The U.S. is improving its tick surveillance programs. But they still paint an incomplete picture as Lyme cases mount

American surveillance programs designed to track the spread of ticks that cause Lyme and other illnesses are making headway, but as cases of these diseases skyrocket across the country, these initiatives are still lagging behind, according to a study released late last year in a top U.S. medical journal.

The report, published in the Journal of Medical Entomology, outlines the progress of the National Tick Surveillance Program (NTSP), an initiative started by the U.S. Centers for Disease Control (CDC) in 2018.

The CDC established the program to foster more cooperation between local, state and federal public health authorities in response to sharply rising rates of tick-borne diseases, including Lyme. 

“Tick and tick-borne pathogen data can be used to fill gaps in epidemiological surveillance,” the report says.

“However, the utility of (these) data is limited by their completeness. National maps showing the distribution of medically important tick species and the pathogens they carry are often incomplete or non-existent.”

Enhancing the accuracy of these maps is increasingly urgent because “the incidence of reported tick-borne disease cases has more than doubled” in the U.S. over the last two decades, the report says. 

The CDC estimates the number of confirmed and probable cases of Lyme disease has now reached 476,000 and it believes there are many more unreported cases. 

Like many other countries, Canada faces the same challenges. For example, a recent study estimates there were five-and-a-half times the number of reported Lyme cases in Manitoba from 2009 to 2018. The U.S. research into the progress of the NTSP over the last seven years could provide valuable data for Canadian public health authorities in tackling this problem.

Several factors hamper surveillance

The study cites several factors that hampered the effort to expand surveillance before the CDC introduced the NTSP, including:

• Lack of consistent funding.
• Limited infrastructure and training.
• A need for guidance on best practices.

The report looks at the efforts by the CDC, as well as state and local public health authorities, to improve surveillance since various species of disease-causing ticks began taking advantage of climate change to expand their ranges into the U.S northeast, the upper Midwest and the Pacific Northwest several decades ago.

The study says before the NTSP, maps used to track the distribution of these ticks “were compiled based on literature review, museum collections, and unpublished state records.”

Reactionary public health funding

 The report adds that “although many entities (e.g., state, local and tribal health departments; parks and agriculture programs; academic researchers) were conducting tick surveillance to inform such maps at local and regional scales, prior to 2018, the data collected were not standardized and were housed in disparate locations, which contributed to numerous records being overlooked or inadequate” for national maps.

“Public health funding to support tick surveillance has largely been reactionary, rather than anticipatory or proactive,” the researchers state.

“In many situations, vector surveillance was initially focused on species transmitting pathogens causing vector-borne diseases of greatest incidence or concern at the time programs were developed (e.g., plague, tularemia, West Nile virus disease, babesiosis). Such programs provided an infrastructure that could be expanded” to include ticks that cause Lyme and other diseases.

NTSP improvements

Under the NTSP, the CDC brought in several measures to improve the surveillance and national mapping of disease-causing ticks, including:

• Issuing guidance for standardization of tick surveillance data collection.
• Developing a data portal (ArboNET Tick Module) to compile tick surveillance records by county across the country.
•  Increasing funding to state public health departments to lead and conduct tick surveillance.
•  Building overall entomological capacity through funding several cooperative agreements that provide entomological training to rebuild the public health entomology workforce.

The researchers say since the inception of the NTSP, 36 U.S. states have begun using more  “active surveillance” measures — including identifying and trapping ticks in infested areas and testing them for disease-causing bacteria — as well as ‘passive techniques,” such as investigating ticks that have already bitten victims and collecting them from hunters that have found them in deer carcasses.

Active surveillance time-consuming and costly

But the report says although these active methods are effective, they’re a challenge for smaller states with limited budgets and understaffed public health workforces.

“Active surveillance is time-consuming and costly, often requiring travel costs to survey distant sites, increased staff time to conduct sampling, and coordination with property owners to obtain permission to access properties to collect ticks. Pathogen testing adds additional costs beyond those associated with specimen collection,” the researchers state.

The report cites examples in several states, such as Massachusetts, New York, New Jersey and California, where improved tick surveillance — both active and passive — has complemented epidemiological surveillance, and has helped educate and inform health professionals as well as the general population. 

But the researchers warn there is much more work to do.

“It is crucial to acknowledge the utility of the data is limited by its completeness,” the study says. 

“In many states in the United States, tick surveillance data are currently insufficient to identify or communicate the risk for tick-borne diseases.”

Citation

Eisen RJ, Foster E, Kjemtrup A, Saunders MEM, Brown J, Green L, Cervantes K, Prusinski MA, White J, Barbarin AM, et al. 2024 Dec 9. Perspectives from federal and state public health departments on their participation in and the utility of Ixodes scapularis (Acari: Ixodidae) and Ixodes pacificus tick and tick-borne pathogen surveillance in the United States. Reisen W, editor. Journal of Medical Entomology. doi:https://doi.org/10.1093/jme/tjae149.