ST. LOUIS — Federal health investigators have confirmed that ticks carry the new virus that sickened two Missouri men.
The Centers for Disease Control and Prevention suspected ticks were a likely source of the Heartland virus, which was named for the St. Joseph hospital where the men were treated in 2009.
A study published Monday and authored by Harry Savage, a CDC research entomologist, said samples from ticks taken from the patients' farms and other land in northwest Missouri have tested positive for the Heartland virus. The study was published in the American Journal of Tropical Medicine and Hygiene, The St. Louis Post-Dispatch reported.
"It's the first time that anyone found the virus in the environment," Savage said. "This is yet another tick-borne disease in the U.S., and it's another reason to take preventative measures to avoid tick attachment and tick bites."
There are no treatments for Heartland virus, which can cause low white blood cell counts, fever, chills, diarrhea and other symptoms. Both Missouri men, who are the only recorded cases of Heartland virus, recovered after nearly two weeks in the hospital.
When the two men arrived at Heartland Regional Medical Center in 2009 complaining of fever and fatigue, physician Scott Folk at Heartland suspected ehrlichiosis, a common tick-borne disease that has infected at least 126 people in Missouri this year. The patients, however, didn't respond to antibiotics used to treat ehrlichiosis. Folk then sent blood samples to the CDC, where researchers determined it was a new insect-borne virus, but were uncertain which insect was carrying the virus.
CDC scientists traveled to northwest Missouri to collect ticks and mosquitoes in an effort to trace the virus. Samples taken last year from the patients' farms and the Honey Creek Conservation Area tested positive for the Heartland virus. About one in 500 nymph, or adolescent, ticks collected near one of the patient's homes contained the virus.
Savage said the Heartland virus is probably spread elsewhere in Missouri too, though there haven't been any other reports of Heartland illnesses. It's likely patients have caught the virus and been misdiagnosed, because there is no quick, reliable test.
Ericka Hayes, an infectious disease specialist at Washington University, said it's not surprising that the Heartland virus was discovered in Missouri because Missouri leads the nation in tick-related diseases. Preventive measures to avoid tick bites include tucking pants into socks, wearing long sleeves and using bug repellent with DEET.
"If you've been outside in Missouri, you should be going over yourself head to toe," Hayes said. She said it takes 24 hours or more for a tick to transmit a disease to a person. "If you can prevent the tick (from attaching), it doesn't matter what disease they're carrying."