth
How large are Enterobius vernicularis (pinworm)
fem:13mm
male: 5mm
Can E.vernicularis cause autoinfection
yes because they are small and can lay eggs outside the body (around anus) can eat them from hands.
Also eggs injested from contaminated surfaces
Life cycle of Enterobius vernicularis
- Eggs deposited on perianal folds
- infection occurs by transferring infected eggs into mouth
- Larvae hatches in small intestine
- adults develop in the colon
- Gravid females migrate outside of anus at NIGHT and lay eggs
- larvae develop in 4-6 hours
how do female E. vernivularis lay their eggs
Produces GLUE to adhere the eggs around anus
What is the diagnostic and infective stage of E.vernicularis
Both the same
Eggs
BUT NOT IN FAECES ITS AROUND ANUS
which region is E.vernicularis most common
high sanitation areas
name the non geohelminth nematodes and which ones are filarian (transmitted by blood sucking insects)/ tissue ( not by insects)
T. trichinella spiralis
T. dracunculus medinesis
F. wuchereria bancrofti
F. loa loa
F. onchocera volvulus
Trichinella spiralis length and infective stage
F= 2mm m= 1mm
infective = larve NO EGGS
Trichinella spiralis life cycle
- Ingesting undercooked meat with encysting larvae
- larvae released from cysts + invade intestinal mucosa + develop into worms
- females release larvae that move to straited muscle and encyst.
- adult worms and larvae develop in the same host so new host is needed to start a new cycle. resovoir hosts = rodents
what does the larvae do in Trichinella spiralis
modifies areas of skeletal muscle cells and turn them into nurse cells
Dracunculus medinesis (guinea worm) length and infective stage
f = 80cm m= 4cm
infective stage = copepods (int host) + larvae
Dracunculus medinesis life cycle
- Humans infected by drinking water with copepods infected with larvae/ eating fish with the infected copepods
- larvae penetrates the hosts stomach + intestinal wall
- after developing to adults and copulation, male worms die
- females migrate towards skin surface
- 1 year after maturation, the f worms makes blister on skin (foot)
- Blister ruptures when contact with water, worm emerges + release larvae
- if ingested by copepod, later it develops into infective larvae
how to cure Dracunculus medinesis
no vaccine for dracunculiasis but filtering h20 is a prevention
Wuchereria bancrofti (thread like worm) length
f = 10cm m= 4cm
Wuchereria bancrofti infective stage and int host
int host = culex mosquito
infective stage = larvae
Wuchereria bancrofti life cycle (mosqs)
- During blood meal, infected mosquito introduces filarial larvae onto human skin
- larvae penetrates wound + develops into aadult and live in lymphatics
- they produce microfilariae + they migrate into lymph + blood channels.
- daytime - larvae live in deep seated blood vessels
nighttime - they migrate to peripheral blood vessels ( to be
available for mosqs) - fem mosqs ingest microfilariae after biting
- microfilariae develop to 1st stage larvae then 3rd stage infective
** parasite DOESNT MULTIPLY in mosquito
what disease does Wuchereria bancrofti cause and its symptoms
Lymphatic filariasis (elephatiasis)
develop swollen legs/arms
Loa Loa (eye worm) length
f= 70mm m= 34mm
Loa Loa int host and infective stage
int host = deer fly (chrysops)
infective = microfilariae/filarial larvae
Loa Loa life cycle (deerfly)
- female births living microfilariae inside skin
- microfilariae travels in blood during the day, nighttime they live in the lungs
- When deerfly takes blood meal from infected human, it ingests microfilariae
- mf lose their sheaths + develop into 1st then 3rd stage filarial larvae.
- larvae invades another person during next blood meal
- 3rd stage larvae transferred from flys mouth to human skin. burrows into wound + enters subcutaneous layer and matures
Onchocera volvulus length
f = 5cm m = 3cm
Onchocera volvulus int host and infective stage
int host = Blackfly
infective stage = filarial larvae
Onchocera volvulus life cycle
- Blackfly takes blood meal + introduces 3rd stage larvae to skin. they penetrate wound
- in subcutaneous tissues, larvae develops to adult microfilariae
- lives in connective tissues (up to 15 years)
- Blackfly ingests microfilariae during another meal
- Develops to 1st then 3rd stage infective larvae + can infect another person
What is condition called if human is accidental host of foreign nematode (non human nematode)
Larva Migrans
Cutaneous or visceral
What is cutaneous migration
Humans acquire filariform through penetration of skin
migration to human connective tissue but larvae cannot become adults worms therefore die
What is visceral migrating larva?
human swallow eggs of foreign nematode
migrate to small intestine and die in liver/lung
Example: Toxocara canis
Nematodes are often species specific, which nematode is non species specific
Trichinella spiralis
How can humans acquire the parasite trichinella spiralis
cycle is completed in 1 host
Can only get parasite if you eat raw infected meat of previous host
humans kind of dead end for parasite as nothing really eats humans
Trichinella spiralis realeses what in small intestine if female already releaes eggs in uterus?
larvae
Which parasite known as guinea worm
Dracunculus medinenis
which is the longest nematode ever
Dracunculus medinenis
fem: 120cm
male: 4cm
how does primary host (human) acquire Dracunculus medinenis
drink contaminated water with copepods
How does the Dracunculus come out
female needs to liberate larva
comes out from foot by blister after a year
What condition does Wuchereria bancrofti cause
Elephantiasis (swollen leg)
Why does Wuchereria bancrofti cause swelling
adult worms die in lymph nodes
causes blockage of lymphatic system
what is the swelling called when Loa loa migrates to subcutaneous layer
Calbar swelling
what is the difference between pseudocoelom and coelom
pseudo: between mesoderm and endoderm layers
coelom: 2 mesoderm layers
Structure of adult and egg of Trichocephalus trichiurus
adult: fem bigger and longer than male. male has coiled end. 2 openings of mouth and anus, excretory and nervous system, pseudcoelom
egg: lemon shaped
