Introduction to Parasites Flashcards
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
Mutuallsm
An association in which both species benefit from the interaction
Parastism
An association in which the parasite derives benefit and the host gents nothing in return but always suffers some injury
Commensalism
An association in which the parasite only benefits without causing harm to the host
3 classes of host
Definitive host
Intermediat host
Paratenic host
Definitive host
Harbous the adult stage of hte parasite or where the parasite undergoes sexual reproduction
Intermediate host
harbours the larval or asexual stages of the parasite. Some parasites have 2 intermediate hosts in their lifecycle
Paratenic host
Host where the parasite remains viable without further development
2 types of parasites
Protozoa
Helminths
Microparasites
Protozoa
Macroparasites
Helminths
6 examples of microparasites
Cryptosporidium P.Falciparum-malaria T.cruzi trypomastigole Trypanosoma cruzi Entamoeba Giardia Lamblia
5 groups of helminth
Cestodes
Trematodes
Intestinal nematode
Tissue nematode
Example of a cestode
Taenia sp
Example of a trematode
Schistosomiasis
Example of an intestinal nematode
Ascaris lumbricoides
Example of a tissue nematode
Wucheria bancrofti
Direct life cycle
Only 1 definitive host
Simple indirect life cycle
2 hosts- intermediate and direct
Complex indirect life cycle
More than 1 intermediate host
Name the type of life cycle:
bird>poo>sourbug>bird
Simple indirect cycle
Name the type of life cycle:
bird>poo>amphipod>amphibian>fish>bird
Complex indirect
Name the type of life cycle:
Bird>poo>bird
Direct
Describe the parasite ascariasis
Macroparasite. Intestinal nematode. Ascaris lumbricoidis.
Who is most commonly affected by ascariasis?
3-8yrs. Areas of poor hygeine
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
2 clinical phases of ascariasis
Lung migration
Intestinal Phase
Describe the lung migration phase of Ascariasis
Loeffler’s syndrome- dry cough, dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis
Describe the intestinal phase of ascariasis
Malnutrition, migration into hepatobiliary tree and pancreas, intestinal obstruction, worm burden
Treatment for ascariasis
Albendazole-prevents glucose absorption by worm-detaches and passes out in faeces
Control for ascariasis
WHO ‘Action against worms’- improve sanitation, education and deworming in communities
Describe the parasite schistosomaisis
Macroparasite. Helminth. Bilharzia disease
What is the intermediate host for schistosomiasis?
Snails
A parasite that causes chronic diseasse resulting in bladder cancer and liver cirrhosis
Schistosomiasis
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
Treatment for schistosomiasis
Praziquantel
Control of schistosomiasis
Chemical treatment to kill snail intermediate hsots. Avoidanance of snail infected waters, education and imrpoved sanitation
Describe the parasite causing Hydatid disease
Macroparasite-cestode. Echinococcus sp.
Usual host for hydatid disease
Human is accidental host- usualy hosts are sheep and dogs.
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
Where do hyatid cysts commonly develop?
70% liver
20% lungs
Control of hydatid disease
regularly worm dogs. Hand ygein. Safe disposal of animal carcasses
Describe the protozoa that carries malaria
Protozoa-sporozoan. 4 species of plasmodium: P.flaciparium p.vivax p.ovale p.malariae
Which type of plasmodium most commonly causes malaria?
P. falciparum
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.
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
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
Returning traveller + fever
Malaria unless proven otherwise
Control for malaria
Insecticide spraying in homes, breeding pools. Nets, chemoprophylaxis
Clinical presentation of malaria
Watery diarrhoea after approx 7 days. Bloating, cramps, fever, nausea, vomiting. Usually self limiting (up to 2 wks)
Causative organism of cryptosporidiosis
Cryptosporidium parvium and hominis- sporazoa.
Describe the life cycle of cryptosporidiosis
Direct life cycle- humans pass oocytes in stools, contaminate water ingested. Animal reservoir (cattle, sheep, goats)
Clinical presentation of cryptosporidiosis
watery diarrhoea after approx 7 days. Bloating, cramps, fever, nausia, vomiting. Usually self limiting (up to 2 wks)
Who are most at risk to cryptosporidium
Regular swimmers (immune to chlorine). Childcare, healthcare, animal workders
Diagnosis of cryptosporidium
Faeces sample: acid fast staining
Treatment of cryptosporidiosis
Paromycin (kills parasite)
Nitazoxanide (broad spectrum antiparasite)
Oetreatide (reduces cramps and frequency)
Commonly used anti-protozoal treatment
Metronidazole
Pentamidine
Nitazoxamide
Pyrimethamine
Commonly used anti helminth
Albendazole
Mebendazole
Ivermectin
Praziquantel
