Tropical infections

32. Tropical infections




Tropical infections are endemic in countries where the climate supports the vector (e.g. mosquitoes for dengue fever) or where sewage is not safely disposed. Clinicians in other countries will encounter these infections in returning travellers or immigrants, who import these infections. Travel clinics have been established to prepare travellers before departure with vaccines (Table 3.32.1) and advice on prevention. Tropical infections may be broadly classified as those causing diarrhoea, fever and skin diseases.


Table 3.32.1 Vaccinations before travel to tropical countries for adults



















































Vaccine Dose Protected period (years)
Diphtheria, tetanus Booster > 5
Poliomyelitis Booster > 5
Hepatitis A 1 dose before departure 10
Hepatitis B 3 doses within 3 weeks before departure >20
Typhoid fever 3 doses of oral vaccine (Ty21a) over 5 days 1
Yellow fever 1 dose > 10 days before departure 10
Rabies (for travellers with wild animal contact) 3 doses within 4 weeks before departure 3
Japanese encephalitis (for rural Asia) 3 doses within 4 weeks before departure 3
Tick-borne encephalitis (for forest trips in northern, central and eastern Europe) 2 doses within 2 weeks before departure 3
Meningococcal meningitis (for Saudi Arabia) Quadrivalent (ACW135Y) polysaccharide vaccine 3
Cholera Not recommended by the World Health Organization  


Diarrhoea


Diarrhoea affects more than 30% of travellers during their journey. Diagnosis can be made by culture and stool concentration for parasites. Common causes are enterotoxigenic Escherichia coli (ETEC), enteropathogenic E. coli (EPEC), Campylobacter, Salmonella and norovirus, which all induce a self-limiting diarrhoea. Cholera is rare in travellers. The rice-water diarrhoea leads within hours to dehydration and requires intravenous fluid therapy more than antibiotic treatment with doxycycline.


Giardiasis is a water-borne infection as Giardia lamblia cysts survive in chlorinated water. Filtration removes the cysts. Stool concentrations are low enough that the parasite may be missed and diagnosis often requires duodenal sampling (e.g. by string capsule test). If untreated, giardiasis can cause a chronic malabsorption syndrome. Treatment options comprise metronidazole, tinidazole, albendazole and nitazoxanide.


Cryptosporidium parvum is a worldwide water-borne infection because its cysts are resistant to chlorination and filtration. Diagnosis can be made by microscopy of modified acid-fast-stained stool smears. Nitazoxanide appears promising for treatment in the first small clinical trials.


Dysentery is a colitis caused by Entamoeba histolytica or Shigella spp. E. histolytica cysts are ingested and release mobile trophozoites, which invade the colonic mucosa. They can transform into cysts, which are excreted with faeces. Diagnosis is made by a fresh stool sample displaying the mobile trophozoites with ingested red blood cells. Entamoeba cysts in stool concentrations need to be differentiated from non-invasive Entamoeba dispar. Treatment options comprise metronidazole, tinidazole, chloroquine and nitazoxanide. Except for the last, a treatment course needs to be followed by the luminal amoebicide diloxanide furoate to eradicate the cysts.


Shigella flexneri and Shigella dysenteriae cause severe colitis, which in many cases require antibiotic therapy, for example quinolones or azithromycin depending on local resistance. Verotoxin-producing Escherichia coli (VTEC) is an invasive E. coli causing colitis and is harboured by cattle. Antibiotic treatment is not recommended, because it may induce haemolytic uraemic syndrome.

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Jul 3, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Tropical infections

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