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Background: The dual antigen iELISA uses two Streptococcus equi subsp equi surface protein antigens composed of N‐terminal portions of SEQ2190 (Antigen A) and SeM (Antigen C). It is currently used to identify animals exposed to S. equi which have developed an immune response to the target antigens. Objectives: To determine the usefulness of the dual antigen iELISA in a population of horses vaccinated with Pinnacle IN. We hypothesised that horses vaccinated for strangles with a live attenuated, non‐encapsulated SeM‐2 strain of S. equi, would seroconvert when tested 5 weeks later by the dual antigen iELISA. Study design: Prospective case‐control study. Methods: Three separate serum samples were obtained from 26 client‐owned horses vaccinated annually with Pinnacle® IN and 26 university‐owned (non‐vaccinates): at annual strangles vaccination (S1), 5‐week post‐vaccination (S2) from vaccinates, and a third (S3) (at 10 weeks) from vaccinates who received a booster. Seropositivity was defined as an OD450 nm value ≥0.5 for one or both antigens. Mixed‐effects ordered logistic regression analysis was used to identify factors associated with a suspect seropositive and seropositive value on the combined Antigen A and Antigen C iELISA. Post hoc pairwise comparisons of linear predictive margins were used to assess the differences in OD450 at a specific time between Antigens A and C. Results: Nineteen of 25 (76%) vaccinates were seropositive at S2 compared to 1 of 26 (4%) non‐vaccinates. When adjusted for sample number, vaccinates were more likely to be seropositive or suspect than non‐vaccinates (OR 14; P =.02, 95% CI 1.62‐122.03). The OD450 value was significantly larger for Antigen C than Antigen A for vaccinates (P <.001; 95% CI 0.13‐0.26) when normalised by age, sex and breed. Main limitations: Guttural pouch sampling for S. equi in seroconverted horses was unavailable. Conclusions: With a high rate of seroconversion to both antigens, the use of the dual antigen iELISA is not recommended in populations vaccinated with Pinnacle® IN. [ABSTRACT FROM AUTHOR]

Objective: To determine whether four isolates of Streptococcus canis (S canis) recovered from dogs diagnosed with ulcerative keratitis at the Animal Health Trust (AHT) were genetically related to other ocular isolates that are registered in the online database. Animal studied: Four S canis corneal isolates. Procedures: Clinical and laboratory records between 2016 and 2017 were searched for dogs with ulcerative keratitis for which microbiology analysis was consistent with the growth of S canis. Genomic DNA was extracted for sequencing (Illumina MiSeq), and multilocus sequence types (STs) were determined using MLST 1.8 relative to the 44 sequence types of S canis available. A neighbor‐joining tree was constructed in MEGA v4.0. A two‐sided Fisher's exact test was used to determine any associations between the isolated strains and ocular infections of dogs. Results: Four strains were isolated from pugs (cases 1‐4) with ulcerative keratitis. Genome sequencing identified ST‐27 (case 1), ST‐9 (case 3), and ST‐13 (cases 2 and 4). STs 13 and 27 are members of Clonal Complex (CC)‐13. Analysis of the multilocus sequence typing database revealed that CC‐13 strains accounted for six of the twelve isolates recovered from the eye exudates of dogs (P =.0078). Conclusions: There is early evidence that the CC‐13 group of S canis is associated with ocular infections in dogs. We provide draft genome sequences toward the future identification of virulence mechanisms associated with streptococcal keratitis in dogs. [ABSTRACT FROM AUTHOR]

Clinical cases resembling strangles are regularly seen in some areas of Croatia. However, there are no data on the prevalence of infection and the clinical forms or geographic distribution of the disease. The aim of this study was to determine the seroprevalence of Streptococcus equi subspecies equi in horses resident in Croatia, in order to estimate the geographic distribution of infection. The study included 291 horse sera from the eight counties where the majority of Croatian horses are kept. Sera were tested by indirect ELISA (iELISA) for the presence of serum antibodies against S. equi protein A (SEQ_2190) and protein C (SeM). Positive horses were detected in all counties. Overall seroprevalence was 16.5 per cent (48/291), ranging from 7.1 to 29.6 per cent. A positive association was observed between the population size of the horses in the counties and the seropositivity rates: the larger the population, the higher the seropositivity. The results of this study suggest that S. equi infection is widespread in Croatia. Further investigation of the clinical manifestations, circulating strains and other characteristics of the disease in Croatia and raising awareness of the disease among horse owners are now required. [ABSTRACT FROM AUTHOR]

The availability of next-generation sequencing techniques provides an unprecedented opportunity for the assignment of gene function. Streptococcus equi subspecies equi is the causative agent of strangles in horses, one of the most prevalent and important diseases of equids worldwide. However, the live attenuated vaccines that are utilized to control this disease cause adverse reactions in some animals. Here, we employ transposon-directed insertion-site sequencing (TraDIS) to identify genes that are required for the fitness of S. equi in whole equine blood or in the presence of H 2 O 2 to model selective pressures exerted by the equine immune response during infection. We report the fitness values of 1503 and 1471 genes, representing 94.5 and 92.5 % of non-essential genes in S. equi , following incubation in whole blood and in the presence of H 2 O 2 , respectively. Of these genes, 36 and 15 were identified as being important to the fitness of S. equi in whole blood or H 2 O 2 , respectively, with 14 genes being important in both conditions. Allelic replacement mutants were generated to validate the fitness results. Our data identify genes that are important for S. equi to resist aspects of the immune response in vitro , which can be exploited for the development of safer live attenuated vaccines to prevent strangles.