Protozoa Flashcards
What parasite is responsible for malaria?
Plasmodium species
Who carries the malaria parasite?
Female anopheles mosquito and humans
What is the infective form of the parasite living in the mosquito’s salivary glands known as?
Sporozoids
Where do the sporozoides first travel in to in the human body? And what occurs here?
Hepatocytes- where they replicate to form schizonts. The hepatocyte will then rupture and many merozoites are released.
What two forms of the plasmodium parasite have the ability to remain dormant in the hepatocytes for a period of time? And what is this referred to as?
P. vivax and P.ovale
Referred to as a hypozoite
Where are merozoites normally found?
In red blood cells, where they feed
Briefly outline the life cycle of merozoites within red blood cells (asexual blood cycle)
- Will move from ruptured hepatocyte into red blood cell (ring stage)
- Will mature in red blood cell into trophozoite
- Trophozoite will mature into schizont and then rupture again
- Releases many merozoites into circulation
How does malaria present clinically?
Fever, chills, sweating, low BP, anaemic, heachache, myalgia, jaundice, nausea, ‘black water fever’ (haemoglobinuria)
If an uninfected mosquito is to bite an infected human, explain what will occur
- Some merozoites in red blood cells (at ring stage) will differentiate into male or female gametocytes
- These will be sucked up by new mosquito
- In mosquito’s stomach will enter sporogonic cycle (form zygote–> ookinete–> oocyte)
- Oocyte will rupture and release sporozyte’s which enter salivary glands
Give two reasons patient with malaria will be anaemic
- Spenic macrophages will destroy infected RBC’s
2. This destruction of RBC’s causes release of inflammatory cytokines (TNF-α and IL-1β) which inhibit erythropoeisis
How do cerebral malaria, acute respiratory distress and placental malaria come about after infection? (same mechanism)
TNF-α and IFN-γ are released and they cause the expression of adhesion molecules on capillary walls. The red blood cells bind to the walls and cause a clot. This also causes further tissue inflammation and leukocyte migration into the vessels.
How does malaria cause renal impairment?
Anaemia and coagulation and inflammation. This causes metabolic acidosis, hypoxia and hyperventilation.
What protozoa causes giardiasis and what are the main clinical presentations of giardiasis?
Giardia Lamblia
Main features: Ongoing offensive diarrhoea (travellers diarrhoea), nausea, abdominal pain.
What disease does Trypanosoma cause? And what spreads this parasite?
African Trypanosomiasis (African sleeping sickness). Is spread by Tsetse fly
How does African Trypanosomiasis typically present, and what are differences between the two types?
Clinical presentation: Fever, lethargy, myalgia, personality change, weight loss, irritability
- Trypanosoma brucei rhodesiense = E/S Africa, causes acute illness in weeks-months
- Trypanosoma brucei gambiense = W/C Africa, causes chronic ilness, lasts for years
What protozoa would you immediately think of if patient presents with bloody diarrhoea?
Entamoeba histolyca (Amoebiasis)
What are the clinical manifestations of a patient suffering from cryptosporidiosis ?
Watery diarrhoea, no blood, abdominal pain and vomiting
How would you diagnose African Sleeping sickness?
Do blood film and CSF (demonstrates level of severity)
What does toxoplasmosis cause most commonly in AIDS patients?
Encephalitis and cerebral abscess
How does toxoplasmosis present commonly?
Neurological signs, fits, fever, headache, possibly confusion
How would you diagnose toxoplasmosis?
Toxoplasma serology and multiple ring-enhancing lesions on contrast enhanced CT/MRI of the brain
How would you diagnose cryptosporidiosis?
Stool microscopy and direct fluorescent antibody (DFA)
What 5 species of plasmodia cause human disease?
- P. falciparum
- P. ovale **
- P. vivax **
- P. malariae
- P. knowlesi
Increasing frequency of malaria is due to 4 reasons, what are they?
- Increased resistance of parasite to anti-malarials
- Increased resistance of mosquito to insecticides
- Ecological and climate changes
- Increased travel to endemic areas
At what time is a bite from a female anopheles mosquito most likely to have taken place?
Night (dusk–>dawn)
Merozoites are released into the bloodstream every …. hours?
P. malariae = every 72 hours
all others = 48 hours
What type of plasmodia is most likely to cause cerebral malaria?
P. falciparum
What is ‘rosetting”?
When knobs caused by parasite inside RBC bind to receptors on endothelial cells and then cause further uninfected RBC’s to bind to them –> clot
What can Quinine cause?
Hyperinsulinism –> Hypoglycaemic patient
To diagnose malaria you would do a thick and thin film under a light microscope x 3 (12 hours apart) What do the thick and thin films show?
Thick = Sensitive but low res, so tells you if malaria plasmodium present or not Thin = Identifies species and parasite count
What percentage parasite count would classify as severe malaria?
<= 2%
What symptoms would class as ‘complicated malaria’ (only for Falciparum)
- Extreme weakness
- Haemoglobinurea
- Impaired conciousness hypoglycaemia
- Parasite count <= 2%
- Spontaneous bleeding/DIC
- Urine pH <7.3
- Pulmonary oedema/ARDS
How would you treat non-falciparum malaria?
PO Chloroquine
How would you treat uncomplicated falciparum malaria?
PO Quinine/ Riamet
How would you treat P.vivax/ovale? And what two things would you check before prescribing it?
Primaquine - G6PD level + pregnancy status
How would you treat complicated falciparum malaria?
IV Artesunate/ Quinine
What is the difference between recrudescence, relapse and reinfection?
Recrudescence = under treated
Relapse = Reactivation due to hypnozoite
Reinfection
