Epidemiology of Bluetongue Virus and Epizootic Hemorrhagic Disease Virus in Beef Cattle on a Ranch in South-Central Florida.

Mary M Merrill,Laurent O Lollis,Samantha M Wisely,Raoul K Boughton,Katherine A Sayler

doi:10.1089/vbz.2018.2406

Mary M Merrill, Laurent O Lollis + Show 3 more

Open Access

https://doi.org/10.1089/vbz.2018.2406

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Abstract

Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) infect a variety of wild and domestic ruminant hosts in the United States, with outcomes ranging from subclinical infection to clinical disease resulting in mortality. Because cattle have been suggested as a temporary reservoir for both BTV and EHDV, ongoing national surveillance for these viruses may benefit from inclusion of domestic cattle as a supplement to current programs, such as surveillance of wild white-tailed deer. To better understand the prevalence of BTV and EHDV in cattle, we surveyed for viral RNA (vRNA) in the blood of 1,604 beef cattle on a south-central Florida cattle ranch over 3 years. While overall prevalence of vRNA in blood was low (<2% for either virus), the occurrence of vRNA was much higher in young animals: in 2016, 24% of animals 2 years old were positive by PCR for either BTV or EHDV. Our results suggest that cattle are a likely temporary reservoir for these viruses in Florida, and could provide additional information on the spatial distribution, viral diversity, and timing of emergence of these viruses, particularly if surveillance was restricted to cattle ≤2 years of age.

Highlights

Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV), both members of the genus Orbivirus in the family Reoviridae, are responsible for disease outbreaks among wild ruminants, white-tailed deer (Odocoileus virginianus), in the United States (Savini et al 2011, Maclachlan et al 2015a, Ruder et al 2015)
For cattle sampled in 2016, for each 1-year increase in age, the odds of detecting EHDV in blood decreased by 14% (OR = 0.86, p < 0.05, 95% Confidence intervals (CIs): 0.73–0.99) (Fig. 1); the odds of detecting BTV in blood decreased by 51% (OR = 0.49, p < 0.001, 95% CI: 0.31–0.68) (Fig. 2); and the odds of detecting either BTV or EHDV decreased by 27% (OR = 0.73, p < 0.001, 95% CI: 0.62–0.83) (Fig. 3)
Based on the overall low observed BTV and EHDV prevalence, the power of our study to detect these associations was very low. These results highlight the potential of domestic cattle herds as BTV and EHDV surveillance tools

Summary

Introduction

Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV), both members of the genus Orbivirus in the family Reoviridae, are responsible for disease outbreaks among wild ruminants, white-tailed deer (Odocoileus virginianus), in the United States (Savini et al 2011, Maclachlan et al 2015a, Ruder et al 2015). BTV infection does not typically cause disease in cattle, disease can result when naıve populations are exposed (Maclachlan et al 2015a). Like BTV, clinical signs of EHDV infection are rarely observed in cattle, certain serotypes or strains of the virus are capable of causing disease and may result in production losses (Howerth et al 2001, Kedmi et al 2010, Savini et al 2011). A study of dairy cattle during an EHDV outbreak in Israel showed that increased EHDV seroprevalence was associated with decreased milk production and increased mortality (Kedmi et al 2010)

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