Billions worldwide are infected with tropical worms. Exclusive, most of these people live in poor countries, kept poor by the effects of worm-related malnourishment.
What can surprise many is that worms also cause the majority of cases of some cancers in these countries.
Published in Frontiers in Medicine
Worms cause cancer
About a million worm species are classified as helminths. A single characteristic unites them: parasitism.
"Helminths take many forms, but all of them harm their host in some way. In humans, they can live in the intestinal tract, urinary tract or bloodstream, causing a variety of illness from malnutrition to organ failure "explains co-editor of the research. Monica Botelho or Portugal's National Institute of Health
"Three species of helminths are classified as class 1 carcinogens by the WHO," adds Botelho. "These are all designated trematodes – after the Latin name for the grisly feeding cavity with which they latch onto their host's insides."
Worm-related cancer is not just a fluke – it's three Trematodes are known informally as 'flukes'. In this case, however, they're anything but. "Endemic regions — predominantly sub-Saharan Africa and Southeast Asia — flukes are responsible for the majority of all bladder and liver cancer cases," says Dr. Joachim Richter, Associate Professor at Berlin and co-editor with Botelho. "Cancer Causes in Sites or Fluke Infection including the bladder wall and the bile ducts of the liver."
But how does a worm cause cancer? According to the research collection, their feeding — and breeding — habits might be blame
"Flukes constantly wound and re-wound their host as they latch on with their feeding cavity, burrow through organs, and deposit eggs in the bladder wall. This leads to chronic inflammation as the body tries endlessly to heal, meaning lots of cell division and thus lots of opportunities for cancer-causing mutations to accumulate over years of infection. 19659004] "Worms and their eggs also excrete proteins that exacerbate this chronic inflammation, further promoting cell division as well as the blood vessel growth required to feed it," adds Richter.
Fluke infections and early stage cancers are often asymptomatic, such as availability of anthelminthic drugs patients often present too late for curative treatment. Fortunately, they have freshwater snails as a first host before infecting humans. "Flukes have been successfully eliminated in Japan by economic development and the filling and drainage of snail habitats," says Richter. "Eradication efforts are underway in Thailand, which has the world's highest rates of liver fluke infection and bile duct cancer – but some high-risk countries like Ethiopia lack a coordinated monitoring or prevention program for fluke-related cancer and need more help." 19659004] Beyond eradication efforts read another twist in the bizarre world of worms and cancer: helminths as a cure for malignancy. —The ominously named 'hyper tapeworm' – is associated with a significantly lower rate of cancer in human hosts, "reports Botelho.
" In fact, there is evidence that proteins produced by hyper tapeworms as well as F. hepatica not only "Cancer-promoting fluke proteins might be repurposed as treatments for other conditions: for example. e that promote new blood vessel growth could help resolve chronic non-healing wounds in diabetics, tobacco users, and the elderly. "
Gene-editing tool CRISPR / Cas9 shown to limit impact of certain parasitic diseases
Monica C. Botelho et al., Editorial: Parasites and Cancer, Frontiers in Medicine (2019). DOI: 10.3389 / fmed.2019.00055
Parasitic worms cause cancer – and could help it (2019, March 25)
retrieved 25 March 2019
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