Could anaplasmosis, which is caused by the Anaplasma phagocytophilum bacterium, spread from China to be the next Lyme disease in the U.S.? After all, both diseases are transmitted by ticks -- small arachnids that live in wooded areas, brushy fields and around the home, and survive by feeding on the blood of the host.
Turns out it found a home a while ago in the U.S. "Anaplasmosis is a disease that is already endemic in some parts of the U.S., particularly the Northeast and upper Midwest," says Dr. Joanna Regan, a medical epidemiologist at a branch of the U.S. Centers for Disease Control and Prevention. However, "more research is needed to assess whether strains of A. phagocytophilum circulating in the U.S. are different from strains currently found in China," she adds.
"In the U.S., the tick responsible for transmission of A. phagocytophilum in the upper Midwest and Northeast is the black-legged tick (Ixodes scapularis). Along the West Coast, the western black-legged tick (I. pacificus) may transmit the organism," Regan explains. States reporting the highest incidence of anaplasmosis in 2008 were Minnesota, Wisconsin and New York (upstate).
Humans and Ticks Get Closer
Anaplasmosis and Lyme disease, named after the town of Lyme, Conn., where it was first identified in 1975, are transmitted by the same ticks. Lyme disease is by far most likely to afflict people in the Northeast, although it has spread more widely and is the most common tick-borne disease reported in the U.S. The Lyme disease bacterium, Borrelia burgdorferi, normally lives in mice, squirrels and other small animals. It's transmitted among these animals -- and to humans -- through the bites of certain species of ticks.
Greater tick densities and encroachment of human development into rural and suburban areas explain the increase in cases of Lyme disease in states with high incidence, such as Connecticut, Massachusetts and New Jersey. Geographic expansion of the ticks explains the rise in cases in states such as Minnesota, Pennsylvania and Wisconsin. Most likely, the same dynamics are at play with the spread of anaplasmosis in China.
The two diseases differ in their symptoms. The first symptom of Lyme disease after the poppy-seed-size tick makes its bite, is usually a bulls-eye-shaped rash in the area of the bite. The rash is followed by flu-like symptoms such as fever, headache and fatigue. If left untreated, Lyme disease can lead to recurrent attacks of painful and swollen joints, numbness in the limbs and heart problems because the infection can spread to joints, nervous system and heart.
With anaplasmosis, the majority of people infected experience nonspecific symptoms five days to three weeks after the tick bite, such as headaches, fever and chills that can be confused with common diseases such as influenza. Some individuals who become infected don't become ill or experience only very mild symptoms and don't seek medical treatment.
While anaplasmosis has a high incidence rate among those age 60-plus, Lyme disease is observed disproportionately in children and in young males compared with other demographic groups.
Anaplasmosis Is Rarely Fatal
Luckily, both infections can usually be treated successfully with a few weeks of antibiotics, particularly doxycycline, according to guidelines developed by the Infectious Disease Society of America. But forgoing or delaying treatment for anaplasmosis can lead to serious, even fatal complications, the CDC says. And because anaplasmosis causes symptoms that are similar to other, less-severe diseases, many people don't receive prompt treatment for it.
While deaths have been reported from anaplasmosis in the U.S., Regan says such fatalities are "uncommon and represent less than 1% of known cases." She adds: "Persons who are of older age and who are immunocompromised are at increased risk for severe infection."
And as if this isn't disturbing enough, Regan notes that in the U.S. "there are already several tick-borne diseases that can cause severe or fatal human illness, including Rocky Mountain spotted fever (caused by Rickettsia rickettsii), ehrlichoisis (caused by Ehrlichia chaffeensis) and anaplasmosis, among others. Physicians practicing in areas where these diseases may occur should maintain a high degree of vigilance when treating patients who have symptoms compatible with tick-borne diseases, and should prescribe doxycycline as the treatment of choice in persons of all ages."
Either way, everyone agrees that the best defense against Lyme disease -- and anaplasmosis -- is by reducing exposure, using insect repellent, removing ticks promptly, landscaping and integrated pest management.