Travel-related Infections Flashcards
What are some of the more important tropical diseases?
Malaria Typhoid Dengue Schistosomiasis Rickettsiosis Viral haemorrhagic fevers Zika
What is the vector for malaria?
Which species of malaria parasite is the most significant?
Female anopheles - the mosquito
Plasmodium falciparum - the parasite - most severe
Vivax, ovale, malariae, knowlesi - ‘benign’
What are the clinical features of malaria?
Fever Rigors Headache Myalgia/Arthralgia Weakness Anorexia Diarrhoea
May get spleno or hepatomegaly
What are some complications of malaria?
Cerebral malaria - encephalopathy Blackwater fever Pulmonary oedema Jaundice Severe anaemia Algid malaria
How is malaria diagnose?
Thick and thin blood films - main
- Giemsa, Field’s stain
Quantitative buffy coat
- centrifugation, UV microscopy
Rapid antigen tests
What are markers of complicated malaria?
Impaired consciousness or seizures Hypoglycaemia Parasite count >2% Low haemoglobin Spontaneous bleeding Haemoglobinuria Renal impairment or pH <7.3 Pulmonary oedema or ARDS Shock
How is uncomplicated malaria (falciparum) treated?
Usually treat for 3 days
- Chloroquine OR
- Mefloquine OR
- Malarone OR
- Riamet (artemether/lumefantrine) OR
- Quinine for 7 days + oral doxycycline/clindamycin
Also
- O2, maintain glucose, correct anaemia, dialysis, transfuse
What is the treatment for complicated malaria?
IV quinine + oral doxycycline/clindamycin IV artesunate (unlicensed) Switch to oral when possible
What is the treatment for the benign forms of malaria?
Chloroquine - 3 days
Riamet - 3 days
Add primaquine for 14 days in vivax and ovale to eradicate liver hypnozoites
What are the pathogens that cause typhoid, what is its incubation period, and how does it present and progress?
Salmonella typhi and paratyphi
Incubation of 1-4 weeks
First week:
- High fever
- Headache
- Adominal pain
- Constipation
- Dry cough
- Lethargy
- neutrophilia, bradycardia
In week two:
- fever peaks
- diarrhoea begins
- tachycardia
- neutropenia, tachycardia
Week three (complications)
- intestinal bleeding
- perforation
- peritonism
- metastatic infections
How is typhoid diagnosed and treated?
Clinically - not easy, by evolution of features
Lab - blood/urine/stool culture of typhi (or paratyphi)
- bone marrow culture also possible
Oral azithromycin - choice for asian-acquired uncomplicated
IV ceftriaxone - if complicated, or concerned about oral absorption
How is dengue transmitted, and how does it present?
Aedes aegypti mosquito
Sudden fever Severe headache, retro-orbital pain Severe myalgia and arthralgia Macular/maculopapular rash Haemorrhagic signs - petechiae, purpura, tourniquet test
How is dengue diagnosed and treated?
Generic tests
- Thrombocytopenia
- Leucopenia
- Elevated transaminases
- Positive tourniquet test
PCR and serology
No specific therapeutic agents - supportive
- complicated e.g. haemorrhagic fever or shock syndrome - IV fluid replacement, platelets, plasma
How is schistosomiasis spread and what strains are there?
Freshwater snails - swimming in contaminated water
S. haematobium
S. mansoni
S. japonicum
What are the clinical features of schistosomiasis?
Swimmers itch - clears after 24-48 hours
> Invasive stage: cough, abdo discomfort, splenomegaly, eosinophilia,
> Katayama fever after ~15 days
+ prostrate, fever, urticaria, lymphadenopathy, diarrhoea
Dysentery/haematuria after few weeks suggests presence of eggs in bowel/bladder
How is schistosomiasis diagnosed and treated?
Clinical diagnosis
Antibody tests
Ova in stools/urine
Rectal snip
Treated with praziquantel - 20mg/kg - two doses 6 hours apart
+ prednisolone if severe
What are the clinical features of rickettsiosis? how is it spread?
Abrupt onset swinging fever Rash - macular or petechial Headache Confusion Endovasculitis Bleeding
From ticks (tick typhus) - rickettsia conorii/africae
How is rickettsiosis diagnosed and managed?
Clinical diagnosis
Serology
Tetracyclines e.g. doxycycline
How is zika transmitted?
Daytime-biting aedes mosquito
Also by sexual contact, blood transfusion
What are the clinical features of zika? How is it treated?
No or mild
- headache, rash, fever, malaise, conjunctivitis, joint pains
- like dengue
Can cause Guillain-Barre
Supportive treatment - no antiviral therapy
What is the most common cause of fever in the returning traveller?
Malaria by far
What are the key questions/things to consider in a suspected tropical illness?
Travel history Precautions that were taken Risks that were taken Symptoms Consider incubation periods
What are some important signs common in tropical diseases?
Rash - typhoid, typhus, dengue
Jaundice - hepatitis, malaria, yellow fever
Lymph nodes - leishmania, trypanosomiasis
Liver - malaria, typhoid, amoebic abscess
Spleen - visceral leishmaniasis, typhoid, malaria
What are some key investigations in suspected tropical illnesses?
FBC Malaria films LFTs Stool microscopy and culture Urine analysis and culture Blood culture CXR
plus specific tests for each suspected illness
