Parasites and the microbiome

Date:
June 12, 2020
Source:
University of Pennsylvania
Summary:
In a study of ethnically diverse people from Cameroon, the presence
of a parasite infection was closely linked to the make-up of the
gastrointestinal microbiome, according to a research team.



FULL STORY ========================================================================== Parasite infections are a constant presence for many people who live in tropical regions, particularly in less industrialized areas. These often chronic conditions are at best unpleasant; more seriously, children
with parasite diseases that cause diarrhea can die of malnutrition
or dehydration.


==========================================================================
In Genome Biology, a study led by University of Pennsylvania scientists investigated the links between parasite infection and the gut
microbiome. Using genetic methods to characterize the gastrointestinal microbiome of 575 ethnically diverse Cameroonian people representing populations from nine villages with meaningful differences in lifestyle,
the researchers discovered that the presence of parasites was strongly associated with the overall composition of the microbiome.

"We found that we could look at someone's microbiome and use it to predict whether someone had a gastrointestinal parasite infection," says Meagan
Rubel, who completed her doctorate degree at Penn and is now a postdoc
at the University of California, San Diego. "Whether or not it was
parasites changing the microbiome or something in the resident microbiota
of a person that made them more susceptible to infection, we can't say,
but the association was strong." Rubel led the study in collaboration
with Penn's Sarah Tishkoff, a Penn Integrates Knowledge Professor in
the Perelman School of Medicine and School of Arts and Sciences, and
Frederic Bushman, a microbiologist in the medical school. In addition
to the microbiome and parasites, the research also examined markers of
immune function, dairy digestion, and pathogen infection, a rich dataset.

The investigation entailed six months of field work, collecting fecal and
blood samples from Mbororo Fulani pastoralists, cattle herders with a diet
high in meat and dairy; Baka and Bagyeli rainforest hunter-gatherers,
who practice a limited amount of farming but also forage for meat and plant-based foods; and Bantu-speaking agropastoralists, who both grow
crops and raise livestock. As a comparison group, the study included data
from two groups of people living in urban areas of the United States,
with a diet heavier in animal fats, proteins, and processed foods.

In the field, the researchers tested for malaria and a number of other pathogens that infect both the blood and gastrointestinal system.



==========================================================================
Of the 575 people tested in Cameroon, the researchers found nearly
40% were infected with more than one parasite before receiving an
antiparasitic treatment, with hunter-gatherers, on average, most likely
to be co-infected with multiple parasites. In particular, the team found
that four soil- transmitted gut parasites tended to co-occur at a rate
much higher than chance: Ascaris lumbricoides, Necator americanus,
Trichuris trichiura, and Strongyloides stercoralis, or ANTS.

"Gut parasites are a global public health concern," says Rubel. "And
you tend to see several of these parasites together in resource-poor
settings where people may not have access to clinical care, piped water,
and soap, so there's more opportunity for them to be transmitted."
Back in the lab at Penn, the researchers used genomic sequencing
tools to take a snapshot of the participants' gut microbiomes. The
composition of the microbiome, they found, could accurately predict a
person's country (U.S. or Cameroon) and lifestyle (urban, pastoralist, agropastoralist, or hunter- gatherer). But after these two variables,
the presence of ANTS parasites could be predicted with greater accuracy
by the microbiome structure than any other variable the research team
studied. Taken together, the microbiome could predict the presence of
these four gut parasites with roughly 80% accuracy.

Infection with these parasites also led to upticks in immune system
activation, specifically turning on pathways that promote inflammatory responses. Parasite infection was also associated with a greater
likelihood of having bacteria from the order Bacteroidales, which are
known to play a role in influencing digestion and immune system function.

In a second part of the study, the Penn-led team assessed the
relationship between the gut microbiome and milk consumption in the
Fulani pastoralist population. Earlier work by Tishkoff and colleagues illuminated how genetic mutations enabling lactose digestion arose in pastoralist communities in Africa, selected through evolution because of
the important nutritional benefits of consuming dairy. In looking at the Fulani's microbiomes, they also tended to have an abundance of bacterial
genes capable of breaking down galactose, a component of lactose, and
fats, compared to other groups. "This enrichment of genes could help
you extract more nutrition from the food you eat," Rubel says.

The researchers believe their findings, the largest-ever study on the
link between gut microbiome composition and parasite infection from
sub-Saharan Africa, can open new possibilities for future work. "The
kinds of microbiome markers we found could be useful to predict the
type of pathogens you have, or to shed light on the interplay between
the microbiome and the immune system," says Rubel.

Eventually, she adds, more research could even illuminate strategies for purposefully modulating the microbiome to reduce the risk of a parasite infection or minimize the harm it causes to the body.


========================================================================== Story Source: Materials provided by University_of_Pennsylvania. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Meagan A. Rubel, Arwa Abbas, Louis J. Taylor, Andrew Connell, Ceylan
Tanes, Kyle Bittinger, Valantine N. Ndze, Julius Y. Fonsah, Eric
Ngwang, Andre' Essiane, Charles Fokunang, Alfred K. Njamnshi,
Frederic D.

Bushman, Sarah A. Tishkoff. Lifestyle and the presence of
helminths is associated with gut microbiome composition
in Cameroonians. Genome Biology, 2020; 21 (1) DOI:
10.1186/s13059-020-02020-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200612172202.htm

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