It's winter in Australia and for the first time in three years thousands of residents are flying to the Indonesian island of Bali to spend the July school holidays basking in the sun.

But Australian officials are becoming increasingly concerned about what they'll bring home and are considering advising travelers to leave their flip-flops -- known as thongs in Australia -- in Bali.

Foot and mouth disease (FMD) is rapidly spreading through cattle in Indonesia, and on Tuesday the first cases were confirmed in Bali, a popular tourist destination with direct flights to seven Australian cities.

“Foot Mouth Disease would be catastrophic if it were to arrive in Australia,” said the country's Chief Veterinary Officer Mark Schipp, who's advising the government on ways to keep the virus out.

FMD is harmless to humans but causes painful blisters and lesions on the mouths and feet of cloven-hooved animals including cattle, sheep, pigs, goats and camels, preventing them from eating and in some cases causing severe lameness and death.

The disease is considered the greatest biosecurity threat to Australian livestock and an outbreak could lead to mass culls of infected animals and shut down Australia's lucrative beef export market for years to come.

“The impacts on farmers if foot and mouth gets in are too gut-wrenching to even contemplate,” said Fiona Simson, president of the National Farmers' Federation. “But it's not just about farmers. Wiping $80 billion off Australia's GDP would be an economic disaster for everyone.”

Australia has started ramping up biosecurity controls at airports, checking luggage for meat and cheese products and warning tourists that dirt on their shoes could inadvertently cause Australia's first FMD outbreak in 150 years.

But one control that hasn't been rolled out yet is footbaths -- containers of potent chemicals that new arrivals step into to kill traces of the disease they may be carrying on their shoes. The problem is that footwear typically worn in laid-back Bali isn't compatible with standard biosecurity measures.

“A lot of people returning from Bali are not wearing boots, they're wearing flip flops or thongs or sandals and you can't really afford to get that chemical on your skin,” said Schipp.

He said officials are considering telling tourists to abandon their shoes.

“Not to wear any shoes at all, or to leave the footwear behind,” Schipp said. “If you're wearing thongs in Bali, then leave them behind in Bali.”

The advice hasn't become an official instruction -- yet -- and is one of several options being considered, he added.

Indonesia outbreak

Foot and mouth is already spreading fast in Indonesia, where the first cases were detected in April. By May Indonesian authorities had alerted Australia, which -- along with New Zealand, Central and North America, and continental Western Europe -- is free of FMD.

Indonesia tried to roll out a vaccination program, but by June 27, only 58,275 of the country's roughly 17 million-strong herd had been vaccinated, Agriculture Minister Syahrul Yasin Limpo said in a tweet.

Schipp said the slow rollout reflected the logistical challenges in a decentralized country comprised of thousands of islands.

“You can have the vaccine available at the national level, but it needs to get out to the provincial and district levels. And then when it gets there, the question is, how are we going to get this into animals? We don't have yards. We can't catch the cattle. We don't have money for petrol. We don't have money for a meal allowance,” he said.

“They're the types of logistical issues that we've been trying to work with them on.”

The timing of the outbreak has been disastrous in Indonesia, coming weeks before Idul Adha, the “feast of sacrifice,” when animals are typically sold in large volumes for slaughter over three days from July 10. After families pray and share a meal together, they sacrifice livestock and distribute the meat to the poor.

An Animal Health Center staff member checks a cow in Bandung, West Java, Indonesia, May 17, 2022.

Mike Tildesley, an expert in infectious disease modeling at the University of Warwick, told CNN it's not the slaughter that dramatically heightens the risk of infection but the “significant movement of animals in the lead up to the festivals.”

“We see this in Turkey -- there is a festival every year (where FMD is endemic) called Kurban which also involves the slaughter of significant numbers of livestock, preceded by vast movement of livestock around the country and a rise in FMD reported cases are typically observed when this occurs,” he told CNN in an email.

“It is also possible for transmission to occur as a result of contact with carcasses, particularly in the first few hours after slaughter and that's why disposal of potentially infected carcasses has to be handled with great care,” he said.

By July 7, Indonesia's outbreak had spread to more than 330,000 animals in 21 provinces, according to the Agriculture Ministry. Thousands more doses of vaccine had arrived from France, and more than 350,000 animals had been immunized.

Fine line between disease and vaccination

When foot and mouth was detected in sheep in the United Kingdom in 2001, the results were devastating. At the time, the government's contingency plans covered an infection on 10 properties, according to a government report.

Instead, the disease spread to 57 locations before it was detected, and then a lack of coordination slowed the rollout of emergency vaccinations. In the seven months it look to eliminate the virus, more than 6 million animals were killed.

The UK was readmitted to the list of countries free from FMD the following year, but the impact went far wider than trade.

The report found that "tourism suffered the largest financial impact from the outbreak, with visitors to Britain and the countryside deterred by the initial blanket closure of footpaths by local authorities and media images of mass pyres."

The entire episode cost the government and the private sector a total of 8 billion pounds ($9.5 billion).

Cattle and sheep burn on a pyre at a farm in Lockerbie, Scotland, during the UK's 2001 FMD outbreak.

Other countries have learned lessons from the UK's response, and typically if an outbreak is detected, a ban on movement would be imposed before animals are culled and sites decontaminated.

For Australia, vaccinating animals is only an option once the virus gets in, because its trading partners don't differentiate between a vaccinated and a diseased animal.

“If we were to vaccinate preemptively, we would lose our animal health status as a country free of foot and mouth disease and we would lose our trade and market access,” said Schipp.

Ross Ainsworth, a veterinarian of 40 years who lives in Bali, says it's too easy for tourists on the island to come in contact with cattle and bring the virus home.

“There are cattle everywhere and those cattle will become infected and they'll be shedding virus,” he said. The virus can stay alive for a couple of days on the sole of a shoe, or a bit longer if it's colder, he said.

“So if you walked out of your villa and stepped in some infected saliva and got in the taxi and flew home, you've got another day and a half of viable virus on your foot, potentially,” he said.

The National Farmers' Federation has welcomed the increased biosecurity controls, but says the government should “continually review” the security settings and potentially subject all incoming travelers from high-risk areas to a biosecurity inspection.

“Every person should be at least questioned by a biosecurity officer, if not subject to an inspection,” said Simson, the NFF President. “We need to also keep looking at shoe disinfecting stations as an option,” she said.

“Whatever it takes. We don't want to look back and wish we'd done more.”

Until potentially contaminated shoes are discarded or footbaths become mandatory, Schipp says the best defense is education. Advertising campaigns are being introduced in airports and on social media -- but Schipp said that doesn't mean telling tourists to stay away from cows.

“Seeing cattle in Bali is part of the experience,” he said. “But it's very easy to wash your hands and to make sure your boots are clean before you come home again.” (CNN)

•PHOTO: International travellers at Ngurah Rai International Airport in Bali, Indonesia, March 7, 2022.

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