An emerging disease spread by ticks is becoming a substantial public health threat in New York State, researchers warn in a new study out this month. The study found that human cases of anaplasmosis have dramatically increased in the state over the past decade, and ticks are found to be carrying the bacteria responsible for it more frequently.
Anaplasmosis is caused by the bacteria Anaplasma phagocytophilum, which needs to invade white blood cells to survive. It’s spread by the same two species of tick known to carry Lyme disease in the U.S., the blacklegged or deer tick (Ixodes scapularis) in the East and the western blacklegged tick (Ixodes pacificus) on the Pacific coast. Early symptoms, which usually appear a week or two after a bite, include fever, headache, and vomiting. But it can also progress to more serious symptoms such as bleeding, organ failure, and ultimately death. These severe cases are more common in people with already weakened symptoms or when the initial infection isn’t promptly treated with antibiotics.
“Unlike Lyme disease, another tickborne infection with similar early symptoms that can become debilitating but rarely causes death, anaplasmosis can kill if left untreated,” study author Melissa Prusinski, a researcher with the New York State Department of Health’s Bureau of Communicable Disease Control, told Gizmodo in an email.
The disease was first recognized in the 1990s, but it wasn’t nationally tracked by health agencies until 1999. Though cases of anaplasmosis remain low relative to Lyme disease, the most commonly reported tickborne illness, its incidence has steadily grown over time. In 2018, there were around 4,000 cases reported nationally, according to the Centers for Disease Control and Prevention, up from 348 cases in 2000 (that said, 2018 was a down year from the highest peak in 2017, which saw 5,762 cases).
This new study, published in the CDC journal Emerging Infectious Diseases, indicates that parts of New York have become a major hotspot of anaplasmosis activity.
Prusinski and her colleagues looked at surveillance data collected by the state between 2010 and 2018. This data not only included reported cases in people but also information from expeditions into tick territory to collect and study live samples.
All told, there were 5,146 anaplasmosis cases reported in New York State (excluding New York City) during those years, with a similar downward year in 2018 as seen nationally. But the general surge was concentrated around the Albany region, with cases skyrocketing eightfold there. The incidence of deer ticks carrying the bacteria also rose, from 2.4% of ticks estimated to have it during 2010 to 4.5% of ticks during 2018. Since 2015, anaplasmosis has become the second most diagnosed tickborne illness in New York, after Lyme.
“Our work has shown that anaplasmosis has increased dramatically in certain regions of New York State in recent years, driven partly by an increase of infected ticks in these areas,” Prusinski said. “The size of the area most impacted by anaplasmosis has been shifting and expanding over time, placing more New York State residents at risk.”
Like other diseases spread by ticks and insects, there are multiple factors behind the rise of anaplasmosis in New York and elsewhere. One important player is climate change, with warmer temperatures over longer periods of time allowing tick populations to grow more dense and survive longer into the year. But there are likely other missing pieces of the puzzle explaining why cases of anaplasmosis in particular have rapidly increased in and around Albany, compared to the more gradual increase seen with Lyme and other tickborne diseases like babesiosis. One theory, Prusinski says, is that the bacteria responsible for human anaplasmosis (another variant, found in deers, doesn’t seem to cause human illness) is becoming more prevalent in both ticks and the small mammals they feed on, but research is ongoing to figure out why.
Though 2018 may have represented a slight decline in anaplasmosis, and the pandemic might have affected reporting last year, Prusinski expects anaplasmosis to continue to be a growing threat to New Yorkers—one that people will need to protect themselves against.
“There is no vaccine to prevent anaplasmosis, but there are several simple steps that people can take to prevent tickborne illnesses by avoiding tick bites,” she said.
Simple tick prevention tips when hiking or doing activities in possible tick-infested areas like the woodlands include wearing light-colored clothing with a tight weave to spot ticks easily; using insect repellent or treating clothing with compounds that kill ticks; and checking your clothes and skin frequently while outdoors and after you get inside. Other tips can be seen here on the Department of Health’s website.