Tag Archives: Parasites

Stone toilet in Israel shows that the rich and powerful in antiquity were suffering from parasites

Despite their advanced sanitation systems, the ancient elites of Jerusalem were plagued by intestinal parasites, new research reports.

The 2,700 year-old toilet. Image credits Yoli Schwartz / The Israel Antiquities Authority.

The findings are drawn from an archaeological site at the ancient Armon Hanatziv royal estate in Jerusalem. The site lies close to the Dead Sea, to the north of today’s Bethlehem. Analysis of soil samples taken from an ancient toilet found that residents of the estate harbored several intestinal parasites, as evidenced by the discovery of parasitic eggs in the samples.

The findings of this study are among some of the earliest discoveries ever made in Israel up to now.

Egg surprise

“These are durable eggs, and under the special conditions provided by the cesspit, they survived for nearly 2,700 years,”  said Dafna Langgut of Tel Aviv University and the Steinhardt Museum of Natural History, a leading researcher in the emerging field of archeoparasitology, and sole author of the study. “Intestinal worms are parasites that cause symptoms like abdominal pain, nausea, diarrhea, and itching. Some of them are especially dangerous for children and can lead to malnutrition, developmental delays, nervous system damage, and, in extreme cases, even death.”

The findings can go a long way towards helping us understand the daily habits of people who once lived in this area, and of how ancient people dealt (or suffered with) infectious disease. This site is particularly valuable in this regard as it showcases the lives of the very rich and wealthy, who were most likely to enjoy the best lifestyle — in regards to resources, practices, and habits — of the time. Sites like this are also relatively hard to get this type of evidence from.

For example, Langgut explains that prior research had compared fecal parasites in hunter-gatherer and farming communities here and elsewhere, helping us better understand what this transition looked like for the people at the time.

One particularly important event for archeoparasitology (the study of parasites throughout human history) is the domestication of animals. At this time, the number of parasitic infections throughout farming communities rose sharply. Hunter-gatherers were generally exposed to fewer parasites and infectious diseases on account of living nomadic lifestyles — this, Langgut adds, is still the case today.

According to the paper, the area Israel occupies today — known as the Fertile Crescent in history — was probably one of the first where human populations suffered from wide-scale intestinal parasitic infection. Various ancient texts have been found throughout Israel referencing such diseases.

Excavation works at the ruins of Armon Hanatziv, or the Commissioner’s Palace, which dates back to the mid-7th century BCE, sometime between the reigns of King Hezekiah and King Josiah, started in 2019-2020.

Pollen found in samples taken from the site suggest that a garden of fruit trees and decorative plants existed around or next to the estate. Together with the lavish architecture and evidence of quality furnishings found at the site, this showcases the sheer level of wealth that was concentrated at the Armon Hanatziv.

During excavations in the garden, archaeologists from the Israel Antiquity Authority also discovered the remains of a primitive toilet: this consisted of a large water reservoir and a cubical limestone slab with a hole drilled in the center. Pollen was found in this structure as well, so the team believes that it was built either in a small room with windows, or in one without a roof, to ensure better ventilation. It was likely constructed in the garden, away from the main building, in an effort to have the plants mask some of the smell.

Toilets were quite a luxury during this time. The earliest examples of toilets in Israel all date to the Late Bronze Age and have been located in palace areas, indicative of their rarity and cost. Due to this, there is a relative lack of opportunities to study the contents of toilets for parasites. Only two such studies had been carried out before according to Langgut, one of which reported the presence of intestinal parasites.

Archaeologists collected 15 samples from the Armon Hanatziv, alongside a few controls from the area. The parasitic eggs were chemically extracted and studied under a microscope to determine their species and measure them. Langgut found eggs of four different species in six of the samples — whipworm, beef/pork tapeworm, roundworm, and pinworm. She adds that it’s the single earliest record of roundworm and pinworm in Israel.

Whipworm and roundworm eggs were the most common in the samples. None of the four control samples yielded any eggs, which ruled out the possibility of outside contamination into the toilet.

“It is possible that as early as the 7th century BCE, human feces were collected systematically from the city of Jerusalem in order to fertilize crops grown in the nearby fields,” Langgut wrote. “The inhabitants were forced to farm inhospitable rock terrain and were told which type of crop to grow. Additionally, the type of fertilizer used might have also been dictated by the Assyrian economy [at this time, Israel was under Assyrian rule].”

Human feces can act as useful and efficient fertilizer. Today, however, they are composted for a few months before use to limit the risk of any viable parasite eggs surviving. It’s very likely that people living in the area at that time were not using this practice, which allowed for the spread of parasites throughout the community. Langgut adds that the presence of tapeworm eggs is indicative that the inhabitants of the palace were eating poorly cooked or raw beef or pork, as these are “the only meats that carry the parasite”.

“While the mere existence of something as rare as a toilet installation seems to indicate that at least some ancient Jerusalemites enjoyed a relatively high level of sanitation, the evidence of intestinal parasite eggs suggests just the opposite,” she concludes. “The presence of indoor toilets may have been more a matter of convenience than an attempt to improve personal hygiene. A toilet was a symbol of wealth, a private installation that only the rich could have afforded.”

The paper “Mid-7th century BC human parasite remains from Jerusalem” has been published in the International Journal of Paleopathology.

What are symbiotic relationships: nature’s matchmaking

Common Clownfish (Amphiprion ocellaris) swimming in their Sea Anemone (Heteractis magnifica) home on the Great Barrier Reef, Australia. Credit: Wikimedia Commons.

There are millions of different species on Earth, many of which have to share the same habitat and resources. Naturally, these creatures have had to find a way to coexist without driving each other to extinction. Earth’s biodiversity hangs in an intricate but delicate web of dependencies in which some animals prey on others and are, in turn, lunch for others higher up the food chain. But the predator-prey paradigm is just one example of many types of relationships animal and plant life can have.

When two or more unlike organisms live together, biologists refer to this relationship as symbiosis (from the two Greek words for “with” and “living”). This ecological relationship is sometimes, but not always, beneficial to both parties. Perhaps the best word to describe symbiosis is balance, even when the relationship between the two different species sounds highly dysfunctional and one-sided. That’s because the ecosystem at large is balanced thanks to symbiosis.

The main types of symbiotic relationships are:

  • Mutualism — the symbiotic relationship that is mutual to both parties. Think win-win.
  • Commensalism — when only one party seems to benefit, but the other species doesn’t really lose either. Think win-neutral.
  • Parasitism — when one species benefits at the expense of the other. Think win-lose.

Mutualism symbiosis

Credit: Pixabay.

Mutualism symbiosis is a relationship between two different species that cooperate in order to access benefits they wouldn’t be able to on their own. It’s what most people usually think of when they hear the word symbiosis. A great example of mutualism symbiosis is that between the clownfish and sea anemones.

Sea anemones are very shrewd predators. While most predators seek out and hunt their prey, sea anemones are campers. They live a static existence, attached to rocks or corals in the sea, catching food that passes by them using their tentacles. These tentacles have stinging cells called nematocysts that release powerful toxins that paralyze prey, making them easy pickings. Once injected with the paralyzing neurotoxin, the prey is guided into the mouth by the tentacles.

Plankton and small fish comprise the main diet of sea anemones, but not clownfish. These fish secrete a substance in the mucus that covers their body that makes them immune to the anemones’ venom. So the clownfish naturally spend a lot of time swimming between the tentacles of the anemones, where they are protected from potential predators that get stunned by the sea anemones.

The brightly colored clownfish are quite conspicuous, so they attract other small fish, which are then caught and devoured by the anemones. One organism provides shelter, while the other brings in food for the service.

On land, another great example of mutualistic symbiosis is that between bees and flowering plants. The flowers provide bees with sweet nectar and pollen, which the worker bees collect as food to feed their colony. In return, bees spread the pollen from flower to flower, allowing the plants to reproduce through a process known as pollination.

Commensalism symbiosis

Cattle egrets (Bubulcus ibis) stand on the backs of bovines where they pick off parasitic bugs like ticks, fleas, and flies. The cows, in turn, disturb the ground revealing grasshoppers or other insects that are then eaten by the egrets. The two organisms form a commensalism symbiosis. Credit: Wikimedia Commons.

Some organisms are just freeloaders, piggybacking on other species with nothing to show in return. On the bright side, the organism that has nothing to gain isn’t harmed either. Scavengers that trail predators to eat the remains of their kill are an example of such a relationship.

Commensalism can be further broken down depending on where the symbiont lives with, on, or inside another species, which plays the role of a ‘host’. We can thus think of four distinct types of commensalism:

  • Inquilinism, where one symbiont depends on the other for shelter. Think of birds living inside a tree hole.
  • Metabiosis, where one organism forms the habitat of another. A prime example of this type of relationship is the hermit crab that uses the shells of dead gastropods as their home, which doubles as a protective shell when they carry it around. Bacteria that colonize our guts also fall within this category, although some may be considered mutualists since they help break down food and help the host access nutrients, among other important health benefits they may offer.
  • Phoresy refers to organisms that attach to others for transport. Barnacles, for instance, cling to whales, which transport the tiny symbiot to plankton-rich waters, where both organisms can feast. There isn’t evidence to suggest that the whales are harmed or lose anything in particular from this one-sided deal though.

Parasitism symbiosis

Sometimes, symbiotic relationships cause harm. This happens when the symbiont (or parasite in this case) benefits from the symbiotic relationship, at the expense of the host, which is harmed.

Parasites may live inside the host’s body (endoparasitism) or on its surface (ectoparasitism). For instance, tapeworms that live inside the intestines of other animals where they consume partially digested food (and thereby deprive the host of nourishment) are endoparasites. Head lice that live on the scalp, where they suck blood and cause itching on the host, are ectoparasites.

Obligate and facultative symbiosis

In many symbiotic relationships, the host and symbiont may derive benefits or inflict harm that wouldn’t have been possible absent the relationship. But if the symbiosis didn’t occur, each could mind their own business and still find a place in the ecosystem independently of one another. This is known as a facultative symbiosis.  For example, there are many tiny insects that live in bird nests, where they consume waste that the birds produce, keeping the nest clean and decreasing the chance for the build-up of bacteria and disease. In the process, they get a free meal from the birds and the birds get free house-cleaning services. But each organism could theoretically survive without one another.

In contrast, there are some symbiotic relationships in which the symbionts are entirely dependent on each other for survival. For instance, lichens consist of fungal and photosynthetic symbionts that cannot survive without one another. Although the fungal and photosynthetic organisms do occur independently in nature, their physiology and morphology change drastically once they come together to form the lichen. In this particular relationship, the fungus ‘farms’ the autotrophic photosynthetic organism by encapsulating it. The photosynthetic symbiont harnesses the sun to produce food for both parties, while the fungus retains water and provides a footing from which the photobiont can absorb nutrients. These relationships are called obligate symbioses and typically develop over time as each organism adapts to the benefits of depending on each other.

All types of symbiosis can be either obligate or facultative. The lichen example is an obligate mutualistic symbiosis, but many parasites are host-specific and as a result have co-evolved with their hosts, without whom they cannot survive. This also means that it’s in the parasite’s best interest not to completely debilitate its host, otherwise, there will be no one left to exploit. Parasites are huge pests, but they’re almost never fatal.

Almost every creature has at least one symbiotic relationship (think of gut bacteria for example), which makes symbiosis essential to the planet’s ecosystems. 

Global warming will kill a third of the world’s parasites, and that’s not even a good thing

Even unpopular parasites are sometimes important to ecosystems, and global warming is wiping them out.

Parasites are a tough sell, and it’s easy to understand why. An eclectic mix of specimens from the Smithsonian’s parasite collection. Credits: Paul Fetters for the Smithsonian Institution/Courtesy of Science Advances

Parasites such as lice, ticks, and fleas are disliked for good reasons — they can sting or bite you and sometimes carry nasty diseases, but they often serve important roles in ecosystems. A new study found that as climate change kicks in more and more, up to a third of all these parasites could be wiped off, with dramatic consequences for everybody.

The evil you know

The first concern is that as some parasites are killed off, their place will be taken by others, and this will almost certainly lead to invasions from the surviving ones. They also keep other creatures in check and fill in some very important links in the food chain. If they go away, other creatures which dine on these parasites will be left without their favorite food and this can propagate on the food chain, much like a domino effect.

In order to reach this conclusion, researchers across eight countries spent years pinpointing the habitats, needs, and current environmental situation of 457 parasite species. They also analyzed the collection of 20 million parasites held at the Smithsonian Institution’s Museum of National History in the US to map their distribution.

Our action (or lack of action) will have a huge impact on the planet’s wildlife — including ecosystems. Different scenarios will carry different outcomes. Image via Wikipedia.

They came up with startling numbers — depending on the future climate scenarios, between 20% and 37% of all parasites will meet their end, making them one of the most threatened groups on the planet.

“It is a staggering number,” said Colin Carlson at the University of California, Berkeley, who led the new work. “Parasites seem like one of the most threatened groups on Earth.”


Because of their bad reputation, parasites are massively understudied. No one wants to fund research, no one really wants to dedicate their career towards studying them, and people overall just don’t like them. Especially in relation to climate change, we don’t really know what the impact on parasites would be, and this is shaping up to be a massive problem.

“Parasites are obviously a hard sell,” said Carlson. “Even if you are grossed out by them – and there are obviously downsides for individual hosts and for humans – parasites play a huge role in ecosystems.”

But they do provide up to 80% of the food web in many ecosystems, and having a wide range of parasites means they compete with one another and keep each other in check.

“If parasites go extinct, we are looking at a potential massive destabilisation of ecosystems [which] could have huge unexpected consequences,” Carlson said, with other parasites moving in to take advantage. “That doesn’t necessarily work out well for anyone, wildlife or humans.”

This is just one of the first studies to focus on this aspect; 457 species is not that much, and we’re just getting a glimpse into what is certainly a complex puzzle. Hopefully, things will change in the future.

The bottom line is even if we don’t like them, understanding parasites is almost certainly useful.

“It is difficult to summarise the net consequence, as we know so little about most parasites,” Carlson said. “Climate change will make some parasites extinct and make some do better. But we would argue the overall phenomenon is dangerous, because extinctions and invasions go hand in hand.”

Journal Reference: Colin J. Carlson et al. Parasite biodiversity faces extinction and redistribution in a changing climateDOI: 10.1126/sciadv.1602422

Some parasitic plants can steal genes then use them against their hosts

A new Penn State university study found 52 cases of nonsexual transfer of DNA — or horizontal gene transfer (HGT) — from a host plants into a parasitic species known as broomrapes (genus Orobanche).

Image credits Joshua Tree National Park / Flickr.

The transferred genes became functional in the parasites, said Claude dePamphilis, professor of biology at Penn State and co-author of the paper. Although HGT is rare in complex life, discovering that it can occur in parasitic plants could help us better defend our crops against them.

The team used genetic data to generate the evolutionary histories of thousands of genes in the parasite plants, dePamphilis said. They then looked at the transcriptomes — the expressed gene sequences — of three of these plants: Triphysaria versicolor (yellowbeak owl’s-clover), Striga hermonthica (giant witchweed) and Phelipanche aegyptiaca (Egyptian broomrape). They also examined the non-parasitic plant Lindenbergia philippensis, and genome sequences from 22 other non-parasitic plants. Because they also considered mithocondrial RNA (which can move between the host and the parasite) as a possible source for the transfers, they had to test all the data and rule out their experimental hosts as the source of genetic material. They found that the “foreign” sequences in the parasites had been derived from entire genes of past hosts, incorporated into the parasites’ genomes.

“[The broomrape family] includes some of the the world’s most devastating agricultural weeds,” said dePamphilis.

“The HGT discovery is really part of our effort to try to better understand how parasitic plants work and how we can better control them. Our hope is that we can use this information to find the best strategies to generate, or breed, resistant host plants.”

The researchers believe this transfer boosts the parasite’s ability to invade their host and overcome its natural defenses. The genes stolen this way could also provide the parasite with increased resistance to infection and pathogens the host plant has evolved to fight against.

HGT is actually pretty common in simple organisms, like bacteria. But complex life, such as you, or me, or a cucumber, transfers genes vertically — through the sexual exchange of DNA, with mutations and natural selection providing the means and incentive for evolution. But the researchers think the close feeding connections between the parasite plants and their hosts increases the chance of genes finding their way to the parasite, where they can become functional.

“Parasitic plants seem to have a far greater rate of horizontal gene transfer than non-parasitic plants and we think this is because of their very intimate connection they have with their host,” said dePamphilis.

Parasite plants push roots into their host, which they use to extract water, sugars, minerals, even nucleic acids such as DNA and RNA, dePamphilis added.

“So, they are stealing genes from their host plants, incorporating them into the genome and then turning those genes back around, very often, as a weapon against the host.”

This kind of plants plague farmers (figuratively speaking) around the world. In some areas, they are so numerous that they’re a major driver behind crop loss. In Sub-Saharan Africa the witchweed (Striga) is one of the biggest source of crop yield loss.

Future research may investigate the mechanism of horizontal gene transfer to help engineer improved plant defenses against parasitic attacks, dePamphilis concluded.

The full paper titled “Horizontal gene transfer is more frequent with increased heterotrophy and contributes to parasite adaptation” has been published in the journal Proceedings of the National Academy of Sciences.

Roundworm infections found to increase fertility in women

A study of 986 Bolivian women found that on average, a lifetime infection  with a type of roundworm named Ascarius lumbricoides led to an extra two children in the family. Their paper, published in the journal Science, suggests that the worm is altering the host’s immune system, making it easier to become pregnant — in effect, the parasite increases female fertility. The researchers hope this discovery will lead to “novel fertility enhancing drugs.”

Infection with a species of parasitic worm increases the fertility of women, say scientists. Image via bbc

“The effects are unexpectedly large,” said Prof Aaron Blackwell, one of the researchers for the BBC News website.

For the Tsimane population in Bolivia, the average family has nine children, and about 70% of the population lives with a parasitic worm infection. The paper suggests that an infected woman’s immune system changes during pregnancy, making their body less likely to reject the fetus. On average, these women had two more children during their lifetime.

“We think the effects we see are probably due to these infections altering women’s immune systems, such that they become more or less friendly towards a pregnancy,” said Prof Blackwell.

Blackwell added that while using the worms as a fertility treatment was an “intriguing possibility,” there is much more work to be done before “we would recommend anyone try this.” But it’s not all roses with parasitic worms. The nine year long study also found that while Ascaris lumbricoides increases fertility in infected women, hookworms had the exact opposite effect, with families showing an average of three less children.

Prof. Rick Maizels, specialized in the workings between parasitic worms and the immune system said: “It’s horrifying that the hookworm effects are so profound, half of women by 26 or 28 have yet to fall pregnant and that’s a huge effect on life.”

Prof Maizels suggested the hookworm may also be causing anaemia and leading to infertility that way.

Bacteria and viruses try to overwhelm the immune system by multiplying rapidly. But parasites have a different strategy, growing slowly and suppressing the immune system, which is why they make vaccines less effective in the host and lighten allergies. This also makes the mother’s drowsier immune system less likely to attack fetal tissue, increasing fertility.

However, the mechanism is yet to be fully understood. Prof Allan Pacey reported that drugs had been administered to the women in an attempt to alter their immune system to boost IVF, but without success.

“It is very surprising and intriguing to find that infection with this particular species of roundworm actually enhances fertility,” said Prof Allan Pacey, a fertility scientist at the University of Sheffield.

He added: “Whilst I wouldn’t want to suggest that women try and become infected with roundworms as a way of increasing their fertility, further studies of the immunology of women who do have the parasite could ultimately lead to new and novel fertility enhancing drugs.”

Currently, one third of global population is believed to be infected with similar parasites.