Between 2009 and 2014, widespread transmission of the tick-borne Heartland virus was evident throughout the central and eastern United States, according to a recent CDC report.
The first cases of Heartland virus (HRTV) were reported in two Missouri farmers in 2009. Since then, seven additional HRTV cases, including two deaths, have been reported in Missouri, Tennessee and Oklahoma.
CDC researchers conducted a retrospective serosurvey to determine the geographic range of HRTV activity. They analyzed banked blood samples from 1,428 animals, including white-tailed deer (n = 396), raccoons (n = 949), moose (n = 22) and coyotes (n = 61). The samples were assayed for HRTV neutralizing antibodies by the plaque-reduction neutralization test with Vero cell cultures. A threshold of 70% relative to HRTV-only controls identified positive samples. Samples were deemed seropositive by testing positive at a dilution of at least 1:40.
According to the results, 103 animals were seropositive for HRTV, including deer (n = 55), raccoon (n =33), coyote (n =11) and moose (n = 4). The seropositive animals were located in Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Maine, Missouri, New Hampshire, North Carolina, Tennessee, Texas and Vermont. The researchers plotted the animals by county and identified 20 clusters of HRTV. They wrote that a neutralization threshold of 80% would have reclassified 14 positive samples as “equivocal,” however, the number of affected states would remain the same.
“We provide evidence of widespread HRTV transmission activity across the central and eastern United States,” the researchers concluded. “These findings should encourage clinicians and public health officials to consider HRTV as a potential source of illness throughout the eastern United States.” – by Jen Byrne
Disclosure: The researchers report no relevant financial disclosures.