Echinococcosis, foxes, and drinking from streams in the Hokkaido outdoors

Posted on Jun 12, 2020
670 9
Posted on Jun 12, 2020
670 9
Since the 1960's, drinking untreated water directly from streams in Hokkaido has been a risky business. The local foxes carry a parasite which causes Echinococcosis (エキノコックス症), a disease with a 90% fatality rate in humans if left untreated. Luckily, avoiding catching Echinococcosis is easy, by practicing good camp and outdoor travel hygiene. Also, residents of Hokkaido are entitled to free Echinococcosis screenings. In this article, inspired by Adventure Hokkaido's recent overview, we do a deeper dive into the history of this disease in Hokkaido. We also outline some of the efforts researchers and the government have gone to in order to minimise the public health effects of Echinococcus in Hokkaido.

Last updated Jan 26, 2021

What is Echinococcosis?

Echinococcosis is a parasitic disease in humans, found in many northern-hemisphere countries. It is considered to be one of the most dangerous worm diseases in the world (Howe et al., 2017). Humans get the disease when they drink water or eat plants contaminated with the feces of animals carrying the Echinococcus tapeworm – primarily foxes in Hokkaido. Humans end up ingesting the tapeworm’s microscopic eggs, which hatch into larvae. These larvae get into the bloodstream and end up in organs around the body – mainly the liver for Echinococcus in Hokkaido. The larvae cause slow-forming, destructive tumors. If left untreated, the WHO reports a 90% fatality rate (Kamiyama, 2019).

In Hokkaido, there’s two strains of the tapeworm that causes the parasitic infection in humans – Echinococcus granulosus and Echinococcus multilocularis (see details on CDC website here). This distinction is worth noting, because while the E. granulosus strain is more prevalent globally, it’s the E. multilocularis that’s much more common in Hokkaido (94% of cases). And it’s the multilocularis strain that tends to end up in humans’ livers.

Echinococcus – a parasitic flatworm/tapeworm.
Echinococcosis – a disease caused by the spreading of Echinococcus larvae in a host (such as humans).


Echinococcosis is a fatal parasite-borne disease. You can catch Echinococcosis in Hokkaido by drinking untreated water from streams. The only way to cure Echinococcosis disease is through surgical removal of cysts on the liver. Avoiding getting Echinococcosis is important – boiling or filtering water, washing hands regularly, and washing wild plants well. A free blood-test screening is available for Hokkaido residents, to test if you have the disease. About 30% of foxes in Hokkaido carry the Echinococcus parasite that cause Echinococcosis in humans.

What does Echinococcosis do to people?

Echinococcosis is a very slow-starting disease. It often takes between 5-10 years for a person to notice any symptoms. Even during this initial period of cyst growth, routine liver function blood work may not indicate anything is amiss. By the time a person notices something is not right – abdominal pain, swelling, or discomfort – for most Hokkaido-dwellers the parasite would have caused a significant tumor in the liver. If left untreated, tumors can rupture, causing fatal septicemia (blood poisoning) and death (Kamiyama, 2019). 

How (not) to get Echinococcosis in Hokkaido

The main way people catch Echinococcosis in Hokkaido is through drinking untreated water from streams etc. Not all untreated water in Hokkaido is necessarily infected, but up to 40% of foxes in Hokkaido carry the Echinococcus tapeworm, and those cute little critters are everywhere. Other routes to infection include eating unwashed plants, particularly spring sansai mountain vegetable shoots. Not washing one’s hands while camping in Hokkaido could also be a route to infection. There’s no human-to-human transmission of Echinococcosis.

The best way not to get Echinococcosis in Hokkaido is to make sure to treat water if taking it from streams (see Adventure Hokkaido’s advice here), wash plants before consuming them, and make sure personal and camp hygiene is on point when camping. A number of huts in Hokkaido have water piped into the hut from nearby streams, so in these huts water must be treated. Also note that the Echinococcus eggs can survive down to well below -20°C (source), so yellow snow isn’t the only type you want to avoid.

When treating water, water needs to be boiled at 100°C for at least 1 minute, or at 60°C for 10 minutes (source). The parasite (or more specifically the eggs) are 0.03mm in diameter, so any good quality water filter will also safely remove the parasite.

Visual description of E. multilocularis parasite, prevalent in Hokkaido (by CDC)

Daisetsu Loop Hike (Hokkaido, Japan)
Image by Rick Siddle

Prevalence in Hokkaido

IN HUMANS | In 1999, Japan passed a law that requires all health centers to report Echinoccocosis infections. In the 20 years from 1999 to 2018, there were 425 reported cases of Echinococcosis infection in Japan, with 95% of those cases in Hokkaido. On average, there’s about 20 new cases per year. Males and females are equally as likely to get the disease, but the median age for confirmed infection is 65 years old.  About 3 or 4 people per year die from Echinococcosis in Japan (source). 

IN FOXES | About 400 foxes per year in Hokkaido are dissected in order to estimate the prevalence of the Echinococcus tapeworm in the wild here in Hokkaido. Contrary to popular belief, not all foxes in Hokkaido carry it. Researchers find around 30% to 40% of foxes have Echinococcus in Hokkaido.

History of Echinococcosis in Hokkaido

The first documented case of Echinococcosis in Hokkaido was in 1936, in an Otaru City resident, originally from Rebun Island. It’s thought she picked up the parasite from foxes introduced to Rebun Island from the central Kuril Islands between 1924 and 1927 (see Inukai et al., 1955). In this way, “[Echinococcus] is a parasite introduced by humans” (Yagi, 2019). From that initial discovery, officials estimate out of Rebun’s population of about 10,000 people, up to 300 were infected and many of them died from Echinococcosis. The Hokkaido Prefectural government came down hard on this discovery. “They dissected every one of the island’s dogs, cats, and foxes,” recounts Kinpei Yagi, a researcher at the Hokkaido Insititute of Public Health

The parasite was fully removed from Rebun Island, and didn’t rear its head again in Hokkaido until 1965, when an unrelated outbreak was documented in Nemuro in eastern Hokkaido. Researchers are not exactly sure how the parasite found its way to Nemuro. Foxes had been introduced into islands off the coast of Nemuro from the Kuril Islands, however, so most evidence points to a human-caused spread. From this second outbreak in Nemuro, over the next 30 years Echinococcus had been confirmed all over Hokkaido (see figure below, translated from Yagi, 2019).

“I take the checkup every three years. Furano City provides this for the residents for free. I personally don’t know anyone who got the Echinococcosis disease. Prevention is more important than anything else”
Adventure Hokkaido guide Yasu-san (2020)

How to find out if you have Echinococcosis

Since 2001, Hokkaido has a mass screening program in place, whereby any resident can get a free test for Echinococcosis at their local public health office. This is a two-step process. First, a resident would get primary screening at their local public health office. If they’re suspected of having Echinococcosis, they would go on to a more in-depth test at a government-approved facility. Like all blood-sample tests for Echinococcosis, however, these tests only detect antibodies. Therefore, they can’t detect the presence of the parasite during the long, slow incubation period. They can only detect the presence of the parasite once the body starts to fight the growing tumor.

In the 297 reported Echinococcosis infections in Hokkaido since 2006, 70% were discovered through abnormalities spotted during ultrasound or other non-invasive inspections of the liver (IASR, 2019). This speaks volumes to the effectiveness of the near-ubiquitous yearly health checks of full-time employed individuals in Japan. 

TWO HOKKAIDO FIRSTS | The primary screening uses a process called ELISA, and the secondary screening uses the Western Blotting procedure. Both procedures have a 95-98% detection rate in Hokkaido, and were adapted to detecting Echinococcosis in the 1980’s by Japanese researchers at the Hokkaido Institute of Public Health.

NOTE: As of June 2020, Sapporo City has paused their Echinococcosis screening program till the end of September 2020.

Our friend Szilvia Nagy, a researcher previously at Hokkaido University, doing Western Blot procedures – unrelated to Echinococcosis, but still very cool 🙂

How to treat Echinococcosis

In humans, the only effective way to treat Echinococcosis infection is by surgical removal of cysts. In Hokkaido, if cysts can be removed completely there’s a 20-year survival rate of 99%. In cases where it’s only possible to remove part of the cyst, surgery is followed by Albendazole medicine treatment – a kind of parasitic worm treatment. In this case, the 20-year survival rate is 62% (Kamiyama, 2019).  Treatment only using parasitic worm medicines such as Albendazole have historically shown mixed results, with significant side-effects (Matsumoto, 2019). If left completely untreated, the WHO reports a 90% death rate.

In order to control the spread of the parasite at the source in Hokkaido, there have been ongoing trials of distributing de-worming bait for foxes. These trials have dramatically positive effects, essentially de-worming entire local populations of foxes. This dramatically reduces the likelihood of humans living nearby ingesting the Echinococcus parasite. However, distributing bait is a costly endeavor. In trial areas, within a year of ceasing the bait trials, fox infection rates generally return to original levels (Uraguchi, 2019).

Attempts have been made at creating a vaccine for Echinococcosis, with some degree of success in controlling the disease in sheep during experiments. However, a successful human vaccine for the disease doesn’t exist. Matsumoto (2019) reports that researchers recently completed the Echinococcus Genome Project, which may pave the way for development of new medicines to combat Echinococcosis. 

Not all water sources are created equal

One of the amazing things about traveling in the outdoors in Hokkaido is an abundance of water everywhere. This includes crystal clear springs where water can be consumed right from the source. Below is one such spring (around here) we found along our route on the Trans-Hokkaido Bikepacking Route (beta). It was welcome relief on a very hot and sweaty grind up a gravel road.

But how do you know the spring is safe?
Unfortunately, for most springs in Hokkaido, social proof is the only thing that will give you any indication that the water source might be potable. That is, if it has indications of human maintenance (pipes, covers, communal cups, etc) then one can usually err on the side of assuming it’s safe. Note that The Ministry of the Environment has a list of well-known springs in Hokkaido on its website. Most (but not all) include notes about water quality inspections: I’m happy to say that the spring in the photo is on the list – but there’s no information about water quality inspections. Either way, I’m more concerned about the 2 litres of water I consumed out of the taps at the Tomuraushi Onsen Campground the same day, before noticing the signs indicating the water should be treated! 

If in doubt, always filter.

Comments | Queries | Discussion

9 thoughts on “Echinococcosis, foxes, and drinking from streams in the Hokkaido outdoors”

  1. Hey rob, appreciate the summary.
    As I am pretty new to water filtering, is there any filter in particular that you recommend which can be bought in Japan?
    I am about to go from Asahidake to Tokachidake this October and am pretty concerned about the water situation.

  2. Pingback: Is it safe to drink the water in the Hokkaido outdoors? - Adventure Hokkaido

  3. Wow, I had no idea!! I’m more of a Tokyo person, but I do get asked a lot about different places in Japan, especially Hokkaido. This will be a great tip to pass on to travellers. Thanks for the post (and a great website too!).

    1. Cheers for the kind words Rohan. For the record, long-time outdoor guides I speak to tell me that ‘no one has ever got Echinococcosis from drinking stream water in the outdoors in Hokkaido – most cases are from residents in areas without treated water supplies’. I.e., the chances of ingesting an egg with your water is pretty darn low. But of course there are very few who drink straight from streams here without boiling or filtering, so it’s always better to be safe than sorry!

  4. Many thanks for the article. In other countries I’ve always used chemical treatments for water in the backcountry (Iodine, or Chlorine Dioxide). Do you know if chemical treatments are effective against Echinococcus?

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