ID: Tropical and travel medicine

• The returning traveller: Approach to the Returning Traveller | Incubation Periods | Viral Haemorrhagic Fever Risk
• Malaria: Malaria Basics | Diagnosing Malaria | Severe Malaria | Treating Malaria | Preventing Malaria
• Other fevers: Typhoid and Paratyphoid | Dengue | Chikungunya, Zika, Yellow Fever and Other Arboviruses | Rickettsial Infections | Rabies
• Other tropical infections: Schistosomiasis | Leishmaniasis and Trypanosomiasis | Filariasis, Leprosy and Melioidosis | Travellers' Diarrhoea | Skin Problems and Eosinophilia After Travel
• Before travel: Vaccines and Advice Before Travel | Travellers With Special Needs
• Revision: Fever After Travel at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

✈️ Tropical and travel medicine — page 5 of the Infectious Diseases chapter. The golden rule: fever in anyone who has been to a malarious area is malaria until proven otherwise — test the same day. Most fevers after travel are malaria, dengue, typhoid, travellers' diarrhoea, or ordinary infections caught abroad (pneumonia, UTI, influenza). A careful travel history — where, when, what they did, and what precautions they took — narrows the list quickly.
Your four questions for every returning traveller: Could this be malaria (test today) or a viral haemorrhagic fever (isolate first)? Where exactly did they go, when did they return, and what did they do? Does the incubation period fit? Is this severe disease needing urgent treatment, and does public health need to know?

Approach to the Returning Traveller

• Travel history:
  • Where — countries and regions (rural or urban, altitude), including stopovers.
  • When — dates of travel and return; date symptoms began (compare with incubation periods).
  • What they did — freshwater swimming (schistosomiasis, leptospirosis), safari and walking in long grass (ticks — rickettsia, tsetse flies), caves (histoplasmosis, rabies from bats), animal contact and bites (rabies), unsafe food and water, unpasteurised dairy (brucellosis), sexual contact, tattoos, injections or healthcare abroad (blood-borne viruses, resistant bacteria), contact with sick people or funerals (Ebola).
  • Who — people visiting friends and relatives (VFR) are at highest risk (longer stays, rural areas, less likely to take precautions or prophylaxis).
  • Precautions — pre-travel vaccines, malaria prophylaxis (which drug, taken correctly, continued after return?), bite avoidance.
• First steps for a febrile traveller from a malarious area:
  • Malaria test the same day (blood films or rapid test) — repeat if negative.
  • FBC (low platelets in malaria and dengue; eosinophilia in worms), U&E, LFTs, CRP, glucose, blood cultures (typhoid), urine, chest X-ray; save serum; HIV test.
  • Consider viral haemorrhagic fever before doing anything if they've been to an affected area within 21 days (see below).
• Remember common things — pneumonia, influenza, COVID-19, UTI, cellulitis and DVT happen in travellers too — but don't let a "simple" diagnosis stop you testing for malaria.
• Clues — eschar (rickettsial infection), rash (dengue, rickettsia, acute HIV), jaundice (malaria, hepatitis, leptospirosis, yellow fever), splenomegaly (malaria, typhoid, leishmaniasis), relative bradycardia (typhoid), eosinophilia (worms), bleeding (VHF, dengue, meningococcus).
• Get help early — discuss with local infectious diseases teams or the national Imported Fever Service.

Incubation Periods

• Malaria is very unlikely in the first 7 days after first arriving in a malarious area — but almost any other timing fits.
• Fever starting more than 21 days after return effectively excludes dengue, rickettsia and VHFs.

Viral Haemorrhagic Fever Risk

• Viral haemorrhagic fevers (VHFs) — Ebola and Marburg (Central, East and West Africa — bats, contact with body fluids, caring for the sick, funerals), Lassa fever (West Africa — rodent urine), Crimean–Congo haemorrhagic fever (ticks and livestock — Africa, Middle East, Turkey, the Balkans, Central Asia). These are high consequence infectious diseases (HCIDs) — rare in the UK but dangerous to staff.
• Suspect VHF if fever (37.5°C or more) began within 21 days of leaving an area with a VHF risk or outbreak, especially with contact with ill people, body fluids, animals or ticks, or with bleeding or severe illness.
• If VHF is possible:
  • Isolate immediately in a side room; minimise staff contact; appropriate PPE.
  • Don't send routine bloods until discussed — contact the infection consultant and follow the national VHF risk assessment algorithm.
  • Test urgently for malaria (the commonest cause of fever in these travellers) with precautions agreed with the lab.
  • High-possibility cases are transferred to a specialist HCID unit; notify UKHSA.
• Features — fever, headache, myalgia, vomiting and diarrhoea, then (in some) bleeding, shock and multi-organ failure.
• Other HCIDs — MERS (Middle East — camels), avian influenza, Nipah virus, pneumonic plague; same principle — isolate and seek specialist advice early.

Malaria Basics

• Malaria — protozoa (Plasmodium) spread by the bite of the female Anopheles mosquito (dusk to dawn); also by blood transfusion and from mother to baby.
• Life cycle — parasites go first to the liver, then infect red cells (causing fever, anaemia and complications); vivax and ovale leave dormant liver forms (hypnozoites) that cause relapses months or years later.
• Species:
  • P. falciparum — most cases in UK travellers (mainly from sub-Saharan Africa); causes almost all deaths; can be severe within hours to days.
  • P. vivax — Asia, Latin America, Horn of Africa; relapses; occasionally severe.
  • P. ovale — West Africa; relapses.
  • P. malariae — can appear years later; nephrotic syndrome.
  • P. knowlesi — South-East Asia (Malaysian Borneo — from macaques); daily fevers; can be severe.
• Symptoms are non-specific — fever (often irregular, not always cyclical), rigors, sweats, headache, muscle aches, cough, vomiting, diarrhoea; jaundice; splenomegaly; children may have seizures. Many patients are misdiagnosed with flu or gastroenteritis.
• Blood tests — low platelets (very common), anaemia, raised bilirubin and LDH, raised CRP, sometimes AKI or low glucose.
• Semi-immunity from living in a malarious area fades within months to a few years of leaving — VFR travellers are not protected.
• Malaria is notifiable in the UK.

Diagnosing Malaria

• Test on the same day — results within hours; never wait until the next day.
• Thick and thin blood films — thick films detect parasites; thin films identify the species and measure the parasitaemia (percentage of infected red cells).
• Rapid diagnostic tests (antigen) — used alongside films (not alone); can stay positive after treatment.
• To exclude malaria — three negative sets of films over about 72 hours (taken 12–24 hours apart); keep testing if fever continues; prophylaxis can reduce parasite numbers and delay diagnosis.
• Also check — FBC, U&E, LFTs, glucose, lactate, blood gas (acidosis), clotting, group and save, urinalysis, blood cultures (bacterial co-infection), HIV test.
• Pregnancy — malaria is more severe and often has a high parasitaemia with hypoglycaemia; involve obstetrics early.

Severe Malaria

• Severe malaria is a medical emergency — mortality is high without prompt treatment; involve critical care and infectious diseases.
• Check glucose often — hypoglycaemia is common (especially in pregnancy, children, and with quinine).
• Careful fluids — avoid overload (pulmonary oedema).
• Treat suspected bacterial co-infection (e.g. Gram-negative sepsis) with broad-spectrum antibiotics if shocked.

Treating Malaria

• Admit all patients with falciparum malaria (it can worsen quickly) — check parasitaemia daily until clear.
• Severe falciparum (or severe non-falciparum) malaria:
  • IV artesunate 2.4 mg/kg at 0, 12 and 24 hours, then daily until able to take oral treatment; then a full course of oral artemisinin combination therapy (ACT).
  • IV quinine only if artesunate isn't immediately available (causes hypoglycaemia, QT prolongation, tinnitus — "cinchonism"; needs a loading dose and cardiac monitoring) — don't delay treatment while waiting for artesunate.
  • Post-artesunate delayed haemolysis — falling Hb 1–3 weeks later; check FBC weekly for about 4 weeks.
• Uncomplicated falciparum malaria — oral artemether–lumefantrine (Riamet — 6 doses over 3 days, taken with fatty food) or atovaquone–proguanil (Malarone — 4 tablets once daily for 3 days, with food); quinine plus doxycycline or clindamycin is an alternative. Don't use the drug the patient took as prophylaxis.
• Non-falciparum malaria (vivax, ovale, malariae, knowlesi):
  • ACT (preferred in many guidelines) or chloroquine where sensitive (chloroquine-resistant vivax occurs in Indonesia and Papua New Guinea).
  • Then primaquine (or tafenoquine) for vivax and ovale to kill liver hypnozoites and prevent relapse — test G6PD first (haemolysis in deficiency); avoid in pregnancy and breastfeeding (use weekly chloroquine until delivery, then primaquine).
  • P. knowlesi can be severe — treat like falciparum if parasitaemia is high.
• Pregnancy — severe malaria: IV artesunate in any trimester; uncomplicated falciparum: artemether–lumefantrine is now considered acceptable in all trimesters (specialist advice); monitor glucose and the fetus.
• Children — weight-based dosing; specialist paediatric input.

Preventing Malaria

• ABCD of malaria prevention (UKHSA):
  • Awareness of risk.
  • Bite avoidance — insect repellent (DEET 50% is first-line, including in pregnancy and for children over 2 months), long sleeves and trousers at dusk, permethrin-treated bed nets, screened or air-conditioned rooms.
  • Chemoprophylaxis — taken correctly, including after return.
  • Diagnosis — seek urgent medical help for any fever during or after travel (up to a year or more), mentioning travel.

• No prophylaxis is 100% effective — fever after travel still needs testing.
• Check interactions (e.g. atovaquone–proguanil with warfarin; doxycycline with antacids and iron) and choose according to destination (use UKHSA or TravelHealthPro maps), health and preference.
• Pregnant women should avoid travel to malarious areas if possible; the asplenic are at very high risk of severe malaria.

Typhoid and Paratyphoid

• Enteric fever — Salmonella Typhi and Paratyphi; faecal–oral from contaminated food and water; most UK cases are in travellers returning from South Asia (Pakistan, India, Bangladesh), often VFR travellers.
• Incubation — usually 7–14 days (range about 5–21 days).
• Features — gradually rising fever ("stepwise"), headache, malaise, abdominal pain, constipation (or diarrhoea), dry cough; relative bradycardia, rose spots (faint pink spots on the trunk — uncommon), splenomegaly, mild hepatitis; low or normal white count.
• Complications (usually in the 2nd–3rd week) — bowel perforation and GI bleeding (ileal ulcers), encephalopathy, myocarditis, hepatitis, relapse; chronic gallbladder carriage.
• Diagnosis — blood cultures (several, before antibiotics); stool and urine cultures; bone marrow culture is most sensitive. Serology (Widal) is unreliable.
• Treatment — resistance is common (quinolone resistance in South Asia; extensively drug-resistant (XDR) typhoid from Pakistan):
  • Severe or unwell — IV ceftriaxone; meropenem if XDR is suspected (e.g. travel to Pakistan).
  • Uncomplicated — oral azithromycin.
  • Adjust to sensitivities; fever can take several days to settle.
• Public health — notify; exclusion and clearance stool samples for food handlers, healthcare workers and young children; household contacts screened.
• Prevention — food and water hygiene ("boil it, cook it, peel it or forget it"); typhoid vaccine (injectable Vi polysaccharide or oral live vaccine) gives only partial protection (about 50–70%) and doesn't cover paratyphoid.

Dengue

• Dengue virus (four serotypes) — spread by Aedes mosquitoes that bite during the day; common in South and South-East Asia, Latin America, the Caribbean, the Pacific and parts of Africa; outbreaks increasingly in southern Europe.
• Incubation — 4–10 days (so fever starting over 2 weeks after return is unlikely to be dengue).
• Febrile phase — sudden high fever, severe headache (behind the eyes), muscle and joint pain ("breakbone fever"), nausea, flushing, then a rash (often with "islands of white in a sea of red"); positive tourniquet test; low white count, low platelets, raised ALT.
• Critical phase (around days 3–7, as the fever falls) — plasma leakage can cause shock. Warning signs:
  • Abdominal pain or tenderness, persistent vomiting, mucosal bleeding, lethargy or restlessness.
  • Fluid accumulation (pleural effusions, ascites), enlarged liver.
  • Rising haematocrit with rapidly falling platelets.
• Severe dengue — shock from plasma leak, severe bleeding, organ failure (liver, heart, brain); more common with a second infection with a different serotype.
• Diagnosis — dengue NS1 antigen and PCR (first week), IgM and IgG serology; always test for malaria too.
• Management — supportive: paracetamol, oral fluids; avoid NSAIDs and aspirin (bleeding); admit if warning signs, high-risk groups (pregnancy, infants, older people, comorbidities), or poor home support; careful IV fluids guided by haematocrit and clinical state (avoid overload in the recovery phase).
• Prevention — daytime bite avoidance; a dengue vaccine is available for some travellers (mainly those who have had dengue before — specialist travel advice).

Chikungunya, Zika, Yellow Fever and Other Arboviruses

Rickettsial Infections

• Spread by ticks, mites, fleas and lice; small intracellular bacteria that infect blood vessel walls.
• African tick bite fever — the commonest in UK travellers (safari in southern Africa); fever, headache, muscle pains, one or more eschars (black scabs at bite sites), regional lymph nodes, sometimes a rash.
• Mediterranean spotted fever — Mediterranean (dogs' ticks); eschar ("tache noire") and widespread rash.
• Scrub typhus — mites in rural Asia and the Pacific; eschar, fever, rash; can cause pneumonitis and encephalitis.
• Rocky Mountain spotted fever (Americas), epidemic typhus (lice — overcrowding), murine typhus (fleas).
• Diagnosis — clinical (eschar plus fever after exposure); PCR of the eschar; serology later.
• Treatment — doxycycline (start on suspicion — rapid response within 48 hours supports the diagnosis); don't withhold in children with severe disease.

Rabies

• Rabies — a lyssavirus spread by saliva from bites, scratches or licks on broken skin from infected mammals — mainly dogs in Asia and Africa; also bats (worldwide, including bats in the UK), monkeys, cats and others.
• Incubation — usually weeks to months (can be years); shorter with bites to the head and neck.
• Features — tingling or pain at the bite site, then encephalitis ("furious" — agitation, hydrophobia, aerophobia, autonomic instability) or ascending paralysis; almost always fatal once symptoms start.
• After a possible exposure (a medical emergency even weeks or months later):
  • Wash the wound thoroughly with soap and running water for 15 minutes; disinfect; don't suture immediately if possible.
  • Urgent risk assessment (UKHSA rabies service) — country, animal, type of contact, previous vaccination.
  • Post-exposure treatment — a course of rabies vaccine ± rabies immunoglobulin (into and around the wound) for unvaccinated people with high-risk exposures; previously vaccinated people need fewer vaccine doses and no immunoglobulin.
  • Also tetanus and antibiotics for the bite (co-amoxiclav).
• Pre-exposure vaccination — for travellers to rabies areas with limited access to care, longer stays, or animal contact; bat handlers and some occupations. It simplifies treatment after a bite but doesn't remove the need for it.

⚠️ Safety Pearl: Any mammal bite or scratch in a rabies-risk country — or a bat bite in the UK — needs same-day rabies assessment, even if it happened weeks ago. Rabies is preventable after exposure but untreatable once symptoms appear.

Schistosomiasis

• Schistosomiasis (bilharzia) — flukes whose larvae burrow through the skin during contact with fresh water (lakes, rivers) in Africa (e.g. Lake Malawi, Lake Victoria, the Nile), and parts of the Middle East, Asia and South America. Salt water and chlorinated pools are safe.
• Stages:
  • Swimmer's itch — itchy rash at the site within hours or days.
  • Acute schistosomiasis (Katayama fever) — 2–8 weeks after exposure: fever, urticaria, cough, wheeze, headache, diarrhoea, marked eosinophilia — often in groups of travellers who swam together.
  • Chronic — S. haematobium (urinary) — haematuria, bladder fibrosis, ureteric obstruction, bladder cancer (squamous), genital disease (infertility, HIV risk); S. mansoni (intestinal) — diarrhoea, liver fibrosis and portal hypertension (varices) with preserved liver function; rarely spinal cord or brain involvement.
• Diagnosis — serology (becomes positive about 6–12 weeks after exposure); eggs in urine (midday sample) or stool; eosinophilia.
• Treatment — praziquantel; repeat after 6–12 weeks (it kills adult worms but not young ones) — so in recent exposure, treat at least 6–12 weeks after the last contact; steroids for Katayama fever (specialist).
• Screen asymptomatic travellers who swam in fresh water in endemic areas (serology at 12 weeks).

Leishmaniasis and Trypanosomiasis

• Leishmaniasis (Leishmania — spread by sandflies):
  • Cutaneous — a slowly enlarging, painless ulcer or nodule with raised edges on exposed skin, weeks to months after travel (Middle East, North Africa, Afghanistan, Central and South America, Mediterranean); biopsy for PCR; specialist treatment (some heal alone).
  • Mucocutaneous (South America) — destruction of the nose and mouth years later.
  • Visceral (kala-azar) — South Asia, East Africa, Brazil, Mediterranean: fever, weight loss, massive splenomegaly, hepatomegaly, pancytopenia, high globulins; more common in HIV; bone marrow or spleen sampling, serology, PCR; liposomal amphotericin.
• African trypanosomiasis (sleeping sickness) — tsetse fly bites (safari in East and southern Africa — rhodesiense; West and Central Africa — gambiense): painful chancre at the bite, fever, lymphadenopathy (posterior neck — Winterbottom's sign), then sleep disturbance, confusion and coma; urgent specialist treatment.
• American trypanosomiasis (Chagas disease) — triatomine ("kissing") bugs in rural Latin America; also blood, organ and mother-to-baby spread:
  • Acute — often unnoticed (swelling of an eyelid — Romaña's sign).
  • Chronic (decades later) — cardiomyopathy (heart failure, arrhythmias, heart block, apical aneurysm, stroke), megaoesophagus and megacolon.
  • Screen Latin American migrants in pregnancy and before donation; benznidazole or nifurtimox (specialist).

Filariasis, Leprosy and Melioidosis

• Lymphatic filariasis (mosquito-borne worms — tropics) — lymphangitis, lymphoedema and elephantiasis, hydrocele; tropical pulmonary eosinophilia (cough, wheeze, very high eosinophils).
• Loiasis (Loa loa — deer fly, Central and West Africa) — Calabar swellings (transient itchy swellings), eye worm crossing the conjunctiva, eosinophilia; specialist treatment (ivermectin can cause encephalopathy with high worm loads).
• Onchocerciasis (river blindness — blackfly, Africa) — intensely itchy skin rash, skin nodules, eye disease.
• Leprosy (Mycobacterium leprae — South Asia, Brazil, parts of Africa; prolonged close contact):
  • Pale or reddish skin patches with reduced sensation, thickened peripheral nerves (ulnar, common peroneal, great auricular), nerve damage leading to injuries and deformity.
  • Long incubation (years); skin biopsy; multidrug therapy (rifampicin, dapsone, clofazimine); treat immune reactions (steroids) to protect nerves; notifiable; much less infectious than people fear.
• Melioidosis (Burkholderia pseudomallei — soil and water in South-East Asia and northern Australia; risk with diabetes, CKD, alcohol excess):
  • Pneumonia, abscesses (liver, spleen, prostate), septicaemia; can reactivate years later.
  • Ceftazidime or meropenem then prolonged co-trimoxazole; warn the lab (hazard group 3).

Travellers' Diarrhoea

• The commonest illness in travellers — usually enterotoxigenic E. coli (ETEC), also Campylobacter, Salmonella, Shigella, norovirus; Giardia and Cryptosporidium if prolonged.
• Most cases settle in 3–5 days — oral rehydration is the key treatment; loperamide for mild to moderate diarrhoea without blood or fever.
• Stand-by antibiotics — sometimes given to travellers to remote areas for severe or bloody diarrhoea with fever (e.g. azithromycin — quinolone resistance is common, especially Campylobacter in Asia); not routinely recommended.
• After return — send stool samples if bloody, severe, prolonged (over 2 weeks) or in high-risk patients; consider Giardia, amoebiasis, Cyclospora, C. difficile (antibiotics abroad), tropical sprue, post-infectious IBS, newly unmasked coeliac disease or IBD.
• Fever with diarrhoea after travel — also consider malaria and typhoid (both can cause diarrhoea).
• Cholera — profuse "rice-water" diarrhoea with severe dehydration (outbreaks in humanitarian settings) — aggressive rehydration; rare in travellers.
• Prevention — hand hygiene, safe water (bottled, boiled or treated), avoid ice, raw salads, undercooked food and street food left out; oral cholera vaccine for selected travellers (aid workers).

Skin Problems and Eosinophilia After Travel

• Skin problems — among the commonest reasons travellers seek help:
  • Infected insect bites and cellulitis (staphylococci and streptococci).
  • Cutaneous larva migrans — itchy, creeping red track on the feet or buttocks after walking barefoot on tropical beaches (dog hookworm) — ivermectin or albendazole.
  • Myiasis — fly larvae in a boil-like lesion with a central pore (tumbu fly in Africa — from drying clothes outdoors; botfly in the Americas).
  • Tungiasis — sand flea burrowed in the toes.
  • Cutaneous leishmaniasis — painless non-healing ulcer.
  • Eschar with fever — rickettsial infection.
  • Sunburn, heat rash, fungal infections, scabies, and STI-related rashes.
• Eosinophilia after travel (over 0.5 × 10⁹/L):
  • Most often worms — Strongyloides, schistosomiasis, hookworm, filariasis, Toxocara, Ascaris.
  • Also drug reactions, allergy, asthma, some other infections.
  • Send Strongyloides and schistosomiasis serology, stool microscopy (3 samples), and urine for schistosome eggs if relevant; refer to an infection or tropical clinic.
  • Screen for Strongyloides before giving steroids (see page 4).

Vaccines and Advice Before Travel

• Seek advice 6–8 weeks before travel (some vaccines need several doses); use TravelHealthPro (NaTHNaC) or Fit for Travel for country-specific advice.
• Check routine vaccines — MMR, tetanus–diphtheria–polio, influenza, COVID-19, pneumococcal (as eligible).
• Travel vaccines (depending on destination and activities):
  • Hepatitis A and typhoid — most developing countries.
  • Hepatitis B — longer stays, healthcare work, sexual risk, medical tourism.
  • Rabies — remote areas, longer stays, animal contact, children.
  • Yellow fever — at registered centres; certificate needed for entry to some countries.
  • Meningococcal ACWY — the African "meningitis belt" and Hajj or Umrah pilgrims (required by Saudi Arabia).
  • Japanese encephalitis, tick-borne encephalitis, cholera, polio boosters for some countries, dengue and chikungunya vaccines for selected travellers.
• Other advice — malaria prevention (ABCD), food and water hygiene, insect and tick bite avoidance, sun protection, safe sex (condoms), avoid animal contact, road safety (the commonest cause of death in travellers), travel insurance, a supply of usual medicines in hand luggage with a list.
• Long flights — keep mobile and hydrated; compression stockings for higher-risk travellers; LMWH only for those at very high risk (specialist advice).
• Altitude illness (above about 2,500 m) — ascend slowly (no more than about 500 m a day in sleeping altitude above 3,000 m, with rest days), recognise symptoms (headache, nausea, fatigue), descend if worsening; acetazolamide can help prevent it; high-altitude cerebral and pulmonary oedema are emergencies (descend, oxygen, dexamethasone, nifedipine).

Travellers With Special Needs

• Pregnancy — avoid malaria and Zika areas where possible; live vaccines (yellow fever, oral typhoid) generally avoided unless the risk is high; DEET is safe; mefloquine is usable in pregnancy; travel insurance and access to obstetric care; VTE risk.
• Immunosuppressed travellers (chemotherapy, biologics, high-dose steroids, transplant, advanced HIV) — avoid live vaccines (yellow fever, oral typhoid, MMR, varicella); weaker vaccine responses; higher risk from food- and waterborne infections; check drug interactions with malaria prophylaxis; stand-by antibiotics and specialist advice.
• No spleen — very high risk of severe malaria (strict prophylaxis and bite avoidance, or avoid travel to malarious areas); up-to-date pneumococcal and meningococcal vaccines; stand-by antibiotics.
• Visiting friends and relatives (VFR) — the biggest group with imported malaria and typhoid; often don't seek pre-travel advice; offer advice opportunistically.
• Older travellers and chronic disease — fitness to fly (oxygen needs in lung disease — see the Respiratory chapters), heat and dehydration (diuretics, SGLT2 inhibitors), insulin and time zones, adequate medication supplies, insurance.
• Children — dehydration risk, DEET for over 2 months, weight-based prophylaxis, rabies risk (children play with animals).

Fever After Travel at a Glance

Spot the Diagnosis