T1 - L4 PARASITOLOGY Flashcards by Chloe Sowerby

what is a parasite?

An organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other’s expense.

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what does symbiosis mean?

living together; close, long term interaction between two different species

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what is mutualism?

an association in which both species benefit from the interaction

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what is parasitism?

an association in which the parasite derives benefit and the host suffers injury

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what is commensalism?

an association in which the parasite only is deriving benefit without
causing injury to the host

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what is a definitive host?

harbours the adult stage of the parasite

human (majority)

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what is a intermediate host?

Harbours the larval or asexual stages of the parasite

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what is a paratenic host?

the parasite remains viable - no development of the parasite occurs

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what are the two categories of parasites?

micro parasites (protozoa) and macro parasites (helminths)

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what are the two categories of helminths?

Plathelminths (flatworms)

Nematodes (round worms)

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Cryptosporidium sp, Giardia lamblia and Entamoeba sp are what type of parasites?

intestinal protozoa

causing diarrhoea]

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P. Falciparum is a parasite causing what disease?

malaria

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T. cruzi trypomastigote is a parasite causing what disease?

Chagas disease

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Leishmania amastigotes is a parasite causing what disease?

leishmaniasis

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what are the two classes of platyhelminths?

cestode
e.g. Taenia sp [tape worm]

Trematode
e.g. Schistosoma sp [schistosomiasis]

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schistosomiasis is caused by which type of helminths?

Macro-parasite (Helminth- Platyhelminth- Trematode/Fluke)

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what are the two classes of nematodes? (round worm)

Intestinal nematode e.g. Ascaris lumbricoides

- Tissue nematode e.g. Wuchereria bancrofti

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what type of nematode causes lymphatic filariasis that leads to lymphedema and elephantiasis?

Tissue nematode

Wuchereria bancrofti

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describe a direct life cycle

only has a definitive host

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describe a simple indirect life cycle

has a definitive host and one intermediate host

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describe a complex direct life cycle

has a definitive and two intermediate hosts and a paratenic host

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list 3 helminth infections? (macro parasites)

Ascariasis

Schistosomiasis (Bilharzia disease)

Hydatid disease (Echinococcus sp.)

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list 4 Protozoa infections? (Micro parasites)

Malaria
Cryptosporidiosis
Trichomoniasis
Giardiasis

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what is Ascariasis?

infection of Intestinal nematode, Ascaris lumbricoides

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Ascariasis is most prevalent in what group of people?

3-8 year olds due to poor hygiene/deprivation

how is Ascariasis acquired?

ingestion of eggs | contaminated food and water

what is the distribution of Ascariasis?

[Africa (mainly), South East Asia and America]

what type of life cycle is Ascariasis?

direct life cycle

if Ascariasis migrates to the lungs, what disease can this cause?

Loefflers syndrome

how would you diagnosis ascariasis?

- stool sample (lab can test for eggs, some patients can pass worms)

how do you treat ascariasis?

Albendazole

how would you control or prevent ascariasis within the community?

- improve sanitation - education (to avoid contaminated water) - community targeted deworming

Schistosomiasis is also known as what?

Bilharzia disease

Schistosomiasis causes chronic disease resulting in what conditions?

bladder cancer liver cirrhosis

what type of life cycle takes place in Schistosomiasis?

indirect lifecycle (2 hosts)

what is the definitive host in Schistosomiasis?

human

what is the intermediate host in Schistosomiasis?

freshwater snails

how is Schistosomiasis transmitted?

Spread through contact with contaminated water with snails

what is the distribution of schistosomiasis?

[Africa (mainly), India, South East Asia and South America] - only where the snail lives - needs intermediate host to complete the cycle

what is the immediate presentation of schistosomiasis?

swimmers itch (allergic reaction)

what is the short term (days) presentation of schistosomiasis?

katayma fever

what is the longer term (weeks) presentation of schistosomiasis?

chronic schistosomiasis (can persist for years)

what is the effect of chronic schistosomiasis on the bladder?

Haematuria Bladder fibrosis and dysfunction Squamous cell CA bladder

what is the effect of chronic schistosomiasis on the liver?

Portal Hypertension Liver cirrhosis Abdo pain Hepatosplenomegaly

how do you diagnose schistosomiasis?

urine sample stool sample serology

how do you treat schistosomiasis?

Praziquantel 40-60 mg/kg with food 3 doses 8-hourly - Treatment of long term complications [If eggs have gone into the spinal cord]

how do you control schistosomiasis within the community?

kill snails avoid snail infested waters Community targeted treatment, education and improved sanitation

what causes Hydatid disease?

Macro-parasite (Platyhelminth- Cestode-Tapeworm) Caused by Echinococcus sp.

what is the life cycle of the parasite causing Hydatid disease?

indirect life cycle

what is the definite host in Hydatid disease?

dogs

what is the intermediate host in Hydatid disease?

sheep, cattle, goats OR accidentally humans

how does Hydatid disease present?

Cysts: 70% liver [mainly], 20% lungs May remain asymptomatic for years

how is Hydatid disease transmitted?

Release of eggs into the environment via dog faeces

what is an oncosphere?

larval/egg form of a tapeworm

how do humans accidentally get Hydatid disease?

eats an organ (containing a cyst) from the intermediate host ● e.g. a liver from the sheep that has a cyst

what is the result of a Hydatid disease cyst rupturing?

- can cause a range of symptoms including fever, skin rash and allergic reaction and which may be fatal. - causes the tapeworm to spread round the body and form cysts in other organs.

how do you treat Hydatid disease?

Surgical removal of the cysts

how do you control Hydatid disease in the community?

- Regularly worm dogs to reduce egg production - Hand hygiene - Safe disposal of animal carcasses/products of conception

what type of parasite is malaria?

Micro-parasite (protozoa- sporozoan) plasmodium

what are the 4 species of plasmodium?

P. falciparum (most significant) P. vivax (causes milder infections) P. ovale P. malariae

which species of plasmodium is the most clinically significant and causes death/severe infection?

P. falciparum

which two species of plasmodium can lie dormant in the liver?

P. vivax P. ovale

how is malaria transmitted?

Transmitted from humans via female anopheles (mosquitos) Victor transmission: need a vector and a human host

what type of life cycle is malaria?

indirect life cycle (2 hosts needed)

what is the definite host in malaria?

human

what is the intermediate host in malaria?

female anopheles (mosquitos)

what does a mosquito inject into a human to cause malaria?

sporozoites a motile spore-like stage in the life cycle

what is the physiological effect on the body of malaria?

- ruptured red cells (anaemia) - blocked capillaries (Renal failure (black water fever), Hypoglycaemia, Pulmonary oedema, Circulatory collapse - cause inflammatory reaction

how does malaria lead to death?

Cerebral malaria (confusion, headache, coma) - an cause your brain to swell, sometimes leading to permanent brain damage. It can also cause fits (seizures) or coma.

what does Cryptosporidium parvum and hominis (micro-parasite, sporozoan) cause?

Cryptosporidiosis diarrhoeal disease

how is Cryptosporidiosis spread?

Human to human spread with animal reservoir (cattle, sheep, goats) Faecal-oral spread

what type of life cycle does Cryptosporidium parvum take to cause Cryptosporidiosis?

direct life cycle

what is the treatment for symptomatic Cryptosporidiosis?

● Rehydration etc. | ● Nitazoxanide

what is the treatment for symptomatic Cryptosporidiosis | in immunocompromised patients?

● Paromomycin (to kill parasite) ● Nitazoxanide (effectiveness is unclear) ● Octreotide (reduce cramps and frequency) ● HIV patients, HAART should be quickly initiated

how do you control Cryptosporidiosis in the community?

● Hand hygiene ● Filter or boil drinking water ● Isolate symptomatic patients in healthcare setting ● Ensure symptomatic children are kept away from school

what type of parasite is Trichomonas vaginalis and what does it cause?

Flagellated protozoan (replicates by binary fission) Trichomoniasis

how is Trichomoniasis transmitted?

sexually transmitted

what are the symptoms/signs of Trichomoniasis?

Men = asymptomatic Women = smelly vaginal discharge, dyspareunia, dysuria and lower abdominal discomfort, punctuate haemorrhages on cervix (“strawberry cervix”).

what type of lifecycle leads to Trichomoniasis?

direct life cycle human to human

what is the treatment of Trichomoniasis?

Metronidazole single dose of 2g or in divided doses for 7 days ● Treat partner simultaneously

how do you prevent Trichomoniasis in the community?

- advise and educate on the prevention of STIs | - Use condoms

what type of parasite is giardiasis?

Flagellated protozoan

how is giardiasis transmitted?

Faecal oral transmission

what are the symptoms of giardiasis and how long do they last?

diarrhoea abdo pain bloating nausea and vomiting 1-3 weeks

what life cycle leads to giardiasis?

direct

how do you diagnose giardiasis?

Identification of cysts or trophozoites in faeces cysts found in patients that are chronic carriers, asymptomatic patients without diarrhoea

what is the treatment for giardiasis?

metronidazole/tinidazole

how do you prevent giardiasis in the community?

- improve hygiene | - boil water