Simple precautions can stop parasites from becoming life-threatening souvenirs, writes Lance Richardson.
Last August, a nine-year old boy went on a fishing camp in the US state of Virginia and caught something unexpected. A freshwater amoeba, Naegleria fowleri, entered his nose, infiltrated his sinuses and inflamed his brain tissue. He died within a week. That same month, a 16-year-old girl died after being infected by the amoeba while swimming in the St Johns River in Florida. An earlier death, in June, involved a Louisiana man and his infected home-water system.
The Naegleria fowleri amoeba remains rare, with no signs of increase, according to the US Centre for Disease Control and Prevention. But its fascination is undeniable. Parasites are the stuff of nightmares, especially for travellers: the Amazonian dip becomes an imagined encounter with the toothpick fish, swimming into sensitive places; the rainforest walk in Cameroon is transformed into gruesome visions of the loa loa, brought home as a stowaway in the eyeball. Even ticks and worms are enough to spoil lunch, particularly if they burrow into your feet.
Reality is usually far less exotic, however.
Increasingly, the parasite most likely to be encountered by modern travellers is the bedbug, which lives in mattresses and feeds on the blood of unsuspecting sleepers. Found everywhere from Brisbane to New York (including the United Nations building in 2010), outbreaks have become so common that a public database has been set up to patrol North America (bedbugregistry.com). Bedbugs are an uncomfortable inconvenience - particularly if they jump in to your luggage - but at least they don't transmit infections the same way that mosquitoes can.
Indeed, mosquitoes remain a big point of concern, with the malaria parasite accounting for 2.23 per cent of deaths worldwide, according to a World Health Organisation report last year. Requiring both mosquito and human hosts to complete its life cycle, cerebral malaria can be fatal in a matter of days.
"Any fever following a visit to a malaria area is malaria until proven otherwise," says Dr Deborah Mills, a Brisbane-based specialist in travel medicine who oversees the Australia-wide Travel Medicine Alliance (drdeb.com.au). She says travellers should employ preventative medication such as Malarone, use mosquito nets, and respond to fevers immediately with blood tests.
When it comes to those other travel ailments - "Delhi belly", "Montezuma's revenge", "Pharaoh's curse" - the prognosis is generally less urgent (if perhaps more embarrassing). According to Mills's book and iPhone app, Travelling Well, travellers' diarrhoea may affect up to 50 per cent of visitors to developing countries, or 11 million people each year. Mostly it passes within a few days and can be traced to bacteria such as salmonella - unsurprising to anybody who has ever eaten a street taco or sat down for a bowl of pho. In more extreme cases, however, gut upsets can be triggered by tiny parasites: the Giardia protozoan looks like a ceremonial mask under the microscope but it causes considerable distress within two weeks of infection; amoebic dysentery is the physical equivalent of Dante's Inferno, unless you're looking for sudden weight loss (and abdominal cramps).
In these cases, the surest means of prevention is intuition and care - if food looks dubious, is cold or is avoided by locals, follow their lead and look elsewhere. Natural products such as Travelan contain antibodies for common types of E. Coli, though they will prove less effective in the case of parasites. A good solution for purifying water is the SteriPEN, which uses ultraviolet light to eliminate microbes and cysts. Mills recommends carrying a small medical kit and getting vaccinations six to eight weeks before departure.
With all the alarming possibilities, it can be tempting to throw in the towel and simply stay home. But add this to that picture of domestic safety: in 2011, a Sydney man ate a garden slug and contracted a lungworm usually found in rats.
Parasites are everywhere, a fact of life. Take precautions, avoid the impulse to eat molluscs, then board your plane and focus on the wonders of travel. So what if you pass a worm? As Mills writes, "be glad it is gone".