Surge in ‘neglected’ deadly parasite that destroys your organs sparks fears it will ‘inevitably’ reach the UK
EXPERTS have sounded the alarm over the surge of a “neglected” parasite that can cause deadly liver failure.
Alveolar echinococcosis (AE) is a rare parasitic disease that spreads from animals to humans and is “of increasing concern worldwide” – but the recent rise in cases has sparked fears that it could reach the UK.
The “silently progressing and infiltrative disease” is caused by the parasite Echinococcus multilocularis, known as the fox parasite as it tends to infect foxes, as well as dogs.
While animals won’t usually show any signs of infection, the parasite can cause serious illness in humans, who may pick it up from contact with fox or dog faeces or handling contaminated plants, soil or berries.
When the parasite enters the body, it can cause tumour-like growths – usually in the liver – that expand slowly over 10 to 15 years, until they cause symptoms such as stomach pain, weight loss and signs of liver failure.
Left untreated, the tapeworms may spread to other organs and can be fatal.
The World Health Organisation (WHO) previously listed AE as one of its 17 most “neglected” diseases in 2014, calling for more to be done to control it.
Swiss scientists have now revealed that cases of AE, though still rare, increased nearly three times over in a 30 year period.
They also revealed that the parasitical disease – once contained in Europe, China, Japan and Siberia – is now spreading to parts of Canada and the United States.
“Previously non-endemic regions such as North America and eastern central Europe are reporting an increasing number of AE patients,” University Hospital Zurich scientists wrote in a report published by the US Centers for Disease Control and Prevention (CDC).
So far, there have been no known domestically acquired cases of E. multilocularis in the UK, meaning it has only been brought in from someone who has travelled.
But as cases of the disease are increasingly spotted European regions, it has stoked fears that the parasite may infect animals and humans in the British Isles.
“It is almost inevitable that E.multilocularis will be introduced into the UK,” veterinary surgeon Ian Wright warned in 2016.
The recent study included all patients who were treated for AE at Zurich University Hospital between 1973 and 2022, about 334 in total.
Researchers analysed patients’ symptoms at diagnosis, AE stage, the treatment strategy used and resulting outcomes, and causes of death.
In 1993, there were about two cases of AE recorded by the institution, while in 2022 that number jumped to 14.
Out of the 334 patients, 151 had some type of surgery to remove the parasites while 315 received drug therapy with the medication benzimidazole.
Over the 50-year study period, 90 patients died but mostly from causes other than the parasitic infection.
Only 13 deaths were directly caused by AE, researchers found.
Researchers also found that people who’d contracted AE had lower survival rates compared with the general population five years after diagnosis – especially those who were diagnosed with AE later in life.
Symptoms of alveolar echinococcosis (AE)
AE is caused by tumor-like or cyst-like tapeworm larvae growing in the body.
AE usually involves the liver but can spread to other organs of the body.
Because the cysts are slow-growing, infection with AE may not produce any symptoms for many years.
Pain or discomfort in the upper abdominal region, weakness, and weight loss may occur as a result of the growing cysts.
Symptoms may mimic those of liver cancer and cirrhosis of the liver.
People who accidentally swallow the eggs of the Echinococcus multilocularis tapeworm are at risk for infection.
People at high risk include trappers, hunters, veterinarians, or others who have contact with wild foxes, or coyotes, or their stool, or household dogs and cats that eat wild rodents infected with AE.
Humans can be exposed to these eggs by ingesting food contaminated with stool from foxes, such as herbs, greens, or berries, or by petting dogs or cats who have the tapeworm and then touching their mouth.
Source: CDC
But AE didn’t seem to be the main driver of their shortened life expectancy.
The researchers also found that without benzimidazole therapy, 90 per cent of patients died within 10 years of contracting the disease but with long-term therapy, they were able to prevent a disease from worsening.
They also concluded that removing all of the parasite-damaged tissue in the body through surgery could improve overall survival but could not slow down the disease.
The study authors speculated that the “the gradual decline of relative survival five years after diagnosis could reflect a generally sicker population”.
“In our cohort, the rise of annual AE cases was accompanied by a substantial increase in incidental findings and a shift toward earlier stages, although symptomatic patients with an advanced disease stage remained the majority,” report authors said.
Alveolar echinococcosis in the UK
While there have been no known domestically acquired cases of E. multilocularis in the UK, the parasitic disease was the cause of death of a woman in 1954, according to the British Pest Control Association.
She had never left the country but is thought to have picked up the parasite after eating unpasteurised Swiss cheese.
A further case was reported in 2002 in a man from Afghanistan who had recently moved to the UK from Pakistan.
In 2022, 27 European countries reported 731 echinococcosis cases, according to the European Centre for Disease Prevention and Control (ECDC).
In the last decade, cases have doubled in France, Germany, Austria and Switzerland.
Baltic countries have also seen an increase in cases, while the disease has become established in regions of Denmark, Sweden, Norway, and the north-western coast of France.
The only countries currently free of E. multilocularis are the UK, Ireland, Malta and Finland.
To remain disease-free, all them conduct yearly fox surveillance programmes for the parasite and report their findings to the European Commission once a year.
There is a risk that dogs who travel with their owners to regions where the parasite is endemic could pick up the parasite.
Writing in Improve Veterinary Practice, Ian Wright said: “The Pet travel scheme currently still requires dogs to be treated with praziquantel between one and five days before entry to the UK.
“This simple treatment has currently prevented endemic foci from developing, and as such it remains vital.
“It has been demonstrated that if this compulsory treatment is abandoned altogether, then it is almost inevitable that E.multilocularis will be introduced into the UK.
“For every 10,000 dogs travelling on a short visit to an endemic country such as Germany, the probability of at least one returning with the parasite is approximately 98 per cent.
“This probability increases to over 99 per cent if dogs have been longer term residents.
“Although the one to five day rule has provided protection against this, it does allow a window of opportunity for infection.
“If E.multilocularis is allowed entry into the UK, the large fox and microtine vole population will make the prevention of endemic E.multilocularis difficult, if not impossible to achieve.”