Protozoa Flashcards
Protozoa
a) define
b) examples in the… i) intestines, ii) vagina, iii) blood
a) Single-celled eukaryotic organisms (definitive nucleus)
b) i) Giardia lamblia,
ii) Trichomonas vaginalis,
iii) Malaria, Trypanosoma spp.
54 year old male: 7-day business trip to Delhi 2-months ago, Loose stools since last day of stay in India. Ongoing offensive diarrhoea daily since return to UK, plus flatulence and abdominal cramps. a) Diagnosis b) Confirmed by...? c) Treatment
a) Giardiasis
b) Stool microscopy for ova, cysts and parasites
c) Metronidazole
45 year old Gambian:
Bitten on arm by insect: lesion developed 2 weeks later → Self-resolved
2 years later: fever, lethargy, myalgia, Weight loss ++, Personality change, Irritability, Increasing daytime somnolence and reduced consciousness
a) Diagnosis
b) How it is transmitted
c) What is Kerandel sign?
d) Ix
a) African trypanosomiasis
(different to American trypanosomiasis - Chagas’ disease)
b) Bites of infected tsetse flies
c) Delayed pain after compression of soft tissues (eg. blow to the tibia)
d) - Blood smear for mobile trypanosomes
- FBC (
23 year old elective student: 2-month visit to rural Botswana, Bloody diarrhoea: treated with metronidazole. On return to UK – Increasing RUQ pain a) Diagnosis b) Investigations and findings c) Management
a) Amoebiasis (entamoeba haemolytica)
b) - FBC - FBC, CRP, LFTs (raised)
- Serology - antibodies present
- Stool sample - trophozoites
- CT liver - abscess
c) - Metronidazole
- Fluid/electrolyte replacement
- Liver abscess - aspirate
34 year old woman: 1 week of watery diarrhoea, abdominal pain and now vomiting. Recent white water rafting. a) Likely diagnosis b) Investigations c) Management
a) Cryptosporidiosis
b) - Stool microscopy: DFA test
c) - Rehydration/ electrolyte replacement
- Anti-emetics, analgesia
- If HIV+ give HAART
36 year old Zimbabwean:
Recent HIV +ve diagnosis: CD4 count 70
- History of progressive left sided weakness, headaches, visual disturbance
a) Diagnosis
b) Other possible presentations of this condition
c) Ix - bloods, feature on CT
d) Rx - normal, in AIDS
a) Toxoplasmosis (toxoplasma gondii)
- usually transmitted via cat faeces or undercooked meat
b) - Isolated lymphadenopathy
- Chorioretinitis (reduced VA and floaters)
- Foetal abnormalities if acquired in pregnancy
c) - Bloods: toxoplasma serology
- CT head: Multiple or single ring-enhacing lesions
d) Normal - pyrimethamine + sulfadiazine + folinic acid
AIDS - co-trimoxazole
42 year old male:
Returned from Safari in Kenya 2 weeks ago. Has had a fever, rigors and myalgia for 36 hours. Presents to ED increasingly drowsy.
- O/E: GCS 10/15, Temp 39.2º, HR 110, BP 90/50, Jaundiced. Splenomegaly.
a) Diagnosis
b) Give 3 severe complications
c) Ix
d) Rx
a) Malaria
b) Blackwater fever, cerebral malaria, renal failure, shock, ARDS, hypoglycaemia (basically all unique to plasmodium falciparum)
c) 3 separate thick and thin films (different times)
d) - If severe: IV ARTESUNATE or IV QUININE
- if uncomplicated: oral
- if non-falciparum: oral chloroquine
Malaria vs. dengue
- Dengue (DAY-biting)
- Malaria (night-biting), some different epidemiology
Malaria protozoa life cycle
- Merozoites reproduce in RBCs and haemolyse approximately every 48 - 72 hours
- Vivax/ovale - hypnozoites lie dormant in liver, can recur years later
Malaria.
a) What is it?
b) Risk factors
c) Clinical features - symptoms and signs
d) Signs of severe disease (think complications)
a) Protozoal infection transmitted via mosquitoes
b) - Travel in endemic area
- Lack of chemoprophylaxis
- Immunocompromised - elderly, pregnant, young children, HIV
c) - FEVER (often tertian/quartian), chills + sweats, headache, myalgia, fatigue, nausea + vomiting, diarrhoea
- Signs: hepatomegaly, splenomegaly, jaundice
d) - Cerebral malaria: reduced GCS, convulsions, coma
- Respiratory: SOB, ARDS
- CV: hypovolaemia, shock, AKI
- Haem: haemoglobinuria (blackwater fever), DIC, bleeding, splenic rupture
- Metabolic: sepsis, hypoglycaemia, acidosis
Malaria: initial management
a) Initial assessment
b) Gold standard investigation
c) Other standard investigations
d) Investigations in very unwell patient
e) Who must be notified?
a) - A-E
- Consider admission (admit all falciparum malaria and any complicated non-falciparum cases)
b) Thick and thin blood smears stained with Giemsa stain:
- If negative: do at least two further films over the next 48 hours, before excluding the diagnosis
c) - Bedside:
- Bloods: FBC (thrombocytopenia, anaemia), LFT (raised), U+Es (?raised creatinine), glucose (low?), G6PD activity (before administation of primaquine)
d) - Bloods: Blood gases, blood cultures, clotting studies.
- Urine and stool culture.
- CXR / lumbar puncture.
e) Public Health England
Malaria: management
a) Severe/complicated falciparum malaria
b) Uncomplicated falciparum malaria / mixed infection
c) Non-falciparum malaria (vivax, ovale, malariae, knowlesi)
d) Only treatment for the eradication of hypnozoites (in vivax/ovale) - beware in who?
a) - 1st line - IV artesunate (+ doxycycline)
- alternatives: IV quinine (safe in pregnancy)
b) - 1st line: Artemisinin combination therapy (ACT)
- alternatives: atovaquone/progaunil (Malarone) or quinine/doxy
c) - 1st line: chloroquine
d) Primaquine
- Seek expert advice in patients with G6PD (primaquine leads to haemolysis) - hence must test G6PD activity before administration
3 diseases that confer some immunity to malaria
- Sickle cell
- G6PD
- Thalaessaemias
Malaria prophylaxis: ABCD
Awareness of the risk of malaria.
- Geography - check foreign office for travel destination
- High-risk groups: backpackers, immunosuppressed, etc
Bite prevention.
- Wear long sleeves and long trousers
- Mosquito nets
- DEET insect repellant
- Insecticide sprays
- Sleep indoors, in air-conditioned rooms
Chemoprophylaxis.
- note: not 100% effective
- Atavaquone/progaunil (malarone),
- doxycycline,
- mefloquine
- Chloroquine (note: some areas have chloroquine-resistant falciparum malaria, eg. sub-Saharan Africa)
Diagnosis and prompt treatment.
- Early admission and treatment reduces risk of complications
Antimalarial drugs.
a) Which drug has the most resistance?
b) Advice for pregnancy
c) Only regimens suitable in pregnancy
d) Which one can cause retinopathy if used for > 6 months?
e) May rarely cause anxiety, vivid dreams, depression and tinnitus
f) Doxycycline - cautions
g) Common side effects of all
a) Chloroquine
b) Avoid travelling to malarious areas; if have to take, consider folic acid also
c) - Quinine + clindamycin
- Chloroquine (if not chloroquine-resistant area)
d) Chloroquine
e) Mefloquine
f) TERATOGENIC, upset stomach, thrush in women, and photosensitivity
g) Headache, nausea, stomach upset
