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Flashcards in Introduction to Parasites Deck (58):
1

Parasites

Organsims that live in or on another organism (its host) and benefits by deriving nutrients at the others expense, does not necessarily cause disease

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Mutuallsm

An association in which both species benefit from the interaction

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Parastism

An association in which the parasite derives benefit and the host gents nothing in return but always suffers some injury

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Commensalism

An association in which the parasite only benefits without causing harm to the host

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3 classes of host

Definitive host
Intermediat host
Paratenic host

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Definitive host

Harbous the adult stage of hte parasite or where the parasite undergoes sexual reproduction

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Intermediate host

harbours the larval or asexual stages of the parasite. Some parasites have 2 intermediate hosts in their lifecycle

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Paratenic host

Host where the parasite remains viable without further development

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2 types of parasites

Protozoa
Helminths

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Microparasites

Protozoa

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Macroparasites

Helminths

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6 examples of microparasites

Cryptosporidium
P.Falciparum-malaria
T.cruzi trypomastigole
Trypanosoma cruzi
Entamoeba
Giardia Lamblia

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5 groups of helminth

Cestodes
Trematodes
Intestinal nematode
Tissue nematode

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Example of a cestode

Taenia sp

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Example of a trematode

Schistosomiasis

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Example of an intestinal nematode

Ascaris lumbricoides

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Example of a tissue nematode

Wucheria bancrofti

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Direct life cycle

Only 1 definitive host

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Simple indirect life cycle

2 hosts- intermediate and direct

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Complex indirect life cycle

More than 1 intermediate host

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Name the type of life cycle:
bird>poo>sourbug>bird

Simple indirect cycle

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Name the type of life cycle:
bird>poo>amphipod>amphibian>fish>bird

Complex indirect

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Name the type of life cycle:
Bird>poo>bird

Direct

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Describe the parasite ascariasis

Macroparasite. Intestinal nematode. Ascaris lumbricoidis.

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Who is most commonly affected by ascariasis?

3-8yrs. Areas of poor hygeine

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Describe the life cycle of ascariasis

Direct life cycle:
eggs in human intestine, shed into environment in faeces. Eating contaminated food/water. eggs pass into intestine. Migrate to portal circulation to alveoli to lungs

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2 clinical phases of ascariasis

Lung migration
Intestinal Phase

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Describe the lung migration phase of Ascariasis

Loeffler's syndrome- dry cough, dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis

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Describe the intestinal phase of ascariasis

Malnutrition, migration into hepatobiliary tree and pancreas, intestinal obstruction, worm burden

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Treatment for ascariasis

Albendazole-prevents glucose absorption by worm-detaches and passes out in faeces

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Control for ascariasis

WHO 'Action against worms'- improve sanitation, education and deworming in communities

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Describe the parasite schistosomaisis

Macroparasite. Helminth. Bilharzia disease

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What is the intermediate host for schistosomiasis?

Snails

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A parasite that causes chronic diseasse resulting in bladder cancer and liver cirrhosis

Schistosomiasis

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4 clinical features of schistosomiasis

Swimmer's itch
Katagoma fever
Urinary-bladder fibrosis and dysfuction, squamous cell CA in bladder
Hepatic-portal hypertension and liver cirrhosis

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Treatment for schistosomiasis

Praziquantel

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Control of schistosomiasis

Chemical treatment to kill snail intermediate hsots. Avoidanance of snail infected waters, education and imrpoved sanitation

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Describe the parasite causing Hydatid disease

Macroparasite-cestode. Echinococcus sp.

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Usual host for hydatid disease

Human is accidental host- usualy hosts are sheep and dogs.

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Describe the life cycle for hydatid disease

Complex, indirect life cycle. Worm in dog's intestine, eggs in faeces, Humans infected if eat contaminated food. Migrate to liver and lungs from hyatid cyst

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Where do hyatid cysts commonly develop?

70% liver
20% lungs

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Control of hydatid disease

regularly worm dogs. Hand ygein. Safe disposal of animal carcasses

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Describe the protozoa that carries malaria

Protozoa-sporozoan. 4 species of plasmodium:
P.flaciparium
p.vivax
p.ovale
p.malariae

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Which type of plasmodium most commonly causes malaria?

P. falciparum

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Describe the transmission of malaria

Vector transmission-anopheles mosquito. Mosquito is infected. Injects parasite into human whilst feeding. Sporozoites enter liver and infect hepatocytes-replication. Hepatocytes rupture.

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Describe the 2 phases of the lifecycle of malaria

Asexual phase: self replicating. Infect other RBCs which rupture following replication.
Sexual reproduction: another mosquito takes a meal fertilises eggs and spreads to others

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Clinical presentation of malaria

Parasites rupture RBCs, block capillaries and cause an inflammatory response. evers/rigor, cerebral malaria (confusion, headache, coma), renal failure, hypogycaemia, circulatory collapse, anaemia, bleeding and DIC

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Returning traveller + fever

Malaria unless proven otherwise

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Control for malaria

Insecticide spraying in homes, breeding pools. Nets, chemoprophylaxis

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Clinical presentation of malaria

Watery diarrhoea after approx 7 days. Bloating, cramps, fever, nausea, vomiting. Usually self limiting (up to 2 wks)

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Causative organism of cryptosporidiosis

Cryptosporidium parvium and hominis- sporazoa.

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Describe the life cycle of cryptosporidiosis

Direct life cycle- humans pass oocytes in stools, contaminate water ingested. Animal reservoir (cattle, sheep, goats)

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Clinical presentation of cryptosporidiosis

watery diarrhoea after approx 7 days. Bloating, cramps, fever, nausia, vomiting. Usually self limiting (up to 2 wks)

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Who are most at risk to cryptosporidium

Regular swimmers (immune to chlorine). Childcare, healthcare, animal workders

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Diagnosis of cryptosporidium

Faeces sample: acid fast staining

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Treatment of cryptosporidiosis

Paromycin (kills parasite)
Nitazoxanide (broad spectrum antiparasite)
Oetreatide (reduces cramps and frequency)

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Commonly used anti-protozoal treatment

Metronidazole
Pentamidine
Nitazoxamide
Pyrimethamine

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Commonly used anti helminth

Albendazole
Mebendazole
Ivermectin
Praziquantel