Background
Streptococcus equi ssp. equi causes characteristic clinical signs that are most severe in young horses, including fever, purulent nasal discharge, and lymph node abscessation in the head region.Hypothesis/ObjectivesClinical, serologic, and microbiologic factors related to unexpectedly mild disease severity in a natural outbreak of strangles in immunologically naïve weanlings were investigated.AnimalsOne‐hundred and twelve warmblood weanlings.MethodsProspective longitudinal observational study of a natural outbreak of strangles. The entire cohort was examined at the peak of the outbreak by deep nasal swabs for culture and quantitative PCR (qPCR) for the presence of S. equi and clinically and serologically in a sequential manner by an optimized ELISA from the index case throughout the outbreak until resolution. Descriptive statistics were calculated and comparisons made using a nondirectional Wilcoxon signed‐rank test.ResultsOutbreak morbidity was 53%, with 9 of 14 horses culture positive and 26 of 53 horses qPCR positive for S. equi lacking clinical signs characteristic of strangles. By resolution, 91 of 112 had seroconverted to Antigen A by ELISA but seroconversion to antigen C (part of the SeM protein) was minimal. Sequencing of the isolates detected no alterations in the SeM protein, but identified a 61 bp deletion in the gene SEQ_0402.Conclusions and Clinical ImportanceAbsence of clinical signs alone in naïve horses may be an insufficient criterion to release horses from strangles quarantine measures. Restricted seroconversion to antigen C may have been associated with decreased clinical severity. The role of a minor gene deletion in SEQ_0402 in the virulence of S. equi warrants further investigation.
There is good agreement between EGG and IgG-RID, with slightly more conservative estimates of immunoglobulins obtained using EGG. Total globulins may be a useful and economic quantitative screening test with cut-offs achieving high sensitivities, but analyser-specific cut-offs may be necessary.
Background: Difficulty in detection of silent carriers of Streptococcus equi is a key reason for its continued spread to immunologically naïve groups of horses. Objective: To determine whether clinical examination, markers of inflammation, or serology differentiate silent carriers of S. equi in recovered comingled horses. Animals: Ninety-eight warmblood yearlings and 72 unaffected mares on a large breeding farm (outbreak A), 38 mature Icelandic horses at a riding stable (outbreak B), and 27 mixed breed horses at a boarding stable (outbreak C). Methods: Prospective observational study 6 months to 2 years after strangles outbreaks. Carriers were defined as any animal positive on culture or qPCR to S. equi from nasopharyngeal lavage or guttural pouch endoscopy and lavage. Most horses had complete physical exams and 1 group included evaluation of white blood cell counts and serum amyloid A. Sera from all horses was tested for antibodies to antigens A and C of S. equi using an enhanced indirect ELISA. Descriptive statistics were calculated. Data were compared using paired t tests, Wilcoxon ranked test, chi square, or the Fishers exact test. Significance was set at P < .05.
Summary:The aim of the present study was to evaluate failure of transfer of passive immunity (FTPI), estimated using electrophoretic gamma globulin concentrations (EGG), during the first 24 hours of life in neonatal foals given either intensive postnatal assistance to nurse or no assistance for the first twelve hours postnatum. Sixty warmblood foals from the same breeding farm were included in this prospective study. Of these, 40 foals (Group 1) were assisted to stand after one hour and nurse after two hours postnatum. They received colostrum by bottle hourly from two hours postnatum until they nursed unaided, as well as by bottle or nasogastric tube after eight hours postnatum if their general condition declined. A further 20 foals (Group 2) received no initial assistance but were given colostrum by bottle or nasogastric tube twelve hours postnatum if they had not nursed or if their general condition declined. A serum protein electrophoresis was performed from samples collected 6, 8, 10, 12, 18 and 24 hours after birth in each foal. In Group 1, 16/40 foals nursed unaided within two hours postnatum, 16/40 foals were assisted to the dam's udder, and 8/40 foals received colostrum by bottle. The median time from birth to the first unassisted intake of colostrum was 141 minutes and 149 minutes in Groups 1 and 2, respectively. The median EGG concentration was lowest at 6 hours postnatum in both groups. At 10 hours postnatum, both groups achieved a median EGG above 8 g/L. The highest median EGG concentration was reached at 12 hours in both groups, after which no significant change in EGG concentrations was observed. No significant difference in EGG concentrations was found between the groups. Moreover, no difference in the proportion of foals with FTPI (defined as EGG < 8 g/L at 24 hours postnatum) was found between the groups. Findings of the present study suggest that EGG concentrations and FTPI are not significantly affected by the postnatal care practices used in this breeding farm. Further investigations are required to evaluate methods of postnatal care that may considerably impact FTPI in neonatal foals.
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