Parasitic Infections Flashcards
what is the definition of invasion?
invasion by and growth of pathogenic microorganisms
what is the definition of disease?
a disordered or incorrectly functioning organ, part, structure or system of the body resulting from the effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalance, toxicity, or unfavourable environmental factors; illness; sickness; ailment.
what is the definition of parasite?
organism living in/on a host and is dependent on the host’s function for nutrition and may cause damage
what are the 2 major classes of parasites?
endo- and ectoparasites
endoparasites split into Protozoa and Metazoa (helminths)
what is the main difference between an endo- and ectoparasite?
ectoparasite lives on the surface of the host whereas endoparasite lives inside the body of the host.
what are the major parasitic protozoa?
1) amoeba e.g. entamoeba histolytica
2) coccidia e.g. plasmodium
3) ciliate e.g. balantidium
4) flagellates e.g. giardia
what are the major parasitic metazoa?
roundworms
flatworms
flukes.
what are the features of parasitic protozoa?
- single-celled organisms
- eukaryotic organisms i.e. complex organelles, genome in nucleus
- varied pathogenesis
- some use insect vectors
- no eosinophilia
what are the feature of parasitic metazoa?
- multicellular organisms
- free living, have intermediate hosts and vectors.
- some just inhabit the gut (geo-helminths) whilst other invade tissues
- eosinophilia if they invade the blood
what is the main haematological difference in protozoa and metazoa infection?
protozoans will not cause eosinophilia
metazoans will cause eosinophilia
examples of protozoa:
- amoeba
- coccidia
- cilliate
- flagellate
- amoeba: entamoeba histolytica and entamoeba dispar
- coccidia: plasmodium, toxoplasma, cryptosporidium
- ciliates: Balantidum coli
- flagellate: Giardia lamblia, Trichomonas, Leishmania
what is a vector?
an organism that transmits a disease or parasite from one organism to another
name examples of vectors and the diseases they transmit?
1) Snail
– transmits schistosomiasis (Fluke, Metazoa, endoparasite).
2) Female anopheles’ mosquito
– transmits malaria (Coccidia i.e. plasmodium protozoa, endoparasite).
3) Chrysops (deer flies)
– transmits Loiasis (Roundworm, Metazoa, endoparasite).
name 2 amoeba (Protozoa) and the diseases they cause
what is the treatment?
Entamoeba histolytica and Entamoeba dispar
– cause ulcers.
(ingestion of mature cysts in food or water, or on hands. Humans are the only reservoir)
treatment: Nitroimidazole derivatives, parmomycine or diloxanide furoate
name 3 coccidia (Protozoa) and the diseases they cause
1) Plasmodium
- malaria (fever, headache, chills, emesis, myalgia, anaemia)
2) Toxoplasma
- mild disease in immunocompromised
3) Cryptosporidium
- diarrhoea, fever, nausea, emesis
name a ciliate (protozoa) and the disease it causes
Balantidum coli –> balantidiasis
-persistent diarrhoea, dysentery, abdominal pain, weight loss, nausea, emesis; all leading to perforation of the colon.
name 3 flagellates (protozoa) and the disease it causes
1) Giardia lamblia –> Giardiasis.
2) Trichomonas
- Transmitted sexually
- vaginal discharge, vulval itching, dysuria, in males discharge and/or dysuria.
3) Leishmania – sand fly vector
- fever, weight loss, skin lesions, anaemia, disfigurement
what are the types of Leishmania (flagellate)?
1) visceral
- irregular fever, weight loss, spleno-/hepato-megaly, anaemia
2) cutaneous
- skin lesions
3) diffuse cutaneous
- skin lesions/leprosy
4) mucocutaneous
- disfigurement as destroys mucous membranes
what are the 3 groups of parasitic metazoa (endoparasites)?
o Roundworms/Nematodes
o Flatworms/Cestodes
o Flukes/Trematodes
name an example of the 3 different metazoa:
- roundworms
- flatworms
- flukes
- roundworm:
Ascaris (Loefflers Syndrome), hookworm, filaria, whipworm, loa loa, strongyloides - flatworm:
Taenia (tapeworms) - flukes:
Schistosoma
what are the features of metazoa/helminths?
o Multicellular parasites.
o Cycles may involve insect vectors and intermediate hosts.
o Adult worms cannot multiply in man
– the number of adults is related to the infection.
o A large burden is found in school-aged children which has a massive effect on their development.
name roundworms (helminth) and the diseases they cause
1) Ascaris–> ascariasis (oral-faecal)
- asymptomatic, abdominal pain, intestinal obstruction, malnourishment (adults feed on contents) , Loeffler’s pneumonia (penetration of lungs )
o Treatment – albendazole or mebendazole
2) Hookworm
-iron-deficient anaemia
o Treatment – albendazole or mebendazole
3) Whipworm
– bloody diarrhoea, anaemia (severe vitamin and mineral loss)
o Treatment – albendazole or mebendazole.
4) Filaria
- elephantiasis (block the lymphatic systems)
5) Loa Loa –> Loiasis
- can get into the eye
name flatworms and the diseases they cause
1) Taenia (tapeworms)
- asymptomatic but can cause stomach upsets
o Treatment – Praziquantel.
e.g taenia solium in neurocystericosis
name flukes and the diseases they cause
Schistosoma
-rash/itch, fever, cough, chills, myalgia
o Treatment – praziquantel.
name ectoparasites and the diseases they cause
1) Sarcoptes scabei –> scabies
- rash and presence of burrows
2) Lice
- head; body; pubic (crabs)
- itches
direct contact transmission
what is the difference in hosts used by protozoa and metazoa (endoparasites) ?
protozoa use insect vectors while metazoa use human hosts
what is the difference in eosinophil reaction in protozoa and metazoa infection?
protozoans do not lead to eosinophilia
metazoans lead to eosinophilia
E.histolytica
- amoebiasis
- cysts in poo food water
- trophozoites –> ulcers
what is the insect vector for Leishmania?
female sandfly
what are the 2 forms of the Leishmania parasite?
Promastigote –> infective
(Infective, flagellated form)
Amastigotes –> replicative form once promastigote is in
(Non motile, non-flagellated)
visceral leishmania (Kala azar)
large liver
large spleen
what causes Loeffler Syndrome (hypersensitive eosinophilic pneumonitis)?
ascaris (roundworm)
which parasite causes elephantiasis?
Wuchereria bancrofti
filaria
what is the insect vector for Loa Loa?
deer flies
what parasite causes neurocystericosis?
by tapeworms (cestodes) namely taenia solium
swiss cheese appearance to the brain on MRI caused
what are the symptoms of neurocystericosis?
- seizures
- blindess
- headache
- dementia
what is the intermediate host of schistosomiasis?
snails
what effect does schistosomiasis residing in the mesenteric vein have?
- portal hypertension
- jaundice
- cirrhosis
