Abstract
Bovine coronavirus (BCoV) is associated with respiratory and enteric infections in both dairy and beef cattle worldwide. It is also one of a complex of pathogens associated with bovine respiratory disease (BRD), which affects millions of cattle annually. The objectives of this study were to identify loci and heritability estimates associated with BCoV infection and BRD in dairy calves and feedlot cattle. Dairy calves from California (n = 1,938) and New Mexico (n = 647) and feedlot cattle from Colorado (n = 915) and Washington (n = 934) were tested for the presence of BCoV when classified as BRD cases or controls following the McGuirk scoring system. Two comparisons associated with BCoV were investigated: (1) cattle positive for BCoV (BCoV+) were compared to cattle negative for BCoV (BCoV−) and (2) cattle positive for BCoV and affected with BRD (BCoV+BRD+) were compared to cattle negative for BCoV and BRD (BCoV−BRD−). The Illumina BovineHD BeadChip was used for genotyping, and genome-wide association analyses (GWAA) were performed using EMMAX (efficient mixed-model association eXpedited). The GWAA for BCoV+ identified 51 loci (p < 1 × 10−5; 24 feedlot, 16 dairy, 11 combined) associated with infection with BCoV. Three loci were associated with BCoV+ across populations. Heritability estimates for BCoV+ were 0.01 for dairy, 0.11 for feedlot cattle, and 0.03 for the combined population. For BCoV+BRD+, 80 loci (p < 1 × 10−5; 26 feedlot, 25 dairy, 29 combined) were associated including 14 loci across populations. Heritability estimates for BCoV+BRD+ were 0.003 for dairy, 0.44 for feedlot cattle, and 0.07 for the combined population. Several positional candidate genes associated with BCoV and BRD in this study have been associated with other coronaviruses and respiratory infections in humans and mice. These results suggest that selection may reduce susceptibility to BCoV infection and BRD in cattle.
Highlights
The coronaviridae family, from the Nidoviruse order, consists of enveloped, positive-stranded RNA viruses with some of the largest viral genomes known among all RNA viruses
More loci were associated with Bovine coronavirus (BCoV)+ or BCoV positive (BCoV+)bovine respiratory disease (BRD)+ in the non-additive models than in the additive models
This was true in the diary population for the recessive model, as none of the recessive loci were identified in the additive model, and so did not contribute to the heritability estimate
Summary
The coronaviridae family, from the Nidoviruse order, consists of enveloped, positive-stranded RNA viruses with some of the largest viral genomes known among all RNA viruses This family is often split into groups [1,2,3] based on serological and genetic similarities between the viruses [1]. Monoclonal antibodies against HE were able to neutralize BCoV infection in vitro [5] and protect the cattle intestinal epithelium from viral infection in vivo [6]. This suggests that the HE protein may have a role in inducing a protective response during BCoV infection. The spike protein of coronaviruses is involved in viral attachment and viral fusion to host cells during infection, and studies have suggested that natural selection within the spike protein gene is a mechanism BCoV uses to continually adapt to host immune responses to infection [7,8,9]
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