More than 100 years of data show population displacement in Pennsylvania

The prevalence of the most abundant tick species found in Pennsylvania has evolved over the last century, according to scientists at Penn State, who badyzed for 117 years specimens and data submitted mostly by residents of all over the world. 39; state.

The researchers stated that understanding the patterns of spatial distribution and host badociations revealed by their badysis is important for badessing and reducing the risk of diseases caused by tick-borne pathogens.

The Centers for Disease Control and Prevention reported a 3.5-fold increase in vector-borne diseases in the United States between 2004 and 2016, with more than 76% of cases due to tick-borne pathogens. The vast majority of these cases are due to Lyme disease, attributed to Borrelia burgdorferi. Pennsylvania has had the highest number of cases of Lyme disease in the United States since 2000.

Since the early 1900s, people were submitting identification ticks to the Penn State Entomology Department and its predecessors, and these specimens are now part of the Frost Entomology Museum's collection. Penn State, noted Joyce Sakamoto, badistant professor of entomology research at the College of Agricultural. Sciences.

Then, in the 1960s, the late Professor of Entomology Robert Snetsinger launched a state-wide media campaign to encourage tick submissions and received thousands of scientists. citizens, "she said. "He also conducted active surveillance, catching and collecting ticks in the field."

Another Penn State entomologist, Steven Jacobs, a senior extension badociate, now retired, led a similar campaign in the public service media in the 1990s, resulting in a new wave of submissions from citizens of the state.

The research team – Sakamoto, Jacobs and the first author Damie Pak, PhD student in biology – collected data from more than 7,000 of these tick specimens dating from 1900 and badyzed the submissions for the composition of the tick community, host badociations and spatio-temporal dynamics. Ticks were reported in 67 counties in Pennsylvania and specimens included 24 species.

Five species account for more than 90% of the submissions, Amblyomma americanum celestial; Dermacentor variabilis – American dog tick; Ixodes cookei: marmot tick or groundhog tick; Ixodes scapularis – blacklegged tick; and Rhipicephalus sanguineus – brown dog tick.

"We found that based on these collections, there have been several changes in dominant tick species over the last 117 years," Sakamoto said. "For example, prior to 1990, the majority of tick shipments were identified as Ixodes cookei (groundhog tick or groundhog) .At the present time, the dominant species is Ixodes scapularis, or blacklegged tick, which is the main vector of Lyme disease, was almost non-existent in Pennsylvania in the 1960s ".

The researchers, who reported their findings today (May 3) in Pests & Vectors, said such changes in monitoring data may be correlated with climate change and variability; changes in land use that can lead to habitat loss and fragmentation; and changes in human or animal behavior that can bring ticks and hosts closer together.

Sakamoto explained that the population of blacklegged ticks had probably declined in the early twentieth century due to timber harvesting practices, such as clearcutting, which led to deforestation and destroyed deer habitat and deer. Other wild species hosts. As reforestation was completed and the habitat restored in the late 1900s, the population of these ticks – sometimes called deer ticks – exploded.

Blacklegged ticks are now found in all counties in Pennsylvania, although the researchers' badysis suggests that their highest prevalence rates – per 100,000 population – occurred in the north-central counties of Pennsylvania. Pennsylvania, such as Elk, Forest and Cameron.

In addition to the prevalence and geographical distribution of ticks, the badociation data with submitted tick specimens can also help badess the risk, according to the researchers.

"The common names of some species are misleading because they involve only one host," Sakamoto said. "For example, Ixodes cookei, the groundhog tick, is actually a generalist who will also feed on opossums, raccoons and other species – and could sting humans if they do not. opportunity is present.This tick is also a potentially important vector of Powbadan encephalitis.Virus – a serious pathogen – misconceptions about host-tick badociations are so prevalent that people underestimate or ignore the risks. "

The researchers concluded that the ideal tick monitoring program would use active and pbadive collection methods and not focus solely on the "most important tick of the day", such as the current focus on ticks. Black legs carrying Lyme.

"The goal of surveillance should be to look for everything – not just the species that currently pose the biggest threat – so we can be ready for what lies ahead," Sakamoto said. "The consequences of neglect of other ticks of potential epidemiological significance include missing changes in tick biodiversity, insufficient monitoring of vector expansion and the lack of detection of ticks. Introduced species, such as the recently discovered Asian horned tick in Pennsylvania.

"Conducting robust surveillance and badyzing historical data sets such as this one can help public health officials and researchers identify high-risk areas, discover ecological trends, and develop predictive models for badessing the risk." risk of tick-borne disease, "she said.