eukaryotic infections Flashcards
endoparasite
organism which lives within
ectoparasite
organism which lives on
metazoans
animal, helminths
protists
- Most unicellular, small
- Lack the level of tissue organisation present in higher eukaryotes
- Free living, symbiotic or parasitic
- Asexual
○ Binary fission
○ Spores and cysts - Sexual
Zygote
protoza
- Unicellular protists
- Most free-living, some are important human pathogens
- Pathogens - parasitic form that can cause disease in humans
○ Primary e.g. plasmodium
Opportunistic e.g. cryptosporidium
protozoal morphology
- Multiple life stages - reproduction, survival, host specificity
- Many have motility - cilia/flagella
- Vacuoles are common - maintain osmoregulation, food ingestion
Energy production through - mitochondria, chloroplasts, hydrogenosomes
EXCAVATA
- primitive protists
- Feeding grove, motile, binary fission
SAR
- Apicomplexa - diverse class with an apicoplast for host cell invasion
- Cytoskeletal structure
AMOEBOZOA
Move and feed with lobe-shaped pseudopods and no shell
Insect/tick vectors
Plasmodium - malaria
Ingestion of infective stages (food (tissue), water)
○ Toxoplasma gondii - toxoplasmosis
○ Giardia duodenalis - giardiasis
Entamoeba histolytica - amoebic dysentery
Venereal transmission
Trichomonas vaginalis
Malaria
- Specialised organelles for invasion and intracellular growth (e.g. liver hepatocytes and RBC’s)
- Mosquito - definitive host
○ Host where organism undergoes sexual reproduction - Human - intermediate host
○ Where the organism only reproduces asexually
○ One in liver
Multiple cycles in blood
- Mosquito - definitive host
malaria life cycle
- transmission to human
- sporozoites enter liver and infect hepatocytes
- mitotic replication - liver cell rupture and merozoites
- intraerythrocytic cycle
- sexual cycle
- transmission to mosquito
- gametocytes mate, undergo meiosis
- migrates though midgut wall, forms oocyst
- sporozoites develop
intraerythrocytic cycle
- merozoite enter cells
- forms ring
- trophozoite
- schizont
- rupture
- re-enters cycle or goes into sexual cycle
plasmodium falcarum sexual stage
merozoites produce gametocytes instead
acute vs chronic malaria
Acute - fever, anaemia (due to destruction of rbc’s)
Chronic - spleno- and hepatomegaly, respiratory distress
Pathogenesis of malaria
Infected RBC can bind and sequester in brain capillaries -> blockage to capillaries, ischemia, neural cell death
Toxoplasma
- Protozoan apicomplexan parasite
- One of the most common infections
- Zoonosis
○ Mammals, humans (intermediate host) - Primary host is wild and domestic cat
○ Parasite replicate in cat GI tract
Produce oocysts that spread in faeces
Life cycle of toxoplasma
- Food-borne
○ Ingestion of cysts in tissue of intermediate host (animal)
○ Unsporulated oocytes pass in faeces
○ Sporulated oocyte spread to human through contaminated food and water
○ Oocytes in feed spread to intermediate hosts
○ Ingested cysts in affected (raw) meat- Zoonotic
○ Ingestion of cat faeces
§ Cat litter tray, children’s sandpits - Maternal
Tachyzoites transmitted through placenta
- Zoonotic
Pathogenesis of toxoplasma
- Oocysts activated in gut
- Tachyzoites penetrate intestinal epithelium
- Invasion of multiple cell types
Tissue cysts form and become dormant
Immunocompromised or pregnant individuals
- Severe pathological consequences
- Immunocompromised
○ Severe toxoplasmosis involving organ damage
○ Reactivation of cyst - Pregnant
○ May lead to toxoplasmosis in foetus
○ Foetal abnormalities
○ Stillbirth - Healthy individuals - tolerated
Chronic infection of cysts
- Immunocompromised
Giardiasis
- Caused by giardia duodenalis
- Faecal/oral route
○ Drinking contaminated water - Symptoms
○ Asymptomatic (5%)
○ Prolonged diarrhoea
○ Dehydration
Greasy stool
- Faecal/oral route
Life cycle of giardiasis
- Hardy cysts survive in faeces
- Cysts ingested
- In SI, excystation -> 2 trophozoites divide asexually, attack to SI mucosa mess with absorption
Cysts to passed in faeces
Pathogenesis of Giardia
- Strict anaerobic flagellate
- Cysts change, excyst in bile
- Become trophozoites and attach to SI cells
Disrupt nutrient and fluid absorption, diarrhoea
Amoebas
- Amoebiasis ○ Caused by entamoeba histolytica ○ Diarrhoea, dysentery, nausea ○ faecal/oral transmission ○ Pathogenesis § Trophozoite invades intestinal cells § Produces cytotoxin and proteases to cleave IgA Perforation of colon
Life cycle of amoebas
- Hard cysts in stool and trophozoites
- Ingested cysts excyst in SI and release trophozoites
- Trophozoite produce cysts encyst - shed in faeces along with trophozoites
- Trophozoite persist in LI lumen = non invasive colonisation
Or invade LI mucosa via cytotoxin = invasive
Human hookworms
Nematodes - roundworms
- Cause acute GI infection, diarrhoea
- Life-cycle - transdermal transmission
Eggs passed in faeces
Human hookworms lifecycle
- Eggs in faeces
- Larva changes into filariform
- Filariform larva penetrates skin
Adults from in SI
Human pinworm - roundworm
- Most common worm infection
- Spread easily, ingesting or inhaling eggs (faecal/oral)
- Causes itching
Females migrate out at night out of the anus and lay eggs
Cestodes - tapeworms
- Taenia solium ○ Pork ○ Taeniasis and cysticercosis - Taenia saginata ○ Beef ○ Taeniasis - Echinococcus granulosus ○ Dog ○ Hydatid Morphology - Long - Suckers and hooks attach Proglottids extend and release into faeces
Taeniasis
- Caused by: Solium (tissue cysterici) and Saginata
Signs and symptoms: often asymptomatic, find proglottids in faeces, loss of appetite, rare blockage
Cysticercosis
- Caused by - solium (by egg, larvae)
Signs and symptoms - skin nodules, swelling, respiratory distress, seizures, mental disturbance (death)
lifecycle for taeniasis
- Pigs and cattle infected by eating eggs, invade intestine to form cysticerci in muscle tissue
- Humans infected by eating cysticerci in poorly cooked tissue, cysts develop and attach to SI wall
Sexually mature proglottids contain eggs which are shed with proglottids in faeces
- Humans infected by eating cysticerci in poorly cooked tissue, cysts develop and attach to SI wall
lifecycle for cysticercosis
If humans ingest eggs, an oncosphere can form and penetrate human intestinal wall to form cysticercus over months
trematodes (flukes)
- Have flattened bodies with suckers
- Blood flukes schistosomes
Schistosomiasis
- Blood flukes schistosomes
Schistosomiasis
- Eggs encapsulate causing immune response, chronic inflammation
- Many are asymptomatic
- Fever
- Portal hypertension
Lesions
Candidiasis
- Candida albicans - opportunistic
- Yeast invades via bodily fluids, surfaces
- Budding cells of varying size
- Thrush - thick white, adherent growth on mucous membrane of mouth
- Vulvovaginal yeast infection - inflammatory condition of genitals causes ulceration and whitish discharge
- Cutaneous candidiasis - chronically moist areas of skin
Invasive candidiasis - if phagocytic system compromised, infection spreads and causes potentially fatal infections
Cryptococcosis
- Common infection of AIDS, cancer, diabetes patients
- Caused by cryptococcus neoformans
- Yeast that inhabits soil
- Escape phagocytes via intracellular macrophages creating lesions
- immunocompromised - infection of lungs, leads to cough, fever
Dissemination to meninges and brain cause neurological disturbance and death
Aspergillosis
- Airborne soil fungus
- opportunistic threat to AIDS, leukemia and transplant patients
- Infection usually in lungs - spores germinate into lungs and form colonies
- Aspergilloma- mass of mycelium invade and disseminate
Invasive aspergillosis can produce necrotic pneumonia and infection of brain, heart and other organs
