Flashcards in Introduction to Parasites Deck (58):
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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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