Seventy years of hemorrhagic disease research in North America

Culicoides sp. are the primary vectors of two hemorrhagic disease (HD) viruses, Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV). In North America, Epizootic hemorrhagic disease (EHD) and Bluetongue disease (BT) cause significant morbidity and mortality in white-tailed deer (Odocoileus virginianus) populations and can cause morbidity in farmed animals, resulting in restricted agricultural trade. Originally, HD was limited to southeastern and southcentral North America but has expanded in distribution to the north and west, resulting in severe disease outbreaks in naïve wildlife populations. To better understand these disease systems in North America, we performed a literature review. Of 2,295 peer-reviewed sources, 422 articles were included in our review. We found most research focused on the host species (n = 206), such as disease prevalence, disease progression, and epidemiology in domestic and wildlife hosts. Vector research covered a range of topics (n = 102) but was limited in distribution, with most field studies conducted in California and Florida, and few in the northeast. Viral research consisted of two topics, virus characterization (n = 58) and diagnostic techniques (n = 23). Relative to the existing literature on this disease system in Europe, where climate change is one of the primary drivers of expansion, the effect climate has on this disease system in North America is still uncertain. The information in our review describes what we know of the vector, host, virus, climatological impacts, and other aspects of HD in North America in relation to other countries and can help researchers identify gaps in our understanding of the HD system.