«14 EXPEDITION MEDICINE David Warrell xpeditions and ﬁeldwork in remote and challenging places are likely to expose E members to greater ...»
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14 EXPEDITION MEDICINE
xpeditions and ﬁeldwork in remote and challenging places are likely to expose
E members to greater environmental extremes and to more unusual hazards than
do other types of travel. The aims of expedition or wilderness medicine are to
improve, through knowledge, planning and skills, the conﬁdence, enjoyment and
achievements of the people who participate in these expeditions.
RISKS OF EXPEDITIONS: REAL AND PERCEIVEDThe risks of exotic infections, such as a viral haemorrhagic fever, plague, rabies or sleeping sickness, attacks by large or venomous animals and even of meeting canni- bals, may loom large in the imagination of expedition members. However, the reality is much more mundane. Travellers’ diarrhoea and other gastrointestinal disturbances are now recognised to be the main cause of expedition illness, whereas the leading causes of expedition mortality are falls and other injuries, road traffic accidents, alti- tude sickness, heat stroke, infections such as malaria, drowning and homicide.
Overall, the health risks of participating in a well-planned expedition are similar to those encountered during normal active life (Anderson and Johnson, 2000).
However, some expedition activities carry much higher mortality rates: 16 per cent of those attempting to reach the summit of Everest will die, 2.9 per cent of Himalayan mountaineers and 1 per cent of those over-wintering in Antarctica, compared with
0.83 per cent of expedition participants in general, 0.014 per cent of Himalayan trekkers and 0.013 per cent of low-altitude joggers (Anderson and Johnson, 2000).
REDUCTION OF HEALTH RISKS BY PLANNINGHealth risk assessment demands consideration of the terrain, altitude, climate, and endemic fauna and diseases of the area to be visited, and the intended aims of the expedition. Much of this information may be available beforehand. During selection 149 03 RGS Expedition Handbk 4/3/04 3:55 pm Page 150
EXPEDITION HANDBOOKof the expedition team, it is important to identify those with special problems (Table 14.1). Depending on the type of expedition, many of these may be accommodated by careful planning. However, the stress of travel in remote areas can destabilise chronic medical conditions and this could, in certain circumstances, cause danger to everyone in the group.
TABLE 14.1 EXPEDITION MEMBERS’ SPECIAL PROBLEMSPregnancy Immunosuppression (by drugs or diseases) Chronic illness (diabetes, epilepsy, asthma, ischaemic heart disease, etc.) Psych
All expeditions should have a designated medical officer, who, in most cases, will not be medically qualiﬁed. All members should attend ﬁrst-aid training, which, ideally, should be aimed at the particular needs of the expedition. Essential ﬁrst-aid skills for all expeditions are clearing the airway and resuscitation, controlling blood loss, treating shock, relieving pain and ensuring the safe evacuation of injured people. Prevention of medical problems on an expedition depends on awareness of local diseases (based on up-to-date information from journals, books, websites and telephone advice services), appropriate immunisations and chemoprophylaxis, a pre-expedition dental check-up and, if possible, resolution of known surgical and medical problems well in advance of the expedition’s departure. Explicit instructions should be given to expedition members about safe and sensible behaviour: in the use of equipment and techniques; and about food and water hygiene; protection from climatic and environmental hazards; as well as safe sex.
Expedition medical kits need to be much more comprehensive than those carried by ordinary tourists. Local medical back-up must be arranged in advance through the expedition’s local agent. Hospitals or other medical facilities nearest to the site of the expedition must be identiﬁed, contacted and, if possible, assessed in advance.
Emergency evacuation of severely ill or injured expedition members must be anticipated and planned well in advance and medical insurance cover should be generous to allow for in-country medical care (especially expensive in North America) and, if need be, repatriation of the sick or injured person. Many newer technical aids have improved safety through communication (radio/satellite telephones) and navigation (satellite location systems).
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THE EXPEDITION MEDICAL OFFICERThis is an essential and responsible role. The expedition medical officer must take the lead in planning and organising pre-expedition medical education, as well as deciding the location of the base camp, making arrangements for food, and providing for the psychological and pastoral needs of the expedition members.
Depending on the particular circumstances, expeditions may feel some responsibility for helping with medical problems of the indigenous peoples of the area. This can be a difficult issue because time, equipment and drugs are always in short supply.
ROAD TRAFFIC ACCIDENTSIt is astonishing that people who have spent much time and money in preventing illness during an expedition should, on arrival at the destination, entrust their lives to untried crazy-looking drivers and unsound vehicles. The risk is much greater in less developed countries, where there has been an epidemic increase in road traffic accident fatalities over the past 20 years and where 85 per cent of these deaths now occur (British Medical Journal, 2002). The risk of accidents can be reduced by avoiding driving at night outside cities, ensuring that the driver is not tired or under the inﬂuence of alcohol, antihistamines or other sedative (or recreational) drugs, avoiding driving alone, watching the driver for signs of fatigue, taking regular breaks and checking the basic functions of the vehicle (steering, lights, brakes, tyres, etc.) before setting off. Using seatbelts reduces the risk of death by 65 per cent.
IMMUNISATIONS/VACCINATIONSThe current wave of dangerously misinformed criticism of immunisations (MMR, Gulf War syndrome, etc.) must not discourage travellers from this most effective form of disease prevention. Do not assume that everyone has received a standard childhood course of immunisations (in the UK: diphtheria, pertussis, tetanus, mumps, measles, rubella [MMR], Haemophilus inﬂuenzae b [Hib], meningococcus C). Even if the traveller received a childhood primary course, boosters will be needed for diphtheria, tetanus and polio (eliminated from the Americas and Europe but still present elsewhere) after 10 years. Other basic immunisations recommended for travellers to almost every less developed country are BCG (for tuberculosis/leprosy), and those for hepatitis A, typhoid and rabies. Special immunisations for travellers to certain parts of the world include yellow fever (equatorial Africa and Latin America), Japanese encephalitis (Asia and New Guinea), meningococcus A (meningitis belt of sub-Sahelian Africa and new epidemic areas) and tick-borne encephalitis (central Europe and Scandinavia). Yellow fever is the only immunisation for which a certiﬁcate is a statutory requirement for travellers from and to endemic areas (Monath and Cetron, 2002), e.g. you will not be allowed to ﬂy from Ecuador to Brazil without a valid yellow fever 151 03 RGS Expedition Handbk 4/3/04 3:55 pm Page 152
Figure 14.1 Distribution of meningococcal meningitis in Africa immunisation certiﬁcate.
Recent deaths from yellow fever in tourists to West Africa and Latin America emphasise the continuing importance of this immunisation.
Cholera vaccine is no longer recommended by the World Health Organization because its adverse effects outweigh its usefulness, although a new oral vaccine is promising. The risk of hepatitis A, acquired from infected food/water, in less developed countries ranges from 300/100,00 to 2000/100,000 unprotected travellers per month of stay.Active immunisation is safe, effective and durable, and there is no longer any justiﬁcation for short-term protection with immunoglobulin. Epidemic meningococcal meningitis occurs in the cool, dry season (December–February) most years in countries of the sub-Sahelian“meningitis belt”of Africa (from Senegal and the Gambia in the west to Sudan in the east) (Molesworth et al., 2002) (Figure 14.1). Travellers to this area, and to other new sites of epidemics, should be given meningococcal group A + C (or ACYW) vaccine. The meningococcal group C vaccine now given to children in the UK does not provide adequate cover in these areas.
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Figure 14.2 Global distribution of rabies and the rabies-related bat lyssaviruses, 2003 Pre-exposure immunisation against classical rabies and the European and Australian rabies-related bat lyssaviruses (Figure 14.
2) is being used increasingly in travellers. (These bat lyssaviruses are related to classical rabies virus and produce clinical effects identical to classical rabies in infected people.) Although the risk of transmission is low, the lack of effective treatment for rabies encephalitis and the fear engendered by a dog bite justiﬁes immunisation now that safe and potent vaccines are available. Cost can be reduced if an ampoule of vaccine is divided among ten vaccinees, each being given one-tenth of the dose by intradermal injection.
Plague and anthrax vaccines cause serious side effects and, if there is real risk of infection, antibiotic prophylaxis or post-exposure treatment should be considered (doxycycline for plague, ciproﬂoxacin for anthrax). Japanese (B) encephalitis (Figure 14.3) and European tick-borne encephalitis vaccines should be considered in travellers to the endemic areas, especially during the seasons of transmission. Hepatitis B is a risk for medical staff whose work involves contact with human blood, to those receiving unscreened blood transfusions in some less developed countries and to those who take the high risk of unprotected sexual activity and intravenous drug abuse.
Typhoid is still prevalent in many less developed countries, especially in the Indian subcontinent. Effective injectable and oral vaccines are available that do not have the serious side effects associated with the old “TAB” immunisation.
Figure 14.3 Geographical distribution of Japanese encephalitis, by endemic countries and regions of South-east Asia, 2003
INFECTIONS STILL PREVALENT IN SOME TROPICAL/LESS
DEVELOPED COUNTRIESTravellers’ diarrhoea This is by far the most common health problem experienced by expedition members.
Many different kinds of food- and water-borne organisms can cause acute and debilitating diarrhoea, usually associated with colicky pain and prostration, and sometimes with vomiting, fever, bloodstained motions (dysentery) and even kidney failure.
Enterotoxogenic Escherichia coli bacteria are responsible for about 50 per cent of cases.
Other important infections are giardiasis and cryptosporidiosis (in which there is explosive watery diarrhoea, abdominal distension, nausea, weakness and passage of exceptionally foul-smelling gas), salmonellosis (especially from undercooked 154 03 RGS Expedition Handbk 4/3/04 3:55 pm Page 155
chicken, eggs and milk products), amoebic and bacillary dysentery and campylobacter infections (blood in the stool), and viruses. Travellers’ diarrhoea is very rarely fatal but can ruin an expedition.
Prevention of travellers’ diarrhoea: food and water hygiene Drinking water should be ﬁltered, boiled, treated with sterilising tablets or commercially bottled. Beware of ice in drinks because this is frequently made from tap water.
The rule for eating is “cook it, peel it or forget it”, but this rule can be difficult to enforce, without causing offence, when receiving hospitality. Especially hazardous are salads (even peeled tomatoes), which may have been fertilised with human faeces, raw egg products such as mayonnaise, undercooked chicken (pink at the bone) or eggs, milk or cheeses (which also carry the risk of brucellosis, listeriosis and campylobacter infection), rare or frankly raw meat (relished in France, the Middle East and Ethiopia) and ice cream. Deep fried food is safer than grilled food and “barbecued” usually means raw in the middle.
TABLE 14.2 PREVENTION OF TRAVELLERS’ DIARRHOEA Food and water hygiene 1.
“Cook it, peel it or forget it!”
2. Drink only water that is boiled/ﬁltered/chemically sterilised/bottled.
3. Beware of ice cubes.
4. Avoid unpasteurised milk and milk products – cheese, ice cream, etc. – and raw eggs.
5. Avoid shellﬁsh and crustaceans, even if boiled.
6. Consider prophylactic antibiotics, e.g. ciproﬂoxacin.
As a result of the wide range of possible causes, prevention with even a broadspectrum antibiotic (“kills all known germs”) such as ciproﬂoxacin (and other ﬂuoroquinolone drugs) will be only partially effective. Early treatment with ciproﬂoxacin (500 mg) after passing the ﬁrst loose stool has proved effective. Other drugs such as doxycycline or co-trimoxazole are less effective.
vomiting and further colicky pain and diarrhoea (“gastrocolic reﬂex”). Ideally, the victim should rest quietly in bed but, if travel or exertion is unavoidable, diarrhoeal symptoms can be damped down with codeine phosphate (Imodium or Lomotil). It may be possible to swallow and retain anti-vomiting drugs such as Stemetil or metoclopramide. Otherwise, these can be given by suppository (through the anus into the rectum).
TABLE 14.3 TREATMENT OF TRAVELLERS’ DIARRHOEA