Tropical Medicine Flashcards
What is the bacteria behind diptheria?
Corynebacterium diphtheriae
What is the pathophysiology of diptheria?
Produces exo-toxin, produced by a β-prophage
Exotoxin inhibits protein synthesis by catalyzing ADP-ribosylation of elongation factor EF-2
What are the clinical features of diptheria?
Diptheria membrane on tonsils caused by necrotic mucosal cells.(Pseudomembrane)
Bulky cervical lymphadenopathy
Neuritis
Heart block
What are viral haemorrhage fevers?
Dengue fever
Ebola
Lassa fever
Yellow fever
What are the features of dengue fever?
Fever
Headache - retrobulbar headache
Myalgia, bone pain and arthralgia (‘break-bone fever’)
Pleuritic pain
Facial flushing (dengue)
Maculopapular rash
Haemorrhagic manifestations e.g. - positive tourniquet test, petechiae, purpura/ecchymosis, epistaxis
Red flags:
- abdominal pain
- hepatomegaly
persistent vomiting
clinical fluid accumulation (ascites, pleural effusion)
What causes dengue fever?
Dengue virus is a RNA virus of the genus Flavivirus
Transmitted by the Aedes aegypti mosquito
incubation period of 7 days
What are severe haematological features of dengue fever?
Disseminated intravascular coagulation (DIC) resulting in:
thrombocytopenia
spontaneous bleeding
around 20-30% of these patients go on to develop dengue shock syndrome (DSS)
How should dengue fever be investigated and managed ?
serology
nucleic acid amplification tests for viral RNA
NS1 antigen test
Typically:
1. lymphopaenia
2. Thrombocytopenia
3. Raised aminotransferases
What is leprosy?
Granulomatous disease primarily affecting the peripheral nerves and skin. It is caused by Mycobacterium leprae.
What are the features of leprosy?
Patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
sensory loss
What are the types of leprosy, and their course?
Low degree of cell mediated immunity → lepromatous leprosy (‘multibacillary’)
- Extensive skin involvement
- Symmetrical nerve involvement
High degree of cell mediated immunity → tuberculoid leprosy (‘paucibacillary’)
- Limited skin disease
- Asymmetric nerve involvement → hypesthesia
hair loss
What is the treatment of leprosy?
Triple therapy: rifampicin, dapsone and clofazimine for 12 months
What is shistosomiasis What are the two forms of schistosomiasis?
Schistosomiasis Haematobium
Schistosomiasis Mansoni
Schistosomiasis japonicum
What are the features of an active schistosomiasis infection?
Swimmers’ itch
Acute schistosomiasis syndrome (Katayama fever)
- fever
- urticaria/angioedema
- arthralgia/myalgia
- cough
- diarrhoea
- eosinophilia
What is the life cycle of schistosomiasis haematobium?
Deposit egg clusters (pseudopapillomas) in the bladder, causing inflammation. The calcification seen on x-ray is actually calcification of the egg clusters, not the bladder itself.
pseudopapillomas in the bladder, they can cause an obstructive uropathy and kidney damage.
What are schistosomiasis haematobium at risk of long term?
Squamous cell carcinoma of the bladder
How is schistosomiasis haematobium treated?
Single oral dose of praziquantel
What is the life cycle of schistosomiasis mansion / japoncium?
Worms mature in liver - hepatosplenomegally/ splenomegaly due to portal system obstruction
Then inhabit the distal colon
What is the life cycle of schistosomiasis mansion / japoncium?
Worms mature in liver - hepatosplenomegally/ splenomegaly due to portal system obstruction
Then inhabit the distal colon
What are schistosomiasis mansion / japoncium at risk of long term?
Liver cirrhosis
Variceal disease
Cor Pulmonale
What bacteria causes botulism?
Clostridium botulinum
How does botulinum toxin work?
It is a neurotoxin: irreversibly blocks the release of acetylcholine
How can a patient get botulism?
Eating contaminated food
What are the features of clostridium botulism?
Patient usually fully conscious with no sensory Disturbance
Flaccid paralysis
Diplopia
Ataxia
Bulbar palsy
How is botulism treated?
Botulism antitoxin
What is meloidosis / whitmore’s disease?
Infection caused by the gram-negative bacterium Burkholderia pseudomallei
Found in trophic and subtropic regions
Endemic in soil and fresh surface water
Sign: Incubation period: 1-21 days ( mean around 9 days)
What is the treatment of meloidosis / whoitmore’s disease?
Initial intensive therapy: IV ceftazidime, imipenem, or meropenem for 10–14 days
Followed by eradication therapy: oral TMP/SMX (plus doxycycline) for 3–6 months
Adjunct therapy: abscess drainage.
How do you differentiate between zika, chickengunya and dengue?
Zika is prevalent in South America.
Chikengunya debilitating joint pain - abrupt onset fevers
How is Zika virus spread?
Mosquito
Complications of Zika virus?
Guillain barre
Microcephally
What is leishmaniasis? How is it spread?
An intracellular Protozoa. It is spread by bites from sandflies
What are the types of leishmaniasis and where are they acquired?
Cutaneous leishmaniasis: Leishmania tropica or Leishmania mexicana - South and Central America
Mucocutaneous leishmaniasis
caused by Leishmania braziliensis - India and Africa
Visceral leishmaniasis (kala-azar)
mostly caused by Leishmania donovani
occurs in the Mediterranean, Asia, South America, Africa
What are the features of visceral leishmaniasis?
Fever, sweats, rigors
Massive splenomegaly. hepatomegaly
Poor appetite (increased appetite and weight loss), weight loss
Grey skin - ‘kala-azar’ means black sickness
Pancytopaenia secondary to hypersplenism
the gold standard for diagnosis is bone marrow or splenic aspirate
How is diphtheria treated?
Management
intramuscular penicillin
diphtheria antitoxin
How is diphtheria grown / investigated?
Culture of throat swab: uses tellurite agar or Loeffler’s media
What is the commonest and most severe type of malaria?
Falciparum malaria
What are the features of severe malaria?
Schizonts on a blood film
Parasitaemia > 2%
Hypoglycaemia
Acidosis
Temperature > 39 °C
Severe anaemia
complications as below
What are the complications of malaria?
Cerebral malaria: seizures, coma
Acute renal failure: blackwater fever, secondary to Intravascular haemolysis, mechanism unknown
Acute respiratory distress syndrome (ARDS)
Hypoglycaemia
Disseminated intravascular coagulation (DIC)
What is the treatment of severe malaria?
Intravenous artesunate
When is plasma exchange indicated in malaria?
Parasite count > 10%
what are the features of yellow fever?
flu-like illness → brief remission→ followed by jaundice and haematemesis.
high fever, rigors, nausea & vomiting. Bradycardia may develop
features of cholera?
profuse ‘rice water’ diarrhoea
dehydration
hypoglycaemia
What type of bacteria is vibrio cholera?
Gram negative bacteria
Treatment of cholera?
Management
oral rehydration therapy
antibiotics: doxycycline, ciprofloxacin
How is typhoid transmitter?
Faecal oral route
What are the features of typhoid?
initially systemic upset as above
relative bradycardia
abdominal pain, distension
constipation: although Salmonella is a recognised cause of diarrhoea, constipation is more common in typhoid
rose spots: present on the trunk in 40% of patients, and are more common in paratyphoid
What causes typhoid? What causes paratyphoid?
Salmonella typhi and Salmonella paratyphi (types A, B & C)
What are the complications of typhoid?
osteomyelitis (especially in sickle cell disease where Salmonella is one of the most common pathogens)
GI bleed/perforation
meningitis
cholecystitis
chronic carriage (1%, more likely if adult females)
What are the features of katamya fever?
fever
urticaria/angioedema - red itchy bumpy rash on ankles / feet
arthralgia/myalgia
cough
diarrhoea
eosinophilia
What are the features of rabies?
prodrome: headache, fever, agitation
hydrophobia: water-provoking muscle spasms
hypersalivation
Negri bodies: cytoplasmic inclusion bodies found in infected neurons
What cytoplasmic inclusions do you see in rabies?
Negri bodies
What type of virus is rabies?
RNA rhabdovirus (specifically a lyssavirus) and has a bullet-shaped capsid
Travels up the neurone in a retrograde fashion
What is the main feature of tetanus?
Opisthontonus - that picture.. you know the one
In non-falciparum malaria, what additional treatment is needed to prevent relapses?
Primaquine
