Serosurvey for Influenza D Virus Exposure in Cattle, United States, 2014–2015

Simone Silveira; Shollie M. Falkenberg; Bryan S. Kaplan; Beate Crossley; Julia F. Ridpath; Fernando B. Bauermann; Charles P. Fossler; David A. Dargatz; Rohana P. Dassanayake; Amy L. Vincent; Cláudio W. Canal; John D. Neill

Disclosures

Emerging Infectious Diseases. 2019;25(11):2074-2080. 

In This Article

Abstract and Introduction

Abstract

Influenza D virus has been detected predominantly in cattle from several countries. In the United States, regional and state seropositive rates for influenza D have previously been reported, but little information exists to evaluate national seroprevalence. We performed a serosurveillance study with 1,992 bovine serum samples collected across the country in 2014 and 2015. We found a high overall seropositive rate of 77.5% nationally; regional rates varied from 47.7% to 84.6%. Samples from the Upper Midwest and Mountain West regions showed the highest seropositive rates. In addition, seropositive samples were found in 41 of the 42 states from which cattle originated, demonstrating that influenza D virus circulated widely in cattle during this period. The distribution of influenza D virus in cattle from the United States highlights the need for greater understanding about pathogenesis, epidemiology, and the implications for animal health.

Introduction

Influenza D virus (IDV; genus Deltainfluenzavirus, family Orthomyxoviridae) is an enveloped, single-stranded, negative sense RNA virus with 7 genome segments and 1 surface glycoprotein, the hemagglutinin-esterase fusion (HEF) protein.[1,2] The first detection of IDV dates back to Oklahoma, USA, in 2011 from pigs exhibiting influenza-like disease,[3] although retrospective seroprevalence data suggest the presence of IDV in goats in the United States before 2002.[4] Subsequently, IDV has been identified in low frequency in pigs in Italy[5,6] and Luxembourg.[7] In addition, evidence suggests IDV circulates in other hosts such as small ruminants, camels, and buffalo in Togo, Kenya, and China[8,9] and small ruminants, feral swine, and equids in the United States.[4,10,11]

Although IDV has been detected in other species, cattle appear to be the main reservoir.[1,12] A variety of sample types and methods of detection have been used to determine the prevalence of IDV in different regions, in various ages, breeds, and numbers of cattle evaluated. The lack of consistency between the methods and cattle evaluated may be a contributing factor to variability in prevalence of IDV in different regions. Seroprevalence data have been reported in cattle from Luxembourg,[7] Japan,[13,14] the United States,[1,15,16] Togo, Benin, and Morocco;[9] the highest reported seropositive rate (80.2%) was in the United States[16] and Luxembourg[7] and the lowest (1.9%) in Benin.[9] Serologic testing provides an indication of IDV exposure but is not a measure of active infections. IDV RNA from respiratory samples of cattle has been detected in several countries: the United States,[1,15,17,18] Italy,[5] France,[19] Ireland,[20] China,[8,21] Japan,[22] and Mexico.[18] Studies from Mexico[18] reported the highest frequency of positive samples (29.7%) and China the lowest (0.7%).[21]

In both experimental and field infections with IDV, mild to moderate respiratory disease has been reported.[23,24] In addition, IDV-positive samples are reported not only from cattle manifesting clinical signs associated with bovine respiratory disease but also from cattle that are asymptomatic and appear to be healthy.[20–22] Experimental infection of calves demonstrated that IDV caused mild to moderate respiratory disease and that peak viral shedding occurred at 4–6 days postinfection; seroconversion was detected as early as day 6 postinfection.[12,23,24] Whereas IDV infection by itself has been associated mainly with mild respiratory illness, IDV has also been implicated as a contributor to bovine respiratory disease complex (BRDC), which is the most costly disease affecting the US cattle industry.[17,18,23,25]

Because there are no commercially available vaccines against IDV, positive serologic assays reflect natural exposure. Given the potential of IDV to contribute to BRDC, inclusion of IDV in vaccination programs has been debated. The frequency of IDV RNA–positive samples from US cattle is 4.8%–18%,[1,15,17,18] and positive samples have been reported in the US cattle population since 2003.[16] The seropositive rate has been reported at 13.5%–80.2%;(15,16) the Upper Midwest region has the highest seroprevalence. The wide variation of seroprevalence could be caused by differences in the age of the cattle evaluated or by differences across regions because of limited sample size and the focus on the Midwest and South Central regions of the country. We conducted a national serosurvey of cattle of a similar age to fully evaluate the potential role of IDV in BRDC infections and the effect of IDV on animal health and productivity.

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