Ticks are small parasitic organisms that can transmit diseases when they bite humans and animals. Lyme disease, transmitted by blacklegged ticks, is one of the most common tick-borne diseases in the United States. Understanding which states have the lowest tick populations can help people reduce their risk of tick bites and associated diseases.
Which states have the fewest reported cases of Lyme disease?
Lyme disease case reports provide an indication of where blacklegged tick populations are lower. According to the CDC, in 2019 the states with the lowest incidence rates of confirmed Lyme disease cases were:
| State | Reported cases per 100,000 people |
|---|---|
| Nevada | 0.2 |
| Arizona | 0.3 |
| New Mexico | 0.5 |
The states of Nevada, Arizona, and New Mexico had the fewest reported cases of Lyme disease based on population. However, Lyme disease case reports alone do not provide a complete picture of tick populations.
Which states are outside of blacklegged tick geographic ranges?
Blacklegged ticks have limited geographic ranges constrained by climate, vegetation, and hosts. According to the CDC, blacklegged ticks are not known to occur in the states of:
- New Mexico
- Arizona
- Nevada
- Utah
- California
- Oregon
- Washington
- Idaho
The absence of blacklegged ticks in these western states likely explains the low incidence rates of Lyme disease. However, other tick species may still be present in these areas.
Which states have the lowest relative humidity?
Blacklegged ticks thrive in areas with a relative humidity of at least 85%. According to NOAA climate data, the states with the lowest average relative humidity are:
| State | Average afternoon relative humidity |
|---|---|
| Nevada | 20% |
| Arizona | 25% |
| Utah | 30% |
The arid climates of Nevada, Arizona, and Utah are unsuitable habitats for blacklegged ticks, contributing to lower populations.
Which states have the least forest coverage?
Blacklegged ticks congregate along the edges of wooded or forested areas. States with lower percentages of forest coverage provide less habitat for ticks. According to data from the US Forest Service, the states with the lowest percentage of forest coverage are:
| State | Forest coverage % |
|---|---|
| North Dakota | 1.0% |
| Nevada | 1.9% |
| South Dakota | 2.2% |
The plains states of North Dakota, Nevada, and South Dakota have limited woodland habitat and unfavorable climates for ticks.
Conclusion
Based on Lyme disease data, blacklegged tick geographic ranges, climate, and land cover, the state with the lowest risk of exposure to blacklegged ticks is Nevada. Nevada has the lowest reported cases of Lyme disease, is outside the known range of blacklegged ticks, has an average relative humidity unsuitable for tick survival, and has little forest coverage for tick habitats. Within Nevada, urban areas and dry desert regions are likely to have the lowest tick abundance.
Other western states with low tick populations include Arizona, New Mexico, Utah, and Idaho. These conclusions apply specifically to blacklegged ticks and Lyme disease risk. Other tick species are found across the United States, so precautions against tick bites may still be warranted during outdoor activities, even in areas with low blacklegged tick populations.