Americans should be aware that diseases spread by kissing bugs, mosquitoes and ticks are sharply on the rise in the U.S., an official from the Centers for Disease Control and Prevention official and two scientists told journalists on June 19.
The webcast hosted by SciLine, a free resource for journalists supported by the American Association for the Advancement of Science, highlighted that the combination of climate change, international travel, changing land use, deforestation, and urbanization of rural areas are all driving vector-borne diseases to the highest numbers ever reported.
Tick-borne diseases such as “Ehrlichiosis, [Rocky Mountain] spotted fever, babesiosis, tularemia, Powassan virus… were all up in 2017,” said Dr. Ben Beard, deputy director of the CDC’s division of vector-borne diseases. “The highest numbers that we’ve ever seen.”
Between 2004 and 2017, there were about 700,000 cases of vector-borne cases reported to the CDC, and ticks accounted for 75 percent of those cases. The number of actual infections was likely ten to 70 times greater than the number reported to the CDC, Beard said.
To combat the increase, the CDC is conducting research to improve diagnostics, to improve surveillance, to track disease trends, as well as expand laboratory capacity with five regional vector-borne disease centers of excellence. The agency has established a national surveillance system for ticks and the pathogens they carry and is leading efforts across six federal departments to develop a national strategy for addressing vector-borne diseases, Beard said.
One of the strategies is related to understanding the role of climate change and its impact on vectors. Warmer temperatures have led ticks to range farther north, said Dr. Lyric Bartholomay, a professor at the University of Wisconsin’s department of pathbiological sciences and director of the CDC’s upper Midwestern Center of Excellence for vector-borne diseases.
“It’s really the temperature at the northern range of a vector that dictates how far it can go,” she said.
However, scientists aren’t certain how much of a role climate is playing in the uptick in the spread tick-borne diseases, she said.
“It’s complicated,” said Beard, because the movement of people and forest animals, increasing populations, deforestation and building into previously rural areas are also important factors.
“In terms of attribution … and what amount is attributed” to climate change, versus all these other factors is “very difficult for us to ascertain,” he said.
Certainly, warmer and wetter weather patterns have an impact on mosquito populations, said Bartholomay, who noted that the extreme flooding in Wisconsin in 2018, “precipitated a really extreme outbreak of pest mosquitoes,” she said.
She added, “climate change absolutely impacts habitat availability and makes it possible for mosquitoes to move into places that they weren’t before.”
Dr. Maria Elena Bottazzi, associate dean at the National School of Tropical Medicine at Baylor College of Medicine and professor of pediatrics and co-director of the Texas Children’s Hospital Center for Vaccine Development, highlighted that there are vectors other than mosquitoes and ticks that spread disease. She noted that Chagas disease is transmitted by the kissing bug. There are 200,000 cases of Chagas disease reported to the CDC annually. The parasite is found in the feces of an insect (called the kissing bug), which is deposited when the bug bites people at night. People get the parasite into the body by scratching themselves at the spot of the feces deposit. Chagas can cause skin swelling and cardiac and gastrointestinal complications.
“This vector is here and have been for awhile, so we really have to raise awareness” about Chagas disease, Bottazzi said. She added that her Center for Vaccine Development has been working on a Chagas vaccine.
For more information on covering vector-borne diseases:
- SciLine’s webcast on vector-borne diseases (June 2019)
- SciLine’s vector-borne disease fact sheet (June 2019)
- Tick season beginning sooner with climate change (AHCJ, May 2019)
- Fast facts on vector-borne diseases (AHCJ, October 2017)