(Photo Credit- CDC)
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Ehrlichiosis (aka HME) is the generic name used to describe an infection that affects the white blood cells of humans and other mammals caused by several varieties of tickborne bacteria.
Similar to Anaplasmosis (HGA), the two are differentiated by the type of white blood cells they affect (HGA affects granulocytes and HME affects monocytes), and the bacterial cause of the infection.
Until recently, Ehrlichiosis has been identified with just two bacterial infections: Ehrlichia chaffeensis and E. ewingii.
Anaplasmosis, on the other hand, is caused by Anaplasma phagocytophilum infection.
The CDC maintains an extensive Ehrlichiosis web page, that includes epidemiological data and prevention advice. The following map shows the incidence of Ehrlichiosis by state in 2008.
Today, the NEJM has an article that describes the discovery of a third bacterial cause of Ehrlichiosis detected first detected in Minnesota and Wisconsin in 2009.
Emergence of a New Pathogenic Ehrlichia Species, Wisconsin and Minnesota
August 4, 2011 | B.S. Pritt and Others
A newly discovered ehrlichia species closely related to E. muris was identified as a cause of illness in three people in Minnesota and one in Wisconsin. The syndrome is described, and the likely vector identified. Physicians need to be aware of this new ehrlichia species to ensure appropriate testing, treatment, and regional surveillance.
Briefly, 4 patients showing signs and symptoms of ehrlichiosis, but who did not test positive for E. chaffeensis or E. ewingii, underwent additional testing.
They were found to be infected by a previously unidentified ehrlichia species, which has provisionally been designated Ehrlichia muris-like (EML).
Subsequently, PCR analysis of 697 Ixodes scapularis ticks collected in Minnesota & Wisconsin showed that 17 were positive for this newly discovered ehrlichia species.
The good news is that this bacterial infection appears to respond well to the same treatment (Doxycycline) as the other forms of ehrlichiosis.
The list of tickborne illnesses that one may encounter in the United States is long, and growing. As my last blog indicated (see NRDC Report: Climate Change and Health Threats) climate change may affect the size and geographic spread of many of these vector-borne diseases.
The CDC lists a number of diseases carried by ticks in the United States, including:
- Anaplasmosis is transmitted to humans by tick bites primarily from the blacklegged tick (Ixodes scapularis) in the northeastern and upper midwestern U.S. and the western blacklegged tick (Ixodes pacificus) along the Pacific coast.
- Babesiosis is transmitted by the blacklegged tick (Ixodes scapularis) and is found primarily in the eastern U.S.
- Ehrlichiosis is transmitted to humans by the lone star tick (Ambylomma americanum), found primarily in the southcentral and eastern U.S.
- Lyme disease is transmitted by the blacklegged tick (Ixodes scapularis) in the northeastern U.S. and upper Midwestern U.S. and the western blacklegged tick (Ixodes pacificus) along the Pacific coast.
- Rickettsia parkeri Rickettsiosis is transmitted to humans by the Gulf Coast tick (Amblyomma maculatum).
- Rocky Mountain Spotted Fever (RMSF) is transmitted by the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), and the brown dog tick (Rhipicephalus sangunineus) in the U.S. The brown dog tick and other tick species are associated with RMSF in Central and South America.
- STARI (Southern Tick-Associated Rash Illness) is transmitted via bites from the lone star tick (Ambylomma americanum), found in the southeastern and eastern U.S.
- Tickborne relapsing fever (TBRF) is transmitted to humans through the bite of infected soft ticks. TBRF has been reported in 15 states: Arizona, California, Colorado, Idaho, Kansas, Montana, Nevada, New Mexico, Ohio, Oklahoma, Oregon, Texas, Utah, Washington, and Wyoming and is associated with sleeping in rustic cabins and vacation homes.
- Tularemia is transmitted to humans by the dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersoni), and the lone star tick (Amblyomma americanum). Tularemia occurs throughout the U.S.
- 364D Rickettsiosis (Rickettsia phillipi, proposed) is transmitted to humans by the Pacific Coast tick (Dermacentor occidentalis ticks). This is a new disease that has been found in California.
This list should help illustrate the importance of everyone becoming `tick aware’, and doing what they can to avoid exposure.
The CDC suggests taking the following precautions:
Preventing Tick Bites
While it is a good idea to take preventive measures against ticks year-round, be extra vigilant in warmer months (April-September) when ticks are most active.
Avoid Direct Contact with Ticks
- Avoid wooded and bushy areas with high grass and leaf litter.
- Walk in the center of trails.
Repel Ticks with DEET or Permethrin
- Use repellents that contain 20% or more DEET (N, N-diethyl-m-toluamide) on the exposed skin for protection that lasts up to several hours. Always follow product instructions. Parents should apply this product to their children, avoiding hands, eyes, and mouth.
- Use products that contain permethrin on clothing. Treat clothing and gear, such as boots, pants, socks and tents. It remains protective through several washings. Pre-treated clothing is available and remains protective for up to 70 washings.
- Other repellents registered by the Environmental Protection Agency (EPA) may be found at http://cfpub.epa.gov/oppref/insect/.
Find and Remove Ticks from Your Body
- Bathe or shower as soon as possible after coming indoors (preferably within two hours) to wash off and more easily find ticks that are crawling on you.
- Conduct a full-body tick check using a hand-held or full-length mirror to view all parts of your body upon return from tick-infested areas. Parents should check their children for ticks under the arms, in and around the ears, inside the belly button, behind the knees, between the legs, around the waist, and especially in their hair.
- Examine gear and pets. Ticks can ride into the home on clothing and pets, then attach to a person later, so carefully examine pets, coats, and day packs. Tumble clothes in a dryer on high heat for an hour to kill remaining ticks.
