Blister beetles are insects, whose bodily fluid contains substances, such as “Cantharidine” and “Pederine”, which can produce blisters. By night the beetles are attracted to light, thus guiding them to humans. When the insect is crushed on the human skin, local irritation (redness, swelling, burning feeling), as well as blisters, will appear after a few hours. The clinical image is one of burns. Sometimes “kissing lesions” are seen at the elbows or knees.
Rubbing the toxin into one’s eyes, may cause irritation or the “Nairobi eye”. The skin should first be rinsed abundantly and then disinfected. Finally the same skin care as for burns (such as a cream with silver sulfadiazine, e.g. Flammazine®) may be applied. Skin injuries caused by Cantharidine heal almost entirely without leaving scars. Injuries caused by Pederine become visible only after 1 or 2 days, the redness is more serious and may persist a couple of months.
The larvae of certain flies use humans as host. In Africa, some flies lay their eggs on, among other things, drying laundry. The larvae subsequently burrow into the skin, in order to develop there. The lesion that they produce resembles a boil, which is more itchy than painful, and at its centre two black spots can be seen (respiratory pores) instead of yellow pus.
Laundry that has been hung out to dry in the tropics is therefore best ironed with a hot iron in order to destroy larvae. In South America some fly larvae get directly on to the skin via mosquitoes.
People who run around barefooted run a greater risk of insect bites, wounds and parasites that get into the body via the skin of the feet, such as ancylostomiasis, strongyloidosis, sand
fleas and larva cutanea migrans.
The latter are two typical skin parasitoses:
- Tungiasis: after fertilization, the female sand flea or jigger (Tunga penetrans) penetrates the skin, especially at the feet and under the toenails. She burrows into the epidermis and continues to grow. After a few weeks a pea-sized, initially itchy and then painful lesion appears resembling a boil but with a central black spot. With a little practice, the adult fly can be completely removed by carefully peeling away the epidermis with a needle or a sharp instrument. Subsequent disinfection of the wound is of the great importance.
- Cutaneous larva migrans is caused by parasites that accidentally infect humans, usually hookworms from dogs or cats. The parasite gets into the skin when this gets in contact with mud or sand fouled with animal excrement e.g. on the beach (only on dry sand but not on the damp part of the beach, below the tide line where it is best to wear shoes and sit on a towel), around swimming pools or by running around barefoot. These parasites usually die after penetration, though some survive and slowly migrate through the epidermis, thereby causing severe itching, threadlike lines of skin rash, mostly on the hands and feet, and sometimes on the buttocks and thighs. This requires specific treatment.
When coming in contact with jellyfish, rinsing the skin with vinegar (5-8% acetic acid) for about 30 minutes is recommended. A topical corticosteroid cream is then applied.
Spiders, scorpions and snakes are most frightening but they only represent a small risk.
- Scorpions are usually most active at night and walking around barefoot after sunset is not a good idea. When you get up in the morning, check your shoes for scorpions that might have crept into them during the night. A scorpion sting is quite painful, but symptoms are usually restricted to a local reaction. In some countries, however, for small children, the sting can be fatal.
- Snakes hide mainly in dense undergrowth and under stones, sometimes in termite mounds or damp, dark garden sheds, etc. After a rain shower snakes often seek out open spaces. They normally stay away from humans and they bite only in selfdefence. About 375 of the approximately 2700 snake species are venomous. Bites by venomous snakes are not always accompanied by an actual injection of venom and symptoms of poisoning. The interval between bite and eventual death is very variable. The prognosis depends on many factors, including the general condition of the individual and the treatment.
Never walk through long grass, or if you do have to walk across pastureland:
- Wear sturdy high boots.
- Make the ground vibrate by treading heavily or by banging with a stick in front of you.
- Use a torch when it is dark.
- Avoid putting an unprotected hand in holes between stones or rocks.
- Whatever you do, do not panic panic;
- Seek suitable medical help as quickly as possible;
- Avoid dangerous procedures such as incision, sucking out the wound, tourniquets, etc. The use of the Aspivenin® suction device for snakebites is very controversial, as in animal trials it only sucked out 30% (at best) of the venom, even when used within three minutes after a snakebite.
- Immobilisation and a lymphatic bandage is the only recommended technique (do not tie off, wrap a wide bandage tightly around the affected limb for a maximum of 1 hour)
- If possible, the dead snake should be brought in for identification (but beware of recently killed snakes since they still have a bite reflex);
- Treatment with antivenom is necessary only in the event of specific symptoms of poisoning such as haemorrhage, local tissue necrosis or paralysis. Antivenom is still effective, even when administered at a late stage. The address of Poison Control Centres can be obtained from the ITM. It is not possible to take antiserum with you if the correct storage temperature cannot be continuously guaranteed, and if there is no one available who is competent and knowledgeable enough to administer the antiserum (more than 50% risk of allergic reactions).
Do not touch dogs or cats because of the real danger of rabies in tropical countries (equally in large towns). Be vigilant especially with children around.
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