Diagnosing The Tropical Traveller

Global travel trends have meant a huge increase in the numbers of people travelling abroad, and to increasingly remote countries. Travel is cheaper, and people generally have a greater proportion of disposable income.
There is a greater awareness of different cultures through the medium of television and more opportunities to travel related to study or work.

• In the 1960's international travellers numbered <100 million. By 2002 this number was closer to 715 million.¹
• Between 1990 and 2000 there was 4.3 % growth annually in the tourism trade, with the largest growth in travel to the Middle East, Asia and the Pacific.²

• Travel departure and return dates
• Countries visited, including stop-overs
• Destinations within the countries; rural or urban
• Climatic conditions, season
• Exposure to bites: insect, arachnid, reptile, mammal
• Exposure to animals, including bites and licks
• Exposure to ill people
• Unprotected intercourse and partners
• Type of food and liquids consumed, how and where prepared
• Vaccination history: review certificate and compliance
• Type of travel
• Quality of travel
• Medications (specific for trip and routine)
• Injuries or illnesses (how and where treated; injections given, blood taken, blood transfused, surgery, sterility of equipment and supplies)
• Timing and sequence of symptoms

Fever

• Malaria:
  • This should be considered in any patient presenting with fever, who has been to a malaria endemic area within the last year.⁴
  • Clinically the patient may complain of fever, chills, sweats, headaches, muscle pains, nausea and vomiting.
  • Severe malaria (P.falciparum) may lead to confusion, coma, neurological signs, severe anaemia and respiratory difficulties.
  • Gold standard diagnosis is finding malarial parasites on a slide.
• Hepatitis A:
  • This takes approximately one month before symptoms appear.
  • These are generally sudden onset of fever, fatigue, nausea and then jaundice.
  • Full recovery takes weeks.
  • The incidence of hepatitis A in travellers to countries of high or intermediate risk of transmission has been found to be 3.0-11.0 per 100,000 person-months abroad for all travellers, and 6.0-28.0 per 100,000 for those presumed to be non-immune.⁵
  • Food that is handled by infected workers is a source of transmission for tourists.
• Typhoid Fever:
  • This is reported from virtually all countries, but is concentrated in developing countries and areas with inadequate sanitation.
  • Fever is the hallmark of the disease.
  • Other features are relative bradycardia, dry cough, constipation and splenomegaly.
  • Rash (rose spots) headache, and diarrhoea may occur.
  • Most people will clear the bacterium from their system, but may continue to shed into stool even when feeling well again, inadvertently infecting others.
• Cholera:
  • Incidence is 2 cases per million travellers.
  • It is actually quite difficult to catch.
• Yellow fever:
  • This is found in parts of South America and Africa.
  • Vaccination is available and certification required for entry to some countries.
  • Also consider Lassa fever for travellers from Nigeria, Sierra Leone and Liberia.
  • Features include fever, exudative sore throat, facial oedema and prostration.
  • Diagnosis is made on serology.
• Dengue fever:
  • Arbovirus infections are the main cause of viral fevers in returned travellers, and tend to have short incubation periods, typically less than 2 weeks.⁶
  • Dengue fever is the most common arborvirus in travellers and is transmitted by Aedes mosquitoes, which tend to be urban and to bite during the day.
  • Dengue fever is present in and increasing throughout the tropics.
• Typhus:
  • This has four different subtypes.
  • It is carried by the human louse.
  • It is found particularly in war-torn countries e.g south America and Africa.
  • It has 100% mortality in epidemic conditions.
• Marburg and Ebola viruses:
  • They are found in the Sudan, Zaire and Kenya.
  • Patients present with fever, myalgia, diarrhoea and vomiting, pleuritic pain, shock and bleeding tendency.
• Rabies:
  • This presents as a non-specific fever ±pharyngitis.
  • The bite site may itch.
  • Common sources are bats and dogs.
• Plague:
  • Is carried by rodent fleas and is common worldwide.
  • The most common is Bubonic, which features tender swelling of the lymph nodes - buboes.
• Brucellosis:
  • Is carried in farm animals and their products.
  • Beware unpasteurised cheeses in countries with poor public health systems.
  • Symptoms are like flu.
• Histoplasmosis:
  • Is transmitted by fungal spore.
  • Recent cases have been through bat caves with guano.
  • Pre-existing lung disease increases the risk to the traveller.
  • Acute disease is mild, chronic is more serious.
  • The fever is accompanied by chest pain and cough.
  • Early referral to the local infectious diseases unit will provide most useful, up-to-date advice on management.

Also consider septicaemia and meningitis.

Diarrhoea

This is the most frequent problem found in travellers. Up to 40% of short-term travellers to developing countries, and up to 70% of long-term travellers will experience at least one bout of diarrhoea.⁷ Most cases of diarrhoea are mild, of short duration and do not require antibiotic treatment.
Because it is caused by eating and drinking contaminated food and water, people travelling in primitive conditions will experience more problems. The highest risk is found with travel to Asia, Africa and Latin America.

• Escherichia Coli and Giardia spp. are the most common causes. Symptoms vary but most people have 4-5 stools per day for 3-4 days. High fever, bloody stools and significant abdominal pain are not associated with Giardia and should prompt referral. Supportive measures, such as Lomotil® or Immodium® may be useful whilst the antibiotic takes affect. Ensure adequate rehydration.
• Salmonella spp., Shigella spp., Campylobacter spp. and Entamoeba histolytica are other potential causes.
• Cholera is a problem where there are high levels of contamination by human waste. This will make the food and water smell so bad that few tourists would ever ingest it. The symptoms are usually limited to a few days of watery diarrhoea. Ensure adequate rehydration, with sugar and salt replacement if severe. Diarrhoea may exceed 1 litre per hour if severe.
• Worms: Roundworms are found off the beaten track in the tropics. Pink-white in colour and up to 6 inches in length. Whipworms are shorter and curved. Found in contaminated food and water in the Tropics. The tapeworm is flatter, like a ribbon.They have been known to reach up to thirty feet. They can be from beef, fish or pork (cysticercosis). All these worm types do not divide in humans, but they may lead to unpleasant and dangerous complications e.g. epilepsy in neurocysticercosis. Medical treatment e.g. niclosamide, praziquantel and albendazole is efficacious.

• Stool for microscopy, culture and sensitivity, to look for enteric pathogens.
• Separate sample for occult blood testing.
• Stool serology for giardia antigens as well as C. difficile antigen.
• In cases of chronic diarrhoea, consider a lactose tolerance test or a Schilling test with intrinsic factor.
• Endoscopy with biopsy and duodenal aspirate or colonoscopy with biopsies and cultures should follow if initial testing in non-diagnostic; also consider ultrasonography, computerised or magnetic imaging studies as well.

Respiratory disease

This is spread through cough and close respiratory contact.

• Influenza:
  • This occurs in the winter season in temperate areas, and year-round in the tropics.
• Tuberculosis:
  • This has a world-wide distribution.
  • Risk of exposure is affected by local TB rates.
  • WHO estimates of TB cases per 100,000 population in 1995 are:⁸
    • Western industrialised countries and Japan - 23
    • Eastern Europe - 41
    • South-Eastern Asia - 241
    • Africa - 242
  • Risk of exposure is likely to be related to duration of stay in high prevalence areas.
  • The nature and circumstances of contact with local people are likely to be important determinants of risk; work in a health care setting is particularly high risk.
  • After infection with M. tuberculosis an immunocompetent individual has a 5-15% lifetime risk of progression to active TB; the risk is highest in the first 1-2 years after exposure.⁹
  • Comorbidity, such as diabetes, long-term steroid therapy, chronic renal failure and malignant lymphoma also increase the risk.
  • However, co-infection with Human Immunodeficiency Virus (HIV) carries the greatest risk of developing active TB, approximately 7-10% per year.¹⁰
  • Clinical symptoms include productive cough, weight loss, night sweats.
  • Suspicions confirmed by CXR should be fast-track referred to local respiratory consultant.
• Severe Acute Respiratory Syndrome (SARS):
  • The first major outbreak of SARS was in Singapore in March 2003; cases were also reported in Toronto.
  • It has very significant morbidity and case fatality.
  • Clinical features include persistent fever, rigors/ chills, myalgia, dry cough, headache and dyspnoea.¹¹
  • Investigations will also reveal lymphopaenia, (particularly CD4 and CD8) thrombocytopaenia, raised APTT, raised D-dimers, and raised ALT, LDH and CK.

First line investigations should include:

• Sputum sample for microscopy, culture and sensitivities
• CXR

Lymphadenopathy

Consider plague, HIV, rickettsial infection, brucellosis, leishmaniasis, dengue, lymphogranuloma venereum and Lassa fever.

Jaundice

Consider viral hepatitis, cholangitis, liver abscess, leptospirosis (90% anicteric), typhoid fever, dengue fever, yellow fever and haemoglobinopathies.

Hepatosplenomegaly

Viral hepatitis, malaria, brucellosis, typhoid fever, leishmaniasis, schistosomiasis and toxoplasmosis should be considered.

Gross splenomegaly

Malaria, visceral leishmaniasis, trypanosomiasis, typhoid, brucellosis, typhus and dengue fever should be considered.

Anaemia

Exclude hookworm, malaria and visceral leishmaniasis as potential causes.

Skin rashes

• Meningococcal disease, yellow fever, dengue, rickettsial infection and viral haemorrhagic fevers can cause petechiae or ecchymosis.
• Prickly heat is a sun sensitivity which gives an intensely itchy erythematous rash, usually in skin fold.
• Dengue fever presents with generalised rash after travel from tropics and Indonesia. Transmission from person to person and mosquito. Severe headaches and fever with intense joint and muscle pain.
• Trypanosomiasis presents with rash, fever and tender lymph glands. Follows travel to South and East Africa, Angola, Sudan, Congo, and Uganda. There is a variable incubation period.
• Cutaneous larva migrans is uncommon but may be found after travel to Thailand and South-east Asia. Red, itchy, mobile lesions which may move up to 1cm per hour. Most common on limbs.
• Leprosy or Hansen's Disease is characterised by multiple symmetrical lesions. Spread is via respiratory droplet from person to person.
• Leishmaniasis results from the bite of an infected sandfly. The bite becomes pruritic and painful. The traveller may present with nasal obstruction and bleeding.

• The majority (56%) of Western travellers having a new sexual relationship whilst travelling, have sex with travellers from other developed countries.¹²
• 25% begin a relationship with a new partner, and 66% do not, or inconsistently use a condom.¹³

The big 4 to remember are gonorrhoea, syphilis, chlamydia and HIV.
In considering treatment for gonorrhoea remember that there is some antibiotic resistance abroad to both penicillin and ciprofloxacin.
If the sexual partner was of developing world origin also consider chancroid, lymphogranuloma venereum and granuloma inguinale.
Sex tourism tends to involve a slightly older group. One study followed a group of Germans, aged 30-40 years visiting Thailand. Only 30-40% used condoms. Their contacts were seen as friends rather than prostitutes, and this lessened their use.

• Any symptomatic patient should be referred to your local genito-urinary medicine clinic for further management.
• Advice required may include future prevention advice and advice on sex whilst waiting for results.

HIV

This is a particular problem in sub-Saharan Africa, the Far East, and recently there have been increased cases from India, Latin America and the Caribbean.¹⁴

• Exposure prophylaxis for HIV is controversial. Three anti-retroviral drugs need to be commenced within 72 hours of exposure.
• Initial investigations should also consider hepatitis B, hepatitis markers and probably hep C also.
• Testing should be repeated at 6 months.
• If the patient is presenting within 2 weeks of contact, an active vaccination course for Hep. B may provide some protection.

• Full blood count including platelets and microscopy; eosinophilia in returning travellers is most likely to be a helminthic infection, followed by allergy or drug reaction.¹⁵ They are also commonly associated with migrating larvae through tissue.
• Blood films for malaria; repeat every 12 hours up to three if previous films negative. Tests should include both thick and thin giemsa-stained blood smears.
• Liver function tests and electrolytes
• Urine analysis and culture as indicated; urine microscopy for S. haematobium eggs
• Culture: blood, urine, sputum, stool, cerebrospinal fluid, lesions as indicated
• Serologies: amoebae, schistosomes, arboviruses, hepatitis (be cautious about interpreting serologies not done at the appropriate time.
• Sputum microscopy as indicated
• Lumbar puncture as indicated
• Tuberculosis skin testing and follow-up radiograph as necessary
• Biopsies of lesions or of bone marrow, especially if suspected typhoid, leishmaniasis, or tuberculosis
• X-rays, ultrasonography, computed radiography, or MRI; x-rays useful with tuberculosis and other pulmonary infections; ultrasonography is useful for abscesses, especially amoebic liver abscess and echinococcal cysts.