The new CDC study shows the distribution at the county level

Photo: As surveillance improves for ticks and the disease-causing germs they spread, so does Americans’ access to knowledge about where the risk of tick-borne disease is greatest. Experts with the U.S. Centers for Disease Control and Prevention’s Division of Vector-borne Diseases have compiled new surveillance data in a report that provides updated county-wide maps of both where black ticks (Ixodes scapularis), shown here, are prevalent, and where they have been found infected with any of seven different types of ticks. Disease-causing germs or pathogens.
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Credit: Susan Ellis,

Annapolis, MD; June 8, 2022 — As surveillance improves for ticks and the disease-causing germs they spread, so does Americans’ access to knowledge about where the risk of tick-borne disease is greatest.

“The more we look for ticks and tick-borne pathogens, the more — and the more information we have — to help protect people from the spread of tick diseases.” Eric Foster, MS, BCE, a medical entomologist in the division of vector-borne diseases of the U.S. Centers for Disease Control and Prevention says. Foster and CDC colleagues compiled that surveillance data in a new report, published May 18 in the American Entomological Society. Journal of Medical Entomology. The report provides updated county-wide maps of both where blacklegged ticks are common and where to find them infected with any of seven different types of disease-causing germs or pathogens.

Of all the diseases transmitted to humans by insects and related arthropods, those spread by ticks account for more than 75% of the infections reported each year. The maps in the new CDC study are important to raise awareness among the public and health care providers about the tick-borne diseases present in their communities and the signs and symptoms to look for in patients. Making this possible is the Centers for Disease Control and Prevention’s Growing National Tick and Tick Surveillance Program, which launched in 2018.

Previously, knowledge of tick distribution and human tick-borne pathogens was limited to data shared by local public health agencies or in academic research.

“Collection efforts were not standardized, and data was often lost due to the lack of a national repository for such information,” Foster says.

Since 2018, the CDC has created a national program that guides local agencies and academic partners on tick surveillance and pathogen testing and gathers all that data in one place.

“This effort fills in gaps in our knowledge by highlighting the presence of ticks and tick-borne pathogens where they were not previously reported or where they appear,” Foster says.

In their new study, CDC researchers combined nationwide tick control records from 2004 through 2021 with additional data on pathogen testing in black ticks from published research studies and from archives on Public Health Department websites.

The results provide the latest picture of the geographic range of seven disease-causing human pathogens known to be transmitted by black ticks (Ixodes scapularis) and the western black tick (Ixodes pacificus). The most prevalent are bacteria Borrelia burgdorferiwhich causes Lyme disease, is present in 476 counties across 29 states and the District of Columbia.

pathogens illness States provinces
Borrelia burgdorferi Lyme disease 30 * 476
Borrelia Miyamotoi Severe relapsing tick fever 25 * 271
Anaplasma phagocytosis Anaplasm 24 * 291
Babesia Mikroti Babesia 17 154
Poisan virus Poisan virus disease 6 55
Borrelia mayonnaise Lyme disease 4 12
Ehrlichia Maurice Euclerensis Ehrlichiosis 2 11

*Total includes District of Columbia

In all cases, the reported distribution of pathogens is much narrower than the known range of black ticks that spread them. But Foster and colleagues caution that the true presence of pathogens may be much broader than what has been discovered.

“These maps display county-wide records of host-seeking ticks that were found to be infected with tick-borne pathogens using strict laboratory criteria,” Foster says.

In areas where pathogens are not detected, “this does not mean that there are no tick-borne pathogens, only that records that meet collection and laboratory criteria have not been published or documented by the CDC in ticks looking for a host.” ”

The National Tick Surveillance Program is an ongoing effort and the CDC hopes to continue updating the maps to provide current and accurate information to the public and health care providers.

Thus, while surveillance and detection of tick-borne pathogens continues to improve, this new CDC research also indicates where more progress needs to be made. Wherever ticks are present, public awareness is critical.

“It is important for the public to understand that any exposure to ticks may pose a risk and that prevention of a tick bite is the best way to reduce that risk,” Foster says. “Anyone who develops symptoms of illness after a tick bite should see their health care provider and report tick exposure immediately.”


For more information, see “Reported District-wide Distribution of Seven Human Pathogens Detected in the Host Search”. Ixodes scapularis And the Ixodes pacificus (Acari: Ixodidae) in the contiguous United States” was published online May 18, 2022, at Journal of Medical Entomology.

Contact: Joe Rominiecki,, 301-731-4535 x3009

About: ESA is the world’s largest organization serving the professional and scientific needs of entomologists and people in related disciplines. Founded in 1889, ESA today has more than 7,000 members affiliated with educational institutions, health agencies, the private sector, and government. Headquartered in Annapolis, Maryland, the association stands ready as a nonpartisan scientific and educational resource for all insect-related topics. For more information, visit

The Journal of Medical Entomology He publishes papers relating to all aspects of medical entomology and medical biology, including the systemic biology of insects, acris, and other arthropods of public and veterinary health interest. For more information, visit, or visit to view the full collection of ESA journals and publications.

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