Saturday 26 September 2015

Heartland Virus found in wild Vertebrates in 13 US states.

The first known cases of Heartland Virus, a form of Phlebovirus in the Family Bunyaviridae, were reported in northwest Missouri in 2009, were two agricultural workers were struck down with an illness that causes fever, leukopenia (a decrease in the number of white blood cells in the blood) and thrombocytopenia (decrease in the number of platelets in the blood). The Virus which caused this disease was subsequently isolated from Lone Star Ticks, Amblyomma americanum, suggesting that this species acted as a vector for the disease, which presumably had a reservoir in some unknown wild (or possibly domestic) animal, however no such host species was located at the time. Further cases of the disease have subsequently been reported in Tennessee and Oklahoma, suggesting that the disease may present an emerging threat to Human health in parts of the US.

A Lone Star Ticks, Amblyomma americanum, the only known vector for the Heartland Virus. James Gathany/Centers for Disease Control/Wikimedia Commons.

In a paper published in the journal Emerging Infectious Diseases on 11 September 2015, Kasen  Riemersma of the Division of Vector-Borne Diseases at the Centers for Disease Control and Prevention in Fort Collins, Colorado and the University of California, Davis, and Nicholas Komar, also of the  Division of Vector-Borne Diseases at the Centers for Disease Control describe the results of a survey for antibodies to the Heartland Virus in wild animals from 19 US states (antibodies are produced by the body to help fight off diseases; an animal exposed to a disease retains the ability to produce antibodies against it for life).

Riemersma and Komar tested blood samples from White-tailed Deer, Odocoileus virginianus, and Racoons, Procyon lotor, two animals common in the area where Heartland Virus was first discovered and thought likely to be possible reservoirs for the Virus, as well as Moose, Alces alces and Coyote, Canis latrans, in Alabama, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Missouri, New Hampshire, North Carolina, Ohio, Pennsylvania, Tennessee, Texas, Vermont, Virginia and West Virginia.

State-level distribution of Heartland virus case reports in humans and seropositive wildlife, central and eastern United States, 2009–2014. Red indicates states with seropositive animals; gray indicates states with no seropositive animals. Year labels indicate the earliest year of detected HRTV activity. Earliest detection was determined by human case reports in Missouri (1 case) and Oklahoma (3 cases) and wildlife serologic data in all other states. Riemersma & Komar (2015).

The Virus was found in all four species of animals, and was detected in Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Maine, Missouri, New Hampshire, North Carolina, Tennessee, Texas, and Vermont. This includes Deer in several states in New England, an area where Lone Star Ticks are not found, and while Deer are capable of migrating long distances across state boundaries, these states were not contiguous with other states where Heartland Virus has been found.

However, at least one other member of the genus  Phlebovirus, Thrombocytopenia Syndrome Virus, which is found in eastern Asia, is known to be spread by several different species of Ticks, suggesting that this might also be the case for Heartland Virus.

See also...

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