Fever in a Returning Traveller Flashcards
State some common causes of a fever in a returning traveller
- Malaria
- Dengue
- Rickettsia
- Typhoid fever
- Primary HIV infection
- Chronic bacterial infections
- TB
- Parasitic infections
What are the most common tropical infections seen in clinical practice?
- Malaria
- Dengue fever
- Typhoid (enteric fever)
What questions must you ask in the history of someone presenting with fever ONCE you have established that they have been travelling?
- Where? (particularly interested in tropic regions)
- When did they go?
- How long did they stay for?
- Find out the time of onset and nature of various signs & symptoms (in other words make a detailed time line)
- Where did they stay? (was it a modern hotel or a hostel in rural area. Did they stay with family & friends?)
- What did they do whilst they were there: recreational activities & exposure?
- What food did they eat?
- Sexual history inlcuding sexual exposure whilst abroad and at home
- Did they have any pre-travel immunizations & chemoprophylaxis?
- PMH and any predisposition to infection e.g. immunosupressed
When asking about pre-travel immunizations and chemoprophylaxis in a returning traveller, what questions do you want to ask?
- Vaccination against specific diseases e.g. hepatitis A, hepatitis B, typhoid, tetanus
- Childhood vaccinations e.g.MMR and others such as yellow fever & rabies when appropriate
- If travel was to malarious area ask whether malaria chemoprophylaxis was taken and ask/investigate as to whether it was taken as directed/correctly. Also ask about personal protective measures e.g. insect repellant, bed-net use etc…
Most of the severe, rapidly progressive infections (e.g. falciparum malaria & haemorrhagic fevers) acquired in tropical or developing countries become apparent within how many months?
1-2 months
State some diseases with the following incubation times:
- 0-10 days
- 10-21 days
- >21 days
- 0-10 days: dengue, rickettsia, GI infections
- 10-21 days: malaria, typhoid, primay HIV
- >21 days: malaria, TB, parasitic infections, chronic bacterial infections e.g. brucella, joint & bone infections, endocarditis
When examining a returning traveller with fever you must do a thorough clinical examination; what specific organ systems/organs must you pay close attention to and why?
- Cardiovascular: pulse rate that is slow for degree of fever- think typhoid fever
-
Skin:
- Maculopapular rash: dengue, leptospirososis, rickettsia, infectious mononucleosis, primary HIV infection
- Rose spots: typhoid fever
- Black necrotic ulcer with erythematous margins: rickettsia
- Petechia, echhymoses or haemorrhagic lesions: dengue, meningococcaemia & viral haemorrhagic fever
- Eyes: conjunctival suffusion in leptospirosis
- Splenomegaly: mononucleosis, malaria, typhoid, brucellosis
- Neurological system: meningo-encephalitis
What investigations would you consider for a returning traveller presenting with a fever?
- FBCs
- LFTs
- U&Es
- Malaria smears +/- antigen detection dipstick x3 over 24-48hrs
- Blood cultures x2
- Urinalysis +/- urine culture
- Stool culture +/- stool for OVA, cysts and pararsites
- CXR
- HIV, hep B, hep C and syphilis serology
- Acute serology tube to be saved in lab
What is malaria?
Infectious disease caused by Plasmodium family of protozoan parasites
(protozoa= single celled organisms)
Discuss how malaria is transmitted
- Spread through bites from female Anopheles mosquitos
- Mosquito feeds on infected blood. Malaria then reproduces in gut of mosquito producing thousands of sporozoites (malaria spores)
- The now infected mosquito goes and bites another human/animal and injects a number of malarial sporozoites
- These malarial sporozoites travel via blood to infect hepatocytes. Once in hepatocytes they can lie dormant as hypozoites for several years (as in P.vivax and P.ovale) or undergo reproduction (at this point no symptoms occur i.e. this is incubation period)
- Sporozoites in liver become schizonts which rupture to release merozoites into bloodstream
- Merozoites invade erythrocytes, reproduce in RBCS over a period of 48hrs, and cause RBCs to rupture; resulting in massive release of merozoites and a haemolytic anaemia
- RBC rupture causes cytokine activation by leucocytes producing characteristic malarial symptoms & fever
State the 5 plasmodium species which can cause malaria
- Plasmodium falciparum
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae
- Plasmodium knowlesi
Which plasmodium species causes the most severe malaria?
P.falciparum
Which two plasmodium species form hypnozoites in liver and consequently have a longer incubation period/can lie dormant for several years?
- Plasmodium vivax
- Plasmodium ovale
What is meant by tertian rhythm, in regards to malaria?
Why do pts get a tertian rhythm?
- Pts with malaria get fever spikes every 48 hours (can also think of as getting fever every other day or every 3rd day if you count first day of fever as day 1)
- Merozoites which are released from schizonts in liver infect and reproduce in RBCs; their reproduction in RBCs takes 48hrs. They then cause RBC lysis and release lots more merozoites. These merozoites will then infect more RBCs and start the 48 hr reproduction cycle again. The RBC lysis causes cytokine activation by leucocytes producing characteristic symptoms & fever
Discuss how you can narrow down what the likely plasmodium species causing the malaria is based on how often pt experiences fever?
- Fever every day: falciparium
- Tertian rhythm (fever every 48hr/every 3rd day/every other day): falciparum, vivax, ovale
- Quartan malaria (fever every 72hrs/every 4th day): malariae
*NOTE: falciparum can have classical tertian rhythm however it can also have daily RBC rupture leading to daily fevers. Plasmodium malaraie clasically has fever every 4th day. Can also use incubation times to help distinguish between falciparum, vivax and ovale.
What animals, and in what region, is Plasmodium knowlesi common?
- Form of parasite found in southeast Asia primates
- Malaria presenation may vary but severe disease can quickly become fatal due to rapid mulitiplicaiton of organisms
State some risk factors for developing malaria
- Travel to an endemic area/where malaria is common
- Lack of chemoprophylaxis
- Lack of personal protective measures e.g. insect repellant, bed-net
- Babies & young children have higher risk of developing malaria
- Using contaminated needles
What regions is malaria common in?
- Sub-saharan africa
- South east asia
Discuss the incubation times of different species of plasmodium causing malaria
- P.falciparum: 7-14 days
- P.vivax & P.ovale: 12-18 days (but can be longer- months to years- due to hypnozoite stage in liver)
- P.malariae: 18-40 days
*Therefore, can see that malaria typically presents within a month of infection
Discuss the difference between thin and thick blood films including what each is used for
Thick
- Analyses larger volume of RBCs
- Sample is ‘laked’ to rupture RBCs
- Used to identify if parasite is present
Thin
- RBCs not lysed/ruptured
- Used to idenitfy Plasmodium species and calculate the % of RBCs infected with parasites
In what regions is dengue fever present?
- South America
- Southeast Asia
- Africa
What are the symptoms & signs of dengue fever?
- Skin flushing (with islands of normal skin) which may develop into maculpapular rash
- Fever
- Headache
- Pain behind eyes
- Myalgia
- Arthraglia
- Nausea & vomitting
- Abdo pain
- Loss of appetite
*
What regions is typhoid fever common in?
- Asia
- Africa
- Middle east
- Southern & central America
*In places with poor sanitisation
State some signs & symptoms of typhoid fever
Symptoms
- Sustained fever
- Anorexia
- Malaise
- Vague abdo discomfort
- Constipation or diarrhoea
- Dry cough
Signs
- Pulse-temperature dissociation (low pulse rate for temperature)
- Hepatosplenomegaly
- Rose spots on chest & abdomen (30-50%- but may disappear before presentation)
