New Tick-Borne Disease Found

By Labmedica International staff writers

Posted on 17 Sep 2012 A new Phlebovirus, dubbed the “Heartland virus,” is being spread to people by ticks common in the Southeastern part of the USA.

The only tickborne Phlebovirus known to cause human disease is severe fever with thrombocytopenia syndrome virus (SFTSV), which was recently identified in central and northeastern China.

Scientists at US Centers of Disease Control and Prevention (CDC; Atlanta, GA, USA) collected leukocytes from two patients on day two of hospitalization. Both men had fever, fatigue, diarrhea, and low levels of blood platelets and white blood cells and had reportedly been bitten by ticks. The symptoms are similar to those of ehrlichiosis, a relatively common tick-borne disease that is caused by bacteria.

The leukocytes were inoculated onto cultures of macrophage-monocyte cell line from a dog with malignant histiocytosis (DH82). Total ribonucleic acid (RNA) was isolated from infected culture media and subjected to next-generation sequencing using quantitative reverse transcription PCR (qRT-PCR). The resulting full-length genome sequences were found to be similar to those of phleboviruses in the Bunyaviridae family, which are single-stranded, negative-sense RNA viruses comprised of three genome segments.

Immunohistochemical staining of the bone marrow of one patient revealed the virus nucleocapsid protein in large mononuclear cells that did not resemble mature granulocytes, erythroid cells, or megakaryocytes. Patient serum samples were tested for the presence of antibodies reactive to the novel virus. In October 2011, more than two years after the onset of infection, blood was collected from both patients and serum samples were tested on enzyme-linked immunosorbent assay (ELISA) to detect immunoglobulin G (IgG) reactive with virus antigen made from inactivated virus-infected cell lysate. Both serum samples were strongly positive, with titers of more than 6,400.

Laura K. McMullan, PhD, and her colleagues concluded that although these two patients had severe disease, the incidence of infection with the novel virus and range of disease severity is currently unknown. This virus could be a more common cause of human illness than is currently recognized. They warn health professionals to be on the lookout for people who fall ill after getting tick bites and who do not get better after antibiotic treatment. The study was published on August 30, 2102, in the New England Journal of Medicine (NEJM).