Medical Issues in the Tropics: a Guide for Yacht Crew

Written by Sara Paterson RN Bsc DTN

Written by Sara Paterson RN Bsc DTN

Having recently completed an advanced diploma in tropical nursing from the London School of Hygiene and Tropical Medicine, Sara Paterson is perfectly placed to advise crew on some of the tropical conditions they risk encountering. Sara talks us through Malaria, Dengue Fever, and spider bites. 


The World Health Organisation advises that 40% of the world’s population is currently susceptible to Malaria, with 300 million reported cases per year, of which 600,000 are fatal.

Malaria is a parasitic disease; the parasite is injected into your blood circulation through the bite of an infected female Anopheles mosquito. The parasite p.falciparum (found mostly on the African continent) is the most deadly type of Malaria, P.Vivax (prevalent in south east Asia and western pacific regions) can also be deadly to humans. 

Whilst there is now a Malaria vaccine, it’s not widely available. At present, it is being trialled in certain African regions only. 


– Malaria is a risk in the ‘malaria belt’ countries of Africa, Asia, and South America, amongst others.

– The female mosquito breeds near stagnant water such as rivers, marinas, rice paddies, and man-made water storage containers. 

– The infected mosquitos mainly bite at dusk and dawn and during the night, making this the riskiest time of day.  

– Symptoms of malaria typically appear 7 – 30 days after a bite, but can occur within hours. In rare cases, however, they may not show up until one year post bite. 

– The symptoms are a flu like illness, with some or all of the following – fever (sometimes coming and going in cycles), sweating, shaking, vomiting and headache. 

– Malaria can turn deadly within 24 hours of symptoms

– Treatment causes symptoms go away within two weeks, however if not properly treated, symptoms can re-occur in cycles over months or years. 

– You are less likely to suffer a fatal infection if you have natural immunity from growing up in a Malaria endemic country, although you can never guarantee full immunity.

– Even if you don’t get sick, if you travel to another region with mosquitos whilst infected with Malaria, you are causing a spread that may cause serious illness in others, which is another reason to protect yourself.  


– AVOID bites in Malaria regions by staying in the air conditioning particularly at dusk, dawn and at night, and wear long clothing.

– PROTECT exposed skin with 50% DEET spray, ensuring good coverage. If you are also using sunscreen, apply sunscreen first and insect repellent second. Use a room spray repellent in sleeping areas and spray down before dusk. 

– MEDICATE using prophylaxis medication, which must be used if you have no natural immunity, but is advisable for everyone travelling to areas endemic with deadly types of Malaria 

– TEST routinely while in a malaria region with small point of care tests, which can be purchased and used to give an idea if Malaria is present, but are not 100% accurate.

– SYMPTOMS – if you suffer any flu like symptoms within a year of being in a Malaria endemic area, with or without a positive test, get to shore urgently for a blood test.

– TREAT – carry emergency medication treatment packs


Dengue Fever is a mosquito-borne viral disease, occurring in tropical and subtropical regions (including some of the Caribbean islands) transmitted by A. Aegypti & Ae. albopictus mosquitos breeding in stagnant water sources (rivers, streams, marinas, water containers by houses). 


– Symptoms occur five to seven days post bite and are any combination of high fever, rash, muscle and joint pain, eye pain, nausea and vomiting.

– Any Dengue symptoms should be urgently reviewed in hospital because on day three to seven after symptoms begin, a critical stage of Dengue can develop, the symptoms for which are: unusual bleeding from nose or gums, blood in vomit or faeces, rapid breathing, severe stomach pain, persistent vomiting, severe headache and severe fatigue, or restlessness. In severe cases, there is serious bleeding and shock, which can be life threatening.

– Those who become infected with the virus for a second time are at significantly greater risk of developing severe Dengue. 


The method is the same as for Malaria, except there’s no medication. There is no known antiviral medication to prevent dengue. 


If you get bitten by any spider or insect, the only symptoms that can be safely treated without visiting a medical facility are a little bump on your skin that gets red, itchy, and may swell up a bit. It might hurt, but no more than a bee sting and usually not for more than an hour or so.

If you have any other symptoms, such as extreme pain, nausea and vomiting, breathing issues, development of an expanding red area, or yellow abscess, and if you are unsure about the type of spider or insect that bit you, you should visit a medical facility promptly. 


– WASH the bite thoroughly with lukewarm soap and water, and a piece of clean gauze. 

– APPLY an antibiotic ointment such as Fucidin or Neosporin three times a day

– ELEVATE the area and keep it still

– MEDICATE with antihistamine and over the counter pain relief

– APPLY a cold compress for 15 minutes each hour

In a final note on protection from insect bites, it is always wise to protect yourself against bites and stings when working in tropical climates. There are numerous other insect borne diseases such as Chagas disease (mainly in south American regions, transmitted by the conenose ‘kissing’ bug), Onchocerciasis (known as river blindness, transmitted by the black river fly in African regions) and Leishmaniasis (transmitted by the sand fly, found in the tropics and southern Europe), all of which you’d want to avoid! And that’s before we get started on simple ticks and other infestations… 

Always remember the MSOS team are here to support you worldwide, including 24/7 365 support from a team of maritime specialist consultant level UK doctors. 


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