Frequency and Intensity of Tick-Borne Diseases Increase in Midwest

Tick-borne diseases are increasing in frequency and intensity in the Midwest. Climate change, population shift from urban to suburban areas, and increased population of white-tail deer have contributed to this change, according to findings reported in PLOS One.¹

“We have seen increases recently in both the number and severity of tick-borne diseases in the Midwest, particularly in the humid climates of Missouri, Kansas, Oklahoma, and Arkansas,” said senior author Ram Raghavan, PhD, MS, assistant professor at the University of Missouri (MU) College of Veterinary Medicine and MU School of Health Professions.² “Since more people get infected by tick-borne diseases each year than any other vector-borne disease, it is important that we better understand what type of ticks are present in our region, where they are located, and what time of year they are most prevalent. This information will help keep us, our families, pets, and livestock safe.”

Tick-borne diseases that affect patients in the United States include Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, anaplasmosis, babesiosis, tularemia, Colorado tick fever, and tick-borne relapsing fever.

Raghavan and colleagues collected and identified various species of host-seeking ticks in Pittsburg, Kansas, once a month between March 2014 and February 2017, except for months when the ground was snow covered or the temperature was below freezing. The researchers targeted periurban areas surrounding Pittsburg that are frequented by people and pets and contain forested and grassland landscapes. A total of 15,946 ticks were collected, the vast majority of which were Amblyomma americanum (79%) followed by Dermacentor variabilis (13%), A maculatum (7%), and Ixodes scapularis (0.73%). A majority of the ticks were most active in the humid spring and summer seasons.

The following factors may have contributed to the rise in tick-borne diseases in this area, according to the researchers:

• Relocation of humans from densely populated urban cities to more suburban areas near forests and grasslands where ticks are often present.
• Increase in outdoor fitness activities such as hiking, biking, and walking, especially during the COVID-19 pandemic and particularly during the warmer spring and summer seasons in the Midwest.
• Warmer temperatures and increased humidity found with climate change, which provide ideal conditions for ticks and the pathogens they carry to thrive.
• Sharp increase in the population of white-tailed deer, which are the primary animal host for the most common tick found in the Midwest (A americanum).

“This comprehensive research study helps us create a baseline understanding of the current situation from a public health perspective,” Raghavan said. “These contributing factors will likely continue to play a role going forward, and now we have meaningful, relevant data to look back on for comparisons to see if certain trends continue in the future.”

Although the findings may not be generalizable to other areas of the United States, the authors noted that the findings are likely to be similar for most areas of eastern Kansas, western Missouri, northern Oklahoma, and northern Arkansas due to the similarities in climate and land cover properties in these areas.

The study is limited by the tick collection method used, which only captured ticks found on vegetation, the study authors noted. This may have limited the collection of D variabilis and A maculatum in larva and nymph stages. 

References

1. Hroobi A, Boorgula GD, Gordon D, et al. Diversity and seasonality of host-seeking ticks in a periurban environment in the Central Midwest (USA). PLoS One. 2021;16(4):e0250272. doi:10.1371/journal.pone.0250272

2. University of Missouri. Ticking upward: MU researcher studies rise of tick-borne diseases in Midwest. News Release. https://showme.missouri.edu/2021/ticking-upward-mu-researcher-studies-rise-of-tick-borne-diseases-in-midwest/

This article originally appeared on Clinical Advisor