Could common parasites cause neurodegenerative plagues?

Renowned TMU expert links man’s best friend to mind’s worst enemies
By Val Crawford

Prof. Ted Fan is accustomed to his research being brushed off by health officials with the general consensus that “parasites won’t kill you.” Budgets are limited, they say, and they want to save lives, not address a complex set of problems that demand equally specific solutions.

But after working for years in TMU’s medical missions in Swaziland, the Marshall Islands and Sao Tome, he would beg to differ. In fact, even common roundworms can cause obstruction and death, especially in children and the elderly, who are the most likely victims and the least likely to be treated.

Prof. Fan disagrees with WHO’s “one pill” parasite treatment goal as ineffective. And recently he published a heavyweight paper in a major journal linking roundworm in dogs to the neural damage that causes Parkinson’s and Alzheimer’s diseases.

So maybe parasites aren’t such a minor matter after all. Even in relatively advanced countries with wonderful health care, they may be much more widespread and undetected than most of us suspect – and causing neurodegenerative epidemics as populations shift toward the elderly.

Infections are common but silent

Most pregnant women are cautioned against cleaning cat boxes because feline toxoplasmosis can damage developing fetuses. A similar-sounding peril may transform our relations with dogs: Toxocara canis or canine roundworm. These are common, but not widely tested for.

This will surely change if his finding that links these parasites to neurodegeneration and blindness is confirmed. A recent screening of 203 TMU students and 102 pregnant women found 8.3% and 33.3% of subjects carried canine toxocara, respectively.

Travelers as well as all who enjoy sushi risk infection with other parasites, Prof. Fan warned. He called pricey salmon a major culprit, noting that all raw fish are “hard to test” and therefore of questionable safety, even given the government’s recent emphasis on food safety.

Another threat comes home with those who do business in China, where schistosomiasis is spreading across that nation with global warming. WHO noted a dozen years ago that vast belts of land that used to freeze in winter no longer get cold enough to kill this parasite. It penetrates the skin whenever it touches contaminated water, whether from puddles splashed by pedestrians or farmers’ and vendors’ contact with damp soil. Female worms release eggs containing live miracidium which may dissolve blood vessels and burrow deep into the human liver and other organs, causing granulomas and even cancers.

While most cases are silent, they are also chronic, and the damage continues until treatment. The same is true of parasites many Taiwanese acquire on their travels, or from eating raw pig liver or seafood.

Malnutrition, anemia, organ failure

TMU’s museum in the United Medical Building has two tubes taller than a grown man that each holds a single tapeworm – some can grow to ten meters. These will lead to deficiency of vitamin B-12 and to severe anemia if untreated.

Another parasite Prof. Fan discussed was ascarid, or common roundworm: this can grow up to 30 cm in human guts, and children can have dozens in untreated cases, stealing their already insufficient nutrition and possibly causing obstructions, rectal collapse and death.

So while most people shrug off the seriousness of parasite infection, those who experience it do not. “People remember this forever!” he laughed, citing a certain sashimi-loving CEO he recalled having a tapeworm of impressive proportions.

Treatment can be easy and quick – one tablet is 95% effective, and three days of treatment gives 100% success. But reinfection can continue endlessly; there’s no immunity to these pests.

Patent pool provides nonprofit cures

Prof. Fan has another weapon against parasites since last summer. That’s when he received a law degree to better understand patents: “Otherwise you face lawsuits.” He hopes that a patent pool will provide a useful platform to address Africa’s neglected tropical diseases (NTDs) which most drug companies are unwilling to address for lack of profit potential.

And of the money that WHO spends on these NTDs (US$90 million was the figure he cited), 77% goes to the “big three” diseases that include AIDS – and exclude parasites. Yet of WHO’s Tropical Disease Research priorities, 11 are parasites and 8 are zoonotic.

“There’s no business interest” in parasites, he said. The patent pool is expected to address this issue because countries will not be required to pay anything in before they can benefit from the resulting patented treatments.

Prof. Fan mentioned developing NTDs drugs with TMU-Shuangho Hospital’s Dr. Yung-Ching Liu, who also offers a program of free exams for travelers. Yet the need exceeds the program’s size, with a half-million Taiwanese returning from work in China who face no screening (although Southeast Asian laborers do). He said it’s “ridiculous” not to check these people, and also was critical that screening of international students extends only to amoebas.

Two years ago he was given an award by the Ministry of Health and Welfare’s chief of infectious diseases – and Prof. Fan used the opportunity to argue for testing of not only foreign students, but also the tens of thousands of Taiwan students who go on international service trips.

He sighed that their universities remain largely clueless about the health threats that these parasites pose – so most of the exposed students are still spreading this problem to their classmates and families.

Four threats at home, many more abroad

While he puts these four groups – returnees from China, foreign and domestic students, and travelers – at the top of Taiwan’s parasite problem list, it is the poor who will sicken and die. “They think no one will die from parasites – but they fail to consider the economic losses” caused by such cases.

Prof. Fan said he himself had a bad encounter with cryptosporidium, which has no medications that effectively prevent or treat it. For a miserable week in the Marshall Islands he was visiting the bathroom up to thirty times a day, trying to stay hydrated as his body explosively expelled this invader.

This is the same parasite that large American cities (notably Milwaukee) found to be a fatal threat to HIV patients, since the tiny oocysts could not be screened out of water supplies until recently.

Such improvements are still years away from reaching Majuro and other low-resource water systems, he said. So the diarrhea-causing protozoa proliferate in the Marshallese tap water system and in rivers in Sao Tome and other African nations that supply water to most rural residents.

Most testing is vastly inadequate even where it is performed – looking for three or four species. Yet in Swaziland he found an average of 11 types of parasites in human samples, in Sao Tome 13, and in the Marshall Islands, 9 species.

Clean, cheap, clever testing kits

At this point he brought out a testing kit that he helped develop that costs only NT20 (US$0.70) per compact tube. It offers a sealed, stable and low-cost alternative to the messy, smelly and less-effective “one-drop smear” method used to this point.

The kits have the further advantages of being storable indefinitely for re-checking of samples, and using two liquid preservatives that any hospital has on hand.

He worries about his older countrywomen who increasingly travel to exotic places. “Rich ladies like Africa” he said, recalling meeting dozens of Taiwanese in a South African airport recently.

As humans age, our immunity goes down – but anyone with runny bowels or a fever should see a doctor immediately. Prof. Fan said a urine specimen, a blood draw and a urinary screening are all cheap and useful tests, and showed a clever slide with multiple windows to test for more threats than past slides.

A higher profile for parasites and screening

Prof. Fan grew solemn as he mentioned lives lost that simple and inexpensive solutions could save. He estimated that 60% of Swazis are HIV-positive, but antiretroviral drugs are unaffordable for many. Similarly, Pap smears could save thousands of women who present with early-stage cervical cancer – but the whole nation has only two technicians who screen for this.

Training, funding and upsizing of programs could address these killers, he said, but parasites get shoved to the bottom of the list of public health priorities. Prof. Fan has written a NT$ 1 million grant so TMU can promote parasite testing in Swaziland by training technicians, and they in turn can train others. As this awaits approvals, he said the lab processing procedure is easy — but identification of different species takes expertise.

This renowned TMU scholar is making waves globally as well as locally. In a recent issue of the Clinical Microbiology Review (a major journal with an impact factor of 17), he linked T. canis to the beta amyloid and Aβ plaque formations that cause neurodegenerative disease via cerebral toxocariasis.

His next two projects continue this work, which five reviewers in his field have already sought to advance as a research priority with great promise. Prof. Fan may deal with parasites, but clearly this threat is not a minor matter – it is very big news indeed.

For interviews or a copy of the paper, contact Office of Global Engagement via