Parasites in humans influence each other via shared food sources

March 13, 2014

Over 1,400 species of parasites – viruses, bacteria, fungi, intestinal worms and protozoa – are able to infect humans. In most cases, the right medicine against a parasite cures the patient. If he or she suffers from an infection by two or more species of parasite at the same time, however, it soon becomes more difficult to diagnose and treat. Medication can even exacerbate the medical condition if one pathogen is killed off but the second flourishes. One reason is the little-understood interactions between the parasites that reside in the same host.

In a study published in Proceedings of Royal Society B, an international team of researchers including Professor Owen Petchey from the Institute of Evolutionary Biology and Environmental Studies at the University of Zurich presents a network that explains how different and parasite groups mutually influence each other in the human body. Surprisingly, the biologists discovered that the parasites are most likely to interact via the food source they share – not the immune response or directly through contact with other parasites.

Complex overview with clear patterns

Co-infections are very common: Simultaneous infestations by different , for instance, affect around 800 million people worldwide. In order to develop effective treatment approaches for co-infections, says Owen Petchey, we need to understand the structures of the parasite communities in a host – in this case individual humans – and the between the parasites better. The ecologists from Zurich, Liverpool, Sheffield and Edinburgh compiled a list of 305 parasite species, 124 resources in the host and 98 immune system components in a meta-study – then analyzed over 2,900 combinations of all these factors in an unprecedented manner.

The network displays clear patterns: The infected part of the body and the same food resource are the most common contact points that can lead to an interaction between the different parasites. "We found twice as many parasites fighting for the same energy source as parasites that elicit the same and are able to interact in that way," explains Petchey. The manner in which the immune system responds to the individual pathogens seems to be of secondary importance, despite the fact that other studies pointed towards precisely this. The direct influence from one parasite to the next is also rarer, with the exception of HIV, Staphilococcus aureus and the Hepatitis C virus, which are known to interact directly with other pathogens.

Personalized medicine in the spotlight

The network-like overview of the various interactions of that can harm humans goes beyond the usual consideration of parasite pairs. "These results can serve as a basis for the development of new, personalized treatment schemes for infected patients," Petchey hopes. The biologist is currently testing his hypotheses of this synthesis study with different organisms.

Explore further: Do parasites evolve to exploit gender differences in hosts?

More information: Emily C. Griffiths, Amy B. Pedersen, Andy Fenton and Owen L. Petchey. "Analysis of a summary network of co-infection in humans reveals that parasites interact most via shared resources." Proceedings of Royal Society B, March 12, 2014. DOI: 10.1098/rspb.2013.2286

Related Stories

Do parasites evolve to exploit gender differences in hosts?

February 28, 2012

Some disease-causing parasites are known to favor one sex over the other in their host species, and such differences between the sexes have generally been attributed to differences in immune responses or behavior. But in ...

Recommended for you

Secrets of a heat-loving microbe unlocked

September 4, 2015

Scientists studying how a heat-loving microbe transfers its DNA from one generation to the next say it could further our understanding of an extraordinary superbug.

Plants also suffer from stress

September 4, 2015

High salt in soil dramatically stresses plant biology and reduces the growth and yield of crops. Now researchers have found specific proteins that allow plants to grow better under salt stress, and may help breed future generations ...

Ancient walnut forests linked to languages, trade routes

September 4, 2015

If Persian walnut trees could talk, they might tell of the numerous traders who moved along the Silk Roads' thousands of miles over thousands of years, carrying among their valuable merchandise the seeds that would turn into ...

Huddling rats behave as a 'super-organism'

September 3, 2015

Rodents huddle together when it is cold, they separate when it is warm, and at moderate temperatures they cycle between the warm center and the cold edges of the group. In a new study published in PLOS Computational Biology, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.