Bourbon, Heartland, and Ticks

By Greg Mercer

The Centers for Disease Control and Prevention recently announced that it has identified the mysterious virus that killed a man in Kansas last spring.  Dubbed the Bourbon virus—after its location in Bourbon County, Kansas—it is an RNA virus in the genus Thogotovirus, according to the researchers who identified the virus.  Thogotovirus includes at least 6 distinct viruses, although only one, the Aransus Bay virus, occurs in the U.S. (but does not infect humans).  Of the genus, only two other viruses are known to infect humans, and the only fatality was the one caused by Bourbon.  Both are spread to humans through ticks.  Ticks are also the vector for the Heartland virus and Lyme disease.

The patient in Kansas experienced nausea, weakness, and diarrhea, followed by fever, anorexia, headache, and other symptoms after being bitten by ticks while working outside.  He was initially treated for tick borne illness with doxycycline, which proved ineffective.  Upon being admitted to the hospital, he was tested for Rocky Mountain spotted fever, Lyme disease, and ehrlichiosis, and treated with broad-spectrum antimicrobial drugs.  Despite treatment, the patient experienced widespread organ failure and died 11 days after becoming ill.  The researchers identified the Bourbon virus in samples through plaque reduction neutralization, originally used to test for Heartland virus antibodies.  Sequencing and analysis then identified the Bourbon virus as a member of Thogotovirus.

The paper from the researchers who identified the virus, linked above, is well worth reading for a look at how emerging viruses are studied and identified, and the challenges of dealing with the first case of a new virus.

The Heartland virus was first detected in 2012, causing fever, fatigue, headaches, muscle aches, and stomach sickness.  Most patients required hospitalization, with most fully recovering.  The CDC has since identified eight cases in Missouri and Tennessee.  Due to the low number of cases, the virus is still not well understood, but all of the patients became sick between May and September, and likely became infected while outdoors.

While researchers assert that the current methods of transmission for both Bourbon and Heartland are unknown, they note that exposure to ticks may be a potential method.  The researchers advise avoiding tick bites as a potential method of preventing infection. The CDC page for avoiding ticks lists guidelines, including using insect repellant recognized by the Environmental Protection Agency and wearing long sleeves and pants outside.

The CDC lists 14 other diseases spread by ticks.  Most recognizable among them is Lyme disease, a common disease to hear about during warm weather.  Interestingly, the CDC tick page also notes the discontinuation of the Lyme disease vaccine in 2002 by its producer, due to lack of demand.  Since the vaccine’s effect diminishes over time, those vaccinated before 2002 are likely no longer protected against Lyme.

It’ll be tick season soon enough so, be generous with that insect repellant!

Image Credit: André Karwath