Leptospirosis is a neglected zoonosis with worldwide distribution. The causative agents are spirochete bacteria of the Leptospira genus, displaying huge diversity of serovars, the identity of which is critical for effective diagnosis and vaccination purposes. Among many other mammalian species, Leptospira infects cattle, eliciting acute signs in calves, and chronic disease in adult animals often leading to abortions. In South America, and including in Uruguay, beef and dairy export are leading sources of national income. Despite the importance of bovine health, food safety, and bovine-related dissemination of leptospirosis to humans, extremely limited information is available as to the identity of Leptospira species and serovars infecting cattle in Uruguay and the South American subcontinent. Here we report a multicentric 3-year study resulting in the isolation and detailed characterization of 40 strains of Leptospira spp. obtained from infected cattle. Combined serologic and molecular typing identified these isolates as L. interrogans serogroup Pomona serovar Kennewicki (20 strains), L. interrogans serogroup Canicola serovar Canicola (1 strain), L. borgpetersenii serogroup Sejroe serovar Hardjo (10 strains) and L. noguchii (9 strains). The latter showed remarkable phenotypic and genetic variability, belonging to 6 distinct serogroups, including 3 that did not react with a large panel of reference serogrouping antisera. Approximately 20% of cattle sampled in the field were found to be shedding pathogenic Leptospira in their urine, uncovering a threat for public health that is being largely neglected. The two L. interrogans serovars that we isolated from cattle displayed identical genetic signatures to those of human isolates that had previously been obtained from leptospirosis patients. This report of local Leptospira strains shall improve diagnostic tools and the understanding of leptospirosis epidemiology in South America. These strains could also be used as new components within bacterin vaccines to protect against the pathogenic Leptospira strains that are actually circulating, a direct measure to reduce the risk of human leptospirosis.

Clostridium haemolyticum causes bacillary hemoglobinuria (BH), an infectious and usually fatal disease that occurs mostly in cattle, which is clinically characterized by jaundice, hemoglobinuria, and anemia. The trematode Fasciola hepatica has been commonly reported as the main predisposing factor that triggers this condition. The authors evaluated 20 naturally occurring cases of bovine BH to characterize the pathology and pathogenesis of the disease. Grossly, the most consistent finding was a large, frequently single focus of necrosis surrounded by a red to purple halo, observed most frequently on the parietal surface of the right and left hepatic lobes. Other findings were jaundice, dark-brown discoloration of kidneys, and red urine in the urinary bladder. Microscopically, characteristic lesions were locally extensive, necrotizing hepatitis with thrombosis and numerous intralesional Gram-positive rod-shaped bacteria, and acute renal tubular necrosis. By immunohistochemistry, many hepatocytes outside the necrotic focus in the liver were positive for activated caspase 3, suggesting that those cells were undergoing apoptosis. Ultrastructural evaluation revealed hepatocyte necrosis, hemolysis, and clumps of vegetative and sporulating bacilli within the liver. Polymerase chain reaction for the C. haemolyticum beta toxin gene was positive in randomly selected liver samples. No gross or microscopic lesions indicative of fascioliasis were detected in the liver of any animal, suggesting that other yet undetermined predisposing factors were associated with these cases of BH.

Simple SummaryGHGs emissions are relevant in evaluating environmental impact of farming systems. Methane (CH4) produced by enteric fermentation accounts for half of all anthropogenic emissions of GHGs in Uruguay, where ruminant production is based on year round grazing of forages. Here we compared milk production and CH4 emissions by dairy cows grazing two contrasting mixed pastures (rich in legumes or rich in grasses) using the SF6 tracer technique adapted to collect breath samples over 5-days periods. There were no differences in milk or CH4 production between the contrasting pastures, probably because of the high herbage allowance that enabled selective grazing by cows.AbstractUnderstanding the impact of changing pasture composition on reducing emissions of GHGs in dairy grazing systems is an important issue to mitigate climate change. The aim of this study was to estimate daily CH4 emissions of dairy cows grazing two mixed pastures with contrasting composition of grasses and legumes: L pasture with 60% legumes on Dry Matter (DM) basis and G pasture with 75% grasses on DM basis. Milk production and CH4 emissions were compared over two periods of two weeks during spring using eight lactating Holstein cows in a 2 × 2 Latin square design. Herbage organic matter intake (HOMI) was estimated by chromic oxide dilution and herbage organic matter digestibility (OMD) was estimated by faecal index. Methane emission was estimated by using the sulfur hexafluoride (SF6) tracer technique adapted to collect breath samples over 5-day periods. OMD (0.71) and HOMI (15.7 kg OM) were not affected by pasture composition. Milk production (20.3 kg/d), milk fat yield (742 g/d) and milk protein yield (667 g/d) were similar for both pastures. This may be explained by the high herbage allowance (30 kg DM above 5 cm/cow) which allowed the cows to graze selectively, in particular in grass sward. Similarly, methane emission expressed as absolute value (368 g/d or 516 L/d) or expressed as methane yield (6.6% of Gross Energy Intake (GEI)) was not affected by treatments. In conclusion, at high herbage allowance, the quality of the diet selected by grazing cows did not differ between pastures rich in legumes or rich in grasses, and therefore there was no effect on milk or methane production.

The widespread use of artificial insemination has allowed the expansion of genetic progress. However, it also brought consequences such as the expansion of lethal hereditary diseases and the increase in inbreeding. The object of this study was to establish a fast and sensitive molecular assay to detect bovine leukocyte adhesion deficiency (BLAD) and deficiency of uridine monophosphate synthase (DUMPS) carriers in Uruguayan Holstein cattle by means of high resolution melting (HRM) curve analysis. By testing previously confirmed carrier and non-carrier animals, we set up a rapid, simple, and inexpensive diagnostic test using PCR followed by HRM curve analysis. The PCR-HRM genotyping method was effective for the discrimination of BLAD and DUMPS homozygous genotypes, and the BLAD heterozygous genotype. We conclude that the PCR-HRM assay is a robust, reliable, and economical tool for the detection of these mutations in the Holstein breed, which may be implemented in genetic selection programs.

No abstract