theme 1:parasitology
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- Created by: medstudent22
- Created on: 04-03-20 16:49
what are the three key points for defining a parasite? (where its found, what it takes, what it gives?)
-lives in/on a host, -relies on host and derives nutrients, -gives nothing in return and can harm host
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what is a host?
organism that harbours the parasite
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what classes of host harbours the adult stage parasite/where it does sexual reproduction and which class harbours the larval form/asexual stage?
-definitive, -intermediate (can have multiple intermediate hosts)
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what class of host harbours a parasite that doesnt need further development but is still viable?
-paratenic
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what is a reservoir host?
-a species infected by a parasite that acts a source of infection for other species
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whats the term for a close long term association between two different species (ie a host and a parsite)
symbiosis
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define the different forms of symbiosis: mutualism, commensalism, parasitism
-mutualism=both species benefit, -commensalism=parasite benefits, host no effect, -parasitism= parasite benefits, host harmed
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what are the 3 groups of parasites?
-protozoa, helminths, arthropods
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what are protozoa? and give the 4 subgroups and e.g.s and what diseases they cause
-micro-parasites, single celled (free living/parasitic), -flagellates (giardia lamblia=giardiasis, trichomonas vaginalis=trichomoniasis), amoeboids (entamoeba,acanthamoeba), sporozoans (plasmodium, cryptosporidium, toxoplasma), trypanosomes
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what are helminths?
-multicellular parasite
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which out of protozoa and helminths can replicate in humans?
-protozoa, helminths cant
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whats the 2 subgroups and there subgroups?
1)platyhelminths (flatworms)-cestodes,trematodes 2)nematodes (roundworms)-intestinal and tissue
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what are arthropods mainly?
ectoparasites-blood sucking/burrow into skin, transmit infection
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what are the 4 subgroups of ectoparasites?
-insects (mosquitos e.g.aedes, anopheles, culcinae), lice (pthiris pubis, pediculus humaus capitus), mites (scabies, chigger mite), arachnids (ticks)
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what do you need to know about parasites?
-distribution (where found), life cycles (how they survive), clinical manifestations (symptoms), diagnosis, treatment, control (preventative)
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outline a direct life cycle?
-1 host, infected and sheds eggs in poo, eggs mature (in environment) and are infective, then eaten by host again
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outline an indirect simple cycle?
-multiple hosts (only one directly consuming parasite), -1 intermediate host eats parasite eggs (mature), this host eaten by other host so is infected, sheds egg in poo
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outline an indirect complex cycle?
-multiple intermediate hosts and paratenic host, --> 1 hosts eats eggs (some development), eaten by another intermediate host (some more development), eaten by paratenic host (no more development), eaten by definitive host who poops out eggs
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what type of parasite causes ascariasis?
-macroparasite, intestinal nematode
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how many/who does ascariasis affect?
-1 billion worldwide, 3-8 year olds most affected
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whats the distribution/what kind of area would ascariasis be found and how is it acquired?
-tropical/poor hygiene areas, -contaminated h2o/veg has eggs, eggs ingested (1 worm=200000 eggs a day), faeco-oral route
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whats the type of life cycle of ascariasis?
-direct as 1 host (human), develop in them, human only source of infection
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what are the two clinical states of ascariasis?
-intestinal phase, -lung migration
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what symptoms in intestinal phase of ascariasis?
-malnutrition, malabsorption, migration into hepatobiliary tree and pancreas, worm burden, intestinal obstruction
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what symptoms in lung migration of ascariasis?
-get loefflers syndrome=dry cough, dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis (eosinophils accumulate in lung)
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what are the 2 ways of diagnosing ascariasis?
1)stool sample=eggs/larvae (worm in intestine), 2)blood count=raised eosinophil as of loefflers syndrome
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how to treat ascariasis?
albendazole= 1)stops worm from absorbing glucose, 2)starved, detaches, passed PR
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WHO 'action against worms' is for control of ascariasis, what does this involve?
-improving sanitation, education, targeted community deworming
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what type of parasite causes schistosomiasis? give egs of species that causes it
-macro-parasite, platyhelminth- trematode/fluke, -schistosoma.haematobium, s.mansoni, s.intercallatum, s.japonicum, s.mekongi
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whats the distribution of schistosomiasis, how many affected?
-africa, 200 million affected, called bilharzia in africa
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describe the life cycle of schistosomiasis
-snail=intermediate host become infected from poo/wee in water, human= infected by skin penetration, to liver, to bladder
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how many days is the initial incubation period of schistosomiasis?
14-84 days
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is schistosomiasis asymptomatic or symptomatic?
can be both
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what syndrome (and what symptoms does this include) accompanies acute schistosomiasis ?name the other symptoms
katayama syndrome (rash, fever, headache, myalgia, resp symptoms, eosinophilia, hepato/spenomegaly), swimmers itch
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can eggs of schistosomiasis travel?
oui, to distant sites -lungs/spine
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what can chronic schistosomiasis lead to?
bladder cancer, liver cirrhosis
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different species of schistosomiasis affect different areas, what two areas?
urinary and hepatic/intestinal
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what species causes urinary symptoms and what symptoms does this include?
s.haematobium, squamous cell CA bladder, haematuria, bladder fibrosis and dysfunction
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what species causes hepatic/intestinal symptoms and what symptoms does this include
all other species, s.mansoni, s.intercallatum, s.japonicum, s.mekongi, portal hyptertension, cirrhosis, abdo pain, hepatosplenomegaly
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To diagnose urinary schistosomiasis-> look for s.haematobium, how?
-terminal stream microscopy, serology
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To diagnose hepatic/intestinal schistosomiasis-> look for s.japonicum, s.mansoni ect, how?
-stool microscopy, rectal snip microscopy, serology
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what is the treatment for schistosomiasis? dosage and how well is it absorbed?
-praziquantel, 20mg/kgx2 4-6 hours apart, well absorbed extensive 1st pass metabolism, inactive metabolites excreted in urine
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how does treatment of s.japonicum differ to the rest of schistosomiasis?
3 doses of praziquantel instead of just 2
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give 4 ways of controlling schistosomiasis?
1) avoid snail infested waters, 2) chemical treatment to kill the intermediate snail hosts, 3)chemoprophylaxis, 4) community targeted treatment, education, sanitation
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what parasite causes hyatid disease?
-macroparasite, platyhelminth (cestode-tapeworm)- echinococcus
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whats the 3 hosts of hyatid disease?
definitive=dog, intermediate=sheep, accidental=human
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think of the intermediate host, where is hyatid disease going to be found?
-wherever sheep are farmed (all over ze world)
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how would hyatid disease present clinically?
-can be asymptomatic for years, find cysts (70% liver, 20% lung), mass effect (compress tissue due to growth of cyst), can get secondary bacterial infection
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what can happen if a cyst ruptures and what does it look like?
-hypersensitivity, waterlily appearance
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what are the two ways of diagnosing hyatid disease?
-serology, histology (careful= if ruptured cyst do not biopsy as may spread)
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how to treat hyatid disease?
albendazole and praziquantel for daughter cysts
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how to control hyatid disease? focus on each host in turn
1) definitive dog=regular deworming, 2)intermediate sheep=vaccines, 3)accidental humans=education, handwashing
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what parasite causes strongyloidiasis? how does it enter human?
-macroparasite-nematode (strongyloides), directly penetrates bare skin
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where is strongyloidiasis more present? how many affected worldwide?
-subtropical/tropical regions, temperate climates, 30-100 mill affected worldwide
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life cycle: what two actions can eggs do in strongyloidiasis? (makes this different to others)
-excreted in stools, OR autoinfection can occur (migrate from intestine to other organs)
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two parts of strongyloidiasis: strongyloides and strongyloides hyperinfection syndrome, what is this?
-when reinfected by larvae and spreads to different organs (disseminated strongyloidiasis), probs due to immunosuppression
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how to diagnose both parts of strongyloidiasis?
1)strongyloides=serology, stool culture (charcoal filtration method), 2)hyperinfection syndrome= harder (direct microscopy/serology neg), stool culture/concentration methods
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how to treat strongyloides?
-ivermectin (200 micrograms/kg for 2 days), albendazole (400mg bd for 7 days)
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how to treat hyperinfection syndrome?
-stop immunosupressive therapy, -ivermectin (200 micrograms/kg per day orally until stool/sputum is neg for 2 weeks)
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3 ways of controlling strongyloides? isnt a global public health strategy currently
1)wear shoes when walking on soil, 2)avoid sewage contact, 3)proper sewage disposal
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what parasite causes malaria? what does it use as a vector?
-microparasite (protozoa-sporozoan - plasmodium), anopheles-vector
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how many people infected each year, how many in uk, how many die
300-500 million people / year, 2000/year in uk, 1-3 million deaths/year (mostly young kids)
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what are the 4 human species of plasmodium and the one monkey one?
-p.falciparum (yikes), p.vivax, p.ovale, p.malariae, monkey=p.knowlesi
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malaria is found in tropics and subtropics, how common is it?
tropic= year round, subtropics= mostly year round
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symptoms of malaria? shakes, noggin, glucose, lungs, kidney, circulation ect
-fever/rigor, cerebral malaria (confusion, headache, coma), hypoglycaemia, renal failure (black water fever-hb straight into urine), pulmonary oedema, circulatory collapse, anaemia, bleeding, DIC
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how does the parasite cause these symptoms?
-rupture RBC, block capillaries, cause inflam reaction
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how are the erthrocytic cycles (how often to replicate in rbc) for 1) p.knowlesi 2)p.falciparum, p.ovale, p.vivax, 3)p.malariae
1)24 hours, 2) 48 hours, 3) 72 hours
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what other symptom does a returning traveller need to have to be assumed to have malaria until proven otherwise, but what else could it be
-fever, may be viral haemorrhagic fever
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3 ways of malaria diagnosis?
1) thin/thick microscopy, 2)pcr for detecting malarial DNA 3)serology=detect antigen in the blood
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initial line of treatment of p.falciparum?
-antimalarials= co-artem or atovaquone-proguanil
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what is the next line of treatment for complicated p.falciparum?
-iv artesunate, then complete full oral course when stop IV
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what complications can arise from iv artesunate and how is this checked for?
-10-15% people on iv artesunate get haemolysis, so 14 days after iv check Hb conc
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how to treat non p.falciparum malaria (p.ovale/vivax/malariae/knowlesei)?
-oral chloroquine 25 mg base/kg over 3 days, usual adult dose is 10 tablets (day 1:6, 2 for day 2/3)
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what is given if chloroquine isnt tolerated well (vomiting/cant swallow)?
-iv quinine, then once can swallow-> full course of oral chloroquine
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what does vivax and ovale need aswell and for what?
-primaquine for 14 days, treat liver to stop recurrence
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what supportive therapy exists for malaria?
-manage seizures, pulmonary oedema, acute renal failure, lactic acidosis, exchange transfusion for hyperparasitaemia
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control methods for malaria? 6 ways
1)insecticide spraying in homes, 2) larvicidal spraying on breeding pools, 3)fill in breeding pools, 4)introduce larvivorous species into mosquito breeding areas, use insecticide impregnated bed nets, chemoprophylaxis
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what is the name and type of the organism that causes trichomoniasis?
-trichomonas vaginalis (flagellated protozoan)
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how is trichomoniasis transmitted and how long is the incubation stage?
-sexually, 5-28 days
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how do symptoms differ in men and women for trichomoniasis?
-men=asymptomatic, women=smelly *** discharge, dyspareunia (painful sex), lower abdo discomfort, dysuria (painful wee), strawberry cervix (punctuate haemorrhages on cervix)
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where is trichomonas vaginalis found, how does it multiply and how is it transmitted?
-in prostatic/vaginal secretions, multiply via binary fission in these secretions, sexually transmitted via these secretions
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what 2 methods are used to identify trichomonas vaginalis from what specimen?
-pcr/direct microscopy in genital specimens
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how to treat trichomoniasis?
-metronidazole and partner simultaneously, (single dose 2g, or 200mg tds for 5-7 days)
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how to prevent people from getting trichomoniasis?
-general advice of preventing STIs, use barrier contraception
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what is giardiasis caused by and how is it transmitted?
-flagellated protozoan, faeco-oral transmission
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how would someone symptomatic with giardiasis present and how long for?
-diarrhoea, abdo pain, bloating, nausea/vomiting, 1-3 weeks
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do people with giardiasis always present with symptoms?
-no, can range from asymptomatic to severe symptoms and malabsorption, can become chronic
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summarise the 3 key points of giardiasis life cycle?
1) direct as 1 host, 2)cysts and trophozoites exit via stool, 3)only cysts survive in environment and contaminate food/h2o/hands
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how to diagnose giardiasis?
-look for cysts/trophozoites in ze poo
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what drug to treat giardiasis?
-metronidazole/tinidazole
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how to prevent giardiasis? vaccine/
-no vaccine, boil water, more about hygiene
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what parasite causes cryptosporidiosis?
-microparasite sporozoan -> cryptosporidium parvum/hominis
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where is Cryptosporidiosis found?
worldwide esp temperate/tropicals
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how is Cryptosporidiosis transmitted? what is a reservoir for it?
-faeco-oral human to human spread with animal reservoir (cattle,sheep, goats)
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how do outbreaks of Cryptosporidiosis occur?
-sporadic cases can lead to them
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does cryptosporidium have a direct or indirect life cycle and explain it?
-direct as 1 host, exits host to contaminate water/food -> ingested
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how long is the incubation period of Cryptosporidiosis?
2-10 days (~7 days)
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symptoms (self limiting): give examples, and how long will they last?
-up to 2 weeks, watery diarrhoea with no blood, bloating, cramps, fever, nausea, vomiting
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which groups of people is Cryptosporidiosis symptoms more severe in?
-very old, very young, immunocompromised (hiv, 60% become chronically infected)
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what does your risk of contraction depend on?
-way of spread and activities
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someone who is a backpacker (camper/hiker), who works in a farm and visits petting zoos and eats infected dairy products,is likely to obtain Cryptosporidiosis by what spread?
animal to human
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what increases the risk of human to human spread of Cryptosporidiosis?
-regular user of swimming pools (resistant to chlorine alot of the time), childcare workers/parents, nursing home residents/carers, healthcare workers lol, travellers
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what sample is required to diagnose Cryptosporidiosis and whats done to it?
-faece sample, acid fast staining/antigen detection by EIA (enzyme linked assay)
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how does treatment of Cryptosporidiosis differ between just symptomatic people and immunocompromsied people?
immunocompromised require many more things than just treating the symptoms
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how to treat the symptomatic Cryptosporidiosis?
-rehydration, nitazoxanide (treats diarrhoea)
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how to treat immunocompromised with Cryptosporidiosis?
-paromomycin (kill parasite), nitazoxanide, octreotide (reduce cramps), HAART for HIV
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what combination therapy would need to be used for severe cases?
paromomycin, nitazoxanide, azithromycin
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how to control Cryptosporidiosis human to human spread?
-boil/filter drinking water, hand hygiene, isolate symptomatic patients in healthcare setting, keep symptomatic kids from school
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how to control Cryptosporidiosis animal to human spread?
-pasteurise milk/dairy products, boil/filter water when camping
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why is schistosomiasis a public health risk?
-anaemia, bladder tumours, hepatic fibrosis with inc risk of oesophageal varices, renal failure, inc risk of HIV transmission, if mum infected can lead to poor birth weights/outcomes, undernutrition/inflamm mediated cachexia (suppression of appetite)
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what are the 2 reasons strongyloidiasis is a public health risk?
1)strongyloidiasis hyperinfection syndrome -> mortality rates of 90% (25 cases in uk since ww2) 2)sexual transmission in msm not in hetero, tho man to wife via larva in bronchial secretions
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Other cards in this set
Card 2
Front
what is a host?
Back
organism that harbours the parasite
Card 3
Front
what classes of host harbours the adult stage parasite/where it does sexual reproduction and which class harbours the larval form/asexual stage?
Back
Card 4
Front
what class of host harbours a parasite that doesnt need further development but is still viable?
Back
Card 5
Front
what is a reservoir host?
Back
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