Analyzing the Movement of Tick Populations
Warmer weather has arrived, along with new questions and concerns over ticks, Lyme disease, and the large number of U.S. cases reported in the Northeast.
According to the CDC, there are 30,000+ cases of Lyme disease reported each year. Since national Lyme surveillance began, in the early 1990s, the number of annual Lyme cases has increased. Seasonal variations have contributed to what appears to be a northward expansion. These shifts are suspected to be associated with global climate change. Increases in temperature, changes in precipitation patterns, increases in extreme weather, and rising sea levels are capable of influencing the life cycle, distribution, and prevalence of vector-borne diseases by altering habitat availability and reproduction rates. Reasons contributing to the seasonal variability of tick activity and the probable northeast spread of Lyme disease are tick and host habitat range expansion, longer seasons for tick activity, and increased human exposure seasonally.
Lyme disease is a tick-borne disease caused by the bacterium Borrelia burgdorferi. It is transmitted to humans in the United States by the tick species Ixodes scapularis, the blacklegged tick or deer tick. Deer ticks require two years to complete their life cycle from egg to larvae to nymph to adult. They obtain one blood meal during each stage in order to molt and survive. If the source of the first blood meal; a mouse, bird, or other small animal is infected with Lyme, the tick also becomes infected and passes it on to its next host which in the Northeast is usually a larger mammal such as a deer or human. The increasing number of Lyme disease cases in the U.S. could be attributed to many factors, some of which are:
1. Habitat Range Expansion
Habitat range expansion occurs when individuals from a population migrate outside of their typical range and are able to survive and reproduce. This occurs through changes in the climate and changes in the environment. Deer tick population and distribution relies on the populations and distribution of their hosts, primarily white-tailed deer and white-footed mice. Depending on how far the host animal travels they have the availability to transport ticks short distances or very long distances.
2. Longer Seasonal Activity
Adult deer ticks are typically active from October-May but can be found year round if the temperature exceeds freezing. As the Northeast experiences earlier springs and longer fall seasons, this allows for an extended active adult tick season. Adult female deer ticks prefer larger hosts such as deer and humans. Once females fully engorge on their blood meal, they drop off the host into the leaf litter where they lay an egg mass (1500-2000 eggs) in late spring, early summer. Larvae emerge from the egg mass in late summer and can attach to any size mammalian host and many bird species. After a blood meal, the larvae will molt and re-emerge the following spring as a nymph.
3. Increased Human Exposure
The spring and summer are times of increased activity for both nymphal ticks and for human recreational activity outdoors. Nymphs are most active May-August. The poppy seed sized nymphs are known to be the most responsible for human disease transmission due to their extremely small size, often going unnoticed when attached. Additionally, the nymphal ticks have experienced increased disease exposure from infected hosts during the prior summer. Although ticks can attach to any part of the body, they often migrate to hard to see areas such as the groin, armpits, or scalp. If gone unnoticed for more than 48 hours the likelihood of disease transmission increases greatly. Public awareness posters, like the one shown above, are a great way to encourage park visitors to “Check Yourself For Ticks Everyday.” This message should also be considered for pets that spend time outdoors.
Benefits of an Integrated Tick Management Program
Reducing human exposure to Lyme disease can be implemented through an Integrated Tick Management (ITM) Program. Successful management efforts rely on knowledge of tick and host species biology so that timely surveillance and applications can be made during the appropriate life stages of the tick, ensuring the most effective control.
Any Integrated Tick Management Program should strive to reduce the risk of tick-borne disease transmission. This is best accomplished through education, surveillance, landscape management, and the judicious control of ticks while minimizing any negative impacts to non-target organisms in the area. Because it is often impossible to eradicate all ticks given their behavior patterns, resilient nature, and breeding potential, the program’s primary goal should be to manage tick populations within tolerable levels and simultaneously help prevent possible transmission of tick-borne diseases such as Lyme. To achieve this goal requires a combination of the most effective and scientifically sound methods of controlling ticks including surveillance, identification, disease testing, landscape management, targeted control, and public education.
Contact Us to Learn More About Effective Tick Management Strategies:
Since 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.