May 26, 2022 at 11:06 a.m.
Webinar focuses on tick-borne illnesses in Wisconsin
Webinar focuses on tick-borne illnesses in Wisconsin
The two most common types of ticks in Wisconsin are the wood tick, or American dog tick, and the deer tick, also known as the blacklegged tick, she explained. The deer tick is responsible for the transmission of the majority of human diseases. Lyme disease is the most prevalent, she said, but there are also rare cases of Anaplasmosis, Ehrlichiosis, Babesiosis, Powassan virus, Relapsing fever and diseases in the spotted fever group, as well.
When looking at reporting of Lyme disease, Paskewitz said, it is estimated that reporting is underestimated approximately tenfold. In recent years, the number of cases reported have been holding steady at 3,000-4,000. However, with the estimated under-reporting, that number is more likely to be 30,000 to 40,000, she said.
Biology
Paskewitz discussed tick biology, as well. In each stage of life, ticks look somewhat similar to their other stages, which makes them easier to identify. It takes between two and three years for an egg to become an adult. The eggs hatch into a six-legged larvae. From there, the next stage is the eight-legged nymph. After this stage, the nymph morphs into an adult. This is the first stage at which sex is determined. Paskewitz said researchers have not been able to determine sex of a tick before it becomes an adult. There are no identifying characteristics, she said.
It is at the nymph stage where ticks do most of their pathogen transmission. They pick up diseases while feeding on small wildlife such as mice, shrews and chipmunks. They can get infected as a larvae or a nymph, and once they carry the disease, they will carry it throughout their life cycle.
Adult ticks feed on larger animals. It can take up to seven days for the female tick to receive a full blood meal. Deer are important to the life cycle of the tick, and ticks can often be found on deer. They are not, however, a vector for transmission. They are not a reservoir for the Lyme disease pathogen, she said. They do keep the cycle going, though, by providing food for the ticks.
Ticks are extremely susceptible to drying out. For that reason, they are not often found in large numbers in open, sunny places, such as manicured lawns. They tend to stay in forest environments and in places where they can stay moist, such as edges of lawns, shrubs or in leaf litter.
History
Paskewitz spoke about the history of deer ticks in Wisconsin. The first ones, she said, were found in 1958 by forestry workers in Lincoln County. It was not until the 1960s that the link between deer ticks and Lyme disease was established.
She spoke about a study that looked at ticks on deer. It started in 1970 on the first day of the gun-deer season. Researchers asked hunters if they could look at their deer and collect all of the ticks off of the deer. They would then bring all the ticks back to the lab and collect data on them. The first survey showed deer ticks in the Northwestern part of the state, as did the 1981 collection efforts. By 1994, researchers were seeing more deer ticks in the central part of the state. By the 2008-2009 portion of the study, deer ticks were seen all over the state. Ticks, she said, have not been static. They have been moving and spreading since they were first found. There are now established populations in all counties in the state.
Looking at the history of virgin forests in the country in the last 100-150 years, the amount of forests that were logged off from 1850-1926 removed a great deal of habitat for ticks. Over harvest of deer in that time period, too, also likely contributed to the smaller area in which ticks could live successfully. Ticks were relegated to a few small habitats that could support them, she said.
Control
Public health entomologist Xia Lee took over the second half of the tick talk. He spoke about control of ticks and prevention of tick bites. One of his recommendations was to create tick safe zones. This would include removing leaf litter, shrubs and invasive species such as Japanese barberry. Invasive species, such as Japanese barberry, honeysuckle and buckthorn create habitat not only for ticks, but for small animals on which nymphs find their blood meals. In his study with removing Japanese barberry, he found a 45% reduction in ticks in the environment, but did not find any substantial difference in ticks on small animals in the area. This was likely because animals are more mobile, he said, and may have traveled outside of the area where the invasive species were removed.
He also studied whether mowing had an effect on the number of ticks both in the environment and on animals in the area. He found that mowing trails did not have any effect on the number of ticks in either the environment or an animals in the area.
Lee also looked at the effectiveness of tick tubes. These tubes were built to attract white-footed mice. They were filled with cotton treated with permethrin insecticide. The idea was the mice would bring the cotton back to make their nests. The ticks feeding on those mice would then be killed by the insecticide. This test proved the tick tubes were effective. There were 54% fewer ticks in the environment after placing these tubes and he saw a 90% reduction in the number of ticks on the white-footed mice in the study.
Prevention
Under the heading of preventing bites, Lees said, "nothing beats DEET." He said people should look for products with 40% DEET in them. Permethrin products used to treat clothing are also very effective, he said.
Lee also recommended wearing high rubber boots. The nymph stage of the ticks tend to be found in lower locations, and rubber boots have been proven to be effective in keeping ticks off of researchers in the field.
Tick removal
When removing a tick, they should be grabbed by the mouth parts, not the body, Lee said. They should then be pulled straight up and out of the skin. Deer ticks have longer mouth parts and also secrete a cement-like glue that binds their mouth parts to skin. This can make them more difficult to remove. Alternatively, a Tick Tornado can be used to twist the tick out and is often more effective.
Beckie Gaskill may be reached via email at [email protected].
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