Last Updated: January 2020

Author: Infectious Disease Epidemiology Program, Vermont Department of Health

Anaplasmosis is caused by an infection with the bacterium, Anaplasma phagophytophilum. This bacterium is transmitted to humans by the bite of infected blacklegged ticks, Ixodes scapularis. The symptoms of anaplasmosis include fever, malaise, headache, fatigue, nausea, and vomiting. Anaplasmosis can be a serious illness, particularly in older individuals and those with weakened immune systems or other illnesses. If not treated promptly, it can also be fatal in a small percentage (1%) of patients.

The rate of anaplasmosis in Vermont has been increasing in recent years. This is may be due to changes in the blacklegged tick population, ecological factors, improved awareness in the public and health care community, or more laboratory testing performed by health care providers.

The incidence of anaplasmosis is an important indicator because it allows us to monitor the burden of disease over time and space. Measuring anaplasmosis using an incidence rate allows us to control for changes in the population of Vermont. It also allows us to compare the disease burden in Vermont with the burden in other states.

• Clinical and commercial laboratories
• Health care providers
• Vermont Agency of Agriculture, Food and Markets
• Vermont Department of Forests, Parks and Recreation
• Vermont Fish & Wildlife Department
• Academic institutions
• Community groups

The best way to prevent anaplasmosis is to prevent tick bites. Visit the Health Department’s "Be Tick Smart” webpage to learn tick bite prevention strategies, how to check yourself for and remove ticks, and what to do after a tick bite.

The Health Department is focused on providing scientifically accurate information to Vermonters about anaplasmosis. Our strategy involves conducting surveillance for the disease in human and the pathogen in ticks, raising awareness about the risks, and educating Vermonters about the best prevention strategies.

The incidence of anaplasmosis was calculated by dividing the number of confirmed and probable cases of anaplasmosis reported to the Health Department each year by Vermont’s estimated population for that same year. That number was then multiplied by 100,000. Not all cases of anaplasmosis that occur in the state are reported to the Health Department.