Paratyphoid: A rising risk for Aussies

By Dr Eddy Bajrovic*

There are many reasons to wash your hands regularly and choose food and beverages with extra care when you travel overseas.
In developing countries, traveller’s diarrhoea, hepatitis A and E, cholera, and polio are among the many diseases linked to poor sanitation and hygiene, typically from eating, drinking (or just handling) something that’s been contaminated.
Another reason is paratyphoid fever, which has become recognised as a growing risk for international travellers – especially in parts of Asia.
Collectively known as enteric fever, paratyphoid and its better-known ‘cousin’, typhoid are caused by two distinct Salmonella bacterium – Salmonella paratyphi (strains A, B, or C), and Salmonella typhi respectively.
Potentially severe and occasionally life-threatening, they cause high fever and inflammation of the intestines when ingested in food or beverages contaminated by the faeces of an infected person.

 The bacterium that keeps on giving…

In addition, around 1-in-20 people who get infected with either bacterium can become an asymptomatic (seemingly well) chronic carrier, continuing to ‘shed’ their infectious bacteria for years after they themselves recover.
Perhaps the best-known case was the infamous ‘Typhoid Mary’.
An immigrant Irish cook, ‘Typhoid Mary’ Mallon infected 53 people in several New York City homes where she worked early last century, killing three of them. With no antibiotics available to treat her chronic infection, Mary eventually was forcibly ‘quarantined’ for 30 years before her death to protect the public.
Every week on average, 2-3 Australian travellers return home infected with typhoid fever, while one returns with paratyphoid, according to national disease data.
Both diseases are becoming increasingly common in the developing countries of Asia (especially India and Indonesia), as well as in Africa, the Middle East, and South America (most notably Chile).
Globally, it’s estimated that there are 22 million cases of typhoid fever and 200,000 deaths each year. Paratyphoid causes an estimated 6 million cases, of which 10-15% will result in death without timely and effective treatment, a 2014 study found. 

Two distinct threats for Aussie travellers

There are two reasons Australian travellers should be aware of the emergence of Paratyphoid A in Asia:
- The strain is now more closely linked to street food – staple fare for both young travellers and older, more adventurous eaters alike.
- There’s no specific vaccine for paratyphoid, only typhoid. Studies show typhoid is more likely to occur in households – factors include an infected family member, poor hand hygiene, sharing food from the same plate, and/or the absence of a toilet – which puts someone staying with family or friends in a developing country at higher risk of the vaccine-preventable typhoid.
Enteric fevers are problematic: confirming diagnosis is often difficult, particularly if you get it while travelling in a developing country.
Patients are often treated for malaria, the more serious disease, which delays recovery, while severe cases have a high mortality rate due mainly to perforation of the intestines and peritonitis.

Travellers need to take special care

Writing in the ProMED travel medicine forum, Dr Henry Wilde, Professor of Medicine at Chulalongkorn University in Bangkok, recently sounded a warning of the growing emergence of S. Paratyphoid A in Asia and its link with street food. He said Bangkok hospitals had begun to see cases of paratyphoid among tourists who has been fully vaccinated against typhoid.
Prof Wilde said the strain now accounts for at least half of the cases of enteric fever in India, China, Nepal, and Indonesia – all popular destinations with Australian tourists. Typhoid is behind the rest.
Rather than rely solely on vaccination for protection, he said travellers should take special care in choosing food and water.
Who should consider being immunised against typhoid?
Vaccination is recommended for those travellers who are: staying longer than 2 weeks, visiting rural areas, living in setting where sanitation is poor, or have ‘adventurous’ eating habits. 

Oral typhoid offers ‘limited’ paratyphoid protection

The vaccine options include:
Two injectable vaccines, Typhim Vi or Typherix. Studies in typhoid-endemic countries show the injectable vaccines provide 50-80% protection against clinical illness, although no specific data is available for travellers.
Injectable combined typhoid-Hepatitis A vaccine (Vivaxim). The typhoid component lasts for 3 years, the Hep A component for at least 10 years when the initial dose is supplemented with a single dose of Hep A vaccine at between 6 and 36 months. Vivaxim is licensed in Australia for anyone 16 or older.
Oral live-attenuated vaccine Ty21a (Vivotif). Three capsules (taken 0, 2, and 4 days) protect for 3 years, while taking a fourth capsule (day 6) provides a further 2 years’ protection.
Unlike the injectable vaccines, the live Tv21a oral vaccine has been shown in limited studies to provide some protection against paratyphoid. A study from Chile indicated 49% protection from infection by Salmonella paratyphi strain B, while Israeli research suggests that the Ty21a vaccine may provide a small amount of protection from serotype A.

On the street, it pays to be selective

Vaccinated or not, travellers need to remember that there may be other diseases lurking in food and water when sanitation and hygiene are wanting.
When it comes to street food, I think it’s a great part of the travel experience.
But not just any street food: it pays to be selective with anything you eat or drink.
Street food is usually safe if:
- It is cooked while you wait.
- It’s served very hot.
- The food stall or cart, and the utensils used, look clean.
Give street food a miss if the stall is dirty, or food is pre-prepared and left in the open unrefrigerated, or kept just warm before being served up to you.

What to eat and drink – and not

Every time you eat or drink, choose the safer options… 
- Food that is cooked and served piping hot.
- Food from sealed packages.
- Hard-cooked eggs.
- Fruits and vegetables you have washed in safe water or that you have peeled yourself.
- Pasteurised dairy products.
- Food served at room temperature.
- Raw or soft-cooked (runny) eggs.
- Raw or undercooked (rare) meat or fish.
- Unwashed or unpeeled raw fruits and vegetables.
- Condiments (such as salsa) made with fresh ingredients.
- Salads.
- Flavoured ice or ice blocks.
- Unpasteurised dairy products.
- Bush meat (monkeys, bats, or other wild game).
- Water, sodas, or sports drinks that are bottled and sealed (carbonated is safer).
- Water that has been disinfected (boiled, filtered, or treated).
- Ice made with bottled or disinfected water.
- Hot coffee or tea.
- Pasteurised milk.
- Tap or well water.
- Drinks chilled with ice made with tap or well water.
- Fruit juice or other drinks made with tap or well water.
- Unpasteurised milk.
Hand hygiene is particularly important when you’re in a developing country far from home. 
Soap and water isn’t always available to keep your hands clean. The next best thing is hand sanitising lotion or wipes containing at least 60% alcohol.
Keep them handy in your backpack or bag, ready for use every time you use the toilet and right before you eat.

* Dr Bajrovic is the Medical Director of Travelvax Australia.

Get more advice on healthy travel for your next overseas trip by calling our travel advisory service on 1300 360 164 (toll-free from landlines). Our experienced medical professionals can also advise you on vaccinations and medication to consider during a pre-travel consultation.