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Background: Equine granulocytic anaplasmosis (EGA) is a common disease in adult horses, but clinical disease in foals is rarely reported. The relationship between equine maternal and neonatal antibodies to Anaplasma phagocytophilum is unclear. Hypothesis/Objectives: That mares in an endemic region would be seropositive for A. phagocytophilum and that mare and foal serum IgG concentrations for A. phagocytophilum would correlate. Additionally, we hypothesized that foal IgG concentrations for A. phagocytophilum acquired by passive immunity would decline by 6 months of age. Animals: Twenty‐two healthy mare‐foal pairs. Methods: This prospective observational study investigated serum IgG concentrations specific for A. phagocytophilum in mares and foals using an immunofluorescent antibody test (IFA). The association between foal titer (as a binary variable) and age in months was assessed using a mixed‐effects logistic regression. Results: A positive correlation between newborn foal antibody titers and mare titers was identified at both the pre‐foaling (τa = 0.38, τb = 0.50, P =.009) and foaling timepoints (τa = 0.36, τb = 0.47, P =.01). In A. phagocytophilum seropositive neonates, it was unlikely that a positive titer would be detected by 3 months of age (OR = 0.002, P =.02, 95% CI: 0.00001‐0.38). Three out of 20 foals seroconverted between 3 and 6 months of age. Conclusions and Clinical Importance: Transfer of specific passive immunity to A. phagocytophilum occurred in 80% of foals born to seropositive mares and declined by 3 months of age. A. phagocytophilum infection should be considered in foals displaying clinical signs consistent with EGA. [ABSTRACT FROM AUTHOR]

Summary: Background: Streptococcus equi subspecies equi (S equi) is the cause of Strangles, one of the most prevalent diseases of horses worldwide. Variation within the immunodominant SeM protein has been documented, but a new eight‐component fusion protein vaccine, Strangvac, does not contain live S equi or SeM and conservation of the antigens it contains have not been reported. Objective: To define the diversity of the eight Strangvac antigens across a diverse S equi population. Study design: Genomic description. Methods: Antigen sequences from the genomes of 759 S equi isolates from 19 countries, recovered between 1955 and 2018, were analysed. Predicted amino acid sequences in the antigen fragments of SEQ0256(Eq5), SEQ0402(Eq8), SEQ0721(EAG), SEQ0855(SclF), SEQ0935(CNE), SEQ0999(IdeE), SEQ1817(SclI) and SEQ2101(SclC) in Strangvac and SeM were extracted from the 759 assembled genomes and compared. Results: The predicted amino acid sequences of SclC, SclI and IdeE were identical across all 759 genomes. CNE was truncated in the genome of five (0.7%) isolates. SclF was absent from one genome and another encoded a single amino acid substitution. EAG was truncated in two genomes. Eq5 was truncated in four genomes and 123 genomes encoded a single amino acid substitution. Eq8 was truncated in three genomes, one genome encoded four amino acid substitutions and 398 genomes encoded a single amino acid substitution at the final amino acid of the Eq8 antigen fragment. Therefore, at least 1579 (99.9%) of 1580 amino acids in Strangvac were identical in 743 (97.9%) genomes, and all genomes encoded identical amino acid sequences for at least six of the eight Strangvac antigens. Main limitations: Three hundred and seven (40.4%) isolates in this study were recovered from horses in the UK. Conclusions: The predicted amino acid sequences of antigens in Strangvac were highly conserved across this collection of S equi. [ABSTRACT FROM AUTHOR]

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]

Background: Rapid point‐of‐care (POC) detection of Streptococcus equi subsp. equi (S. equi) would theoretically reduce the spread of strangles by identifying index and carrier horses. Hypothesis: That the eqbE isothermal amplification (LAMP) assay, and the same eqbE LAMP assay tested in a microfluidic device format, are comparable to a triplex real‐time quantitative polymerase chain reaction (qPCR) assay that is commonly used in diagnostic labs. Samples Sixty‐eight guttural pouch lavage (GPL) specimens from horses recovering from strangles. Methods: Guttural pouch lavage specimens were tested for S. equi retrospectively using the benchtop eqbE LAMP, the eqbE LAMP microfluidic device, and compared to the triplex qPCR, that detects 2 S. equi‐specific genes, eqbE and SEQ2190, as the reference standard using the receiver operating characteristic area under the curve (ROC). Results: The 27/68 specimens were positive by benchtop eqbE LAMP, 31/64 by eqbE LAMP microfluidic device, and 12/67 by triplex qPCR. Using the triplex PCR as the reference, the benchtop eqbE LAMP showed excellent discrimination (ROC Area = 0.813, 95% confidence interval [CI] = 0.711‐0.915) as did the LAMP microfluidic device (ROC Area = 0.811, 95% CI = 0.529‐0.782). There was no significant difference between the benchtop LAMP and LAMP microfluidic device (ROC Area 0.813 ± 0.055 vs 0.811 ± 0.034, P =.97). Conclusions: The eqbE LAMP microfluidic device detected S. equi in GPL specimens from convalescent horses. This assay shows potential for development as a POC device for rapid, sensitive, accurate, and cost‐efficient detection of S. equi. [ABSTRACT FROM AUTHOR]