It’s tick season, along with an increased risk of Lyme disease, and it turns out that tiny spiders are tougher than scientists previously thought.
A recent study in environmental studies The black-scattered tick (Ixodes scapularis) is shown to be really good at surviving extreme cold and heat in nature. Previous lab research suggests that even short periods of particularly warm or cold conditions should easily kill ticks, but a Washington State University-led analysis reveals that this is only the case for tick larvae in the environment. Instead, ticks and nymphs overcome hot and cold times with little effect, dying when they apparently run out of energy. The findings could ultimately provide valuable insights into the spread of Lyme disease and other vector-borne pathogens.
“We thought we were going to see some evidence that if there was a very dry period, all ticks could be more likely to die,” said Jesse Bruner, lead author of the study and assistant professor of biological sciences at Washington State University. “However, only the caterpillars were affected by the heat and dry conditions. The effect of cold weather was less of an impact. Somehow, they hunker down and survive great.”
The black-skinned tick is a notorious carrier of pathogens responsible for various diseases, including Lyme disease, the most common vector-borne disease in North America. Over the years, these ticks have greatly expanded their range across the eastern United States and Midwest, challenging previous assumptions about their preferred habitats. While one of the culprits is likely climate change, scientists have not yet determined why ticks are abundant in some areas while rare in others.
To address the knowledge gap, the US Department of Defense provided funding to Brunner and a team of collaborators from the Curry Institute for Ecosystem Studies to prepare an unprecedentedly large field study at three military bases located across the US East Coast. By placing more than 9,000 ticks in soil pulp containers and observing their survival and development over a three-year period, the researchers were able to gather valuable data about the ticks’ response to climatic conditions.
Their work suggests that while extreme weather conditions don’t seem to have as much of an effect on tick mortality as previously thought, it does cause them to burn through their food faster. This means that hot weather can shorten the time for ticks to find a walking host close by to feed on. This was particularly true in the case of tick larvae. The researchers found that their average survival times were nearly halved when exposed to frequent periods of hot, dry weather.
The researchers also found that something else that seemed to be happening on a small scale was killing ticks. Soil core packs located within a few meters of each other often had surprisingly different rates of tick mortality. In one container, the researchers found that 80% of the ticks survived, and in another container next to it, none of the ticks survived. The reason for these large differences in tick survival is not clear, but the study results point to the influence of environmental factors such as arthropods or fungi.
The implications of the research are far-reaching, given the public health impact of tick-borne diseases. The study findings underscore the importance of targeting interventions during the larval stage, when ticks are most vulnerable. By focusing on this stage of development, the researchers hope to develop effective strategies, such as vaccinating host species for tick resistance, that can significantly reduce tick numbers and reduce the risk of disease transmission.
Moving forward, the research team plans to investigate the factors that lead to tick death and dig deeper into the role that host species, such as mice, deer, and yes, humans, play in tick survival.
“The ultimate goal is to develop a comprehensive framework that can effectively predict and manage tick populations,” Bruner said. “This, in turn, could lead to improved public health outcomes.”
In addition to Brunner, the research was conducted by Curry Institute for Ecosystem Studies scientists Shannon Ladow, Mary Killilea, Elizabeth Valentine, Megan Scherer, and Richard Ostfeld.
Jesse L. Bruner et al., Off-host survival of black-crusted ticks in eastern North America: a multi-stage, multi-year, multi-site study, Available here. environmental studies (2023). DOI: 10.1002/ecm.1572
the quote: Ticks Demonstrate Adaptability to Extreme Temperatures (2023, June 1) Retrieved June 1, 2023 from https://phys.org/news/2023-06-resilient-extreme-temperatures.html
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