From livestock to uncontrolled wildlife, nasty but ubiquitous large parasites like tapeworms have a much greater impact on the overall body health of their mammalian hosts than previously known, new research from the University of Alberta suggests.
“Parasites don’t have to kill the animal to control a population,” says Kyle Shanebeck, a Ph.D. student in the Department of Biological Sciences of the Faculty of Science who led the research.
Shanebeck explained that all wildlife has at least one, and often several, parasites. The less deadly a parasite, the more common it is within a population, with potentially stronger negative effects.
“They can affect the animal’s ability to absorb nutrients, which can affect digestive health and behavior, making them more aggressive and even changing where they forage,” he said. “These parasites also suppress or weaken immune action, as the body expends energy to mount an immune response to fight them, which can make a secondary infection worse.”
For the study, Shanebeck’s team organized the different effects of parasites on the host based on their impact on an animal’s energetic state. A meta-analysis of parasites in wild, laboratory and domestic mammalian hosts yielded 142 peer-reviewed studies documenting 599 infection-condition effects. “We consistently found strong negative effects of infection on host energetic conditions across taxonomic groups.”
Large parasites, such as tapeworms, flatworms and flukes, eat carbohydrates, making them less available to the animal. Shanebeck likens it to a power grid, where energy is diverted when faced with a supply challenge, depleting reserves. “Rolling blackouts” occur when the body begins to make decisions between survival and reproduction.
For example, parasitic worms in cattle will not kill the animal, but the resulting immune stress and other conditions such as diarrhea can affect milk production, taking a financial toll on farming activities. In less controlled natural environments, the overall health effects of parasites are more difficult to measure, which may be one reason why these effects are considered negligible.
Traditionally, assessing population health in wildlife has focused on pathogenic diseases — the often fatal diseases that can spread between species — and possibly from animals to humans.
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Kyle M. Shanebeck et al, The energetic costs of sublethal worm parasites in mammals: a meta-analysis, Biological Assessments (2022). DOI: 10.1111/brv.12867
Provided by the University of Alberta
Quote: Parasites may take a heavier toll on mammalian population health than previously thought, study suggests (July 2022, July 27) retrieved July 28, 2022 from https://phys.org/news/2022-07-parasites-heavier-toll – health-mammal.html
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