An organism's immune response to an external pathogen plays an important role in understanding infection and transmission behaviors, according to a new study from the University of Colorado Boulder (CU Boulder).
This pattern was found to apply to planktons exposed to parasites or humans exposed to pathogens and researchers believe that it could shed light on how to respond to future pandemics. Researchers presented their findings in the report "Host controls of within-host disease dynamics: insight from an invertebrate system," appearing in the latest edition of The American Naturalist journal.
With the new findings, researchers are hoping for valuable insight for understanding and preventing the transmission of diseases within and among animals. From parasitic flatworms passed from snails to humans in other countries to zoonotic spillover events that led to global pandemics such as COVID-19 and West Nile fever.
ALSO READ: Scientists Confirm Climate Change has Diversified Plankton
The Secrets of Immune Response
"One of the biggest patterns that we're seeing in disease ecology and epidemiology is the fact that not all hosts are equal," says Tara Steward Merrill, lead author of the new study and a postdoctoral fellow in ecology from the University of Illinois, Urbana, in a report from CU Boulder. Sher further explains that in the context of infectious disease research, it is important to build the factor of host immunity into the existing understanding of how disease spreads.
Among the most common transmitters (vectors) of diseases are invertebrates, carrying pathogens between humans or in zoonotic cases, from animals to humans. Vector-borne diseases - like malaria, dengue, and Lyme disease - are responsible for about 20 percent of all infectious diseases around the world, responsible for more than 700,000 deaths annually.
But the new study raises the possibility of invertebrates fighting off diseases and eliminating the possibilities of transmitting the diseases onto humans.
Researchers were observing a tiny species of planktons (Daphnia dentifera) through its lifecycle after being exposed to a fungal parasite (Metschnikowia bicuspidata). They soon discovered that some of these planktons have an immune response against the fungal spores from entering their bodies, while others were able to clear the infection within a time frame after ingesting the fungi.
Stewart Merill adds that the results of their study show several defense mechanisms available to invertebrates such as planktons that reduce the odds of infection, requiring the need to understand these defenses to better understand how infection works.
Observing the Planktons' Self-Recovery
The UC Boulder news release explains that Stewart Merrill began working on these planktons during her first year as a doctoral student at the University of Illinois. If the planktons fail to stop the fungal parasites, these spores start attacking their guts, fill its body and continue growing, leaving only the host when it dies.
Upon observing this phenomenon, she noticed something unprecedented. Some of the planktons actually recovered. Later on in her study, she discovered that when faced with the same levels of fungal exposure, the success or failure of the host depends on its internal defenses and immune response during the early stages.
Based on this discovery, researchers created a simple probabilistic model that assesses the host's capability - a model applicable to a wide range of animals, opening the possibility of using the same model for human diseases. Furthermore, illustrating that not all hosts have the same responses in disease transmission and that exposure is not a sure factor for infection, the model can also be used for COVID-19.
RELATED ARTICLE: COVID-19 Transmission Linked to Triangular-Shaped Spikes Found on Virus
Check out more news and information on Zoonotic Diseases in Science Times.
