Novel tick-borne phlebovirus identified during outbreak investigation in Tasmania
An investigation of a disease outbreak among shy albatrosses in Tasmania led to the discovery of a novel tick-borne phlebovirus with zoonotic potential, according to recent findings.
The findings underscore the need for increased scrutiny and awareness regarding these emerging diseases, researchers said.
In the study, researchers investigated a 2002 disease outbreak in a shy albatross colony on a small island in the Hunter Island Group of northwestern Tasmania, characterized by weight loss and death. The investigators collected blood samples and ticks from healthy and diseased birds and sent them to the Commonwealth Scientific and Industrial Research Organization’s Australian Animal Health Laboratory in Geelong, Victoria, Australia, for testing.
First, an enzyme-linked immunosorbent assay (ELISA) and a hemagglutination inhibition assay were used to screen the samples (n=38) for antibodies against avian influenza, infectious bursal disease, fowlpox and Newcastle disease. The researchers identified neutralizing antibodies for Newcastle disease (titer of 64) in one serum sample, but detected no antibodies against any of the other suspected viruses.
Next, they inoculated chicken embryos, chicken embryo fibroblast and skin cells, and Vero cells with pooled tick homogenates (n=5). No viruses were identified in the chicken embryos or chicken cells, but cytopathic activity was identified on the third passage in Vero cells inoculated with two tick pools — one taken from diseased birds and one from healthy birds.
Upon electron microscopy analysis, the researchers discovered morphological similarities in the viral particles from both cultures, which resembled bunyavirus particles. Subsequent testing with antibodies against various known bunyaviruses did not show any cross-reactivity. PCR analysis was also unsuccessful in detecting any specific sequence from the virus.
The researchers then suspended the investigation until 2011, when the Australian Animal Laboratory implemented next-generation sequencing. With this new capability, the researchers found that the virus was a new member of the genus Phlebovirus and was closely related to two zoonotic infections circulating in Asia and North America. The first was a tick-borne bunyavirus that caused an outbreak of severe fever with thrombocytopenia syndrome in China in 2009. The severe fever with thrombocytopenia syndrome virus (SFTSV) has since been responsible for more than 150 human infections, with a mortality rate of approximately 12%. The second virus was a novel tick-borne phlebovirus that affected two men from two distinct farms in northwestern Missouri that same year, named the Heartland virus (HRTV).
The virus identified in the shy albatrosses was tentatively called the Hunter Island Group virus (HIGV), named after the location where the ticks were found.
Because HIGV was extracted from ticks found in healthy and diseased birds, the researchers considered it unlikely that the virus was responsible for the illness in the albatrosses. This was confirmed by the results of ELISA and Western blot testing of the 38 serum samples, none of which yielded positive results.
“The findings from this study demonstrate the key role that a vigilant pathogen investigation has in any diagnostic assessment,” the researchers wrote. “The study findings also suggest that zoonotic phleboviruses genetically related to SFTSV, HRTV and HIGV may be widely distributed in different parts of the world.”
Disclosure: The researchers report no relevant financial disclosures.