L15 Helminths Flashcards
what are endoparasites
single celled protozoa
or multiple celled
what are examples of multicellular animals
trematoda (flukes)
cestoda (tapeworms)
nematoda (nematodes_
what are the platyhelminths
flat worms
- tremadtoda
- cestoda
what is the the prevalence of disease and deaths with helminths
not the most deaths but very prevalent
not all just about deaths when it comes to disease
what are the human ‘worm’ parasites
round worms
flat worms
what is the generalised anatomy of nematodes
cuticle - tough outer layer
glycoprotein/glycolipid coverage
what is the cuticle for in nematodes
environmental resistance in free-living relatives
what is the glycoprotein/glycolipid for in nematodes
often immunogenic
where do nematodes mate
generally in the host
how do nematodes mate
they are dioecious - have male and female organs
what is the phylogeny of nematodes
many free-living lineages multiple lineages show parasitism with: - vertebrate - invertebrate - plant significant parasites of man in several line
how are some nematode parasites transmitted by ingestion
ingestion of eggs
eat infected host
ingestion of larvae
ingestion of larvae (in host)
how are nematode parasites - filaria transmitted
mosquito
black fly
deer fly
midge
what are the most direct routes that the nematode parasites infect
ingestion or skin penetration
how long is soil transmitted helminths in the soil until they are infective
3-4 weeks
how does soil transmitted helminths infect
via eggs in contaminated soil or skin penetration
examples of soil transmitted helminths that infect via contaminated soil
ascaris
trichuris
examples of soil transmitted helminths that infect via skin penetration
hookworm
what is the environment soil transmitted helminths require
warm wet
where are soil transmitted diseases the biggest burden
poverty
poor sanitation
how does trichuris infect
direct
what is the lifecycle of trichuris
infected
live in gut and expelled as eggs
into soil and taken back up
what is the adult habitat of trichuris
caecum, colorectum
what is the lifespan of trichuris
1-3 years
what does trichuris infection cause
90% asymptomatic
what is ascaris lumbricoides known as
giant roundworm
what is trichuris trichiura known as
whipworm
what is the lifecycle of ascaris
eggs ingested
larvae escape from intestine
in bloodstream go to liver then heart then lungs
escape into alveolae
migrate up trachea
brought up in mucus and then swallowed again = back to intestine where adults made
how many eggs do ascaris lay a day
200,000
when is the ascaris associated with pathology
migration and adult ascaris
what do the larvae of ascaris cause
eosinophilia
pneumonitis
what do the adults of ascaris cause
malnutrition
small bowel obstruction
wandering Ascaris: biliary tract obstruction, pancreatitis, liver abscess
what is the effect of acaris
high killing - high morbidity
what is necator americanus known as
new world hookworm
how do hookworms gain access into the host
larvae in soil climb vegetation, sense warm blooded animals, attach to skin and burrow through skin into blood stream
how much blood do hookworms take a day
30-200ul
what do hookworms cause
intestinal blood loss
iron deficiency - anaemia
where do adult hookworms live
small intestine
what do adult hookworms do
attach to intestine wall & take blood
hookworm lifecycle
burrow into skin migration via lungs larvae migrate to trachea swallowed adults in small intestine eggs in faeces
what is different about the hookworm lifecycle
double route
what are wuchereia bancrofti known as
filarial roundworm
what is the vector of wuchereia bancrofti
mosquitos
what are the hosts of wuchereia bancrofti
humans
what are the hosts of necator americanus
humans
what is the transmission of necator americanus
skin penetration
what are the hosts of ascaris lumbricoides
human
what are the hosts of trichuris trichirua
human
what is the transmission of trichuris trichirua
ingestion of eggs
what is the filarial lifecycle
transmitted by biting fly
adults migrate to lymphatics (Brugia, Wuchereria)
or develop in skin
mate and produce live young (microfilariae) – circulate in blood
what is the mortality like of lymphatic filariasis and onchocerciasis
low
what is the morbidity like of lymphatic filariasis and onchocerciasis
high
what are the human parasites of platyhelminths
digenea - trematoda
eucestoda - cestoda
what is the lineage of platyhelminths
largely free living group
what is the lineage of neodermata
entirely parasitic lineage
what is the generalised morphology of platyhelminths - trematoda
attachment structures
digestive sac
tegument
what is the generalised morphology of platyhelminths - cestoda
attachment structures
what is the tegument function for the platyhelminths
protective
highly dynamic
absorption of nutrients
secretion/turnover of glycocalyx
how do tapeworms absorb nutrients
lost intestines
only via skin
what is the generalised morphology of trematodes
blind sac intestine
mouth
intestines
eggs coiled in uterus
what is the intestine of trematode like and why
very reduced intestine so body can fill with eggs/teste to reproduce
how are human infecting trematodes catergorised
by sites of infection/disease
how many people suffer from liver or lung fluke infections from trematodes
around 40-100 million
how many people suffer from schistosoma - trematodes
around 600 million infected
250,000 mortality per annum
what are schistosoma mansoni, haemotobium, japonicum known as
blood fluke
what are the schistosoma mansoni, haemotobium, japonicum hosts
snails
humans
what is the lifecycle of schistosoma spp.
cercariae burrow through skin of humans larvae mature and mate in the circulatory system (dioecious)
eggs move to the intestines or the urinary bladder
where do schistosoma spp. infect
contact contaminated water
what are the cestode specialisations
no digestive system segmented body (strobila)
how do cestodes absorb nutrients without a digestive ssytem
through cuticle
what is the function of the cestode segmented body (strobila)
release of mature segments (proglottids) transmits eggs to faeces
what is taenia saginata known as
beef tapeworm
what are the hosts of taenia saginata
cattle
humans
what is the generalised cestode lifecycle
develop in intermediate host in tissues taken up by predator (human) eating contaminated food from undercooked meat eggs hatch in intestine eggs made passed out in faeces
where are the taenia human cestodes as adults
attach to intestinal epithelium
what do echinococcus human cestodes infect
humans are accidental intermediate hosts
how are humans infected by echinococcus human cestodes
food/water contaminated from dog faeces
what is the zoonosis of echinococcus human cestodes
larvae create cysts in tissue as intermediate host
what does echinococcus human cestodes cause
hydatid disease
what can taenia human cestodes cause
nutritional burden
intestinal blockage if tapeworm large
what do Th0 cells become
differentiate into number of different T helper cell types
what are the major types of T helper cells
Th1
Th2
Th17
Treg
what causes the Th0 differentiation direction
direction comes from cytokines and interaction with dendritic cells
what do th1 and th2 release
cytokines
what do cytokines do
that reinforce response direction (IFN-γ, IL-4)
what is the th1/th2 polarisation
Th1/Th2 inhibit each other = response can be polarised towards Th1 or Th2
what is the effect of Treg cells
suppress activity of other Th types (calming effect)
what do Treg cells make
anti-inflammatory IL-10
what induces Treg
TGF-β
what does the presence of helminths cause
elicits a strong Th2 response in host
create Th2 polarisation
what is the effect of th2 in host
beneficial
lower Th1, less inflammation
what is the effect of th2 in parasite
beneficial
less cytotoxicity
how can Th2 be measured
IL4 is a marker for Th2 response
what do helminths secrete
- cytokine mimics
- non-protein signatures
- protease inhibitors
- antioxidants
what do protease inhibitors do
block inflammatory signalling cascades
examples of protease inhibitors
cystatins/serpins
examples of cytokine mimics
TGF-β-mimics
examples of non-protein signatures
host-like glycans
what is the function of anti oxidants
block cytotoxic killing
effect of immunosuppression and th2 polarisation
greater susceptibility to microbes
reduced efficacy of vaccines
what is required due to greater microbe susceptibility
require th1 response
what is required due to reduced efficacy of vaccines
helminth burden serious issue for success of vaccine trials into neglected tropical diseases
may need to pre-treat with anti-helminthic
what are the soil transmitted helminths
ascaris
hookworm
trichuris
what are the filarial nematodes
filarial roundworm
what are the platyhelminths
trematoda
cestoda
what are the trematoda
schistosoma spp.
what are the cestoda
taenia saginata
cestode