PARASITES & OTHER DISEASES
Parasitic diseases are common in the local population in many travel destinations and although you should not worry, it is advisable to be aware of some of these diseases and how they can be avoided.
DENGUE FEVER 
Prevalence: Common in many parts of the tropics
Dengue fever is caused by one of four virus serotypes which are spread by Aedes species of mosquito. These mosquitoes bite during the day. The epidemics of dengue fever are often seasonal, during or just after rainy seasons. Check the NATHNAC link for current outbreaks.
Symptoms come on very suddenly, with fever, severe headache, and muscle and joint pains, with a rash typically developing after 3-5 days. Nausea, vomiting and diarrhoea are also common. The acute phase usually lasts a week, and although serious complications are uncommon, post-viral fatigue syndrome is common, so take it easy for a few weeks if you can. Rarely, dengue fever can develop into a more serious form, called dengue haemorrhagic fever, which in turn can lead to dengue shock syndrome, which can be fatal. The haemorrhagic form occurs more commonly in subsequent attacks with a different serotype of dengue virus.
Treatment is symptomatic: keep your fluid intake up (not alcohol!) so that you don’t dehydrate, and pain should be relieved with paracetamol, not aspirin or ibuprofen. Hospital care is indicated in severe illness or if complications occur.
Diagnosis is usually made clinically. Self-diagnosis of dengue in a malarious area could be very dangerous – All illnesses with fever should be considered to be malaria until proven otherwise. In places with good medical facilities a blood test can be done at 8 days after the onset of fever to confirm the diagnosis. It can be useful if you are a long-term or recurrent traveller to know if you have had dengue as subsequent episodes should be monitored more closely for complications.
Prevention, as with all insect-borne diseases, is by using insect repellent (containing DEET), covering up with clothing where possible and sleeping/resting under a mosquito net impregnated with permethrin.
AFRICAN TRYPANOSOMIASIS (sleeping sickness) 
Prevalence: Patchy distribution in sub-Saharan Africa
African trypanosomiasis is a potentially lethal disease caused by a microscopic parasite spread by tsetse flies. These flies are large, brown and give a painful bite, often resulting in a boil on the skin if the fly is carrying the parasite. In different parts of Africa the flies favour either shady riverside habitats or the bases of tree trunks in the savannah regions. An important feature of the disease is swollen glands, especially on the neck, accompanied by fever, headaches and joint pain. Use insect repellent (50% DEET) and wear long, loose clothing to prevent being bitten by tsetse flies.
SOUTH AMERICAN TRYPANOSOMIASIS (Chagas’ disease) 
Prevalence: Mexico, Central and South America
South American trypanosomiasis is transmitted by ‘kissing bugs’ that feed by sucking blood when you are asleep, often from your face. Parasites are passed out of the bug not in saliva but in faeces, and you become infected if you scratch the bite and rub the faeces into the wound. The bite is surprisingly painless even though the bug may feed for more than 10 minutes. The bugs typically live in the cracks of mud huts or in thatched roofs, but they also live behind furniture and pictures on the wall. The disease is serious in that, if undiagnosed or untreated in the acute phase (the first few weeks), damage to the heart and digestive system is irreversible and can lead to health problems in the future. It is strongly advised that you do not sleep in rural dwellings in Latin America without an insecticide-treated bed net, and make sure you tuck it under your mattress!
LEISHMANIASIS
Prevalence: Patchy distribution worldwide
- The most serious is visceral leishmaniasis, which can be lethal if untreated. Symptoms include fever, anaemia, weight loss, and enlarged liver and spleen.
- Less serious is mucocutaneous leishmaniasis, only present in Central and South America, which causes a skin ulcer and spreads to disfigure the nose and throat.
- Least serious is cutaneous leishmaniasis which causes self-healing ulcers, often leaving a scar.
Sandflies bite from dusk throughout the night and insect repellent should be used. If you are going to a known endemic area, consider buying a sandfly net, which is a finer mesh than a mosquito net and will keep out sandflies. Make sure it is insecticide-impregnated every 6 months with permethrin. If you develop a skin ulcer that persists, or the symptoms of visceral leishmaniasis, seek medical attention.
ONCHOCERCIASIS (River Blindness) 
Prevalence: Patchy distribution in equatorial Africa and equatorial Latin America
Onchocerciasis is a chronic disease caused by small parasitic worms which are transmitted by the bite of black flies which live near rivers. The worms take up residence in your skin, producing itchy skin and nodules. They also show a preference for the eye but blindness only occurs after many years of infection. If you are concerned see a doctor on your return.
LYMPHATIC FILARIASIS
Prevalence: South-East Asia, India, Equatorial Africa, some parts of Latin America
Lymphatic filariasis is a parasitic infection which initially causes fever and inflammation of the skin. When chronic the disease affects the lymphatic system which results in swelling, usually of the legs. It occurs mainly in the least developed countries of the world and usually travellers are not at high risk. The parasitic worms are spread by mosquitoes which bite at night, so use a good insect repellent containing DEET and an insecticide-treated mosquito net.
PLAGUE
Prevalence: Isolated foci in Africa, Asia and Latin America
Plague is fortunately rare. It is spread through the bite of infected rodent fleas. Don’t lose any sleep about this but use insect repellent (containing DEET) if you are staying in very rough, rural housing. If you develop a large, red, painful boil in your groin or armpit, see a doctor soon.
LEPTOSPIR OSIS
Prevalence: Worldwide distribution
Leptospirosis is a bacterial disease spread through animal urine, usually from the rat. It can be lethal but unless you will be working in sewers you will probably be at low risk of the disease. However, if you are working in rural areas or shanty towns, especially in the rainy season, don’t mess about in the flood water and cover any cuts and grazes with waterproof dressings.
SOIL-M EDIATED PARASITIC WORMS
Prevalence: Very common in the tropics
Be aware of washing your hands before you eat and don’t go barefoot as some worms will penetrate your skin. See your GP if you have any intestinal symptoms that continue on your return to the UK, and let them know where you have travelled to.
CUTANEOUS LARVA MIGRANS
Prevalence: Southeast Asia, Latin America, and the Caribbean basin
Cutaneous larva migrans is a characteristic itchy creeping skin eruption, usually of the foot. It is due most commonly to a dog or pig hookworm, passed in faeces. The worm can enter your skin when walking barefoot in sand or dirt in the tropics. Treatment is by medication (even though this is a self-limiting disease with the larva dying and the lesions resolving - but this can take from 4 weeks to 1 year).
MYIASI S
Prevalence:
A rather unpleasant boil with a little surprise in store. The Bot fly lays an egg under the skin and the larva feasts on your subcutaneous tissues. A reactive boil forms but the larva has formidable hooks which allow it to prevent efforts to removal by squeezing it out. The technique for removal is to coat the area in a thick layer of Vaseline and wait for it to come up for air, whereupon it can be grabbed!
RIFT VALLEY FEVER
Prevalence: Kenya, Tanzania and Somalia
Rift Valley Fever is a viral disease primarily affecting domestic animals including cattle, sheep and goats. It can be transmitted to humans via mosquito bites or through contact with body fluids (including milk) and meat of infected animals. The majority of cases experience a brief flu-like illness but the disease can progress and become fatal. Avoid insect bites using insect repellent (containing DEET), long, loose clothing and consider buying a bed-net impregnated with insecticide. Boil fresh milk, cook meat thoroughly and avoid direct contact with raw meat.
CHIKU NGUNYA VIRUS
Prevalence: India, Sri Lanka, Indian Ocean Islands, Africa
Chikungunya Virus, like Dengue Fever, is spread by day-biting Aedes mosquitoes. The illness presents as rapid onset on joint pains, muscle pain, high fever, conjunctivitis and rash. Avoid mosquito bites by using DEET insect repellent, long, loose clothing and consider buying a bed-net impregnated with insecticide.
SCHISTOSOMIASIS (Bilharzia) 
Prevalence: Africa (90% of cases), some parts of Latin America and South-East Asia
Schistosomiasis is a disease caused by blood flukes acquired when wading or swimming in infested fresh water lakes and streams. When you are in the water, microscopic parasites burrow through your skin and migrate through your body until they come to their final destination in the veins of the bowel or bladder. Light infections may pass unnoticed but more severe infections may cause blood in the urine or faeces, together with other symptoms. Avoid swimming in freshwater lakes or rivers, or if you do, request a blood test 12 weeks after returning from your trip. In addition It is wise never to go barefoot, but to wear protective footwear when out, even on the beach. Other diseases and parasites can be caught from sand and soil, particularly wet soil.
Leishmaniasis embraces a range of diseases caused by different types of microscopic parasites and they occur in many countries of the world. All are spread by sandflies, which are smaller than mosquitoes and are quite hairy. |
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