Why save parasites from extinction?

Parasites are perhaps the most maligned organisms on Earth. A human scourge since prehistoric times, they still account for anywhere from 20% to 40% of illnesses from infections in developing countries, which can lead to nutritional deficiencies and poor health.

Their plague-like reputation, however, is getting an overhaul: Researchers are just beginning to understand the positive role they can play in ecosystems. The yellow rattle, Rhinanthus minor, for example, is a European native parasitic plant that siphons water away from grasses, sucking them dry. But this, in turn, turns grasslands into wildflower meadows, which attract insect pollinators. 

Conservation programs often ignore parasites even though they are part of a larger ecosystem, and it is assumed that many parasites are threatened with extinction without much knowledge of how they impact the environment. 

Against this backdrop, the International Parasite Resource Bank (iPRB) at Chungbuk National University in Cheongju, South Korea, has been expanding its services and its reach since 2021. The goal: to collect, store and provide researchers around the world with parasite specimens for study. These include not only those that cause human and animal diseases but non-pathogenic parasites as well. 

“We leverage our rich experience and knowledge to provide researchers the products, services and resources they require to carry out significant life science research,” says Dongmin Lee, Ph.D., research professor at Chungbuk National University and chief operating officer of the iPRB.

The link between Parasites and Economy

The iPRB was first established in 2005 by Keeseon S. Eom, Ph.D., chair and professor at Chungbuk National University's medical school. Keeseon was inspired to study parasites by Han-Jong Rim, Ph.D., who played an integral role in South Korea’s human parasite eradication program that began in the late 1960s. 

At the time, more than 90% of South Koreans were infected with helminth parasites; today that number is 2%, more or less. Better human health brought about by parasitic infection control was a major contributor to the country’s rapid economic growth in the 1980s and ‘90s, says Dongmin. 

Even though parasites pre-date humans, we still understand very little about them.

Of the global total of roughly 100,000 to 350,000 species of helminth endoparasites that infect vertebrates, 85-95% are poorly documented, says Dongmin, and the majority of human parasitic illnesses are caused by just a fraction of them: Clonorchis, Ascaris, Entamoeba, Toxoplasma, Cyclospora, Giardia, and Cryptosporidium. 

Because parasitic infections can siphon nutrients from their hosts, they cause mineral and vitamin deficiencies that predispose people to diseases. 

Symptoms are sometimes delayed, which is why they can go undetected for years. Parasitic infections are more common in children and are a major cause of malnutrition, which compromises learning and growth.

Strongyloides parasites in Bangladesh

In Bangladesh, a country where parasitic infections in children are still common, Adrian Streit, Ph.D., who studies parasitic nematodes at the Max-Planck-Institute for Developmental Biology in Tübingen, Germany, is collaborating with iPRB’s satellite location in the country to study Strongyloides parasites - a type of roundworm that enters the body via exposed skin. There are over 50 species of Strongyloides parasite but only three infect humans, and only one of them is a pathogen prevalent in densely populated areas, explains Streit.

In his lab, Streit performs molecular analyses on field samples to identify Strongyloides species. He also grows the worms in surrogate hosts and stores the live samples. 

“In the long term, that’s where biobanking is going to be of most importance to us,” he says. “Biobanks can keep material available to the research community longer than the life expectancy of a lab.” 

A self-described “lab biologist,” he relies on the clinical parasitologists and the experts at the iPRB in Bangladesh to collect the samples from the field, which they send to Streit for further study. Based on the research, the iPRB plans to support a human parasite eradication effort in the country. 

While museums such as Smithsonian National Museum in Washington D.C. and the Natural History Museum in London have repositories of parasites, “they are generally reluctant to distribute material to be analyzed in a way that destroys it, such as for DNA extraction,” says Streit. “And they don’t store live specimens.” 

Protocols for parasite conservation

iPRB’s biobank includes not only parasite specimens, but also morphological descriptions and such details as who what, when, where, and how a sample was collected and the results of genetic analyses. The biobank stores specimens in several forms: live, frozen, dried, as well as fixed in alcohol and formalin. It also stores parasite eggs. The lab uses QIAGEN's stabilization reagent during the sample preservation process. 

Currently, microscopy is the standard tool to look for parasites in a sample. But the iPRB aims to develop a protocol for molecular analysis to recommend to the Korean Ministry of Environment because the method is more accurate. 

iPRB has chosen QIAGEN’s workflow solutions for molecular analyses because automation reduces the potential for human error and ensures the consistent and reliable quality of the data, says Dongmin. The lab employs QIAGEN’s TissueLyser II to free DNA from samples, and the DNeasy Blood & Tissue Kit to extract genomic DNA.

To analyze DNA, the lab uses QIAgility to make their PCR master mix and QIAcuity digital PCR to amplify sample DNA. “The biggest advantage of QIAcuity is that it is easy to use,” says Dongmin. Other products require more hands-on time and the protocols are complicated, he adds. With QIAcuity, the master mix is dispensed into nanoplates in a similar way to qPCR, but then only the plates are put into the device and read, so no specific expertise is required. “Best of all, results are available within two hours,” he adds. 

Because of its high sensitivity, QIAcuity is especially useful when studying parasites, Dongmin says, since parasite nucleic acid can be present in very low amounts in a sample. The lab also uses QIAxcel - QIAGEN’s automated electrophoresis analysis of DNA and RNA samples—to simplify the process and save time. “Thanks to this, we are able to reduce labor costs while maintaining reliable quality control.”

iPRB is also experimenting with extracting nucleic acids from soil using QIAGEN’s DNeasy PowerSoil Pro kits and QIAcube Connect to detect and identify parasite species. 

The iPRB has applied to the International Standard Guidelines for Parasite Banking for ISO20387 compliance - a certification given to institutions that adhere to ISO standards in systematically importing, preserving and distributing bio-information.

Changing the environment through host behavior

Because parasites cause human disease, any talk of preserving them or studying their role in the environment often gets relegated to the fringes of scientific endeavor. But this ignores many fascinating and important aspects of parasitic behavior and how they affect ecosystems, says Skylar Hopkins, Ph.D., assistant professor in the department of applied ecology at North Carolina State University in Raleigh.

By altering an animal’s behavior, parasites can make more food available to organisms up the food chain. In Japan, for example, crickets infected with nematomorph worms leap into streams. The adult worms then burst out of their hosts. Meanwhile, the dead crickets are gobbled up by fish, namely endangered Japanese char. The crickets provide up to 60% of the fish’s calories. The parasite, because it makes more food available to char, also affects the populations of other species that serve as fish food, and thereby influences the stream’s overall ecology.

Since 2005, Keeseon has been traveling to Tanzania to collect parasites from wild animals in the Serengeti. The iPRB recently established a base camp in Serengeti National Park through which it will conduct joint research activities with other scientists. It will also collect and preserve parasites that infect humans and animals, which may inform local human parasite eradication and conservation efforts.

“I am excited to see that one of iPRB’s explicit goals is to aid parasite conservation efforts,” says Hopkins. They have recognized that this effort can also benefit the many parasite species that do not harm humans, domestic species, or sensitive wildlife.”

“I like to remind people that while parasites aren’t ‘good’ for us and should be controlled, species that do not infect humans play critical roles in our ecosystems, including ways that directly benefit us,” says Hopkins.

She points to a species of the “zombie fungus” that infects caterpillars in the Tibetan Plateau as an example. People earn a living harvesting it for use in traditional medicine. But the fungal species is threatened with extinction because of climate change and harvesting pressures, she adds. In concluding their 2020 paper discussing a global parasite conservation plan, Carlson, Hopkins and their colleagues wrote: “We can’t care about or conserve what we do not know exists.”