Central & South America health

23/01/2015 16:35

Written by Bradt Travel Guides

People new to exotic travel often worry about contracting tropical diseases but, with the right vaccinations and a sensible attitude to malaria, the chances of a serious incident are small. In fact the greatest risk to your health in South America is road accidents. Sadly these are all too common, so be aware and do what you can to reduce risks. Try to travel during daylight hours, always wear a seatbelt and refuse to be driven by anyone who has been drinking.  Also, listen to local advice about areas where violent crime is rife.

Zika virus

Zika virus is a flavivirus which is similar to dengue and was first reported in 1947 in Uganda. It is spread by the day-biting Aedes mosquito. Since November 2014, it has been reported in South America where there is a strong association with congenital malformations in new born babies (microcephaly). All travellers to countries where zika virus occurs are at risk of infection. The longer time that you spend in the destination, the more at risk you will be.

The infection is often asymptomatic and in those with symptoms the disease is usually mild with an itchy rash, fever, joint pains and red sore eyes. Severe disease is uncommon.

Travellers are advised to use DEET-based repellents during the daytime on all exposed skin. In areas where mosquitoes are particularly prevalent then covering up and using a permethrin spray on clothing would also be advised.

Pregnant women need to discuss their travel plans with healthcare professionals and should, wherever possible, cancel the trip. Women wishing to become pregnant who are travelling in moderate- to high-risk Zika virus areas should use barrier methods of contraception whilst travelling, and for two months after leaving the affected area. If travelling with their partners, then barrier precautions need to be used during the trip and for six months after leaving. For up-to-date details follow the link here.  

Travel insurance

Don’t think about travelling without a comprehensive medical travel insurance policy: one that will fly you home in an emergency. It is worth testing the company that you pick by posing a scenario and seeing how they respond.  Make sure that the policy covers any activities in which you might be wanting to participate.

Immunisations

Preparations to ensure a healthy trip to South America require checks on your immunisation status: it is wise to be up to date on tetanus, diphtheria and polio (now given as an all-in-one vaccine, Revaxis, that lasts for ten years), and hepatitis A. Immunisations against yellow fever, typhoid, hepatitis B and rabies may also be recommended. Other suggested vaccines could include BCG for TB, and MMR for measles, mumps and rubella.

Whether or not you need to have the yellow fever vaccine depends on the countries you are travelling to and from. There are two reasons for immunising against yellow fever, firstly to protect against the disease and, secondly, as a certificate requirement to gain entry into a particular country. The World Health Organisation (WHO) recommends that this vaccine should be given to those aged nine months and over. It is now accepted that, for most people, the vaccine offers protection for many decades. As of the 11th July 2016, all countries now have to accept that yellow fever vaccine lasts for life, regardless of when it was given. This means that as long as you have had the yellow fever vaccine and have a certificate, then you won’t need to have the vaccine again unless you were immunocompromised at the time it was given or were under the age of two, when it will need to be repeated. If you have had the vaccine but have lost the certificate and are travelling to a country where there is a certificate requirement for entry, then you are likely to need the vaccination again. If you have never been vaccinated, you need to seek specialist advice from a registered yellow fever centre. Whether or not you need the vaccine has to be determined on an individual basis, based on the risk of the disease versus the risk to the traveller. There are certain medical conditions that mean the vaccine would be contra-indicated. If you are unable to have the vaccine then you may be advised to avoid the risk areas within certain countries, for example the Amazon basin. While the risk of yellow fever is not as high as in West Africa, the disease has a significant mortality rate in people who catch it who have never come into contact with the disease before and have never been vaccinated, ie are not immune.

Hepatitis A vaccine (Havrix Monodose or Avaxim) comprises two injections given about a year apart. The course costs about £100, but may be available on the NHS; protects for 25 years and the first injection can be administered even close to the time of departure.

Hepatitis B vaccination should be considered for longer trips (two months or more) or for those working with children or in situations where contact with blood is likely. Three injections are needed for the best protection and can be given over a three-week period if time is short for those aged 16 or over. Longer schedules give more sustained protection and are therefore preferred if time allows. Hepatitis A vaccine can also be given in a combination with hepatitis B as ‘Twinrix’, though two doses are needed at least seven days apart to be effective for the hepatitis A component, and three doses are needed for the hepatitis B. Again this rapid schedule is only suitable for those aged 16 or over.

Children aged 1 to 15 can be vaccinated with a junior version of this vaccine but the minimum time frame for the three doses is a period of eight weeks. Children aged 1 to 15 can also be vaccinated with Ambirix which consists of two doses given six to12 months apart. One dose gives full protection against the hepatitis A and some protection against hepatitis B (though less than Twinrix). Having the second dose completes the course giving long term protection against hepatitis A and five years against hepatitis B. This vaccine is useful for children who are less tolerant of injections are only have time for one dose before travel.

The newer injectable typhoid vaccines (eg: Typhim Vi) last for three years and are about 75% effective. Oral capsules (Vivotif) are also available for those aged six and over. Three capsules taken over five days gives protection for approximately three years but may be less effective than the injectable forms as they rely on good patient compliance. Vivotif is also a live vaccine, which is not suitable for everyone.  Typhoid vaccine should be encouraged unless the traveller is leaving within a few days for a trip of a week or less, in which case the vaccine would not be effective in time.

Vaccinations for rabies are ideally advised for everyone, but are especially important for travellers visiting more remote areas, especially if you are more than 24 hours from medical help and definitely if you will be working with animals (see Rabies).

Experts differ over whether a BCG vaccination against tuberculosis (TB) is useful in adults: discuss this with your travel clinic.

In addition to the various vaccinations recommended above, it is important that travellers should be properly protected against malaria in those countries where it is prevalent.  For detailed advice, see below.  

Ideally you should visit your own doctor or a specialist travel clinic to discuss your requirements, if possible at least eight weeks before you plan to travel. 

Travel clinics

A full list of current travel clinic websites worldwide is available on www.istm.org. For other journey preparation information, consult http://travelhealthpro.org.uk (UK) or http://wwwnc.cdc.gov/travel/ (US). Information about various medications may be found on www.netdoctor.co.uk/travel. All advice found online should be used in conjunction with expert advice received prior to or during travel.

Avoiding insect bites

As the sun is going down, don long clothes and apply repellent on any exposed flesh. Pack a DEET-based insect repellent – ideally around 50% (roll-ons or stick are the least messy preparations for travelling) – for use on all exposed skin and even some unexposed areas such as under socks. Insect repellent should be applied after sun screen, ideally after a 20-minute interval. You also need either a permethrin-impregnated bed-net or a permethrin spray so that you can ‘treat’ bed-nets in hotels. Permethrin treatment makes even very tatty nets protective and prevents mosquitoes from biting through the impregnated net when you roll against it; it also deters other biters. Otherwise retire to an air-conditioned room or burn mosquito candles/coils or sleep under a fan. Coils and fans reduce rather than eliminate bites. Travel clinics usually sell a good range of nets, treatment kits and repellents.

Mosquitoes and many other insects are attracted to light. If you are camping, never put a lamp near the opening of your tent, or you will have a swarm of biters waiting to join you when you retire. In hotel rooms, be aware that the longer your light is on, the greater the number of insects will be sharing your accommodation.

Aside from avoiding mosquito bites between dusk and dawn, which will protect you from elephantiasis and a range of nasty insect-borne viruses, as well as malaria, it is important to take precautions against other insect bites.

In lower lying areas of South America you are at risk of day-biting mosquitoes (Aedes) that can carry dengue fever and zika virus, so it is important to apply DEET-based repellents on all exposed skin during daylight hours, as well as when the sun goes down. In more rural areas such as the Pantanal inBrazil or theAmazonBasin in any country it is wise to wear long, loose (preferably 100% cotton) clothes that have been impregnated with permethrin that will kill the mosquitoes on contact. You can buy this clothing spray from most camping shops and pre-treat your clothes at home.  

Protection from the sun

Give some thought to packing suncream. The incidence of skin cancer is rocketing as Caucasians are travelling more and spending more time exposing themselves to the sun. Head for the shade between 11.00 and 15.00 and, if you must expose yourself to the sun, build up gradually from 20 minutes per day. To avoid burning, cover up in tightly woven clothing that is loose to allow air to circulate and wear a broad brimmed hat. Be especially careful of exposure in the middle of the day and of sun reflected off water and, when swimming, wear a T-shirt and lots of waterproof suncream (at least SPF 25 and a UVA of 4 stars or more). Sun exposure makes people prematurely wrinkly and increases the risk of skin cancer. The glare and the dust can be hard on the eyes, too, so bring UV-protecting sunglasses (British standard BS2724 1987) and, perhaps, a soothing eyebath. Remember children are particularly vulnerable and an SPF of factor 50 is recommended.

Personal first-aid kit

 A minimal kit should contain:

  • A good drying antiseptic, eg: iodine or potassium permanganate (don’t take antiseptic cream)
  • Water purification tablets (chlorine dioxide) or a filter bottle eg: Aquapure
  • A few small dressings (Band-Aids)
  • Suncream
  • Insect repellent; anti-malarial tablets; impregnated bed-net or permethrin spray
  • Aspirin or paracetamol
  • Antifungal cream (eg: Canesten)
  • Antibiotics for severe diarrhoea/bacillary dysentery 
  • Tinidazole for giardia or amoebic dysentery (see below for regime)
  • Antibiotic eye drops, for sore, ‘gritty’, stuck-together eyes (conjunctivitis)
  • A pair of fine pointed tweezers (to remove hairy caterpillar hairs, thorns, splinters, coral, etc)
  • Alcohol-based hand rub and soap (either a bar in a plastic box or as a liquid)
  • Condoms or femidoms
  • Needle and syringe kit accompanied by a letter from a healthcare professional
  • A digital thermometer (for those going to remote areas) and malaria treatment for longer or more remote travel

Long-haul flights, clots and DVT

Any prolonged immobility including travel by land or air can result in deep vein thrombosis (DVT) with the risk of embolus to the lungs. Certain factors can increase the risk and these include:

  • Previous clot or close relative with a history 
  • People over 40 but > risk over 80 years
  • Having had an operation in the past two months
  • Cancer
  • Broken leg in a plaster
  • Some blood clotting disorders
  • Recent severe illness such as pneumonia, heart failure or a heart attack
  • Obesity
  • Pregnancy
  • Hormone therapy such as HRT or the combined oral contraceptive pill
  • People who are very tall (over 6ft/1.8m) or short (under 5ft/1.5m)

A deep vein thrombosis (DVT) causes painful swelling and redness of the calf or sometimes the thigh. It is only dangerous if a clot travels to the lungs (pulmonary embolus). Symptoms of a pulmonary embolus (PE) include chest pain, shortness of breath and sometimes coughing up small amounts of blood and commonly start three to ten days after a long flight. Anyone who thinks that they might have a DVT needs to see a doctor immediately.

Prevention of DVT

  • Keep mobile before and during the flight;
  • Bend and straighten your legs, feet and toes every half an hour when seated.
  • Drink plenty of fluids during the flight
  • Avoid taking sleeping pills and drinking excessive tea, coffee and alcohol
  • Consider wearing compression stockings (flight socks) ­– these must be measured and worn correctly. Ill-fitting stockings can actually increase the risk of DVT.

If you think you are at increased risk of a clot consult with a doctor. You may be prescribed blood-thinning drugs to lessen the risk or be advised not to travel.

Common medical problems

Water sterilisation

You can fall ill from drinking contaminated water so try to drink from safe sources, eg: bottled water where available. If you are planning to visit more remote areas where safe bottled water is unlikely to be available then consider buying a water filter system such as Aquapure. The filter in this system will remove all micro-organisms (bacteria, viruses, protozoa) and silt, etc, and will filter around 350 litres of water before it stops working. No chemicals are involved so it works immediately and it is environmentally friendly as there is no need to dispose of the plastic bottles. Failing that, boil water thoroughly or sterilise with chlorine dioxide tablets. The latter are not the most pleasant tasting and take about 10 minutes to be effective. They do not work if the water contains any particulate matter.

Travellers’ diarrhoea

Travelling in South America carries a fairly high risk of getting a dose of travellers’ diarrhoea; perhaps half of all visitors will suffer and the newer you are to exotic travel, the more likely you will be to suffer. By taking precautions against travellers’ diarrhoea you will also avoid typhoid, paratyphoid, cholera, hepatitis, dysentery, worms, etc. Travellers’ diarrhoea and other faecal-oral diseases come from getting other people’s faeces in your mouth. This most often happens from cooks not washing their hands after a visit to the toilet, but even if the restaurant cook does not understand basic hygiene you will be safe if your food has been properly cooked and arrives piping hot. The most important prevention strategy is to wash your hands before eating anything. You can pick up salmonella and shigella from toilet door handles and possibly bank notes. The maxim to remind you what you can safely eat is:

PEEL IT, BOIL IT, COOK IT OR FORGET IT.

This means that fruit you have washed and peeled yourself, and hot foods, should be safe but raw foods, cold cooked foods, salads, fruit salads which have been prepared by others, ice cream and ice are all risky, and foods kept lukewarm in hotel buffets are often dangerous. That said, plenty of travellers and expatriates enjoy fruit and vegetables, so do keep a sense of perspective: food served in a fairly decent hotel in a large town or a place regularly frequented by expatriates is likely to be safe.  If you are struck, see below for treatment.

Treating travellers’ diarrhoea

It is the dehydration that makes you feel awful during a bout of diarrhoea and the most important part of treatment is drinking lots of clear fluids. Sachets of oral rehydration salts  give the perfect biochemical mix to replace the fluids and electrolytes you are losing in the diarrhoea. If you don’t have any to hand then any dilute mixture of sugar and salt in water will be suitable substitute: try Coke or orange squash with a three-finger pinch of salt added to each glass (if you are salt-depleted you won’t taste the salt). Otherwise make a solution of a four-finger scoop of sugar with a three-finger pinch of salt in a 500ml glass and add a squeeze of lemon or orange juice to improve the taste.  The juice also adds potassium, which is lost in diarrhoea. Drink two large glasses after every bowel action, and more if you are thirsty. These solutions are still absorbed well if you are vomiting, but you will need to take sips at a time. If you are not eating you need to drink three litres a day plus the same amount as whatever is pouring into the toilet. If you feel like eating, take a bland, high carbohydrate diet. Heavy greasy foods will probably give you cramps.

Some people like to carry an antibiotic either because they will be remote from medical help or to treat travellers’ diarrhoea quickly. Drugs such as ciprofloxacin and rifaximin can be used to shorten travellers’ diarrhoea if they are started early enough in the illness. If the diarrhoea is bad, or you are passing blood or slime, or you have a fever, you will probably need a longer course of antibiotics in addition to fluid replacement. Some travellers also like to take antibiotics with them to treat bacillary dysentery – eg: azithromycin, ciprofloxacin or norfloxacin. Which drug to take, whether to treat simple travellers’ diarrhoea or bacillary dysentery, depends on the sensitivity of the organisms in the countries being visited and personal medical history so seek expert advice before you travel. If the diarrhoea is greasy and bulky and is accompanied by sulphurous (eggy) burps, one likely cause is giardia. This requires a different treatment (tinidazole for preference but metronidazole will do). Again some people like to take these medications with them.

Always seek medical advice as soon as possible if you have symptoms of giardia or you are vomiting or have other symptoms of bacillary dysentery or if simple diarrhoea fails to settle after a couple of days. Similarly, if the diarrhoea fails to settle after two doses of ciprofloxacin or the three-day course of rifaximin, then you should seek medical advice. Remember, children can succumb rapidly to dehydration and it is not advisable to give them antibiotics without first consulting a doctor.

Eye problems

Bacterial conjunctivitis (pink eye) can occur when travelling inSouth America; people who wear contact lenses are most open to this irritating problem. The eyes feel sore and gritty and eyelids will often be stuck together in the mornings. They will need treatment with antibiotic drops or ointment. Lesser eye irritation should settle with bathing in salt water and keeping the eyes shaded. If an insect flies into your eye, extract it with great care, ensuring you do not crush or damage it otherwise you may get a nastily inflamed eye from toxins secreted by the creature. The elongated and colourful blister beetles carry warning colouration to tell you not to crush them anywhere against your skin.

Prickly heat

A fine pimply rash on the trunk is likely to be heat rash; cool showers, dabbing dry, and talc will help. Treat the problem by slowing down to a relaxed schedule, wearing only loose, baggy, 100%-cotton clothes and sleeping naked under a fan; if it’s bad, you may need to check into an air-conditioned hotel room for a while.

Skin infections

Any mosquito bite or small nick in the skin gives an opportunity for bacteria to foil the body’s usually excellent defences; it will surprise many travellers how quickly skin infections start in warm humid climates and it is essential to clean and cover even the slightest wound. Creams are not as effective as a good drying antiseptic such as dilute iodine, potassium permanganate (a few crystals in half a cup of water), or crystal (or gentian) violet. One of these should be available in most towns. If the wound starts to throb, or becomes red and the redness starts to spread, or the wound oozes, and especially if you develop a fever, antibiotics will probably be needed: flucloxacillin (250mg four times a day) or cloxacillin (500mg four times a day). For those allergic to penicillin, erythromycin (500mg twice a day) for five days should help. See a doctor if the symptoms do not start to improve within 48 hours.

Fungal infections also get a hold easily in hot, moist climates so wear 100%-cotton socks and underwear and shower frequently. An itchy rash in the groin or flaking between the toes is likely to be a fungal infection. This needs treatment with an antifungal cream such as Canesten (clotrimazole); if this is not available try Whitfield’s ointment (compound benzoic acid ointment) or crystal violet (although this will turn you purple!).

Malaria

Malaria risks in South America are variable depending on altitude and other climatic aspects. The Anopheles mosquito that transmits the malaria parasite should be assumed to be present at all altitudes below 1,800 metres. Take country-specific advice from a travel clinic expert.

Malaria prevention

There is not yet a vaccine against malaria that gives enough protection to be useful for travellers, but there are other ways to avoid it. Seek current advice on the best antimalarials to take: usually atovaquone/proguanil (eg: Malarone), doxycycline or mefloquine (particularly for small children or for adults who have used it before).

Atovaquone/proguanil (eg: Malarone) is highly effective in preventing falciparum malaria which is the most serious type of the disease. It has the advantage of having relatively few side effects and need only be continued for one week after returning. However, it is expensive and because of this tends to be reserved for shorter trips. Atovaquone/proguanil may not be suitable for everybody, so advice should be taken from a doctor. The Advisory Committee for Malaria Prevention has advised that it is safe to take atovaquone/proguanil for as long as it is tolerated, ie: far longer than the product licence suggests. There is a paediatric form of the tablet for children weighing under 40kg and the dose is calculated by body weight. 

The antibiotic doxycycline (100mg daily) is a credible and cheaper alternative. Like atovaquone/proguanil it can be started two days before arrival. In about 1–3% of people there is the possibility of allergic skin reactions developing in sunlight; the drug should be stopped if this happens. It is unsuitable for children under 12 years, in breastfeeding mothers and in pregnant women over 11 weeks’ gestation. It can be used for people with epilepsy but can sometimes make anti-epileptic medication less effective so the dose may need to be increased.

Mefloquine (Lariam) is a very effective drug but ideally needs to be started two-and-a-half weeks (three doses) before departure to check that it suits you and to ensure that it has reached an effective level; stop it immediately if it seems to cause depression or anxiety, visual or hearing disturbances, severe headaches, fits or changes in heart rhythm. Side effects such as nightmares or dizziness are not medical reasons for stopping unless they are sufficiently debilitating or annoying. Anyone who has been treated for depression or psychiatric problems, has diabetes controlled by oral therapy or who is epileptic (or who has suffered fits in the past) or has a close blood relative who is epileptic, should probably avoid mefloquine. Small children tend to tolerate this drug very well, and as it is a weekly dosing tends to be more convenient for them. 

In the past doctors were nervous about prescribing mefloquine to pregnant women, but experience has shown that it is relatively safe and certainly safer than the risk of malaria. If mefloquine is not suitable then other antimalarial tablets can be considered. That said, there are other issues, so if you are travelling to malarial areas whilst pregnant, seek expert advice before departure.

All tablets should be taken with or after the evening meal, washed down with plenty of fluid and, with the exception of atovaquone/proguanil (see above), continued for four weeks after leaving. 

Despite all these precautions, it is important to be aware that no anti-malarial drug is 100% protective, although those on prophylactics who are unlucky enough to catch malaria are less likely to get into serious trouble. In addition to taking anti-malarials, it is therefore important to avoid mosquito bites between dusk and dawn (see Avoiding insect bites).

There is unfortunately the occasional traveller who prefers to ‘acquire resistance’ to malaria rather than take preventive tablets, or who takes homeopathic prophylactics thinking these are effective against this killer disease. Homeopathy theory dictates treating like with like so there is no place for prophylaxis or immunisation in a well person; bone fide homoeopathists do not advocate it. It takes at least 18 months residing in a holoendemic area for someone to get some immunity to malaria so travellers to South America will not acquire any effective resistance to malaria.  The best way is to prevent mosquito bites in the first place and to take a suitable prophylactic agent.

Diagnosis and treatment

Even those who take their malaria tablets meticulously and do everything possible to avoid mosquito bites may contract a strain of malaria that is resistant to prophylactic drugs. Untreated malaria is likely to be fatal, but even strains resistant to prophylaxis respond well to prompt treatment. Because of this, your immediate priority upon displaying possible malaria symptoms – including a rapid rise in temperature (over 38˚C), and any combination of a headache, flu-like aches and pains, a general sense of disorientation, and possibly even nausea and diarrhoea – is to establish whether you have malaria, ideally by visiting a clinic. From seven days or more into your trip, assume that any high fever over 38oC lasting more than a few hours is malaria regardless of whether you have any other symptoms or not. Also remember that it is still possible to develop malaria several months (technically up to a year) after leaving a malarial area so make sure that you tell the treating doctor where you have been.

Diagnosing malaria is not easy, which is why consulting a doctor is sensible: there are other dangerous causes of fever in South America, which require different treatments. Even if you test negative, it would be wise to stay within reach of a laboratory until the symptoms clear up, and to test again after a day or two if they don’t. It’s worth noting that if you have a fever and the malaria test is negative, you may have typhoid or paratyphoid, which should also receive immediate treatment.

Carrying a course of malaria treatment may be recommended for travellers on long overland trips, or those working or volunteering in more remote Amazon regions areas where access to good medical care is very limited.  Some people advocate taking a rapid diagnostic test kit with them, though these have been shown to be difficult to use by people who are sick or who haven’t had a lot of practice using them. Ideally you should get to medical help as soon as possible and let those with experience make the diagnosis. With malaria, it is normal enough to go from feeling healthy to having a high fever in the space of a few hours (and it is possible to die from falciparum malaria within 24 hours of the first symptoms). In such circumstances, assume that you have malaria and act accordingly – whatever risks are attached to taking an unnecessary cure are outweighed by the dangers of untreated malaria. Experts differ on the costs and benefits of self-treatment, but it is hard not to agree that treatment may save your life. There is also some division about the best treatment for malaria, but either atovaquone/proguanil (eg: Malarone) or Coarthemeter are the current treatments of choice. Discuss your trip with a specialist ideally before you travel.

Other insect-borne diseases

Malaria is by no means the only insect-borne disease to which the traveller may succumb. Others include dengue fever, sleeping sickness and river blindness (see also, Avoiding insect bites).

Dengue fever

Dengue fever is more common than malaria in many parts of South America and there are many other similar arboviruses, such as Chikungunya. These mosquito-borne diseases may mimic malaria but there is no prophylactic medication against them.

The dengue fever virus belongs to the family Flaviviridae, genus flavivirus (which includes yellow fever and Japanese encephalitis). The mosquitoes that carry the dengue fever virus typically bite during the daytime, so it is worth applying repellent if you see any mosquitoes around. Symptoms include strong headaches, rashes, excruciating joint and muscle pains and high fever.

Viral fevers usually last about a week or so and are not usually fatal. Complete rest and paracetamol are the usual treatment; plenty of fluids also help. Some patients are given an intravenous drip to keep them from dehydrating. It is especially important to protect yourself if you have had dengue fever before, since a second infection with a different strain can result in the potentially fatal dengue haemorrhagic fever.

Chagas disease                                                                                                                 

Also known as American trypanosomiasis, Chagas disease is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi (T. cruzi). In Latin America the disease is mostly vector borne, where it is transmitted to humans by contact with the faeces or urine of the triatomine bugs, which are also known as kissing bugs in some countries. The bugs live in the cracked walls of poorly constructed houses in both rural and suburban areas. They are active at night when they feed on human blood. The bugs typically bite on the face and then defecate next to the wound. The parasite enters the body when the infected faeces are smeared into the open wound or into mucous membranes such as the eyes or mouth. Travellers can also contract this disease by eating infected food.

Chagas disease has two phases. The acute phase lasts for about two months after the initial infection. Most cases during this phase have few or no symptoms. Less than half have skin lesions or present with fever, headache, enlarged lymph nodes, abdominal or chest pain. During the chronic phase, the parasites hide in the heart or digestive muscles. About a third of patients suffer from cardiac disorders and up to 10% have digestive problems. Long-term death can occur from heart failure.

Benznidazole and nifurtimox can effectively treat Chagas disease if given early in the acute phase. They are less effective the longer a person has been infected.  It can be reduced or avoided by the following:

  • Avoid sleeping in a mud, thatch or adobe house. These types of residences are more likely to harbour triatomine bugs.
  • Use permethrin-impregnated bed-nets when sleeping in thatch, mud or adobe houses.
  • Use insecticides to remove insects from your residence.
  • Use DEET-based insect repellent on all exposed skin.

Onchocerciasis                                                                                                                  

This disease, which is also known as river blindness, is hypoendemic in Brazil, Venezuela and Colombia. The risk of infection is greatest in the dry season.

It is caused by a nematode worm (Oncocerca volvulus) and is spread by the bite of a black fly (Simulium species) which breeds in fast flowing water. The black fly bites mostly at dawn and dusk. The microfilaria released by the black fly cause skin irritation with intense itching which usually occurs months or years later. The cornea can be affected, leading to blindness (hence the name), but this is rare in travellers.

Usually infection follows multiple bites, so those staying in the endemic countries listed such as aid workers, missionaries and military personnel are potentially at higher risk. Travellers who are living near rivers, particularly camping, are again at higher risk. The risk for most travellers is low. The recommended treatment is ivermectin, which needs to be given every six months for the life span of the adult worms or for as long as the infected person has evidence of skin or eye infection.

Prevention

Cover up and use DEET containing insect repellents on all exposed skin. Sleep under permethrin-impregnated mosquito nets.

Leishmaniasis                                                                                                                       

In South America this disease is caused by a protozoan parasite (Leishmania braziliensis). It is spread by the bite of an infected sand fly (Phlebotomus sp.) which is mainly night biting and is most prevalent in forest or jungle areas.

There are two forms of the disease: cutaneous (affecting the skin) and visceral (affecting the organs). Brazil has the highest prevalence of both these forms in South America. The visceral form is usually fatal without treatment but thankfully the disease is rare in travellers. Those at highest risk are those trekking or living in the jungle. Treatment with liposomal amphotericin B is used for the visceral form and in most cases treatment is not needed for the cutaneous form but amphotericin B can be used.

Prevention

As sand flies bite close to the ground the risk is reduced if beds are raised off the ground and you sleep under a permethrin impregnated bed-net. Sand flies are small enough to be able to get through the mesh of the net.

Schistosomiasis (bilharzia)

Schistosomiasis affects only a handful of countries in South America, namely Brazil, Venezuela, Suriname, Guyana and French Guiana. It is caused by a microscopic flatworm (fluke) of the genus Schistosoma. The form that exists in South Americais Schistosoma mansoni

It is an unpleasant problem that is worth avoiding, though can be treated if you do get it.

The risk is greatest for travellers who swim and bathe in fresh water (not sea or chlorinated water), particularly slow moving or sluggish water, or who are exposed to water provided for washing from local lakes or rivers. By understanding a bit about the life cycle then it is easier to prevent the disease, or recognise that you have it and therefore get treatment.

Eggs of the flatworm are excreted in faeces, which are then washed into the lake. The eggs hatch and the larvae that emerge infect certain species of snail. The snails then produce about 10,000 cercariae (larvae) a day for the rest of their lives. Winds will disperse the snails and cercariae. The snails in particular can drift a long way, especially on windblown weed, so nowhere is really safe. However, deep water and running water are safer, while shallow water presents the greatest risk. The larvae penetrate intact skin, and find their way to the liver where they continue to multiply.

Although the adults do not cause any harm in themselves, after about 4–6 weeks they start to lay eggs, which cause an intense but usually ineffective immune reaction, including fever, cough, abdominal pain, and a fleeting, itching rash called ‘safari itch’. The absence of early symptoms does not necessarily mean there is no infection. Later symptoms can be more localised and more severe, but the general symptoms settle down fairly quickly and eventually you are just tired.

Schistosoma mansoni end up in the gut wall and can lead to abdominal pain, diarrhoea and symptoms of anaemia due to blood loss – either frank or occult. Often though there are no symptoms at all. With long-standing untreated infection complications such as fibrosis / stenosis of the bowel can occur. Liver involvement can lead to hepatosplenomegaly, cirrhosis and portal hypertension.

Although bilharzia is difficult to diagnose, it can be tested at specialist travel clinics. Ideally tests need to be done at least six weeks after likely exposure and will determine whether you need treatment.  Fortunately it is easy to treat at present.

Avoiding bilharzia

If you are bathing, swimming, paddling or wading in fresh water, which you think may carry a bilharzia risk, try to get out of the water within ten minutes.

  • Avoid bathing or paddling on shores within 200m of villages or places where people use the water a great deal, especially reedy shores or where there is lots of water weed.
  • Dry off thoroughly with a towel; rub vigorously.
  • If your bathing water comes from a risky source try to ensure that the water is taken from the lake in the early morning and stored snail-free, otherwise it should be filtered or Dettol or Cresol added.
  • Bathing early in the morning is safer than bathing in the last half of the day.
  • Cover yourself with DEET insect repellent before swimming: it may offer some protection. 

HIV/AIDS                                    

The prevalence of HIV is higher in nearly all South American countries than theUKand the risk of sexually transmitted infections is greater whether you sleep with fellow travellers or locals. About 80% of HIV infections in British heterosexuals are acquired abroad. If you must indulge, use condoms or femidoms, which help reduce the risk of transmission. If you notice any genital ulcers or discharge, get treatment promptly since these increase the risk of acquiring HIV.  If you do have unprotected sex, visit a clinic as soon as possible; this should be within 24 hours, or no later than 72 hours, for post-exposure prophylaxis.

Rabies

Rabies is carried by all warm-blooded mammals (beware the village dogs and small monkeys that are used to being fed in the parks) and is passed on to man through a bite, scratch or a lick (note that doctors now understand that even without an obvious wound, there is still a risk of infection from the saliva of an infected animal). You must always assume any animal is rabid as they can often look well but still be infectious. Seek medical help as soon as possible after any potential exposure. Meanwhile scrub the area that has been contaminated with animal saliva with soap under a running tap or while pouring water from a jug for a good 10–15 minutes. The source of the water is not important at this stage but if you do have antiseptic to hand then put this on afterwards. The soap helps stop the rabies virus entering the body and along with an antiseptic will guard against wound infections, including tetanus.

Pre-exposure vaccination for rabies is advised for everyone, but is particularly important if you intend to have contact with animals and/or are likely to be more than 24 hours away from medical help. Ideally three doses should be taken over a minimum of 21 days. All three doses are needed in order to change the treatment needed following an exposure.

If you are bitten, scratched or licked over an open wound by any mammal, then post-exposure prophylaxis should be given as soon as possible, though it is never too late to seek help, as the incubation period for rabies can be very long. Those who have not been immunised before will need 4–5 doses of rabies vaccine given over 28–30 days and may also be advised to have a product called Rabies Immunoglobulin (RIG) either human or horse. The RIG is injected round the wound to try and neutralise any rabies virus present and is a pivotal part of the treatment if you have not had pre-exposure vaccine. RIG is expensive and may not be readily available as there is a global shortage so it is important to insist on getting to a place that has it.  Another reason for having good insurance.

Tell the doctor if you have had two or more doses of the pre-exposure vaccine, as this will change the treatment you receive. If you have had all three doses then you will no longer need to have RIG and will only need a couple of doses of vaccine, ideally given three days apart. If you have had two doses then in most cases you won’t need RIG but would still need to get five post-exposure doses of rabies vaccine over about 28 days. And remember that, if you do contract rabies, mortality is 100% and death from rabies is probably one of the worst ways to go.

Tick-borne diseases

Rocky mountain spotted fever

This is caused by the obligate intracellular gram-negative spirochete bacteria Rickettsia rickettsii. It is spread by the bite of ticks that live on rodents and dogs and is more risky for travellers if they are camping and hiking in rural areas.

The incubation is 2–14 days. The patient presents with an acute onset of fever, headache, abdominal pain, hypotension, rash, myalgia and arthralgia to name a few. There is a case fatality of 1.4%. It is treatable with tetracyclines, such as doxycycline 100mg twice daily for 7–14 days.

Prevention is always better than cure, so if you are going to be walking in rural areas ensure that you are dressed appropriately with long sleeves, long trousers tucked into boots and a hat. At the end of the day check each other for ticks.

Ticks should ideally be removed as soon as possible as leaving them on the body increases the chance of infection. They should be removed with special tick tweezers that can be bought in good travel shops. Failing that you can use your finger nails: grasp the tick as close to your body as possible and pull steadily and firmly away at right angles to your skin. The tick will then come away complete, as long as you do not jerk or twist. If possible douse the wound with alcohol (any spirit will do) or iodine. Irritants (eg: Olbas oil) or lit cigarettes are to be discouraged since they can cause the ticks to regurgitate and therefore increase the risk of disease. It is best to get a travelling companion to check you for ticks; if you are travelling with small children, remember to check their heads, and particularly behind the ears.

Spreading redness around the bite and/or fever and/or aching joints after a tick bite imply that you have an infection that requires antibiotic treatment, so seek advice.

Snakebite

Snakes rarely attack unless provoked, and bites in travellers are unusual. You are less likely to get bitten if you wear stout shoes and long trousers when in the bush. Most snakes are harmless and even venomous species will dispense venom in only about half of their bites. If bitten, then, you are unlikely to have received venom; keeping this fact in mind may help you to stay calm. Many so-called first-aid techniques do more harm than good: cutting into the wound is harmful; tourniquets are dangerous; suction and electrical inactivation devices do not work. The only treatment is anti-venom. In case of a bite that you fear may have been from a venomous snake:

•           Try to keep calm – it is likely that no venom has been dispensed.

•           Prevent movement of the bitten limb by applying a splint.

•           Keep the bitten limb BELOW heart height to slow the spread of any venom.

•           If you have a crêpe bandage, wrap it around the whole limb (eg: all the way from the toes to the thigh), as tight as you would for a sprained ankle or a muscle pull.

•           Evacuate to a hospital that has the relevant anti-venom.

And remember:

NEVER give aspirin; you may take paracetamol, which is safe.

NEVER cut or suck the wound.

DO NOT apply ice packs.

DO NOT apply potassium permanganate.

If the offending snake can be captured without risk of someone else being bitten, take this to show the doctor – but beware since even a decapitated head is able to bite.  

Updated 09 March 2017

Back to the top


Post Comments

There are no comments on this article yet.


Submit Comment

You must be logged in to post a comment. Click here to log in.