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Tick Season: Numbers, Diseases and Studies, all on the Rise

Traci Eatherton
for Tri-State Livestock News
Ticks are usually found in brushy areas or tall grass and trees.
Faina Gurevich, Getty Images

While March may have come in like a lion with freezing temperatures, the first month of spring is also the beginning of the dreaded tick season, which, according to experts, may also be on the lion’s path with heavier than normal infestations.

For 2021, “pest” forecasters are predicting that the warm-weather months in the US will be a boon for tick populations, and the weather conditions could extend tick season beyond the average. While http://www.pest.org has Wyoming and Montana as average for tick populations, the Plains, including Nebraska and the Dakotas, will likely see above-average infestations.

Black-legged ticks are spreading into new areas due to climate change, and they are bringing tick-borne diseases with them. Credit: USDA.

Ticks, which are related to arachnids (spiders), are parasites of any animal with a vertebra, according to the University of Wyoming. UW primarily sees two types of ticks in its diagnostic lab for identification – winter ticks and rocky mountain wood ticks.



Those are just two of approximately 900 species of ticks around the world, according to the Centers for Disease Control. The United States contends with only about 90 of them.

But these 90 pests are wreaking havoc on humans and animals. According to a CDC and Prevention report published in 2018, reported cases of tick-borne disease such as Lyme Disease, Rocky Mountain Spotted Fever and anaplasmosis more than doubled from 22,000 cases in 2004 to 48,000 cases in 2016. Ticks were responsible for 94 percent of vector-borne diseases in 2014.



Dog ticks can transmit cattle fever and other animal and human diseases. Photo by CDC/James Gathany

Tick Diseases in Animals

The six-legged critters are elusive transporters of a number of serious animal diseases, and along with the diseases, ticks cause skin wounds that may lead to bacterial infections or become a host for screwworms.

“Ticks are notorious spreaders of disease in man and beasts,” said William Marlatt, DVM, Belle Fourche Veterinary Clinic. Marlatt said that cattle can be afflicted by anaplasmosis, tick paralysis, Texas Cattle Fever, and possibly “Q fever,” and horses can get equine piroplasmosis.

“I have personally seen a tularemia outbreak in the past in western South Dakota. It in volved a cat, a few foals, and a sheep flock. The effects on the flock of sheep was particularly devastating,” Marlatt added.

Marlatt said the most common problems with tick infestation in livestock is blood loss, causing potential anemia, pain from multiple bites, secondary infections from the bites, and stress. He added that in some cases, death can be the result from a tick infestation on an animal. The winter tick (Dermacentor albipictus) is a particular problem in deer, moose, and elk, including the captive ones.

“Since there are several diseases that ticks may transmit, the clinical signs are varied. Certainly, an animal with weight loss, poor thrift, and ticks are seen attached, should be checked out,” Marlatt said.

According to the American College of Veterinary Internal Medicine, both dogs and horses are susceptible to Lyme disease. The number of canine Lyme disease cases increased from 245,971 in 2015 to 336,200 in 2019. Increases in the numbers of other tick-borne diseases were also reported, including canine anaplasmosis, up from 117,203 in 2015 to 207,825 in 2019, and canine ehrlichiosis, up from 107,985 in 2015 to 186,075 in 2019.

Tick Diseases in Humans

According to http://www.pest.org, there are a number of tick diseases that are dangerous to humans, but the two most common in the Plains region are Lyme disease and Rocky Mountain Spotted Tick Fever.

Lyme disease is spread by deer ticks (blacklegged ticks) in the eastern U.S., and in the western U.S., it is spread by the western blacklegged tick and the Rocky Mountain wood tick. Lyme disease typically shows itself as a “bull’s-eye” rash with a ring of red skin around a red and swollen tick bite, according to pest.org. Additional symptoms are fever, fatigue, and headaches, and if left untreated, the disease can spread to the nervous system.

There are more than 30,000 cases of Lyme disease reported to the CDC each year, but the agency expects the actual number of cases to be 10 times that amount.

Rocky Mountain Spotted Fever is a severe bacterial disease that can affect human organs if left untreated for an extended period of time. It is spread by a number of ticks, including the Rocky Mountain wood tick, the American dog tick, the brown dog tick, and more.

The primary symptoms of Rocky Mountain spotted fever are a fever, headaches, nausea, and a rash. It can take up to two weeks for symptoms to appear, according to pest.org, but rashes usually show up within four or five days. Kidney failure, brain inflammation, lung inflammation, limb amputation and even death can all be results if untreated.

Another tick born disease, Babesiosis, is transmitted by the deer tick or blacklegged tick. It is far more rare than Lyme disease or Rocky Mountain spotted fever, but the symptoms are just as severe, and include fever, chills, nausea, body aches, and fatigue, and if left untreated can cause death, according to the New York Department of Health. Babesiosis is most commonly found in the Northeast in states such as New York and Connecticut. About 1,000 to 2,000 cases are reported every year.

Tularemia is spread by the American dog tick and the Rocky Mountain wood tick, among others. It can infect humans and animals, and it can be spread from infected animals to humans. General symptoms include fever, abdominal pain, fatigue, and nausea, though other symptoms differ depending on which version of tularemia you have. These symptoms range from chest pain to ulcers to conjunctivitis. Cases of tularemia have been reported in every continental state and Alaska, according to pest.org.

Ehrlichiosis is spread by the lone star tick in the Southeast and Midwest. This disease can cause symptoms like general soreness around the body, fever, abdominal pain, diarrhea, and rash. The symptoms typically take around 5 to 14 days to develop.

Anaplasmosis is spread by deer ticks or blacklegged ticks. Anaplasmosis is most often found in the same general region as Lyme disease, which includes the Northeast and Midwest. Cases of anaplasmosis have increased d from a few hundred cases in 2000 to more than 5,000 in 2017.

Tick Control on the Ranch

So, what to do about these pesky creatures? Obviously the best answer would be to avoid them, but in the ag business, that probably is not an option.

Cutting back brush and weedy areas in pastures can help, according to extension specialists, and for the adventurous, adding guinea hens to the family flock can also be a benefit in and around the homestead, as they are tick-eating machines.

Chemicals are also useful, for both humans and animals. But with livestock, pay attention to withdrawal times, and follow instructions.

“Treatment usually involves topical administration of a permethrin,” Marlatt say s. “This works well in cattle, sheep, goats, and horses.”

Fipronel 1 percent, a broad use incecticide, is another option for ticks on horses, according to Marlatt, and amitraz, an acaricide used in the control of ticks, mites, and lice, has been successfully used in captive deer and elk for winter tick control, and some other species, according to Marlatt.

“DO NOT put amitraz on a horse,” Marlatt warned. In a study published in the National Library of Medicine, researchers found that 3 out of 4 horses displayed typical clinical signs of tranquillization, depression, ataxia, muscular incoordination and impaction colic lasting up to 6 days, following the use of amitraz.

Ivermectin, another option for tick control, is not always ideal, as it only affects the ticks actively feeding on the animal, according to Marlatt.

“Ivermectin can reduce tick numbers but doesn’t seem as effective as other products,” Marlatt said.

While these are just a few options, tick control is something to take seriously, and working with a veterinarian or extension specialist is recommended.

Repelling Ticks

Once again, the best tick control is to avoid ticks, which is not completely possible. So a plan B for avoiding ticks includes knowing exactly where to expect ticks – grassy, brushy, and wooded areas, and on animals.

CDC recommends treating clothing and gear with products containing 0.5% permethrin. Permethrin can be used to treat boots, clothing and camping gear and remain protective through several washings. Alternatively, you can buy permethrin-treated clothing and gear.

Another option is using Environmental Protection Agency registered insect repellants containing DEET, picaridin, IR3535, Oil of Lemon Eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone.

Products containing OLE or PMD should not be used on children under 3 years of age, according to CDC.

Tick Research

Annually-reported cases of tickborne disease more than doubled between 2004 and 2018, according to CDC, with seven new tickborne germs discovered. But a clear gap exists in our public health infrastructure, according to researchers. That gap has opened the door for tick studies and a number of universities in the United States are actively studying tick populations and tick diseases.

In December 2019, the Kay Hagan Tick Act (named after former Senator Kay Hagan, who passed away in 2019, due to complications from the tick-borne disease known as the Powassan virus) was signed into federal law, authorizing $150 million for tick-borne disease research.

The University of South Dakota research, led by Hugh Britten, Ph.D., a professor in the Department of Biology, is working with the South Dakota Department of Health (DOH) to survey tick populations throughout eastern South Dakota to learn more about tick-borne diseases.

The goal for Britten and his team is to carry out systematic surveys for black-legged, or deer, ticks in eastern South Dakota. The black-legged tick is an important vector for borrelia burgdorferi, the causative agent of Lyme Disease.

“Tick surveillance has become a priority in recent years as Lyme Disease and other tick-borne illnesses have spread in the U.S.,” said Britten. “The black-legged tick had not been reported present in South Dakota until 1992 when it was found on a deer in Brookings County and a dog in Codington County. It is hypothesized that some tick species carry important human disease organisms and have been able to expand their geographic ranges due to global climate change.”

Britten credits his graduate and undergraduate student researchers, who have made multiple discoveries to advance the tick research. He said that the project began with Lauren Maestas, a former graduate assistant in the department.

“Lauren was fascinated by ticks but came to USD to research fleas and plague in small rodents and prairie dogs,” said Britten. “As a side project, he did some tick surveillance in eastern South Dakota and discovered a black-legged tick population in four counties between 2015 and 2017.”

Britten and Maestas began to collaborate with researchers at Texas A&M University and found that one of the black-legged ticks was carrying the Lyme Disease organism. Maestas published two papers on his findings, which caught the attention of Joshua Clayton, Ph.D., M.D., the state epidemiologist with the South Dakota DOH, in 2019.

Holly Black, an undergraduate student within the biology department, discovered an established population of lone star ticks in Clay and Union County — counties the Centers for Disease Control and Prevention once considered to be outside the range for that species of ticks.

“The lone star tick is a primary vector for human monocyte ehrlichiosis and carries the causative agents of tularemia, spotted fever rickettsioses like Rocky Mountain spotted fever and the development of a red meat allergy,” said Britten. “It is important that Holly made this discovery as health care professionals can now become informed and diagnose patients accordingly.”

According to Hanna DeLange, USD public relations specialist, the final results of this study are scheduled to be released soon.

University of Idaho researchers are leading a nearly $6 million National Science Foundation (NSF) cooperative agreement, using large and complex data sets to improve prediction and response measures for tick-borne diseases.

“Tick-borne disease is widespread, but it’s not only a human illness. It can infect animals such as horses and cattle, too,” said Xiaogang “Marshall” Ma, computer science assistant professor and research team lead. “For big agricultural states such as Idaho, having the proper response protocols in place is essential to protect our communities as well as our economy.”

U of I is part of the four-year NSF project with the University of Nevada, Reno, and Dartmouth College. Researchers are designing a data framework to organize data and track movement of tick-borne diseases across the U.S., particularly east to west, where reported cases are low and data points are widespread.

“The thing about tick data is, once you get out of the Midwest and East Coast, these data are very sparse,” said Lucas Sheneman, grant participant and director of U of I’s data management center. “Databases that are out there are so siloed, they don’t communicate with each other. What we’re proposing is developing one comprehensive data framework to offer compatible resources to scientists and the general public.”

Ma said the data framework will help researchers analyze the role numerous factors, including outdoor activity, geographical location, and climate, play in tick-borne disease transmission. Socioeconomic factors will also be considered.

In Texas, coauthors of a study at Texas A&M, including Pete Teel, Ph.D., said that while Texas has monitored and controlled ticks since 1893, a nationwide database is needed.

The study’s authors surveyed 140 vector-borne disease professionals working at state, county and local agencies in fall 2018. Reaching even that many respondents proved challenging, the authors said. No central database of tick-management programs or contacts was available.

“Ticks are responsible for the majority of our vector-borne illnesses in the U.S., and our programming does not adequately meet the need in its current form, for both surveillance and control,” Emily Mader, public health researcher, and lead author, shared in a press release.

In Texas, early detection and control have led to discoveries of exotic ticks, Teel said. These efforts kept the ticks from becoming established.

“These ticks could have introduced several devastating diseases with high risks for humans, livestock and wildlife,” he said. “National databases for the kinds of ticks that are present, and how those populations change with time and space, would be hugely informative for public health and animal health needs.”

Another recent study published in the journal Global Ecology and Biogeography used machine learning to identify bird species with the potential to transmit the Lyme disease bacterium to feeding ticks. The team developed a model that identified birds known to spread Lyme disease with 80 percent accuracy and flagged 21 new species that should be prioritized for surveillance.

“Birds don’t spread Lyme directly to people, but they can carry infected ticks to new locations with no history of Lyme occurrence. A tick could drop off a bird and into a garden or yard, where it could later bite and infect a person. If local medical practitioners are unfamiliar with Lyme symptoms, proper diagnosis could be delayed. Identifying where ticks are spreading could improve medical response to Lyme and other tick-borne diseases,” shared Daniel Becker, Department of Biology, Indiana University.

 


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