Micro - Fever in the Returning Traveller Flashcards
What are the causes of fever in a returning traveller
Tropical diseases e.g. malaria, typhoid, dengue, viral haemorrhagic fever, Chikungunya
Bacterial diarrhoea e.g. E. coli, cholera
UK e.g. UTI, pneumonia, influenza
STIs e.g. HIV seroconversion
What diseases do mosquitos carry
Malaria [Anopheles Mosquito]
Elephantiasis
Dengue
Yellow fever
West Nile virus
Zika virus
What is malaria and what are the risk factors
Protozoal infection (Plasmodium spp.) spread by female Anopheles mosquito (bites at night, attracted by heat + CO2)
Returning traveller from endemic areas (Asia / Africa / South America) – ask about whether they took malaria prophylaxis while away
Describe the life cycle of malaria
- Bite
- Exo-erythrocytic cycle: Liver stage (where the parasite lies dormant in the liver = hypnozoite stage) → schizont formed
- Erythrocytic stage: trophozoite (ring stage) → schizont → ruptured schizont → Malaria breaks down red cells → haemolysis
What are the types of malaria and what are the features on blood film
Falciparum: P. falciparum (most common and most severe)
- Double dotted rings
Non-falciparum: Symptoms less severe, 48hr tertian fever
- P. vivax: Schüffner’s/Schaffner’s dots
- P. ovale: Schüffner’s/Schaffner’s dots, enlarged red cells, comet forms
- P. knowlesi: daisy-head appearance, square ring forms
How is malaria prevented
A, B, C, D:
Awareness of risk - geographical (high altitudes - different transmission), individualise e.g. pregnancy, season, accomodation
Bite prevention e.g. bite repellent, insecticide-treated nets (ITNs)
Chemoprophylaxis e.g. malarone, mefloquine, doxycycline (varies by region)
Diagnose promptly and treat without delay
What are the symptoms of malaria
Fevers – cyclical or continuous with spikes
Malaria paroxysm – chills, high fever, sweats
What are the features of severe malaria
End-organ damage:
High parasitaemia (>2%) or ONE schizont
Altered consciousness with/without seizures
ARDS or pulmonary oedema
Metabolic acidosis (pH <7.3)
Renal failure, haemoglobinuria (blackwater fever)
Hepatic failure
Severe anaemia (<8g/dl)
Coagulopathy ± DIC
Circulatory collapse / shock (BP <90/60)
Hypoglycaemia (<2.2)
How is malaria diagnosed
3x thick and thin blood smears (Field’s or Giemsa stained)
- Thick = screen for parasites
- Thin = identify species and quantify parasitaemia (how many RBCs are parasitised)
FBC: thrombocytopenia
Malaria antigen detection testing
- Paracheck-PF (Detect plasmodial HRP-II)
- OptiMAL-IT (Detect parasite LDH)
What classifies mild and severe parasitaemia
Mild = not vomiting, low parasitaemia, ambulant
Child, severe = >2%
Adult, severe = >10%
What is the management for non-falciparum malaria
- Chloroquine (3 days)
- Primaquine for hypnozoites (14 days) - MUST CHECK G6PD BEFORE
What is the management for mild falciparum malaria
- Artemisinin Combination Therapy (ACT): artemisinin + lumefantrine
- Oral malarone
What is the management for severe falciparum malaria
- A-E
- Correct hypoglycaemia
- IV fluids (careful not to overload0
- IV artesunate
What is dengue fever and how is it spread
Flavivirus
Vector: Aedes aegypti mosquito
Short incubation (matter of days)
Urban disease
What are the clinical features of dengue fever
Main features: Fever (high), Headache (retro-orbital), Myalgia, Erythrodermic rash (50%)
Other features: Bleeding, Hepatitis
Severe: Encephalitis, Myocarditis
Can progress to dengue haemorrhagic fever and dengue shock (those previously infected with a different serotype) after day 4-5 (as fever comes down)
What investigations should be done for dengue fever
Serology (IgM 5-7 days)
PCR
Dengue cross-reacts with other flavivirus IgG (JE, yellow fever)
What is the treatment for dengue fever
Self-limiting: supportive treatment
Identify high risk patients: high Hct, low platelets
What is typhoid fever caused by
Salmonella typhi or paratyphi (Gram-negative rod)
Insidious onset (incubate 7-18 days; up to 60d)
Most from South Asia (Indian Subcontinent)
What are the clinical features of typhoid fever
High prolonged fever
Headache
Rose spots (rare)
Constipation
Dry cough
What are the complications of untreated typhoid fever
- Fever, fluctuations with bradycardia, malaise, headache, cough, epistaxis
- Extreme fatigue, high fever, plateau, bradycardia, delirium, rose spots, distended and painful abdomen, hepatosplenomegaly
- Complications
- intestinal haemorrhage (bleeding in congested Peyer’s patches)
- Perforation in the distal ileum → septicaemia
- Respiratory complications
- Encephalitis
What is the treatment for typhoid fever
Oral rehydration solution
Empirical ceftriaxone (IV, 2g) →Azithromycin (PO, 500mg BD, 7 days)
Vaccinate (Vaccine is only partially protective against S. typhi and offers no protection against S. paratyphi)
What is mononucleosis caused by and what are the features on investigations
EBV or CMV
Tonsillar enlargement with exudates
Atypical lymphocytosis
Monospot
IgM +ve for EBV/CMV
What is Rickettsial disease
Arthropod vector (ticks, lice, mites)
Spotted fever (RMSF, MSF, African tick bite fever)
Typhus - epidemic (lice) and endemic
Scrub typhus
Fever, headache, myalgia ± eschar
Obligate intracellular bacteria
Invades endothelial cells → vasculitis
What investigations/treatment is indicated for rickettsial disease
Diagnosis: acute and convalescent serology
Treatment: doxycycline
What is suggested by skin rash + eosinophilia
KATAYAMA FEVER
associated with swimming in fresh water
