Insect Predators May Protect Us from Infectious Diseases

Insect predators such as dragonflies and other aquatic bugs may help protect us from infectious diseases, according to a new study.

In recent decades, humans have altered biodiversity around the globe as the result of activities including deforestation, man-made climate change and pollution. Meanwhile, outbreaks of infectious diseases like chikungunya, lime disease, malaria, and others have spiked among human populations. Researchers at Penn State, as described in the journal PNAS, believe there is a link between the two events.

"In the last century, there has been an unprecedented global increase in infectious diseases and a concomitant decline in and homogenization of biodiversity," study author Jason Rohr, a biologist at the University of South Florida, said in a news release. "The controversial 'dilution effect hypothesis' suggests that the two phenomena might be linked, or that biodiversity often decreases disease risk."

According to the findings, small predators aren't just important for the health of an ecosystem, but are vital to human health as well.

Most biodiversity research focuses on the variation of parasite hosts, but this study turned its attention on the diversity of species that attack parasites. Specifically, the study combined lab experiments, field surveys and mathematical modeling to better understand how the presence of dragonflies influenced infections of parasitic flatworms called trematodes in frogs.

Rohr and his colleagues found that dragonfly larvae were a good indicator of diminished rates of parasitic infections in the frogs - and that a diversity of insect predators was even better.

"In our wetland survey, our microcosms and disease models, we discovered that there were fewer flatworms in frogs where there were more species of flatworm predators," said Rohr. "Additionally, the field study indicated that the diversity of these predators was a better predictor of flatworm infections than nutrients, frog immunity or the diversity and abundance of hosts."

Prior research has also shown that decreased small predator diversity results in more crop pests, such as locusts and caterpillars. Therefore, the scientists believe their results beg for the introduction of small insects in order to both manage crop pests and prevent parasitic diseases in humans.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).