by George Looby, DVM
In recent years, ticks have become increasingly common. As a human health issue, they first came on the scene when the causative agent of Lyme Disease was first identified in 1975. The tick that carries the organism that causes Lyme Disease was given the name Ixodes scapularis commonly known as the black-legged tick. This tick has the ability to carry Lyme Disease and several others including Granulocytic anaplasmosis, Babesiosis and Borellia miyamotoi, commonly at the same time.
Much has been written about tick prevention and control and recently a new one has appeared on the scene. It is well known that tick’s preferred habitat is low lying shrubbery at the edges of fields and lawns. In some areas, a low growing invasive shrub named the Japanese barberry has taken over, crowding out native plants. This plant was imported into the Eastern U.S. in the late 1880’s as a replacement for the common barberry in landscape plantings. As with many other invasive plants it escaped from cultivation and now grows wild throughout the region. Its dense thickets prevent native trees and wildflowers from regenerating and also creates a humid environment under which ticks thrive. A Connecticut Agricultural Experiment Station research team found that managing barberry can effectively manage tick numbers for up to five years.
Control of the Japanese barberry is neither easy or quick. It is a tenacious plant that seems to be able to withstand a great deal of physical abuse. The best way is to dig up the plants and dispose of them in an area where they will not take root again. Hand work is slow and expensive unless the landowner is doing the work himself. Chemical sprays are effective especially in terrain where the use of machinery is difficult or impossible. Flame throwers are effective in the right hands with repeat treatments often necessary. Bush hogs and similar equipment can keep the growth down but it rarely completely kills the bush.
Recently found in Southern New England is the lone star tick. It has long been found in Texas where it is a carrier of the various organisms that cause animal and human diseases such as ehrlichiosis, southern tick-associated rash illness (STARI) and spotted fever, among others. The females are prolific egg producers with an annual average of 3,000 eggs per female. This tick has successfully overwintered in Connecticut and its northward migration is thought to be due at least in part to the increasingly warm winters. Control of the deer population is critical in the control of ticks and this is often difficult to accomplish in heavily populated areas such as Fairfield County in Connecticut. In areas such as that they seem to be almost as common a backyard pest as squirrels.
A finding that is tick related is the so-called red meat allergy. When a tick feeds on a non-human source such as white tailed deer it may pick up a particular type of carbohydrate called alpha gel, which humans and other primates do not possess. This material once in the system sets the stage. When that person eats red meat from almost any source there is a chance that the individual will develop an allergic reaction.
The University of Missouri, College of Veterinary Medicine has recently received a grant of $460,000 to study the tick-borne disease Anaplasmosis. The approach being used by Dr. Bill Stich and his associates is to try and develop a new means of controlling this disease in cattle. The Stich team will attempt to develop a vaccine using extracts from tick tissue to protect cattle against the disease. For many years, a variety of methods have been used to attempt to control ticks ranging from dips, sprays, and pour–ons with disappointing results. Caught in the early stages, the disease is responsive to antibiotics but it is an expensive and time consuming method of treatment. The use of antibiotics in food producing animals has been greatly restricted making the use of antibiotics even in sick animals somewhat less common than previously. The bacteria that most often causes the disease in the U.S. is called Anaplasma marginale. It is estimated that 80 percent of beef cattle in the U.S. are infested with ticks, making it readily apparent that a more effective means of controlling the disease is in order. This level of infestation makes the likelihood that a good percentage of those infested will also be infected with Anaplamosis.
The goal of the research will be to attack the germs before they can be transmitted to cattle. The strategy will be to use the immune response of the cattle to interfere with tick molecules that are required for the survival of the disease-causing bacteria in the ticks. To do this the team is targeting the two main parts of the tick where tick transmitted germs are most often found, namely the gut and the salivary glands. Understanding how disease causing organisms are maintained in the ticks that transmit them is the key. The team will examine just how tick molecules are involved in the development of bacteria and how immunization can be created to target the tick molecule.
As the season changes from fall to winter it is not a time to become complacent about tick control. The black-legged tick can remain active throughout the winter months especially on days when the temperature is in the 50-degree range. All of the well circulated means of tick control should be observed: Thorough examination of the body when undressing; using clothing that can be tucked in; staying away from areas which ticks prefer; and using repellents designed for such use.
Ticks that are removed should be submitted to one of two laboratories in the State of Connecticut for analysis to determine if it is carrying one of the known disease causing organisms:
- Connecticut Veterinary Medical Diagnostic Laboratory, 61 North Eagleville Rd., Storrs, CT 06269 or call 860-486-3738
- The Connecticut Agricultural Experiment Station, Tick Testing Laboratory, Slate Laboratory, Room #303, 123 Huntington St., Box 1106, New Haven, CT 06504