Abstract
Uruguay is one of the main exporters of beef and dairy products, and cattle production is one of the main economic sectors in this country. Rotavirus A (RVA) is the main pathogen associated with neonatal calf diarrhea (NCD), a syndrome that leads to significant economic losses to the livestock industry. The aims of this study are to determine the frequency of RVA infections, and to analyze the genetic diversity of RVA strains in calves in Uruguay. A total of 833 samples from dairy and beef calves were analyzed through RT-qPCR and sequencing. RVA was detected in 57.0% of the samples. The frequency of detection was significantly higher in dairy (59.5%) than beef (28.4%) calves (p < 0.001), while it did not differ significantly among calves born in herds that were vaccinated (64.0%) or not vaccinated (66.7%) against NCD. The frequency of RVA detection and the viral load were significantly higher in samples from diarrheic (72.1%, 7.99 log10 genome copies/mL of feces) than non-diarrheic (59.9%, 7.35 log10 genome copies/mL of feces) calves (p < 0.005 and p = 0.007, respectively). The observed G-types (VP7) were G6 (77.6%), G10 (20.7%), and G24 (1.7%), while the P-types were P[5] (28.4%), P[11] (70.7%), and P[33] (0.9%). The G-type and P-type combinations were G6P[11] (40.4%), G6P[5] (38.6%), G10P[11] (19.3%), and the uncommon genotype G24P[33] (1.8%). VP6 and NSP1-5 genotyping were performed to better characterize some strains. The phylogenetic analyses suggested interspecies transmission, including transmission between animals and humans.
Highlights
Neonatal calf diarrhea (NCD) is a syndrome of worldwide distribution and the major cause of mortality of dairy calves before weaning [1]
Rotavirus A (RVA) is widespread in dairy farms in Uruguay, and viable viral particles have been detected in sources of drinking water used for calves [9], suggesting water contamination and waterborne transmission
The frequency of RVA detection was significantly higher in samples from diarrheic (72.1%, 173/240) than non-diarrheic (59.9%, 163/272) dairy calves (OR: 1.73, 95% CI: 1.19–2.50; p < 0.005; Figure 1d)
Summary
Neonatal calf diarrhea (NCD) is a syndrome of worldwide distribution and the major cause of mortality of dairy calves before weaning [1]. Rotavirus A (RVA) is the main pathogen associated with NCD [6,7]. A; genus Rotavirus; subfamily Sedoreovirinae; family Reoviridae) is a nonenveloped virus with a triple-layered capsid and a genome composed of 11 segments of double-stranded RNA [8]. RVA is widespread in dairy farms in Uruguay, and viable viral particles have been detected in sources of drinking water used for calves [9], suggesting water contamination and waterborne transmission. In 2008, a complete genome classification system, named genotype constellation, assigning a specific genotype to each of the 11 genome segments was developed [10]
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