Tickborne diseases increasingly threaten the health of people in the United States. The growing threat includes newly discovered disease-causing germs, an increasing number of reported tickborne illnesses, expanding geographic ranges for ticks, and a novel tick species found in the US. New tools for preventing tickborne diseases are urgently needed, and everyone should take steps to help protect themselves from tick bites.
New Germs Identified
Over the past two decades, seven new tickborne germs that can cause illness have been identified in the United States: Borrelia mayonii, Borrelia miyamotoi, Ehrlichia ewingii, Ehrlichia muris eauclairensis, Heartland virus, Rickettsia parkeri, and Rickettsia species 364D. New laboratory tests that look for DNA are finding new germs in ticks and people. CDC’s Advanced Molecular Detection (AMD) program has supported research to more broadly detect bacteria that may be causing illness in patients with suspected tickborne disease.
Reported Cases Increasing
Recently state and local health departments have reported a record number of cases of tickborne diseases. The reported numbers of cases of Lyme disease, anaplasmosis/ehrlichiosis, spotted fever rickettsiosis (including Rocky Mountain spotted fever), babesiosis, tularemia, and Powassan virus disease all increased. Reported cases capture only a fraction of the overall number of people with tickborne illnesses. Even so, the number of reported cases of Lyme disease in the United States has tripled since the late 1990s.
Range Expanding
The geographic range of some ticks that spread germs also continues to increase. One example is the lone star tick, which continues to expand from its original territory in the southeastern United States into the northern and mid-western states.
In addition, the number of counties in the northeastern and upper midwestern United States that are considered high-risk for Lyme disease increased by more than 300% between 1993 and 2012. CDC’s tick surveillance program is tracking changes in where ticks (and germs in ticks) are found to better understand when and where people are at risk for tick bites and tickborne diseases.
Aside from causing infections, recent studies in the United States and other countries suggest that ticks may play a role in causing an allergy to mammalian meat (alpha-gal allergy).
New Tick Species
A new tick species, Haemaphysalis longicornis (the Asian longhorned tick) has been identified for the first time in the United States. In other countries, bites from longhorn ticks can make people and animals seriously ill.
How to Predict
Predicting the number of Lyme disease or other tickborne infections, including how an upcoming season will compare with previous years, is complicated. Ticks that spread germs to people can have up to 2- to 3-year lifecycles, and many factors can affect their numbers, including temperature, rainfall, humidity, and the availability of hosts for the ticks to feed on, such as mice, deer and other animals. In any given year, the number of ticks in an area will be different from region to region, state to state, and even county to county.
Know Your Risks
We cannot easily forecast how severe each tick season will be. However, we do know that every year hundreds of thousands of people are bitten by ticks and get sick. Therefore, people should be aware that ticks could be in the areas where they live, work and play. Everyone should take steps to help protect themselves and their loved ones, including pets.
While not all ticks spread the same germs, ticks can be found in every state. However, in the continental United States, some diseases occur more frequently in some areas than others:
Reported cases of Lyme disease, anaplasmosis, babesiosis, and Powassan virus disease are concentrated in the Northeast, mid-Atlantic, and upper Midwest, with pockets of lower risk along the West Coast. The range of the tick that transmits Lyme disease also is expanding.
Other serious tickborne diseases include Rocky Mountain spotted fever, ehrlichiosis, and Rickettsia parkeri rickettsiosis. More than 60 percent of spotted fever rickettsiosis cases (including RMSF) occur in five states: Arkansas, Missouri, North Carolina, Oklahoma, and Tennessee.
What You Can Do
Taking steps to protect yourself and your family from getting a tick bite is the best defense against tickborne diseases. Although the CDC recommends the use of permethrin on clothes, pets and in tick-preventative products, permethrin has been known to cause neurotoxicity in dogs, cats, and people.
Instead, we recommend doing the following:
Avoid areas with high grass and leaf litter and walk in the center of trails when hiking.
Treat dogs for ticks using non-toxic solutions such as Phleaz Organic Flea and Tick Lotion. Dogs are very susceptible to tick bites and to some tickborne diseases. They may also bring ticks into your home. Check dogs and cats regularly for ticks and remove quickly using tweezers.
Bathe or shower as soon as possible after coming indoors to wash off and more easily find crawling ticks before they bite you.
Conduct a full-body tick check using a hand-held or full-length mirror to view all parts of your body upon returning from tick-infested areas. Parents should help children check thoroughly for ticks. Remove any ticks right away.
Put dry clothes in a dryer on high heat for 10 minutes to kill ticks after you come indoors. If the clothes are damp, dry thoroughly and then tumble dry on high for 10 more minutes.
Resources - CDC Media Relations, (404) 639-3286, media@cdc.gov., Paul Mead, MD, MPH, Lyle Petersen, MD, MPH, Gil Kersh, PhD.
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