Protozoan Disease Flashcards
What are protozoa?
Microscopic unicellular eukaryotes that lack a rigid cell wall
What is the basic life cycle of Entamoeba histolytica?
- Infection occurs via ingestion of cysts
- excystation in the small intestine
- trophozoites colonise the large intestine
- cysts passed in faeces
What disease is caused by Giardia lamblia?
Giardiasis
List four medically important protozoa.
- Plasmodium spp.
- Entamoeba spp.
- Giardia spp.
- Cryptosporidium spp.
What is a trophozoite?
The active, motile feeding stage of a protozoan organism
True or False: Protozoa can only be parasitic.
False
What is the global occurrence of malaria caused by Plasmodium spp.?
249 million cases
What is the primary source of infection for Cryptosporidium parvum?
Ingestion of faecally contaminated food or water
What is the incubation period for Cryptosporidium parvum infection?
5 to 28 days
What are the common symptoms of giardiasis?
- Diarrhoea
- Pain
- Cramps
Fill in the blank: The infective stage of Entamoeba histolytica is called _______.
trophozoite
What is a common method for preventing Cryptosporidium infections?
Awareness and practice of good personal hygiene
What treatment is used for symptomatic Entamoeba histolytica infection?
Metronidazole and iodoquinol
What is the life cycle of Giardia lamblia characterized by?
Excystation in the small intestine, trophozoites released, attach to the digestive tract
Name one laboratory diagnosis method for Giardia lamblia.
Identification of cysts in faeces
What is the role of oocysts in Cryptosporidium parvum’s life cycle?
Oocysts are produced and re-released back into the environment
True or False: Cysts of Giardia lamblia are resistant to chlorine.
True
What are the two strategies employed by parasitic protozoa to locate a host?
- Have a resistant stage in their life cycle
- Have a second host
What is the typical outcome for most cases of Cryptosporidiosis and how can it be treated?
Self-limiting
However, it can be treated with rehydration plus nitazoxanide.
What are the protective structures formed by Entamoeba histolytica called?
Cysts
Fill in the blank: The disease caused by Entamoeba histolytica is known as _______.
amoebic dysentery
What is the significance of asymptomatic carriers in protozoan infections?
They are important reservoirs for future infection
What is the infective dose for Cryptosporidium parvum?
10 – 100 oocysts
What are the two most common species of Plasmodium causing malaria?
Plasmodium falciparum and Plasmodium vivax
Fill in the blank: Malaria is transmitted by the _______ mosquito.
Female Anopheles
List the three key stages of the Plasmodium life cycle.
- Human liver stages (pre-erythrocytic cycle)
- Human blood stages (erythrocytic cycle)
- Mosquito stages (sporogonic cycle)
What are common early symptoms of malaria?
- Fever
- Headache
- Chills
What severe condition can result from Plasmodium falciparum infection?
Cerebral malaria
What is the gold standard for malaria diagnosis?
Microscopy
True or False: Thick blood smears are used for species-level identification of Plasmodium.
False
What is the purpose of primaquine in malaria treatment?
Targets liver stage parasites
What is the primary mechanism of the RTS,S vaccine?
Targets circumsporozoite protein (CSP) on sporozoites
Prevents the parasites from emerging from the liver and progressing to the erythrocytic stage.
List two antimalarial drugs used in combination with artemisinin.
- Quinine
- Doxycycline
Fill in the blank: The first widespread antimalarial was _______.
Quinine
What is the function of insecticide-treated nets (ITNs) in malaria prevention?
Most effective preventative measure against malaria
What is the significance of the sterile insect technology (SIT) project?
Releases sterile males to reduce mosquito population
What is the main challenge in developing malaria vaccines?
Requires herd immunity approach
What are the limitations of drug treatment for malaria?
- No drug is effective against all stages
- Resistance can develop rapidly
What is the effect of chemoprophylaxis on malaria risk?
Reduces malaria risk by approximately 90%
What are the blood stage vaccines designed to prevent?
Development of asexual stage infected erythrocytes
How does the RTS,S vaccine impact the malaria life cycle?
Prevents parasites from emerging from the liver
What are the three vaccine target sites for malaria?
- Pre-erythrocytic vaccines
- Blood stage vaccines
- Transmission blocking vaccines
Describe the Asexual development (humans) lifecycle
•Female infective Anopheles mosquito takes blood meal and injects sporozoite stage parasites
•Sporozoites infect liver cells within 30 minutes and develop into schizonts
•Schizonts rupture and release merozoites
•Merozoites infect RBC’s –Pass through blood cell stages
•Some mature into gametocytes and are ingested by another Anopheles mosquito
What are the advantages and disadvantages of blood smear diagnosis?
•Advantages
–Cheap
–Fast
–Low technology
•Disadvantages
–Extensive training
–Rigorous quality control
–Drug treatment may make it difficult to ID species
What are rapid diagnostic tests?
These are lateral flow devices which uses blood as the sample
•Capable of a rough species-level ID.
•May miss low level parasitaemia.
•Confirmed using microscopy.
What is PCR?
PCR uses primers, short synthetic DNA fragments, to select a DNA segment to amplify. Then, multiple rounds of DNA synthesis amplify that segment.
PCR can also be used to provide species-specific diagnosis if required
What is PCR?
PCR uses primers, short synthetic DNA fragments, to select a DNA segment to amplify. Then, multiple rounds of DNA synthesis amplify that segment.
PCR can also be used to provide species-specific diagnosis if required
What does Quinine (chloroquine / mefloquine) target?
Target blood stage parasites.
What does Doxycycline target?
Used in combination with quinine for blood stage target
What does Primaquine target?
Targets liver stage parasites.
What is Artemisinin combination therapy (ACT) and what does it target?
Artemisinin is a plant derived compound.
•Has faster elimination and broader efficacy across Plasmodium life-cycle.
•Effective against all Plasmodium species.
•Due to concerns about resistance, artemisinin is combined with another drug.
Target - blood stage parasites, inhibits development of gametocytes.
What is Artemisinin combination therapy (ACT) and what does it target?
Artemisinin is a plant derived compound.
•Has faster elimination and broader efficacy across Plasmodium life-cycle.
•Effective against all Plasmodium species.
•Due to concerns about resistance, artemisinin is combined with another drug.
Target - blood stage parasites, inhibits development of gametocytes.
Name the three target sites for malaria
- Pre-erythrocytes vaccine
- Blood stage vaccine
- Transmission blocking vaccine
What does the blood vaccine do?
Prevent the development of the asexual stage infected erythrocyte and the merozoite.
What does the transmission blocking vaccine do?
Generate antibodies against the sexual stages of the parasite
Antibodies impair development
Requires herd immunity
What Protozoa causes amoebic dysentery?
Entamoeba histolytica
What Protozoa causes cryptosporidiosis?
Cryptosporidium parvum
What Protozoa causes giardiasis?
Giardia lamblia
