NEAFWA 2018

AUTHORS: Andrew B. Allison, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine; Julie C. Ellis, Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University; Chris Dwyer, U.S. Fish and Wildlife Service, Northeast Region

ABSTRACT: The emergence of novel viral pathogens resulting in large-scale outbreaks of disease in animals and humans is one of the most important challenges facing veterinary, natural resource, and public health officials today. For example, understanding how orthomyxoviruses such as influenza A virus emerge from their normal wildlife reservoir (ducks, shorebirds) to cause epidemic or pandemic disease is at the forefront of current global health concerns. Beginning in 1998, cyclic mortality events occurring on a near annual basis have been documented in common eiders (Somateria mollissima) along the coast of Cape Cod, Massachusetts. During field investigations of these outbreaks, most affected eiders were found dead, although sick birds exhibiting a variety of clinical signs including incoordination, respiratory distress, diarrhea, and convulsions have been observed. In 2010, we isolated a novel orthomyxovirus named Wellfleet Bay virus (WFBV) that, based on its repeated isolation during subsequent and retrospective outbreaks and the detection of viral antigen in pathological lesions, is the primary etiological agent of these die-offs.  

WFBV is a new member of the genus Quaranjavirus, which was first recognized as a genus within the family Orthomyxoviridae in 2011 and is comprised of bird-associated viruses from Africa and Oceania that are tick-transmitted. However, WFBV represents the first detection of a quaranjavirus in the continental USA. Although the identification of WFBV in part may resolve the enigma of these mass mortality events, many questions still remain including (i) how the virus is transmitted in nature, (ii) the normal host range of the virus (what species it can infect), and (iii) the factors influencing the apparent temporal (cyclic) and spatial (Cape Cod) occurrence of the outbreaks. In addition to WFBV, another novel orthomyxovirus (called Bourbon virus [BRBV]) was recently identified in the Midwestern USA, which has been associated with human deaths. Like WFBV, this virus is also suspected to be transmitted in a tick-wildlife cycle and is the first member of its genus (Thogotovirus) known to cause disease in North America. Currently, the epidemiological or ecological factors driving the apparent recent emergence of tentative tick-borne orthomyxoviruses as wildlife and public health threats in the USA are unknown and require further study.