Tropical diseases Flashcards
Traveller in Bangladesh has copious watery diarrhoea, severe dehydration
a) Cause
b) Pathophysiology of the diarrhoea
c) treatment
a) Cholera - causes “Rice water” diarrhoea, copious amounts, severe dehydration
b) Cholera endotoxin B attaches to GM1 receptor on small bowel mucosa, this leads to entry of the A1 subunit which causes sustained cAMP release and subsequent massive water/electrolyte secretion
c) Erythromycin, Doxy or cipro
- Rehydration
Amoebiasis
a) Endemic areas
b) Presentation and finding on colonoscopy
c) Investigations
d) Management
a) Entamoeba histolytica, endemic in South and Central America, West Africa and Southeast Asia
b) 90% of infections are asymptomatic
- 10% cause dysentery, with ulcerated colonic mucosa, may have a palpable mass (amoeboma)
- Some progress to liver cystic disease - RUQ pain, fever, weight loss, malaise, (between 8 weeks and 1 year of incubation)
c) - Stool for ova cysts and parasites (may need 3-6 samples)
- Antibody tests for liver amoebiasis
d) - Asymptomatic cysts on faeces - Diloxanide furoate
- Dysentery: Metronidazole
- Amoebic liver cysts: Metronidazole +/- drainage
Typhoid fever
a) Endemic areas
b) Presentation
c) Cause of GI bleed in some cases
d) Investigations
e) Management
a) Salmonella typhi, endemic in Africa and Asia
b) - Fever to 40C worse in the evenings
- Fagets sign (absence of tachycardia given high fever)
- Dicrotic carotid pulse
- Rose coloured blanching rash
- May have constipation, distension, or “pea-soup” diarrhoea
c) Peyer’s patches ulceration, or DIC
d) Blood cultures usually positive
- also take urine and stool cultures
e) - Mild: azithromycin or cipro
- Severe: IV cephalosporins
Giardiasis
a) Endemic areas
b) Presentation
c) Diagnosis
d) Treatment
a) India, North/East/Sub-Saharan Africa, Eastern Europe, Central/South America
b) 1-2 weeks post-exposure: Diarrhoea, steatorrhoea, foul-smelling, flatulent, bloating (generally lasts around 4 weeks)
Later, may have weight loss, IBS and reactive arthritis
c) 3x stool samples, or 1x stool antigen test
- Trophozoites (pear-shaped), sucking disks and flagella, as well as cysts*
(As stool samples are often falsely negative in giardia)
*Cryptospiridiosis would cause the cysts but not other features
d) Metronidazole
Cutaneous larva migrans
a) Cause
b) Presentation
c) Treatment
a) Hookworm - ancylostoma brasiliense
b) - Intensely itchy tortuous skin rash
- Common in beach holidays
- May also cause abdominal pain and IDA
c) Albendazole/ other antiparasitic
Filariasis
a) Cause
b) Disease associated
a) Wuchereria bancrofti
b) Lymphatic filariasis - elephantiasis
Leishmaniasis
a) Endemic areas
b) Presentation
c) Treatments
a) South Asia, East Africa, Brazil, Mediterranean
- Caused by sandfly bite
b) Cutaneous lesion at site of bite
- may later cause mucocutaneous ulceration (e.g. in the oral mucosa)
- more rarely there is a visceral form which causes hepatosplenomegaly and bone marrow failure
c) Amphotericin, and many other treatments
Loa Loa
Eye worm - causes river blindness
Peruvian cattle farmer with fever, weight loss, bone pain, abdo pain, splenomegaly, pancytopenia, confusion and ataxia
a) Cause
b) Diagnosis
c) Treatment
a) Brucellosis
Brucella bacteria, from unpasteurised milk/cheese or contact with contaminated cattle/meat
- Common in India and other developing countries
b) - Blood cultures (note - very slow growing, may take around 5 days to grow)
- Liver biopsy may show non-caseating granulomas (vs. caseating in TB)
- Bone marrow aspirate and culture gold standard
c) Doxycycline + rifampicin for 6 weeks
Lepromatous leprosy vs tuberculoid leprosy
Lepromatous - AFB grown at site
Tuberculoid - no AFB, just T-cell infiltrates
(T for TB and T-cells)
Both can cause peripheral neuropathy, often distal to the skin lesions
Hypoaesthetic plaque like lesions
a) Diagnosis
b) How is it diagnosed
c) Treatment
Leprosy
AFB on skin biopsy
Rifampicin, clofazimine, dapsone for 2 years
Schistosomiasis (AKA bilharzia)
a) Risk factor
b) Different bugs and their presentation and investigations
c) Management
a) Swimming in fresh water lakes in Africa (especially East Africa - lake Victoria, lake Malawi)
- Causes “swimmers itch” within hours
- Weeks later, when eggs start hatching - Katayama fever (fever, rash, LN, HSM, wheezing)
- Eosinophilia, raised LFTs
b) Schistosoma mansoni:
- Intestinal presentation
- Risk of liver failure
- Can cause extra-intestinal features
- Stool sample for ova
Schistosoma haematobium
- Urinary presentation - dysuria, haematuria, haematospermia
- Risk of ESRD and bladder Ca
- Urine microscopy and culture for ova
c) Management: praziquantel (take at night one-off dose; may need repeating in a few months)
Malaria subtypes
a) All stages of the cycle visible on blood film..? (treatment?)
b) Uncommon in West Africans due to lack of Duffy red cell antigen receptor for this subtype
c) Most characteristic feature of falciparum
d) How many blood films are needed to exclude malaria?
a) P. ovale* –> chloroquine
(as opposed to p. falciparum where only trophozoites and gametocytes are visible on film)
*think ovale = oval = all stages of cycle
b) P. vivax
c) Falciparum gametocytes
d) 3 blood films (if in exam it says a malarial blood film was done, this doesn’t exclude)
Malaria treatment
a) Severe malaria (falciparum or otherwise)
b) Uncomplicated falciparum malaria
c) Non-falciparum malaria
d) Treatment for p. ovale/vivax hypnozoites in the liver (must screen for what first?)
a) - IV artesunate
- 2nd line: IV quinine
b) Artemisinin combination treatment (ACT), e.g. Artemether with lumefantrine
c) ACT or chloroquine*
*Not to be used for falciparum treatment due to high levels of resistane
d) After acute treatment with ACT/chloroquine:
- Primaquine to treat hyponozoites
- Screen for G6PD first (primaquine can cause haemolysis)
American trypanosomiasis (Chagas disease)
a) Romana’s sign
b) Other features
c) Endemic areas
d) vs African trypanosomiasis
a) Periorbital swelling and conjunctivitis
b) Fever, myalgia, LN, HSM, myocarditis and arrhythmias, heart failure, dilated oesophagus and colon
c) Latin America
d) - Different trypanosomes causing it.
- African - chancre present. Causes more sleepiness. Haemolytic anaemia
- American - more arrhythmias, oesophageal and colon issues long term
