Ticks

Ticks are arachnids: tiny spiders that swell up after a few days' bloodsucking. They carry a host of nasty diseases, including Lyme disease, which can cause serious complications, including meningitis. The best way to avoid ticks is to use plenty of insect repellent and cover up from head to toe when outdoors in tick-infested areas like Canada and Alaska.

Sharks

Don't enter the water if you are bleeding ... sharks can smell blood and track it to its source. In areas where shark attacks are on record: avoid wearing bright colours, which attracts them, don't swim at night and never swim alone. If a shark does gets you, the jury is out on whether to fight or be passive - reports show both strategies have been successful. Unprovoked shark attacks on humans are on the rise, apparently, and the vast majority take place in the sunshine paradise of Florida.

Fire ants

Every year, up to 60% of people in the south-eastern US and Puerto Rico get stung by these venomous little insects. Like their relative, the bee, they can cause anaphylactic shock to anyone who is allergic to them: symptoms begin with faintness and wheezing, and end with a massive drop in blood pressure and, if unlucky, death. (If you could be allergic and do get stung, take antihistamines immediately). Usually, though, victims feel a burning sensation, followed by severe itching. A pus-filled pimple forms, and occasionally surgical drainage and even amputation are necessary.

Malaria

Malaria can be fatal. If travelling to one of the many parts of the world where infected mosquitoes are rife - Central and South America are hotspots, as is Africa - it is essential to take the precautions of covering up, using Deet repellent and taking anti-malarial medication, starting before you travel. Symptoms of fever, shivering, joint pain and headaches may appear months after your trip.

Crocodiles

More aggressive than alligators, crocs show no mercy when it comes to snapping up humans. None the less, they are now a protected species in many countries, and in Malawi's Lower Shire Valley in southern Africa, for example, this has reportedly led to, on average, two people being killed daily. Lake Victoria in Uganda is another croc hotspot, where around 100 of the reptiles wait patiently underwater for human prey.

Sea snakes

These relatives of the cobra spiral through the tropics in their hundreds of thousands. The good news is that they usually bite only in self-defence. The bad news is that when they do bite, their neurotoxic venom can lead to paralysis, muscle destruction and kidney failure. Early signs of a bite are muscle aches and pains, and swollen glands. It could be life-threatening if there is dark urine, vomiting, droopy eyelids and an inability to move the eyes. Antivenin - the antidote -should be administered, and if the victim is wearing a wetsuit, they should keep it on until they get to hospital.Otherwise, another form of compression should be used to halt the venom's flow through the nervous system.

Leishmaniasis

Disfigurement by skin ulcer, anyone? This disease is caused by single-celled organisms transmitted by sandflies, and afflicts an estimated 12 million people worldwide. Saudi Arabia, Kuwait, Iran, Iraq and Afghanistan are hotspots. The parasites like to bed down in their hosts' bloodstreams and cause grotesque sicknesses of the skin, liver and spleen. There are no preventative drugs, so just make sure you cover up your skin well. The most horrific complication is "sponge face", in which the victim's nose and throat teem with leishmania parasites until the nostrils implode or even fall off, leaving a wide circle where the mouth and nose used to be. The victim is left unable to eat or breathe normally, and usually does not respond to treatment.

Cobras

Capable of rearing up as high as four feet, a king cobra can be 12 feet long or more. On striking, their ribbed necks expand to form a hood, and fangs pump venom that targets the victim's nervous system, causing intense pain and possible death. One member of the cobra family, the krait, can kill an adult in under 10 minutes. In 1998, a hotel guest at a Thai hotel investigated something moving in a grassy spot behind the hotel. Peering into the grass to see what was there, he was bitten by a cobra. He was treated in hospital and was said to have made a "full recovery", only losing his right index finger.

Jellyfish

If you feel a slimy string of tentacles wrapping insidiously around your torso while swimming in northern Australia, you could be in big trouble. Jellyfish inhabit oceans and seas all over the world, but the box jelly of northern Australia is the deadliest, blamed for at least 63 deaths there since 1884. The pale, trunk-shaped stingers, which weigh up to 12lbs, are kept out of popular beaches by enclosures, but there is too much coastline to keep them out altogether. Sting victims are covered with livid weals that look like whiplashes and will usually be screaming in agony. Antivenin can be injected quickly to save lives; white vinegar deactivates the stinging tentacles.

Rabies

The name comes from the Sanskrit word for violence and strikes fear into the hearts of many. Rabies tortures the limbic system - the part of the brain that controls rage. If not vaccinated, you can be fatally infected by the saliva of any biting mammal with the disease - from bats to dogs to humans. Symptoms begin with fever, escalating to itching and pain at the bite site. The illness usually then develops into "furious" rabies, which involves hydrophobia - a petrifying fear of water, to the extent that the sight of it can spark full-body arching spasms in which the torso is supported by the head and feet. Hallucination, aggression and terror follow, with frothing at the mouth and spontaneous orgasms, before coma and death. Check whether an inoculation is required before travelling to remote areas and avoid wild animals. If bitten by a mammal, go to hospital immediately and demand the human diploid cell vaccine.

Funnelweb spider

Think the black widow is bad? Of all the stomach-turningly scary spiders in the world, this one may have the edge. The hairy, two-inch-wide Sydney native's bite is frequently fatal; and it isn't afraid of humans at all. When scientists first captured funnelwebs and opened the jars that contained them, the spiders reared up, ran out of the jars on webs, and bit the researchers with fangs dripping with venom. Symptoms of being bitten include hair standing on end, skin turning blue, depression and frothing at the mouth. Australians administer antivenin, then bandage the affected limb and immobilise it with a splint on the way to hospital for further treatment.

· With thanks to Bitten, by Dr Pamela Nagami (£11.99, Fusion Press)