Parasitic worms that infect pets such as dogs and cats are more likely to jump into humans than other worm species, according to new research from the University of Georgia. Center for Ecology of Infectious Diseases.
The study also identified three species of worms that do not currently infect humans, but have a more than 70% chance of spreading to humans in the future.
“The close relationships we have with pets are the main reason people can become infected with new species of parasitic worms,” said Ania Majewska, lead author of the study and PhD from the Odum School of Ecology. “Daily behaviors like playing with and feeding our pets increase the opportunities for these parasites to infect people.”
Parasitic worms, or helminths, are estimated to infect 1.5 billion people worldwide, according to the World Health Organization. Many of these parasites infect humans, causing a number of serious illnesses, including schistosomiasis and filariasis.
Posted in The journal of the Royal Society Philosophical Transactions B, the study focused on 737 species of parasitic worms that primarily infect wild and domestic mammals. Of these, 137 are known to be able to infect people.
The researchers classified the characteristics of the worm species and built a machine learning model to determine which characteristics were most often associated with transmission to humans.
They found that worms that can infect pets or fish are more likely to cause human infection than worms that infect other animal species. Geographically widespread parasites were also more likely to pass from animals to humans.
Analyzes showed that three species of worms currently unknown to infect humans have characteristics that make them very likely to be able to do so: Paramphistomum cervi, a flatworm found primarily in cattle and some wildlife; Schistocephalus solidus, a fish-based tapeworm that also infects birds and rodents; and Strongyloides papillosus, a pinworm found largely in cattle.
The study marks the first time that these species have been identified as likely to infect humans, suggesting they are candidates for surveillance and further study.
It is relatively easy for dogs and cats to become infected with parasitic worms, especially if they are allowed to roam during the day.
“Our pets can get infected with helminths without our realizing it,” said Majewska. “Dogs and cats, especially those who roam freely outside, come into direct or indirect contact with wild animals, their droppings and other sources of helminths. “
Dogs and cats are not the only route of transmission, however.
Fish also harbor a variety of parasitic worms. People can easily get infected by eating raw, undercooked, or improperly prepared fish. The roundworm that causes herring worm disease, for example, infects thousands of people each year, mostly in areas where consumption of raw fish is common, such as Japan and parts of Europe.
“Human parasitic infections by worms have ancient origins and we will always be associated with them,” said lead author John Drake, Emeritus Professor of Ecology Research and Director of CEID. However, due to climate change and increased demand for animal protein, we expect infections from human parasitic worms to continue to increase. More research is needed to understand how parasitic worms spread to humans can be managed. “
The co-authors of the study include Barbara Han and Tao Huang of the Cary Institute of Ecosystem Studies.
This study was funded by the Ecology and Evolution of Infectious Diseases program of the National Science Foundation. It is part of a special issue of Philosophical Transactions B devoted to the macroecology of infectious diseases. This issue was edited by Patrick stephens, associate researcher at the Odum School of Ecology and member of the Center for Infectious Disease Ecology. Other editors for the issue include Shan Huang of the Senckenberg Biodiversity and Climate Research Center and Maxwell Farrell of the University of Toronto.
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