Ticks and Lyme Disease in the News

Features - Public Health

Lyme disease numbers are at an all-time high and a new tick is moving rapidly throughout the country. Here’s an update on what you need to know about ticks and tick-borne diseases.

August 11, 2019

Susan Ellis; Bugwood.org
The Lyme disease bacterium, Borrelia burgdorferi, is spread through the bite of infected ticks. The blacklegged tick (right) spreads the disease in the northeastern, mid-Atlantic, and north central regions of the United States.

Hopefully by now, PMPs across the United States and territories have heard about the invasive Asian longhorned tick (ALT), Haemaphysalis longicornis, which was discovered in new Jersey in late 2017. New Jersey was the first state to report the tick, which was found on a sheep. The Rutgers Center for Vector Biology confirmed that longhorned ticks, which are native to northeastern Asia, have been present in New Jersey since at least 2013. The lab determined this through DNA analysis of a tick specimen collected from a dog in Union County during the spring or early summer of 2013. This finding was also confirmed by USDA National Veterinary Services Laboratories (NVSL) experts.

What makes this tick different is its ability to clone itself. This tick can reproduce asexually, meaning a single unfertilized female can produce many offspring without mating, allowing these ticks to spread rapidly. Identification is difficult as it resembles a rare rabbit tick. Researchers look for two triangular, hornlike spurs on the adult Asian longhorned tick’s mouthparts. If a suspected Asian longhorned tick is found in the field, it is best to bring ticks back to the office for proper identification.

Since 2017, 45 counties (or county equivalents) in New Jersey and eight other states — Arkansas, Connecticut, Maryland, North Carolina, New York, Pennsylvania, Virginia, and West Virginia — have reported finding the tick on a variety of hosts, including people, wildlife, domestic animals and in environmental samples. The Centers for Disease Control and Prevention (CDC) says, “The presence of H. longicornis in the United States represents a new and emerging disease threat. Characterization of the tick’s biology and ecology are needed, and surveillance efforts should include testing for potential indigenous and exotic pathogens.”

This tick primarily feeds on livestock and can transmit diseases such as Severe Fever With Thrombocytopenia Syndrome (SFTS). It can be found on domestic animals including cats, dogs, goats, horses and sheep. Wildlife carriers/hosts include coyote, white-tailed deer, gray fox, groundhog, opossum, raccoon and, of course, humans.

LYME DISEASE. Vector-borne diseases such as Lyme disease are in the news and infection rates are on the increase in the U.S. The American Journal of Tropical Medicine and Hygiene says, “Mosquito-borne and tick-borne disease incidence is increasing in the United States, with a tripling of reported cases annually from 27,388 cases in 2004 to 96,075 cases in 2016. Two distinct trends account for this increase: steadily increasing tick-borne disease incidences and interspersed, sporadic outbreaks caused by an expanding array of domestic and invasive mosquito-borne pathogens. Acceleration of many underlying causes of these trends, such as expanding travel and trade, urbanization, changing land use, increasing temperatures, and population growth, portends that public health and health-care delivery systems will continue to face an expanding spectrum of vector-borne pathogens of increasing incidence and distribution.”

The CDC reports 75 percent of Lyme disease cases are contracted in residential backyards. A CDC report from 2014 shows 2,589 confirmed cases of Lyme disease in New Jersey. Blacklegged tick activity in New Jersey was down in some areas due to a wet spring and cool temperatures. Regional activity varies with this tick due to many circumstances such as weather, host health and availability. Recent data from CDC shows that tick-borne disease cases are significantly higher than mosquito-borne diseases from 2004-2016 (downloadable here). Nationwide cases of Lyme disease are thought to be around 300,000 in the U.S.

Blacklegged ticks (Ixodes scapularis), formerly called deer ticks, are the primary vector for Lyme disease. Lyme disease is an illness caused by infection with a spirochete; a corkscrew shaped bacterium Borrelia burgdorferi (boar-ELL-ee-uh burg-dorf-ERR-eye).

To effectively manage disease-causing ticks and to create a tick-resistant garden or property, residents need to be educated and understand how the blacklegged tick lives. It takes two years for this tick to complete its life cycle. Females lay eggs in May. Eggs hatch into larvae in July into early August and feed on mice, chipmunks and birds. They drop off and molt to nymphs, over-winter, and appear the following spring with May, June and July being the peak months for nymphal activity. They appear before newly hatched larvae and feed on rodents and birds — many already infected and others that they now infect.

Nymphs molt to adults that feed on large mammals including deer, humans and pets. Female adults are active in fall and on warm winter and spring days. A blood-filled female blacklegged tick produces one batch of 2,000 to 3,000 eggs, then dies. Most ticks don’t survive to the next stage. Most larvae do not successfully feed to become nymphs and many nymphs do not successfully feed to become adults. And many adults do not find a host.

Nymphs overwinter and stay active in rodent burrows, such as burrows made by chipmunks, white-footed and deer mice. Ticks can be active in leaf-litter, keeping warm in winter months. Ground-foraging and ground-nesting birds are another preferred food for blacklegged larval ticks. Ticks pick up the spirochete while feeding on field mice and other reservoirs of Lyme disease. Birds readily pick up the ticks when they’re on the ground and in one study it was found that more larval ticks came from robins and other birds than from mice. Deer are infected with the spirochetes and mount a detectable antibody response, however, the deer immune system is good at eliminating the bacteria so that is part of the reason they are disease free, but this is the main reason they are not reservoirs for the spirochete; i.e., they can’t infect the ticks feeding on them. More than 90 percent of adult ticks feed on deer. Studies on islands with high deer densities (more than 100 deer/square mile) have superabundant tick populations. Islands without deer do not appear to support I. scapularis or B. burgdorferi.

Having a fenced property with no deer means short-circuiting the blacklegged tick’s life cycle. If female ticks aren’t off deer to lay eggs, they’re not going to have so many ticks feeding on rodents. That means no larvae (or fewer nymphs) and even fewer adults.

Some other tips to keep ticks out of your customer’s property include removing leaf litter; clearing tall grasses and brush around homes and at the edge of lawns; placing a 3-foot wide barrier of wood chips or gravel between lawns and wooded areas to restrict tick migration into recreational areas; mowing the lawn frequently; stacking wood neatly and in a dry area (which discourages rodents); keeping playground equipment, decks and patios away from yard edges and trees; and discouraging unwelcome animals (such as deer, and stray dogs) from entering the yard by constructing fences.

Integrated Pest Management control practices are best for tick reduction programs. Once IPM methods are employed, most PMPs use backpack or powered mist sprayers with residual insecticides to control ticks that are questing and waiting for a host to walk by. Dr. Kirby Stafford of the Connecticut Ag Tick Research Center, speaking at the PCT Public Health Virtual Conference, said that his field data shows control with backpack sprayers and powered mist blowers yield the same results.

The North Central IPM Center has a publication titled “Tick Management Options.” This document lists information about products and treatments. Since most yard treatment programs are geared toward mosquitoes, many PMPs are strengthening their programs to focus more on ticks. Several products for ticks actually kill ticks where sprays can not reach them, such as in the nests of field mice. This IPM bulletin mentions products like Thermacell Tick Control Tubes or Damminix Tubes with permethrin. Tick Box and the 4-Poster Deer Self-treatment Device are also mentioned. Personal protection, such as repellents, and how to avoid ticks before and after exposure in tick-infested areas are covered as well. This bulletin can be found here.

William A. Kolbe, is a board certified entomologist for WAKOLBE Consulting. He has a bachelor’s degree in entomology with a minor in ecology from the University of Delaware. Kolbe started his career in professional pest management in June 1974. He can be reached at wakolbe@gmail.com.