1. Parasites Flashcards by Eleanor Barnard

What is a parasite?

An organism that lives in/on another organism (HOST) and benefits by deriving nutrients.
-NB. doesn’t necessarily cause disease

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What is meant by symbiosis?

A close, long-term interaction between 2 different species.

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What is meant by mutualism?

An association in which both species benefit from the interaction.

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What is meant by commensalism?

An association where parasite only is deriving benefit without causing injury to the host.

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What is meant by parasitism?

An association where the parasite derives benefit and the host gets nothing in return but always suffers some injury.

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What are the 3 classes of host?

Definitive
Intermediate
Paratenic

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What is a definitive host?

Harbours adult parasite/where parasite carries out sexual reproduction.
-Normally man in human parasitic infections

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What is an intermediate host?

Harbours larvae/asexual stages.

-Some parasites have more than one intermediate host

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What is a paratenic host?

Where parasite remains viable without further development.

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What are the 2 main types of parasite?

PROTOZOA (mirco)

HELMINTHS (macro) - worms

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What are the 4 main subdivisions of protozoa?

Flagellates
Amoeboids
Sporozoans
Tryponosomes

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What are the 2 main subdivision of helminths?

Platyhelminths (flatworms)

- Nematodes (round worms)

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What are the 2 main subdivisions of platyhelminths (flatworms)?

Cestodes (tape worms)

- Trematodes (flukes)

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What are the 2 main subdivisions of nematodes (round worms)?

Intestinal nematodes

- Tissue nematodes

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Give an example of a cestode.

Taenia sp

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Give an example of a trematode.

Schistosoma sp

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Give an example of an intestinal nematode.

Ascaris lumbricoides

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Give an example of a tissue nematode.

Wuchereria bancrofti

|&raquo_space; elephantitis

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Give the 3 types of life cycle of a parasite?

Direct
Simple indirect
Complex indirect

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What is a direct life cycle?

Parasites infect a single host (no intermediate hosts).

- eg. bird eats infective eggs&raquo_space; mature&raquo_space; sheds parasitic eggs

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What is an indirect life cycle?

Parasite life cycle involves 2 hosts (1 intermediate).

-eg. bird sheds parasitic eggs&raquo_space; slowbug eats them&raquo_space; infective larvae in slowbug&raquo_space; bird eats slowbug

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What is a complex indirect life cycle?

Parasite life cycle involves more than 2 hosts.

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Name 5 parasites to study in greater depth.

Ascariasis
Schistosomiasis
Hydatid disease
Malaria
Cryptosporidiosis

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What type of parasite is ascariasis?

Intestinal nematode

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Where is ascariasis mainly distributed?

East Asia

What type of life cycle does ascariasis have?

Direct life cycle | ingest eggs >> develop in faeces >> gut >> portal circulation >> lungs >> swallowed >>back into intestine

How is ascariasis spread?

Poor hygiene | -faecal-oral (ingest eggs)

What are the symptoms of ascariasis?

- INTESTINAL (malnutrition, worm burden) | - LUNG MIGRATION (Loefflers syndrome - dry cough, haemoptysis, wheeze)

How is ascariasis treated?

Albendazole (benzimidazole) | -prevents glucose absorption by worm

What type of parasite causes Schistosomiasis (AKA Bilharzia)?

Trematode/fluke | S. mansoni, S. intercallatum, etc.

Where is Schistosomiasis mainly distributed?

Africa

What type of life cycle does Schistosomiasis have?

Indirect life cycle | -snails are intermediate host

What are the symptoms of Schistosomiasis? (3)

- Swimmers itch - Katayama fever - Chronic Schistosomiasis

What are the symptoms of S haematobium (type of Schistosomiasis)? (3)

URINARY - Haematuria - Bladder fibrosis - Squamous cell bladder cancer

What are the symptoms of S. mansoni/intercallatum/japonicum/mekongi (types of Schistosomiasis)?

HEPATIC/INTESTINAL - portal hypertension - liver cirrhosis

How is Schistosomiasis diagnosed?

``` URINARY -serology -terminal stream microscopy HEPATIC/INTESTINAL -serology -stool microscopy -rectal snip microscopy ```

How is Schistosomiasis treated?

Praziquantel (increases ionic permeability tetanic concentration >> detachment)

How is Schistosomiasis prevented?

- Chemicals to kills snails - Chemoprophylaxis - Avoid infested water

What type of parasite causes hydatid disease?

Platyhelminth-Cestode-Tapeworm | macro-parasite

What causes hydatid disease?

Echinococcus sp. | granulosus = cystic, multilocularis = alveolar

What are the normal host in hydatid disease?

Sheep & dogs | -humans are accidental hosts

What type of life cycle does hydatid disease have?

Indirect | -humans = intermediate hosts

What are the symptoms of hydatid disease?

- Cysts (70% = liver, 20% = lungs) - 2* bacterial infection - cyst rupture >> hypersensitivity NB. may remain asymptomatic for years

How is hydatid disease diagnosed?

Imaging | Serology

How is hydatid disease prevented?

- Regularly worm dogs - Hand hygiene - Safe disposal of carcasses

What parasite is malaria caused by?

Protozoa-sporozoan -Plasmodium (micro-parasite)

What 4 species of Plasmodium cause malaria?

P. falciparum (70%) P. vivax P. ovale P. malariae

What type of life cycle does malaria have?

Indirect | -anopheles(mosquito) = vectors

Where is malaria mainly distributed?

Africa (& Asia/South America)

What are the basic stages of the malaria life cycle?

Mosquito bite >> liver >> blood >> mosquito drinks blood

What is the clinical presentation of malaria?

- ruptured RBCs block capillaries >> inflammatory reaction - fever & rigors - cerebral (confusion, coma) - renal failure - hypoglycaemia - anaemia

How is malaria diagnosed?

- Thick & thin microscopy - Serology (detect antigen) - PCR (detect malarial DNA)

What parasite is Cryptosporidiosis caused by?

Cryptosporidium parvum & hominis | -sporozoan, mirco-parasite

What are the symptoms of Cryptosporidiosis?

- diarrhoea with mucus - bloating, cramps, nausea, fever - usually self-limiting (>2 weeks)

How is Cryptosporidiosis spread?

Faecal-oral route - human-human spread - human-animal spread

Who are most at risk of Cryptosporidiosis?

HUMAN-HUMAN SPREAD: pool user, healthcare workers, parents, travellers HUMAN-ANIMAL SPREAD: backpackers, campers, farm workers

How is Cryptosporidiosis diagnosed?

Faeces sample (acid fast staining/antigen detection by EIA)

How is Cryptosporidiosis treated?

SYMPTOMATIC - rehydration, nitazoxanide

How is Cryptosporidiosis treated in immunocompromised patients?

- Paromomycin (kill parasite) - Nitazoxanide - Octreotide (reduce cramps) - HAART (HIV patients)

How is Cryptosporidiosis prevented?

Hand hygiene Pasteurise dairy products Boil drinking water

Name 5 commonly used anti-protozoal treatments.

``` Metronidazole Pentamidine Nitazoxanide Pyrimethamine Anti-malarials ```

Name 4 commonly used anti-helminthic treatments.

Albendazole Mebendazole Ivermectin Praziquantel