By Dr Eddy Bajrovic*
A leafy salad laden with freshly washed garden vegetables… It’s hard to imagine a healthier choice for lunch or dinner, right?
Light on the carbs and heavy on the feel-good factor, it’s the virtuous alternative to other not-so-healthy choices from the menu at your holiday resort or hotel, or the local restaurant.
But, a garden salad can be decidedly unhealthy overseas, as six Australian travellers learned following a holiday in Bali.
The five women and a man were belatedly diagnosed with fascioliasis, a severe liver disease caused by ingesting parasitic liver fluke worms called fasciola, whose immature forms can be found on plants grown or washed in water – particularly water cress.
All six ate salads in Bali and developed severe illness lasting many months after their holiday. Several had invasive investigations involving surgery and one even had infected sections of their liver removed when they were initially diagnosed with cancer.
Numerous diseases linked to salads
That most of the patients were women did not surprise Dr Mel Figtree, an infectious diseases specialist at Sydney’s Royal North Shore Hospital. She was the lead author of a paper** published recently in the Medical Journal of Australia, which described the cases.
“Women are more likely to choose a salad from the menu than men,” Dr Figtree said.
“But, travellers don’t think twice about eating a salad because they’re a very familiar and healthy choice back home in Australia.
“A green salad looks so fresh and inviting anywhere that it’s hard to imagine that they could cause a problem while you’re on holiday.
“But, fascioliasis is just one of a number of potentially severe diseases associated with salads.”
Fascioliasis occurs in 50 countries, mainly in the world’s developing regions: it’s estimated that 40% of Bali’s cattle are infected. In developed countries like Australia, cattle and other livestock ‘hosts’ are drenched to kill the parasites.
The six cases from Bali were diagnosed between 2011 and 2014. In fact, so rarely is fascioliasis seen in Australia that it took between six and 12 months and intervention by specialists to correctly diagnose and treat them.
Larvae attach to growing cress
Fasciola have a complex, but fascinating life cycle.
When an infected animal defecates into surface water, eggs produced by the adult liver flukes are in turn eaten by a certain aquatic snail, which then serves as an ‘intermediate’ host.
The fluke larvae later released by the snail into the water attach themselves to the leaves and stems of water cress and plants as hard-shelled cysts.
When the cyst-laden plants are eaten by an animal – or a person – they become host to the unwelcome invader and the parasite’s life cycle begins anew. Less commonly, the parasites are consumed in untreated drinking water.
Once a person is infected, they can be free of symptoms for a few days or a few months. Then follows two clinical phases: the first ‘acute’, the second ‘chronic’.
Diagnosis often delayed
While confirmed fascioliasis is rare in travellers worldwide, it is almost certainly underreported among Australians returning from Asia, Dr Figtree said. Many people who accidentally ingest the parasites have very mild symptoms – if any – early in the course of the infection and go undiagnosed.
(Fascioliasis is not widely seen among the Balinese, possibly because it’s undiagnosed or under-reported there. Ironically, it could be that they simply don’t share the same love of salad as the popular island’s foreign visitors, including the million-plus Australians who visit each year.)
It’s the rarity of cases and the long lag in the appearance of symptoms – usually well after the holiday – that can complicate and delay diagnosis, and severely impact the victim’s health.
Patients respond well to triclabendazole, a drug used to treat livestock. However, it is not licensed for human use in Australia and must be sourced through a veterinary supplier.
Water a common source of travel illness
Drinking water – or food grown in or washed with it – is risky wherever the local water supply is untreated and there’s little or no sanitation infrastructure.
Water-borne diseases can be caused by viruses, protozoa, bacteria, or intestinal parasites like fasciola. Some invade tissue or the circulatory system through walls of the digestive tract.
Most of the organisms that cause the very common travel complaint, travellers’ diarrhoea are waterborne.
And, even small amounts of those water-borne microorganisms that are among the most commonly diagnosed in returned travellers, such as Giardia and Shigella, can cause illness.
Best bet? Avoid the salad
In a developing country, it’s especially hard to ensure the safety of leafy salad vegetables and fruit that can be eaten without peeling.
“It’s very difficult to remove pathogens from all the tiny crevices on the surface of leafy salad vegetables or from certain fruit that has come into contact with contaminated soil or water,” Dr Figtree said.
“The tap water used to wash them in the kitchen may also be suspect – even in an upmarket hotel or resort.
“When holidaying in a developing country, the safest approach for travellers is to forgo leafy salads and unpeelable fruit – even when they look fresh and healthy.”
Don’t take risks with water…
In a developing country, travellers should presume all tap or well water is contaminated.
Drink bottled water (after first checking that the seal is unbroken) even in your hotel or resort. Use bottled water to brush your teeth, too.
It also generally safe to drink:
• Boiled water. It needs to be boiled for 1 minute (or 3 minutes at altitudes above 2000 metres.)
• Purified water. Modern travel water purifiers will eliminate any organic material and organisms.
• Chemically disinfected water. The simplest method is to use iodine-based tablets, as long as the water isn’t cloudy or contaminated with leafy matter or other organic material - that’s when you need a water purifier. (Iodine should be avoided if you are pregnant, allergic to iodine or have a thyroid condition.)
• Carbonated soft drink, beer, wine and spirits are usually imported and therefore safe. Just remember – no ice (freezing preserves germs; it does not kill them).
… or with food choices
From the menu, the safest choices are:
• Freshly cooked (fried, boiled, steamed) food.
• Peelable fruits – bananas, citrus fruits, etc.
• Food from cans or sealed packs.
• Local food served in well patronised, busy restaurants.
• Food prepared by you
But, avoid:
• Uncooked, undercooked food, or reheated food.
• Salads, raw vegetables, or fruit that’s usually eaten unpeeled.
• Locally made ice cream and dairy products (imported brands are safe).
• Oysters, clams, mussels, barbecued prawns, or mud crabs.
• Food that has been exposed to flies.
• Dishes requiring a lot of food handling to prepare.
Read more about fasciola and safe water and food.
* Dr Bajrovic is the Medical Director of Travelvax Australia.
** Fascioliasis in Australian travellers to Bali. Mel Figtree, Miles H Beaman, Rogan Lee, Michelle Porter, Eric Torey, Thomas J Hugh and Bernard J Hudson. Med J Aust 2015; 203 (4): 186-188. Available online at: https://www.mja.com.au/journal/2015/203/4/fascioliasis-australian-travellers-bali?utm_source=MJA+news+alerts&utm_campaign=61c5783461-MJA_news_vol_203_Issue_4_17_Aug_20158_13_2015&utm_medium=email&utm_term=0_8c7e70a099-61c5783461-41477261
For expert advice on preparing for healthy overseas travel, or to book a pre-travel medical consultation, call Travelvax Australia’s obligation-free travel health advisory service on 1300 360 164 (toll-free for landlines).