Streptococcus equi Infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles-Revised Consensus Statement

Differences in the genome, methylome, and transcriptome do not differentiate isolates of Streptococcus equi subsp. equi from horses with acute clinical signs from isolates of inapparent carriers

Streptococcus equi subsp. equi (SEE) is a host-restricted bacterium that causes the common infectious upper respiratory disease known as strangles in horses. Perpetuation of SEE infection appears attributable to inapparent carrier horses because it neither persists long-term in the environment nor infects other host mammals or vectors, and infection results in short-lived immunity. Whether pathogen factors enable SEE to remain in horses without causing clinical signs remains poorly understood. Thus, our objective was to use next-generation sequencing technologies to characterize the genome, methylome, and transcriptome of isolates of SEE from horses with acute clinical strangles and inapparent carrier horses—including isolates recovered from individual horses sampled repeatedly—to assess pathogen-associated changes that might reflect specific adaptions of SEE to the host that contribute to inapparent carriage. The accessory genome elements and methylome of SEE isolates from Sweden and Pennsylvania revealed no significant or consistent differences between acute clinical and inapparent carrier isolates of SEE. RNA sequencing of SEE isolates from Pennsylvania demonstrated no genes that were differentially expressed between acute clinical and inapparent carrier isolates of SEE. The absence of specific, consistent changes in the accessory genomes, methylomes, and transcriptomes of acute clinical and inapparent carrier isolates of SEE indicates that adaptations of SEE to the host are unlikely to explain the carrier state of SEE. Efforts to understand the carrier state of SEE should instead focus on host factors.

Antimicrobial prescribing patterns in equine ambulatory practice

Antimicrobial resistance is one of the most important public health risks facing our world today. Antimicrobials are commonly prescribed in equine veterinary medicine, but limited information exists documenting their use in practice. The goal of this study was to investigate antimicrobial prescription patterns in regards to prescription frequency, duration, drug class, clinician and affected body system in an equine ambulatory setting via retrospective analysis of billing and electronic medical records. Risk factors associated with antimicrobial prescription including the nature of the visit, submission of a culture, body system affected and clinician were assessed using multivariable regression. We found that antimicrobials were prescribed in 8.5 % of visits with a median number of 3.5 (IQR 0.8-12.2) animal-defined daily doses (ADD), defined as the number of daily doses of all antimicrobials prescribed to a patient at a single visit. Aminoglycosides were the most common class of antimicrobials prescribed and trimethoprim sulfamethoxazole was the most common drug prescribed overall. Amikacin was primarily used for patients presenting with musculoskeletal signs, and the median number of ADDs for visits where amikacin was prescribed was 1 (IQR 0.9-1.9), while the median number of antimicrobial ADDs for all other visits was 4.4 (IQR 0-14.1). Statistically significant differences in antimicrobial use patterns existed across clinicians, months, years and affected body systems. Horses presenting with ocular (OR 1199; 95 % CI 204-7,037; p < 0.001) and integumentary (OR 365; 95 % CI 87.2-1532; p < 0.001) signs were most likely to be prescribed an antimicrobial. Emergency visits (OR 5.61; 95 % CI 3.19-9.89; p < 0.001) and submission of a bacterial culture (OR 3.58; 95 % CI 2.11-6.09; p < 0.001) were associated with an increased likelihood of an antimicrobial prescription. This observational study was the first to quantitatively characterize antimicrobial use patterns in equine ambulatory practice in the United States, which is an important step needed to determine appropriateness of use and develop and evaluate antimicrobial stewardship guidelines.

Respiratory Distress in the Adult and Foal

Respiratory distress in the horse and foal is an emergency. Managing equine respiratory distress in the field starts with appropriate assessment of the patient to determine whether the breathing obstruction stems from the upper or lower respiratory tract or is nonrespiratory in origin. From a thorough, but efficient, physical examination to point-of-care ultrasound and endoscopy, the veterinarian has many tools in the field to help diagnose the patient.

Diagnostic testing patterns for Streptococcus equi subsp. equi in Ontario horses during the years 2008 to 2018

This retrospective study describes testing patterns and the incidence of Streptococcus equi subsp. equi in Ontario to assess the utility of laboratory data for surveillance purposes. Laboratory records for equine infectious disease test submissions were extracted from the Animal Health Laboratory (AHL) at the University of Guelph for the years 2008 to 2018. Yearly and seasonal trends in S. equi testing and the proportion of tests that returned positive results were assessed. The number of samples submitted for S. equi testing decreased over the 11-year period (odds ratio = 0.96, 95% confidence interval: 0.92 to 0.999; P = 0.04). A generalized linear model identified a significant seasonal effect for animals recognized as clinically ill, with the highest test positivity noted in the winter. Although this study identified important trends in the incidence of S. equi in Ontario, the variability in information accompanying test submissions made the data challenging to interpret, highlighting the need for more complete diagnostic submission data for S. equi.

The clinical and histopathologic effects of potentiated chlorhexidine in the upper respiratory tract of horses

OBJECTIVE

To describe the bactericidal and fungicidal properties of a 0.0005% chlorhexidine (CHD) solution potentiated with EDTA-Tris buffers (CHD-EDTA-Tris) and evaluate the safety of 0.0005% CHD-EDTA-Tris in the upper respiratory tract (URT) of normal horses.

STUDY DESIGN

Clinical, prospective study.

ANIMALS

Eight healthy, skeletally mature horses.

METHODS

In vitro-serial dilutions of CHD-EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal and fungicidal activity against Aspergillus fumigatus, Escherichia coli, Staphylococcus aureus, Streptococcus equi subspecies ssp. equi, Streptococcus equi ssp. zooepidemicus, and Pseudomonas aeruginosa. In vivo-eight healthy horses were topically treated twice with 30 ml of 0.0005% CHD-EDTA-Tris. Mucosal samples from each location were evaluated for the presence of inflammation or pathologic lesions.

RESULTS

Solutions containing CHD were superior in fungal and bacterial killing to those without. In vitro-a 0.005% CHD-EDTA-Tris was 100% effective against all bacterial and fungal species evaluated, while a 0.0005% CHD-EDTA-Tris was less efficacious against A. fumigatus and S. equi ssp. equi. In vivo-a 0.0005% CHD-EDTA-Tris did not cause any clinical, gross, or histologic abnormalities when topically applied to the equine URT.

CONCLUSIONS

A 0.0005% CHD-EDTA-Tris was highly effective for killing of common bacterial and fungal isolates in the equine upper respiratory tract. Short-term topical treatment of the equine URT with dilute CHD did not cause gross or histological inflammation in the tissue.

CLINICAL SIGNIFICANCE

A 0.0005% CHD solution with EDTA-Tris should be considered for treatment of clinically relevant inflammatory or infectious conditions or in the URT of the horse.

Nicoletella semolina in the airways of healthy horses and horses with severe asthma

Background

Nicoletella semolina was identified in the airways of horses and its low prevalence could be because of its difficult differentiation from other Pasteurellaceae.

Objectives

To develop a molecular method for the identification of N. semolina and to evaluate its prevalence in the mouth and the airways of healthy and severe asthmatic horses.

Animals

Six healthy and 6 severely asthmatic horses in phase I, 10 severely asthmatic horses in phase II, and 10 healthy horses in phase III.

Methods

Cohort (phases I and II) and cross‐sectional (phase III) studies. Quantitative polymerase chain reaction primers targeting the sodA gene were optimized. N. semolina was quantified in oral and nasal washes and in bronchoalveolar lavage fluid (BALF; phase I, sampled twice), in nasal washes and BALF (phase II, sampled twice), and in nasal washes (phase III).

Results

N. semolina was found in the nose of 5, 10, and 9 horses in phases I, II, and III, respectively (first sampling for phases I and II). Six BALF from 5 different horses were positive for N. semolina in phase II. In phase I, there was no significant difference in the nasal loads of healthy horses (median (range): 2.04 × 10⁴ copies/mL (0‐2.44 × 10⁵)) and asthmatic horses in exacerbation (3.75 × 10² (0‐4.84 × 10⁶); Wilcoxon's rank sum test, P = .57).

Conclusions and Clinical Importance

N. semolina is commonly found in the airways of horses. The potential pathogenicity of N. semolina remains to be elucidated, but the molecular technique we developed will facilitate future studies.

Nasopharyngeal Microbiomes in Donkeys Shedding Streptococcus equi Subspecies equi in Comparison to Healthy Donkeys

Streptococcus equi subsp. equi (S. equi) is the pathogen causing strangles, a highly infectious disease that can affect equids including donkeys of all ages. It can persistently colonize the upper respiratory tract of animals asymptomatically for years, which serves as a source of infection. Several strangles outbreaks have been reported in the donkey industry in China in the last few years and pose a great threat to health, production, and the welfare of donkeys. Nasopharyngeal swab samples for culture and PCR are used widely in strangles diagnosis. Additionally, microbiomes within and on the body are essential to host homoeostasis and health. Therefore, the microbiome of the equid nasopharynx may provide insights into the health of the upper respiratory tract in animals. There has been no study investigating the nasopharyngeal microbiome in healthy donkeys, nor in donkeys shedding S. equi. This study aimed to compare nasopharyngeal microbiomes in healthy and carrier donkeys using 16S rRNA gene sequencing. Nasopharyngeal samples were obtained from 16 donkeys recovered from strangles (group S) and 14 healthy donkeys with no history of strangles exposure (group H). Of those sampled, 7 donkeys were determined to be carriers with positive PCR and culture results in group S. In group H, all 14 donkeys were considered free of strangles based on the history of negative exposure, negative results of PCR and culture. Samples from these 21 donkeys were used for microbial analysis. The nasopharyngeal microbiome composition was compared between the two groups. At the phylum level, relative abundance of Proteobacteria was predominantly higher in the S. equi carrier donkeys than in healthy donkeys (P < 0.01), while Firmicutes and Actinobacteria were significantly less abundant in the S. equi carrier donkeys than in healthy donkeys (P < 0.05). At the genus level, Nicoletella was detected in the upper respiratory tract of donkeys for the first time and dominated in carrier donkeys. It is suspected to suppress other normal flora of URT microbiota including Streptococcus spp., Staphylococcus spp., and Corynebacterium spp. We concluded that the nasopharyngeal microbiome in S. equi carrier donkeys still exhibited microbial dysbiosis, which might predispose them to other airway diseases.

Globetrotting strangles: the unbridled national and international transmission of Streptococcus equi between horses

The equine disease strangles, which is characterized by the formation of abscesses in the lymph nodes of the head and neck, is one of the most frequently diagnosed infectious diseases of horses around the world. The causal agent, Streptococcus equi subspecies equi, establishes a persistent infection in approximately 10 % of animals that recover from the acute disease. Such 'carrier' animals appear healthy and are rarely identified during routine veterinary examinations pre-purchase or transit, but can transmit S. equi to naïve animals initiating new episodes of disease. Here, we report the analysis and visualization of phylogenomic and epidemiological data for 670 isolates of S. equi recovered from 19 different countries using a new core-genome multilocus sequence typing (cgMLST) web bioresource. Genetic relationships among all 670 S. equi isolates were determined at high resolution, revealing national and international transmission events that drive this endemic disease in horse populations throughout the world. Our data argue for the recognition of the international importance of strangles by the Office International des Épizooties to highlight the health, welfare and economic cost of this disease. The Pathogenwatch cgMLST web bioresource described herein is available for tailored genomic analysis of populations of S. equi and its close relative S. equi subspecies zooepidemicus that are recovered from horses and other animals, including humans, throughout the world. This article contains data hosted by Microreact.

Horses vaccinated with live attenuated intranasal strangles vaccine seroconvert to SEQ2190 and SeM

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.

Streptococcal Infections in Marine Mammals

Marine mammals are sentinels for the marine ecosystem and threatened by numerous factors including infectious diseases. One of the most frequently isolated bacteria are beta-hemolytic streptococci. However, knowledge on ecology and epidemiology of streptococcal species in marine mammals is very limited. This review summarizes published reports on streptococcal species, which have been detected in marine mammals. Furthermore, we discuss streptococcal transmission between and adaptation to their marine mammalian hosts. We conclude that streptococci colonize and/or infect marine mammals very frequently, but in many cases, streptococci isolated from marine mammals have not been further identified. How these bacteria disseminate and adapt to their specific niches can only be speculated due to the lack of respective research. Considering the relevance of pathogenic streptococci for marine mammals as part of the marine ecosystem, it seems that they have been neglected and should receive scientific interest in the future.

Validation of a point-of-care polymerase chain reaction assay for detection of Streptococcus equi subspecies equi in rostral nasal swabs from horses with suspected strangles

This study aimed to validate a point-of-care polymerase chain reaction (PCR) assay for detection of Streptococcus equi subsp. equi (S. equi) in rostral nasal swabs from horses with suspected acute strangles and to compare the results against the molecular gold standard of quantitative polymerase chain reaction (qPCR). Two hundred thirty-two individual swabs of rostral nasal passages were characterized by qPCR as S. equi positive, S. equi subsp. zooepidemicus (S. zooepidemicus) positive, or S. equi and S. zooepidemicus negative. The specificity and sensitivity of the point-of-care PCR assay were 89% and 84%, respectively. The limits of detection of the qPCR assay and the point-of-care PCR analyzer were 3 and 277 eqbE target genes of S. equi, respectively. Overall agreement and short turnaround time make the point-of-care PCR assay a potential molecular diagnostic platform that will enhance the capability of equine veterinarians to timely support a diagnosis of strangles and institute proper biosecurity protocols.

Immunogenicity of Streptococcus equi subsp. equi recombinant SeM protein and bacterin in mice

ABSTRACT: The infection caused by Streptococcus equi, known as strangles, affects the respiratory system of horses, causing high morbidity and rapid spread among the herd. Bacterin vaccines, composed of inactivated whole cells of S. equi, have variable efficacy and duration. Infected animals produce specific antibodies against SeM, the immunodominant antigen of S. equi. This makes it a promising target for vaccine development. In this context, the objective of this work was to evaluate a vaccine combining S. equi bacterin and recombinant SeM protein. Mice were vaccinated with bacterin (S. equi ~1.2 × 108CFU/ml); rSeM protein (20μg); bacterin-rSeM combination; or PBS (Control Group) and challenged with a suspension of S. equi, containing 10 × LD50. All vaccinated mice survived the challenge and produced anti-rSeM and anti-S. equi antibodies, which were assessed by indirect ELISA. The Control Group reached endpoint criteria 96 h after infection. These results demonstrate that a vaccine combining the S. equi bacterin with rSeM protein protects mice against strangles. This combination vaccine could potentially protect horses and overcome the limitations of currently available strangle vaccines.

Isolation of Campylobacter fetus subspecies fetus from an abdominal abscess in an adult mare

A 12-year-old Warmblood mare was referred for evaluation of behavioral changes not explained by general physical examination or lameness evaluation. Transrectal ultrasound examination was performed to determine if the behavioral changes were related to ovarian abnormalities, and a large abscess was found near the base of the cecum. Laparoscopic-guided aspiration and lavage of the abscess cavity followed by injection of benzyl penicillin G was carried out. Culture of the lavage sample yielded Campylobacter fetus subspecies fetus, an organism not previously reported as an etiological agent in abdominal abscesses in horses. The mare was treated after surgery with an extended course of antibiotics (minocycline per os q12h for 10 days followed by enrofloxacin per os q24h for 42 days). The mare resumed work in competitive eventing 10 months after surgery, and the behavioral complaints had resolved according to the owner. Key clinical message: We describe the diagnosis and treatment of a mare with an abdominal abscess from which Campylobacter fetus subspecies fetus was cultured. This organism has not previously been reported as an etiological agent in abdominal abscesses in horses.

Investigation of a 24-Hour Culture Step to Determine the Viability of Streptococcus equi Subspecies equi Via Quantitative Polymerase Chain Reaction in Nasal Secretions From Horses With Suspected Strangles

Polymerase chain reaction (PCR)-based detection assays for Streptococcus equi subspecies equi often overestimate the prevalence of samples containing viable organisms. The objective of this study was to determine if viability could be determined using genome quantitation and detection of messenger RNA (mRNA) transcripts for the SeM gene of S. equi in pre- and post-cultured samples. Nasal secretions collected from 42 horses with suspected strangles were tested by culture and by quantitative PCR (qPCR) before and 24 hours after a culture step. Viable S. equi was determined based on the detection of S. equi via culture, the detection of mRNA transcripts for the SeM gene of S. equi by qPCR, and/or an increase in absolute number of SeM target genes of S. equi between pre- and post-cultured samples. Viability was determined in 28/42 samples based on isolation of S. equi (11 samples), the presence of mRNA transcripts for the SeM gene of S. equi (25), and/or an increase in absolute quantitation of the SeM gene of S. equi between pre- and post-culture (17). The overall agreement between culture alone and the three criteria to determine viability was 59%. The overall agreement for the detection of mRNA transcripts and increase in absolute target genes was 88% and 74%, respectively. The combination of mRNA transcripts and increase in absolute target genes was able to determine the viability status in all 42 samples. In the absence of a culture-positive result for S. equi, the determination of viability can be achieved by using molecular strategies applied to samples undergoing a 24-hour culture step.

Modification of empirical antimicrobial regimens in large animal medicine

BACKGROUND

Empirical antimicrobial regimens can be modified following new diagnostic information or when empirical treatment fails. Little is known about the frequency or clinical context in which these modifications occur. We characterised these modifications in a large animal hospital to identify when antimicrobial use could be optimised.

METHODS

Chart reviews were performed for all inpatients and outpatients administered antimicrobials at a large animal veterinary referral and teaching hospital in 2017-2018 (n=1163 visits) to determine when and why empirical regimens were modified. Multinomial logistic regression was performed to identify factors associated with reasons for modification.

RESULTS

Empirical antimicrobial regimens were modified in 17.3 per cent of visits. The main reasons were parenteral-oral conversions in horses and failure of disease prevention or treatment in ruminants. Empirical therapy for disease prevention was more likely to be modified because of complications in ruminants and in animals on the emergency/critical care service. Empirical therapy for disease treatment was more often modified for reasons other than de-escalation in ruminants and in animals with longer lengths of stay.

CONCLUSIONS

Empirical antimicrobial regimens were modified infrequently and mostly for purposes of parenteral-oral conversion in horses and lack of response in ruminants. De-escalation of antimicrobials administered for disease treatment, when guided by diagnostics, is a major tenet of judicious antimicrobial use. However, more research is needed to determine when and how antimicrobial regimens administered for disease prevention should be modified.

Markers of long term silent carriers of Streptococcus equi ssp. equi in horses

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.

RESULTS

Apart from weanlings at 6 months in outbreak A, there was no significant association between any clinical markers or serology with carrier state (P = .06-1). Moreover, 3/12 culture positive carriers were seronegative to S. equi.

CONCLUSIONS AND CLINICAL IMPORTANCE

Silent carriers of S. equi do not differ clinically or on markers of inflammation to their noncarrier herd-mates. Moreover, serology alone will not distinguish carriers in comingled horses.

Vaccination of yearling horses against poly-N-acetyl glucosamine fails to protect against infection with Streptococcus equi subspecies equi

Strangles is a common disease of horses with worldwide distribution caused by the bacterium Streptococcus equi subspecies equi (SEE). Although vaccines against strangles are available commercially, these products have limitations in safety and efficacy. The microbial surface antigen β 1→6 poly-N-acetylglucosamine (PNAG) is expressed by SEE. Here we show that intramuscular (IM) injection alone or a combination of IM plus intranasal (IN) immunization generated antibodies to PNAG that functioned to deposit complement and mediate opsonophagocytic killing of SEE ex vivo. However, immunization strategies targeting PNAG either by either IM only injection or a combination of IM and IN immunizations failed to protect yearling horses against infection following contact with infected horses in an experimental setting. We speculate that a protective vaccine against strangles will require additional components, such as those targeting SEE enzymes that degrade or inactivate equine IgG.

Pharmacokinetic and pharmacodynamic integration for optimal dosage of cefquinome against Streptococcus equi subsp. equi in foals

Cefquinome is administered in horses for the treatment of respiratory infection caused by Streptococcus equi subsp. zooepidemicus, and septicemia caused by Escherichia coli. However, there have been no attempts to use cefquinome against Streptococcus equi subsp. equi (S. equi), the causative agent of strangles. Hence the objective of this study was to calculate an optimal dosage of cefquinome against S. equi based on pharmacokinetics and pharmacodynamics integration. Cefquinome (1.0 mg/kg) was administered by intravenous and intramuscular routes to six healthy thoroughbred foals. Serum cefquinome concentrations were determined by high-performance liquid chromatography. The in vitro and ex vivo antibacterial activity were determined from minimum inhibitory concentrations (MIC) and bacterial killing curves. The optimal dosage was calculated from the integration of pharmacokinetic parameters and area under the curve (AUC_24h/MIC) values. Total body clearance and volume of distribution of cefquinome after intravenous administration were 0.06 L/h/kg and 0.09 L/kg, respectively. Following intramuscular administration, a maximum concentration of 0.73 μg/mL at 1.52 h (T_max) and a systemic bioavailability of 37.45% were observed. The MIC of cefquinome against S. equi was 0.016 μg/mL. The ex vivo AUC_24h/MIC values representing bacteriostatic, and bactericidal activity were 113.11, and 143.14 h, respectively. Whereas the %T > MIC for bactericidal activity was 153.34%. In conclusion, based on AUC_24h/MIC values and pharmacokinetic parameters, cefquinome when administered by intramuscularly at a dosage of 0.53 mg/kg every 24 h, would be effective against infection caused by S. equi in foals. Further studies may be necessary to confirm its therapeutic efficacy in a clinical environment.

Strangles Awareness Week: a new initiative to help stamp out strangles

Abigail McGlennon of the Animal Health Trust and Andrea Vilela of the Redwings Horse Sanctuary describe the creation and impact of a new initiative to tackle strangles in UK horses.

Diagnosis, Surveillance and Management of Streptococcus equi subspecies zooepidemicus Infections in Chinchillas (Chinchilla lanigera)

During a 6-mo period, two 5-6 mo old female chinchillas (Chinchilla lanigera) were examined at the University of Colorado Anschutz Medical Campus after the discovery of firm, nonmobile masses in the left ventral cervical and left axillary region. Other than these findings and mild weight loss, both chinchillas' physical exams were normal. Bloodwork revealed an inflammatory leukogram characterized by leukocytosis, toxic neutrophils, lymphopenia, and monocytosis with mild, nonregenerative anemia. At necropsy, both masses were identified as abscesses. Streptococcus equi, subspecies zooepidemicus (S. zooepidemicus) was isolated in pure culture. Histology of the lungs, liver, spleen, and kidneys showed a marked increase in the numbers of both polymorphonuclear leukocytes and lymphocytes. Both animals were deemed unsuitable for research and were euthanized under isoflurane anesthesia by an intracardiac injection of pentobarbital sodium solution. S. zooepidemicus is an opportunistic, commensal organism found in the upper respiratory tract of horses. This organism has been documented to cause disease in other species and is zoonotic. Infections in humans have been reported, resulting in glomerulonephritis, endocarditis, septic arthritis, osteomyelitis, meningitis, and death. To aid in diagnosis and prospective surveillance of this bacteria, oral and nasal swabs were collected from the remaining cohort of chinchillas, and a qPCR screening assay was implemented. Within 12 mo, 4 of 41 additional females tested positive by culture or qPCR, resulting in a disease prevalence of 14% (6 of 43). However, only 2 of the additional 4 S. zooepidemicus positive animals developed clinical signs. The potential for the spread of infection, zoonosis, and adverse effects on research demonstrate that surveillance for S. zooepidemicus should be considered in a biomedical research environment.

Descriptive network analysis of a Standardbred horse training facility contact network: Implications for disease transmission

Infectious respiratory disease is a common cause of morbidity among racehorses. Quantification of contact patterns in training facilities could help inform disease prevention strategies. The study objectives were to: i) describe the contact network among horses, locations, and humans at a Standardbred horse training facility in Ontario; ii) describe the characteristics of highly influential individuals; and iii) investigate how management changes alter the network metrics and discuss the potential implications for disease transmission. Proximity loggers detected contacts among horses, staff, and locations (n = 144). Network metrics and node centrality measures were described for a 2-mode and horse-only contact network. The 2-mode network density was 0.16. and the median node degree was 20 [interquartile range (IQR) = 12 to 27]. Yearlings and floating staff were most influential in the network suggesting biosecurity programs should emphasize reducing contacts in these groups. Removing highly influential staff or co-housing of age groups resulted in changes to network diameter and density.

Surveillance of equine strangles: a new initiative

Abigail McGlennon from the Animal Health Trust introduces a new project to gather information on cases of strangles in horses throughout the UK.

Disseminated septic arthritis caused by Streptococcus equi infection

We describe a rare case of bloodstream infection and disseminated septic arthritis in a relatively fit and well 73-year-old retired farmer and gamekeeper, due to the zoonotic organism Streptococcus equi The presence of the organism in multiple joints led to slow clinical response to treatment and was complicated by relapse of infection and lengthy disability. Source control was achieved with multiple joint washouts and spinal cord decompression. Following this, a 6-week course of intravenous antibiotics was required for complete clearance of infection. After a long period of rehabilitation, the patient made a good recovery. This case demonstrates that S. equi can cause life threatening and difficult to treat sepsis in humans and requires a high index of suspicion in people who have regular contact with equine species, cattle and unpasteurised milk.

Antibiotic resistance in bacteria associated with equine respiratory disease in the United Kingdom

INTRODUCTION

Respiratory diseases account for the highest number of clinical problems in horses compared with other body systems. While microbiological culture and sensitivity testing is essential for certain cases, knowledge of the most likely bacterial agents and their susceptibilities is necessary to inform empirical antibiotic choices.

METHODS

A retrospective study of microbiological and cytological results from upper and lower respiratory samples (n=615) processed in a commercial laboratory between 2002 and 2012 was carried out. A further study of lower respiratory samples from horses with clinical signs of lower respiratory disease from May to June 2012 was undertaken.

RESULTS

Both studies revealed Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa, Pasteurella species, Escherichia coli and Bordetella bronchiseptica as the most frequently isolated species. S equi subspecies zooepidemicus and subspecies equi were susceptible to ceftiofur (100 per cent) and erythromycin (99 per cent). Resistance to penicillin (12.5 per cent of S equi subspecies equi from upper respiratory tract samples) and tetracycline (62.7 per cent) was also detected. Gram-negative isolates showed resistance to gentamicin, trimethoprim-sulfamethoxazole and tetracycline but susceptibility to enrofloxacin (except Pseudomonas species, where 46.2 per cent were resistant). Multiple drug resistance was detected in 1 per cent of isolates.

CONCLUSION

Resistance to first-choice antibiotics in common equine respiratory tract bacteria was noted and warrants continued monitoring of their susceptibility profiles. This can provide information to clinicians about the best empirical antimicrobial choices against certain pathogenic bacteria and help guide antibiotic stewardship efforts to converse their efficacy.

Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers

BACKGROUND

Serology is commonly used as a means of identifying horses that might be chronic and silent carriers of S. equi but its sensitivity is rarely examined.

OBJECTIVES

The study was designed to investigate the sensitivity of serological testing for antibodies against S. equi antigens A and C to detect guttural pouch carriers of S. equi.

STUDY DESIGN

Retrospective clinical study.

METHODS

As part of routine surveillance and quarantine procedures horses arriving at a welfare charity quarantine unit were subject to both microbiological sampling of guttural pouches and also serological testing for antibodies directed at S. equi antigens A and C. Laboratory results and endoscopic findings were examined to determine associations between serological results and guttural pouch carriage of S. equi.

RESULTS

Of 287 included horses, 9 (3.1%) were found to be guttural pouch carriers. There was no significant association between serological status and guttural pouch carriage of S. equi Only one of the nine carriers (11%) was seropositive using a cut-off of OD ≥ 0.5, and only three of nine (33%) using a cut-off of OD ≥ 0.3.

MAIN LIMITATIONS

Horses examined in this study were new arrivals at a welfare centre rather than from a general, well-managed, equid population. As a retrospective clinical study, the laboratory test results could not be repeated for further confirmation.

CONCLUSIONS

Caution is advised when relying on seronegativity to antigens A and C in order to discount the possibility of chronic carriage of S. equi in guttural pouches.

Optimizing 16S rRNA gene profile analysis from low biomass nasopharyngeal and induced sputum specimens

BACKGROUND

Careful consideration of experimental artefacts is required in order to successfully apply high-throughput 16S ribosomal ribonucleic acid (rRNA) gene sequencing technology. Here we introduce experimental design, quality control and "denoising" approaches for sequencing low biomass specimens.

RESULTS

We found that bacterial biomass is a key driver of 16S rRNA gene sequencing profiles generated from bacterial mock communities and that the use of different deoxyribonucleic acid (DNA) extraction methods [DSP Virus/Pathogen Mini Kit® (Kit-QS) and ZymoBIOMICS DNA Miniprep Kit (Kit-ZB)] and storage buffers [PrimeStore® Molecular Transport medium (Primestore) and Skim-milk, Tryptone, Glucose and Glycerol (STGG)] further influence these profiles. Kit-QS better represented hard-to-lyse bacteria from bacterial mock communities compared to Kit-ZB. Primestore storage buffer yielded lower levels of background operational taxonomic units (OTUs) from low biomass bacterial mock community controls compared to STGG. In addition to bacterial mock community controls, we used technical repeats (nasopharyngeal and induced sputum processed in duplicate, triplicate or quadruplicate) to further evaluate the effect of specimen biomass and participant age at specimen collection on resultant sequencing profiles. We observed a positive correlation (r = 0.16) between specimen biomass and participant age at specimen collection: low biomass technical repeats (represented by < 500 16S rRNA gene copies/μl) were primarily collected at < 14 days of age. We found that low biomass technical repeats also produced higher alpha diversities (r = - 0.28); 16S rRNA gene profiles similar to no template controls (Primestore); and reduced sequencing reproducibility. Finally, we show that the use of statistical tools for in silico contaminant identification, as implemented through the decontam package in R, provides better representations of indigenous bacteria following decontamination.

CONCLUSIONS

We provide insight into experimental design, quality control steps and "denoising" approaches for 16S rRNA gene high-throughput sequencing of low biomass specimens. We highlight the need for careful assessment of DNA extraction methods and storage buffers; sequence quality and reproducibility; and in silico identification of contaminant profiles in order to avoid spurious results.

Novel Streptococcus equi strains causing strangles outbreaks in Arabian horses in Egypt

Strangles displays a major challenge to veterinary medicine worldwide. However, no data on Streptococcus equi subsp. equi (S. equi) M protein alleles have been reported so far from Arabian horses. We report here for the first time the S. equi SeM alleles causing strangles in Arabian horses, and the associated risk factors for the disease. Duplicate samples from one hundred Arabian horses with acute strangles in confirmed outbreaks and sporadic cases were analysed by phenotypic methods and multiplex polymerase chain reaction (PCR) targeting streptokinase precursor, seeI and sodA genes. PCR and sequencing of S. equi SeM gene were employed for strains typing, and the four superantigens were determined among the allelic variants. Direct-sample PCR confirmed and highly positively correlated (r = .85) with the phenotypic results, and detected S. equi in five samples more than the conventional culture. A combination of multiplex PCR from samples and culture could successfully identify S. equi (92%), S. zooepidemicus (5%) and S. equisimilis (3%). SeM typing demonstrated five SeM alleles, including four previously unidentified alleles that were deposited in the PubMLST-SeM database. SeM-139 and SeM-141 are related to some strains that were recently recovered from donkeys in China. SeM-140 and SeM-199 are related to a group of alleles from horses in Europe. Variation in the presence of seeM, seeH and seeL superantigens was found across the four novel alleles without interference with the severity of strangles and clinical presentation seen in different outbreaks. Horse age was the most important factor in developing strangles, followed by seasonality and the diagnosis of strangles in the previous year. These new findings comprise a significant contribution to the horse industry through the identification of novel S. equi SeM types that may bolster measures for strangles control as the identified SeM alleles will certainly help in the development of SeM-containing vaccine.

Evolution of In Vitro Antimicrobial Susceptibility of Equine Clinical Isolates in France between 2016 and 2019

The present study described the evolution of antimicrobial resistance in equine pathogens isolated from 2016 to 2019. A collection of 7806 bacterial isolates were analysed for their in vitro antimicrobial susceptibility using the disk diffusion method. The most frequently isolated pathogens were group C Streptococci (27.0%), Escherichia coli (18.0%), Staphylococcus aureus (6.2%), Pseudomonas aeruginosa (3.4%), Klebsiella pneumoniae (2.3%) and Enterobacter spp. (2.1%). The majority of these pathogens were isolated from the genital tract (45.1%, n = 3522). With the implementation of two French national plans (named ECOANTIBIO 1 and 2) in 2012-2016 and 2017-2021, respectively, and a reduction in animal exposure to veterinary antibiotics, our study showed decreases in the resistance of group C Streptococci, Klebsiella pneumoniae and Escherichia coli against five classes, four classes and one class of antimicrobials tested, respectively. However, Staphylococcus aureus, Escherichia coli and Enterobacter spp. presented an increased resistance against all the tested classes, excepted for two fifths of E. coli. Moreover, the percentages of multi-drug resistant strains of Staphylococcus aureus and Enterobacter spp. also increased from 24.5% to 37.4% and from 26.3% to 51.7%, respectively. The data reported here are relevant to equine practitioners and will help to improve knowledge related to antimicrobial resistance in common equine pathogens.

Update on Diseases in Chinchillas: 2013-2019

Chinchillas have been used mostly as fur animals and as animal models for human ontological diseases and only recently have been recognized as excellent, long-lived, and robust pet rodents. This review aims to provide updated information on emerging disease conditions in pet chinchillas, such as Streptococcus equi subsp zooepidemicus and Pseudomonas aeruginosa. Furthermore, this review article provides updated information on previously documented disorders, such as urolithiasis and middle ear disease, in chinchillas. This article is intended to serve as a complement to the current veterinary reference literature and to provide valuable and clinically relevant information for veterinarians treating chinchillas.

Identification of genes required for the fitness of Streptococcus equi subsp. equi in whole equine blood and hydrogen peroxide

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 H2O2 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 H2O2, respectively. Of these genes, 36 and 15 were identified as being important to the fitness of S. equi in whole blood or H2O2, 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.

Development of a nested PCR assay for detection of Streptococcus equi subspecies equi in clinical equine specimens and comparison with a qPCR assay

Streptococcus equi subsp. equi is a Gram positive bacterial pathogen commonly associated with strangles in horses, a respiratory disease characterized by abscessation of submandibular and retropharyngeal lymph nodes which can lead to obstruction of the airway. Several real-time PCR (qPCR) assays have been developed for detection of S. equi from horses with many targeting conserved regions of the S. equi cell wall-associated M-protein (SeM), a major virulence factor and immunogen of S. equi. Our objective was to develop a nested PCR (nPCR) targeting SeM and an 18S rRNA internal control gene for detection of S. equi from horses with potential improvement in detection sensitivity compared to a qPCR. Primers and probes from the Kansas State Veterinary Diagnostic Laboratory (KSVDL) S. equi clinical testing assay were utilized for all qPCR testing. Primers flanking the SeM qPCR target region were selected for an initial end-point PCR step of the nested assay; PCR product from the end-point reaction then served as template for the qPCR reaction step of the nested assay. Sample nucleic acid was also tested directly with qPCR to allow for assay comparison. Nucleic acid from clinical specimens (n = 188) submitted to KSVDL were tested in parallel with each assay. The nPCR and qPCR assays identified 22.9% (43/188) and 13.3% (25/188) of samples positive for S. equi, respectively. None of the samples positive by qPCR were negative by nPCR. The PCR products from all positive samples were submitted for DNA sequencing. Each of the 25 samples positive by both assays had a high nucleotide identity match (>96%) to the SeM gene. Among the samples positive by nPCR but negative by qPCR, 17 of 18 were sequence confirmed for SeM at greater than 96% nucleotide identity. Based on the nPCR Ct (37.8) of the one sequence un-confirmed case, it is likely that the S. equi bacterial load in this sample was below the necessary concentration for successful sequencing. Limit of detection (LOD) for the nPCR was established at a Ct of 37, and based both on the LOD of the qPCR assay (Ct of 37), as determined by standard curve data, and on the highest nPCR Cts (~37) of clinical samples able to result in SeM sequence-confirmation. As demonstrated by sequencing confirmation, the nPCR assay targeting the SeM gene is highly specific to S. equi. The increased sensitivity of the nPCR, compared to the qPCR, may reduce the number of false negative sample results in clinical testing and provide a superior detection method during low bacterial shedding periods.

Comparison of whole genome sequences of Streptococcus equi subsp. equi from an outbreak in Texas with isolates from within the region, Kentucky, USA, and other countries

Strangles, caused by Streptococcus equi subspecies equi (S. equi) is an infectious disease of horses with worldwide distribution, but there are limited data available regarding strain variation using whole genome sequencing among and within outbreaks in the United States (US), and how US isolates compare with S. equi isolated globally. To address this knowledge-gap, we compared the whole genomes of 54 S. equi isolates from Texas and Kentucky and those of 230 publicly available sequences of S. equi isolates collected from other countries. Our results show that despite minimal variation among isolates within an outbreak some mutations do occur among individual outbreak isolates. Some S. equi strains from the US are closely related to S. equi isolates from other countries, likely reflecting international dissemination of isolates. Collectively, these data improve our understanding of phenotypic and genotypic variation of isolates within an outbreak, and the international distribution of S. equi. We also identify a novel variant of the S. equi M-protein, and observed cases of strangles that were caused by the modified-live vaccine but that were not recognized as vaccine-associated at the time of clinical sample submission.

Molecular detection of Streptococcus equi subspecies equi in face flies (Musca autumnalis) collected during a strangles outbreak on a Thoroughbred farm

The objective of this study was to detect Streptococcus equi subspecies equi (S. equi) (Lactobacillales: Streptococcaceae) using quantitative polymerase chain reaction (qPCR) in flies collected from a farm with a documented outbreak of strangles. A total of 1856 face flies [Musca autumnalis (Diptera: Muscidae)] were collected using conventional fly traps. The flies were processed for nucleic acid purification and tested for the presence of S. equi by qPCR. A total of 10/1856 flies (0.54%) tested qPCR-positive for S. equi. The results may implicate the presence of face flies as a risk factor for the transmission of S. equi and highlight the need to institute proper husbandry measures, biosecurity protocols and fly control in order to reduce the potential for infection in at-risk horses.

Serological responses of Australian horses using a commercial duplex indirect ELISA following vaccination against strangles

OBJECTIVE

To determine the nature of serological responses in Australian horses using a commercial duplex indirect ELISA (iELISA) following vaccination against strangles.

DESIGN

A group (n = 19) of client-owned horses from five properties were recruited to receive a primary course of a Streptococcus equi subsp. equi (S. equi) extract vaccine. Serological responses were determined by duplex iELISA incorporating S. equi-specific fragments of two cell wall proteins, SEQ2190 and SeM (antigens (Ag) A and C, respectively).

METHODS

The horses were administered a primary strangles vaccination course. Blood was collected immediately prior to each of the three vaccinations at 2-week intervals and additionally at 28 and 56 days following the 3rd vaccination (V3).

RESULTS

Significant increases in mean antibody levels of horses following vaccination were limited only to AgC, which was significantly increased at T2/V3, 14 days following V2 (ratio of geometric means = 3.7; 95% confidence interval (CI): 1.6, 8.4; P = 0.003). There was no increase in mean antibody to Ag A (ratio of geometric means = 1.4; 95% CI: 0.6, 3.2; P = 0.39). Four horses (22%) exceeded the test cut-off for AgC following vaccination.

CONCLUSION

Vaccination of Australian horses is unlikely to interfere greatly with detection of strangles using the duplex iELISA. No responses would be anticipated to AgA following vaccination with Equivac© S/Equivac© 2in1 and only a minority are likely to respond to AgC. We conclude that the results of this study validate the usefulness of the duplex iELISA to assist control measures for strangles outbreaks in Australian horse populations.

Influence of penicillin treatment of horses with strangles on seropositivity to Streptococcus equi ssp. equi-specific antibodies

Background

Antibiotic treatment of horses with strangles is reported to impair the development of immunity to subsequent exposure to Streptococcus equi ssp equi (S. equi). However, apart from a single clinical report, evidence‐based studies for this hypothesis are lacking.

Hypothesis/Objective

To determine whether penicillin treatment during clinical strangles influences the development or persistence of seropositivity to S. equi‐specific antibodies.

Animals

A natural outbreak of strangles with 100% morbidity in 41 unvaccinated mature Icelandic horses.

Methods

A prospective longitudinal study of acute clinical strangles from onset through full recovery approximately 10 months after the index case. Horses were monitored clinically 6 times for S. equi, as well as serologically for antibodies to antigens A and C of S. equi using an enhanced indirect ELISA. Seven horses received penicillin within 11 days of onset of fever (Group 1), 5 between 16 and 22 days after onset of fever (Group 2), and the remainder (Group 3, n = 29) received no antibiotics during clinical disease. The proportions of seropositive horses in each group were compared using an extension of Fisher's exact test with P < .05 as the level of significance.

Results

Although all horses were seropositive to S. equi within 2 months of the index case, significantly fewer horses treated early (Group 1) remained seropositive by 4 to 6 months (P = .04 and .02, respectively).

Conclusions and Clinical Importance

Findings support earlier suggestions that penicillin administered during acute strangles can interfere with persistence of humoral immunity to S. equi.

Streptococcus equi in Equine: Diagnostic and Healthy Performance Impacts

Although the strangles disease of Streptococcus equi was discovered many decades ago in 1,251 by Jordanus Ruffus, it has still remained a major frequently diagnosed infection in horses all over the world. The S. equi subspecies pathogen is known to be often resistant to antibiotic treatment, and it makes the antibiotics inefficient; hence, this review was conducted to study how the disease can be managed. The age-long sign of this infection is the oozing of pus through the mucous and skin membranes. Affected horses lose appetite, develop fever, and become depressed, which result in them losing weight and becoming lethargic, reducing their physical activity especially when they are being raised for athletic and sport purposes. This article reviews various solutions proffered by several researchers about the healthy performance impacts of S. equi in equine.

Survival of Streptococcus equi subsp. equi in Normal Saline Versus Phosphate-Buffered Saline and at Two Different Temperatures

Streptococcus equi subsp. equi causes strangles in horses. Sampling to detect carriers is important for the control of the disease, and maximizing the sensitivity of this procedure is necessary. To provide a basis for the choice of sampling solution and transport temperature for samples, comparisons were made between the survival of Streptococcus equi subsp. equi in normal saline versus phosphate-buffered saline and at two different temperatures (cold and room temperature). At present, normal saline is used to sample the nasopharynx as well as the guttural pouches, and the sampling solution is transported without special cooling. The results revealed no significant difference in bacterial concentration levels between the two sampling solutions, but a significantly higher concentration of viable bacteria in the samples kept cold compared with room temperature. Hence, a change of sampling solution is not warranted, but maintaining the cold chain during storage and transport to the laboratory may be important for clinical samples.

A Conserved Streptococcal Virulence Regulator Controls the Expression of a Distinct Class of M-Like Proteins

Streptococcus equi subspecies zooepidemicus (SEZ) are group C streptococci that are important pathogens of economically valuable animals such as horses and pigs. Here, we found that many SEZ isolates bind to a monoclonal antibody that recognizes poly-N-acetylglucosamine (PNAG), a polymer that is found as a surface capsule-like structure on diverse microbes. A fluorescence-activated cell sorting-based transposon insertion sequencing (Tn-seq) screen, coupled with whole-genome sequencing, was used to search for genes for PNAG biosynthesis. Surprisingly, mutations in a gene encoding an M-like protein, szM, and the adjacent transcription factor, designated sezV, rendered strains PNAG negative. SezV was required for szM expression and transcriptome analysis showed that SezV has a small regulon. SEZ strains with inactivating mutations in either sezV or szM were highly attenuated in a mouse model of infection. Comparative genomic analyses revealed that linked sezV and szM homologues are present in all SEZ, S. equi subspecies equi (SEE), and M18 group A streptococcal (GAS) genomes in the database, but not in other streptococci. The antibody to PNAG bound to a wide range of SEZ, SEE, and M18 GAS strains. Immunochemical studies suggest that the SzM protein may be decorated with a PNAG-like oligosaccharide although an intact oligosaccharide substituent could not be isolated. Collectively, our findings suggest that the szM and sezV loci define a subtype of virulent streptococci and that an antibody to PNAG may have therapeutic applications in animal and human diseases caused by streptococci bearing SzM-like proteins.IMPORTANCE M proteins are surface-anchored virulence factors in group A streptococci, human pathogens. Here, we identified an M-like protein, SzM, and its positive regulator, SezV, in Streptococcus equi subspecies zooepidemicus (SEZ), an important group of pathogens for domesticated animals, including horses and pigs. SzM and SezV homologues were found in the genomes of all SEZ and S. equi subspecies equi and M18 group A streptococcal strains analyzed but not in other streptococci. Mutant SEZ strains lacking either sezV or szM were highly attenuated in a mouse model of infection. Collectively, our findings suggest that SezV-related regulators and the linked SzM family of M-like proteins define a new subset of virulent streptococci.

Differences in microbiome and virome between cattle and horses in the same farm

Objective

The ecosystem of an animal farm is composed of various elements, such as animals, farmers, plants, feed, soil, and microorganisms. A domesticated animal’s health is largely connected with the reservoir of bacteria and viruses in animal farms. Although a few studies have focused on exploring the gut microbiome of animals, communities of microbiota and viruses in feedlots have not been thoroughly investigated.

Methods

Here, we collected feces and dust samples (4 groups: cattle feces, C_F; horse feces, H_F; cattle dust, C_D; and horse dust, H_D) from cattle and horse farms sharing the same housing and investigated their microbiome/virome communities by Illumina sequencing.

Results

Dust groups (C_D and H_D) showed higher microbial diversity than feces groups (C_F and H_F) regardless of animal species. From the microbial community analysis, all the samples from the four groups have major phyla such as Proteobacteria (min 37.1% to max 42.8%), Firmicutes (19.1% to 24.9%), Bacteroidetes (10.6% to 22.1%), and Actinobacteria (6.1% to 20.5%). The abundance of Streptococcus, which commonly recognized as equine pathogens, was significantly higher in the horse group (H_D and H_F). Over 99% among the classified virome reads were classified as Caudovirales, a group of tailed bacteriophages, in all four groups. Foot-and-mouth disease virus and equine adenovirus, which cause deadly diseases in cattle and horse, respectively, were not detected.

Conclusion

Our results will provide baseline information to understand different gut and environmental microbial ecology between two livestock species.

Antibody kinetics and immune profile analysis of a Streptococcus equi DNA vaccine expressing the FljB and SeM fusion protein in murine and equine models

Strangles is a highly prevalent, extremely contagious, and occasionally lethal infectious disease affecting horses worldwide. Prophylactic antibiotics are ineffective in prevention of disease but are recommended for exposed horses at the first sign of fever and any horse obviously ill from strangles or with complications and there is an urgent need of a cost-effective, safe, efficacious vaccine. In the present study, we sought to develop effective vaccines by fusing the Streptococcus equi subspecies equi (S. equi) antigen SeM with the flagellin of Salmonella abortus equi FljB. We also explored the immunogenicity and efficacy of this candidate vaccine in mice and horses by intramuscular injection. Mice and horses immunized with FljB-SeM DNA vaccine showed high levels of specific antibody and increased production of IFN-γ and IL-4. This confirmed that both Th1 and Th2 type responses were induced. The mice survival rate was significantly higher after immunization with FljB-SeM than with SeM alone. The FljB-SeM DNA could strengthen both the Th1 and Th2 immune responses compared to SeM and could provide better protection against S. equi. This technique could help develop a candidate vaccine for S. equi infection.

Tratamiento quirúrgico de condroides en las bolsas guturales de un equino mediante abordaje Whitehouse modificado. Reporte de caso

Una yegua de raza caballo criollo colombiano (CCC) de 34 meses de edad fue remitidaal Centro de Veterinaria y Zootecnia de la Universidad CES, en la ciudad de Medellín(Colombia), para la extracción quirúrgica de condroides en ambas bolsas guturales. Lapaciente se intervino en estación utilizando neuroleptoanalgesia y a continuación, seempleó la técnica Whitehouse modificado en cada bolsa gutural para extraer la totalidadde los condroides. Posteriormente, se realizó tratamiento antibiótico y antinflamatoriopre y post quirúrgico con trimetoprim-sulfadiazina y flunixin meglumine vía sistémica;además, penicilina G sódica local. Luego de la intervención la paciente fue dada de altasin complicaciones y finalmente se evidenció la resolución completa de la condiciónrespiratoria. El reporte de este caso permitirá conocer con detalle la técnica Whitehousemodificado, así como sus retos quirúrgicos y consideraciones, ya que a la fecha en Colombiano hay otros reportes al respecto en un CCC.

An outbreak of strangles associated with a novel genotype of Streptococcus equi subspecies equi in donkeys in China during 2018

BACKGROUND

Strangles is a highly contagious respiratory disease of equids caused by the bacterium Streptococcus equi subspecies equi.

OBJECTIVES

To identify the cause of an outbreak of strangles that occurred on donkey farms within the Shandong Province of China and determine the prevalence of the disease.

STUDY DESIGN

Cross-sectional.

METHODS

Samples were taken from clinically affected animals to measure the prevalence of strangles within the population of donkeys at six intensive farms in China and identify the SeM type of isolate recovered from affected animals. Diagnosis was confirmed by bacterial isolation, biochemical tests and PCR. Epidemiological data were analysed using Chi-square test and a Fisher's exact two-sided test. The SeM gene of S. equi isolates recovered from affected animals was determined and compared with the SeM database PubMLST-seM.

RESULTS

In July and August 2018, an outbreak of strangles occurred on six donkey farms within the Shandong Province of China. The overall prevalence of disease within the different donkey herds was 13.4%. Younger animals were worst affected with 40.3% (83/206) of donkey foals aged under 1 year exhibiting clinical signs compared with 12.5% (191/1525) of donkeys aged one to 2 years and 3.8% (17/442) of donkeys over 2 years of age. Analysis of SeM sequencing data identified that the farms were affected by the same strain of S. equi, SD201807, which contains the novel 136 allele of SeM.

MAIN LIMITATIONS

Healthy donkeys were not sampled in this study.

CONCLUSIONS

The number of intensive donkey breeding farms in China has risen recently. The higher numbers of animals that are in closer proximity to one another raise the potential for the transmission of infectious diseases such as strangles. This is the first description of a strangles outbreak among donkey herds in China. The Summary is available in Chinese - see Supporting information.

Long term silent carriers of Streptococcus equi ssp. equi following strangles; carrier detection related to sampling site of collection and culture versus qPCR

After strangles outbreaks, Streptococcus equi ssp. equi (S. equi) can persist in clinically normal silent carriers for months to years. Two naturally occurring outbreaks of strangles with 53 and 100% morbidity, respectively, were followed longitudinally to assess occurrence of carrier state and optimal detection methods Outbreak A involved 98 yearling warmbloods, and outbreak B 38 mature Icelandic horses. Fully recovered horses were sampled at least 6 months after index cases using nasal swabs (one sampling occasion only) nasopharyngeal lavage and guttural pouch visualisation and lavages for culture and qPCR to S. equi. Any horse with at least a single sample positive was deemed a carrier. Descriptive statistics and sensitivity and negative predictive values were calculated. Comparisons were made with McNemars and Fishers exact tests. Carrier rates in outbreak A were 3% based on culture and 15% based on qPCR and for outbreak B 13% based on culture and 37% based on qPCR. All culture positives were also qPCR positive. One carrier culture negative sampled after an additional 8 months was culture positive to S. equi, indicating that qPCR positives should be suspected to carry live bacteria. Findings indicate that reliance on guttural pouch sampling and appearance does not capture all silent carriers. All culture positives were identified by qPCR and even horses positive by qPCR but culture negative should be suspected carriers of live bacteria.

Strangles, convalescent Streptococcus equi subspecies equi M antibody titers, and presence of complications

Background

Streptococcus equi subspecies equi infection elicits M protein antibody titers in equids. Interpretation of titers is not generally accepted.

Hypothesis

The magnitude of S. equi M protein (SeM) antibody titer after infection (titer ≥1:12 800) will be useful to monitor for the presence of complications or the risk of development of complications.

Animals

Forty‐eight horses on 1 farm involved in strangles outbreak.

Methods

Clinical and observational study. S. equi M protein antibody titers were measured on all horses 8 weeks after infection and select horses 12 and 28 weeks after infection. Horses were categorized: no disease, uncomplicated case, persistent guttural pouch (GP) infection, or complicated cases (metastatic abscesses, purpura hemorrhagica, secondary infections, and dysphagia). Category was compared to titer.

Results

Twenty‐eight of 48 (58%) developed clinical signs of S. equi infection. Of those, 11 (39%) had uncomplicated strangles, 9 (21%) had persistent GP infection, 5 (18%) were complicated cases, and 3 (11%) had both persistent GP infection and complications. Thirty‐three percent of horses (16 of 48) had SeM antibody titers ≥1:12 800 eight weeks after infection. Of horses with titers ≥1:12 800, 6 of 16 had evidence of complications. Of complicated cases, 6 of 8 had titers ≥1:12 800. In this outbreak, the sensitivity (75%; 95% CI [confidence interval] 45‐105) for a SeM antibody titer ≥1:12 800 detecting complications was higher than the specificity (43%; 95% CI 23‐64).

Conclusions and Clinical Importance

This outbreak demonstrates that SeM antibody titers can be increased after infection (≥1:12 800) in the absence of complications of strangles.